# Talk:Quark/Archive 2

## Rare Decay?

the picture at the begining has a mistake. it states that the deacay s -> u is rare. that's actually the only way that quark can decay and therefore must be considered commom —Preceding unsigned comment added by Dauto (talkcontribs) 02:10, 4 February 2008 (UTC)

## Delisted from GA

In order to uphold the quality of Wikipedia:Good articles, all articles listed as Good articles are being reviewed against the GA criteria as part of the GA project quality task force. While all the hard work that has gone into this article is appreciated, unfortunately, as of February 15, 2008, this article fails to satisfy the criteria, as detailed below. For that reason, the article has been delisted from WP:GA. However, if improvements are made bringing the article up to standards, the article may be nominated at WP:GAN. If you feel this decision has been made in error, you may seek remediation at WP:GAR.

I've delisted this from GA as it has insufficient inline citations. The requirement for inline citations was only added to the good article critera in 2006, and this article may have been passed beforehand. I'll add in to our unreferenced GA task force. Once sufficient references are added hopefully it can easily regain GA status. --jwandersTalk 11:50, 15 February 2008 (UTC)

## Color, Colour, or Colo(u)r?

Alternate?

[[dark.]][[arias.]] (talk) 14:07, 11 March 2008 (UTC)

Wikipedia policy on form of English used is to keep an article consistent with itself. If it is written primarily in British English, then the entire article should be consistent. No form of English is preferred over any other, unless the article subject matter itself provides a bias.PhySusie (talk) 14:11, 11 March 2008 (UTC)

## Wording issue in "Origin of the word" section

It currently reads "The word was originally coined by Murray Gell-Mann as a nonsense word rhyming with 'pork', but without a spelling. Later, he found the word 'quark' in James Joyce's book Finnegans Wake, and used the spelling but not the pronunciation." The American Heritage Dictionary defines "coin" as "to devise (a new word or phrase)". So if Joyce used the word before, Gell-Mann didn't coin it. So I propose an alternate phrasing along the lines of: "Murray Gell-Mann originally referred to the particle with a nonsense sound rhyming with 'pork'. Upon later encountering the word 'quark' in in James Joyce's book Finnegans Wake, he assigned its spelling to his sound - although retaining his original pronounciation." Ribonucleic (talk) 19:56, 3 April 2008 (UTC)

## Why is something italicized in the introductory paragraph?

The sentence in question reads: "Their names were chosen arbitrarily based on the need to name them something that could be easily remembered and used."

I see no need to emphasize something; if anything it is confusing. —Preceding unsigned comment added by 130.15.164.75 (talk) 03:57, 9 April 2008 (UTC)

## Zweig

I cannot believe George Zweig isn't mentioned. Sure, he used the word "Ace" instead of "Quark", but he was the first to recognize the constituents of hadrons as "real", unlike Gell-Mann. —Preceding unsigned comment added by KamielC (talkcontribs) 10:46, 10 April 2008 (UTC)

## New image

Please comment of the new table of elementary particles at Wikipedia:Graphic_Lab/Images_to_improve#String Theory. Thanks. Dhatfield (talk) 22:57, 28 June 2008 (UTC)

## Free quark

Free quark is now a redirect that points to Quark#Free quarks. Reyk YO! 01:18, 1 July 2008 (UTC)

I added the results that fermilab saw of singly produced top quarks[1] —Preceding unsigned comment added by Edconrad (talkcontribs) 17:52, 9 March 2009 (UTC)

The singly produced top quark is not a free quark in the sense of color confinement. According to the standard model, top-quarks should be produced strongly in quark-antiquark pairs from a high energy gluon which is how they were first observed. In this case an excited W decays into a t and b which is much harder to detect experimentally. Appelte1 (talk) 02:00, 16 March 2009 (UTC)

## Should we merge articles?

Five of the articles in Category:Stub-Class physics articles of Top-importance are about individual flavours of quarks; do we really need a separate article about each one of them? Should we consider merging those articles here? For example, there aren't three separate articles for each flavour of neutrinos, or two articles one for the W boson and one for the Z boson. -- 14:09, 20 August 2008 (UTC)

I would suggest that we keep them seperated, as they could be expanded into something like the top quark, and there are plenty of information about individual quarks that would be overkill for the quark article (such as history of discovery, significance, detailed properties, where they are currently studied, etc...)Headbomb {ταλκWP Physics: PotW} 08:09, 7 October 2008 (UTC)
To amplify Headbomb's remarks, the quarks are phenomenologically very different because of their different masses. There's a lot to say about them individually. -- SCZenz (talk) 08:22, 7 October 2008 (UTC)
Plus we get to eat lab soup. Headbomb {ταλκWP Physics: PotW} 08:26, 7 October 2008 (UTC)

## Arrangement

I am unsure on how quarks are arranged with different sub-atomic particles such as protons and neutrons... Can anyone help me? --absolutely confused —Preceding unsigned comment added by 71.3.176.39 (talk) 20:35, 18 September 2008 (UTC)

## History Section

The history section appears to have been written with a strong bias towards theoretical physicists. I see the names of about a dozen theorists but no experimental physicists are named. Many experimental results were crucial to determining the existence and properties of quarks including some that were rewarded with the Nobel Prize for Physics (I can think of at least 5 experimentalists who have the Nobel Prize for work in quark physics).

For a complex scientific field such as this, the history should reflect the hand-in-hand nature of experiment and theory. —Preceding unsigned comment added by 129.42.208.182 (talk) 16:58, 22 September 2008 (UTC)

I re-wrote it yesterday, completely, with a chronicling of only empirical observations. —Anonymous DissidentTalk 16:27, 24 September 2008 (UTC)

## Flavor

The article calls the choice of the term flavor "arbitrary", but they come in several flavors to mean "there are several varieties of them" is common slang, predating QCD — see, for example, http://www.catb.org/jargon/html/F/flavor.html. I think the second part of that sentence ought to be changed, but I can't find a decent wording for it making this point. Any ideas? -- 15:12, 25 September 2008 (UTC)

The fact that the term color is arbitrary is not dubious, as you have marked it. It is arbitrarily named and has nothing to do with the colour spectrum. —Anonymous DissidentTalk 22:23, 25 September 2008 (UTC)
Neither has “DDT commands come in two flavors.” anything to do with the color spectrum (or with taste, which is more relevant here — did you get confused with color charge?). But "arbitrary" suggests that somebody deliberately picked that term for reasons he didn't state (as Franklin did when he decided that vitreous electricity was "positive" and resinous electricity was "negative", forcing us to lie about the direction the current flows in metals, among other things).
But I don't think anybody did that with flavor. Probably people were saying "quarks come in three flavors" by analogy to the MIT slang I cited above, and then the usage stuck and became standard. -- 23:06, 25 September 2008 (UTC)
You don't have evidence for that. My book reference, however, suggests that it was arbitrary, insofar as that it was a randomly picked everyday word that was easy to understand. My book source is an academic reference, and I see no strong grounds to dispute it. —Anonymous DissidentTalk 09:57, 26 September 2008 (UTC)
Well, I'm adding a parenthetical note about the MIT usage, but without stating any conclusion. Feel free to remove it if you think it's too irrelevant. -- 10:28, 26 September 2008 (UTC)

## Opening sentence

The opening sentence should be a good definition of the topic, which the current sentence is not. I would suggest something like "A quark (IPA: /kwɔrk/, IPA: /kwɑːk/ or IPA: /kwɑːrk/) is an elementary particle classified as a fermion, it is one of the two basic constituents of matter, and comes in 6 flavors up, down, charm, strange, top, and bottom." —Preceding unsigned comment added by Ravedave (talkcontribs) 17:18, 25 September 2008 (UTC)

I agree. I'm fixing it. -- 17:31, 25 September 2008 (UTC)
I've adapted the opening sentence of Lepton. Sounds right now. (Even gluinos would be elementary fermions which participate in strong interaction if they existed, but WP:NOTCRYSTAL, so we don't need to be that pedantic until gluinos are discovered.) -- 17:46, 25 September 2008 (UTC)

Shouldn't there be at least a trace of skepticism noted in the opening of this article? We are, as scientists, supposed to be open to new interpretations and modifications. The Quark is noted as an "Elementary Particle." Now, "Elementary Particles" have been defined as such by particle physicists from the time of the discovery of the neutron, on the basis that they--somehow-- exist, as such, within atoms and are released by the "atom smashing" experiment in question. Somehow, it does not seem to have ever entered into the scientific consciousness that all of these "elementary particles" may be alternative, "short-lived," states of matter which are created within the circumstances. The quark seems to have its validity as a constituent of these units. If they are not "elementary," neither is it. Additionally, there is no true experimental evidence for any of the quarks, that is. there is no data of their mass and Compton Wavelength (or radius, if one prefers that notation)... They are actually still hypothetical, despite the extensive elaboration of the model. I would think that a more accurate opening would be that the quark is a proposed "elementary particle" which has been used as an explanation for certain experimental observations...." Giving the quark credence as necessarily having existence in the sense that the other "fundamental particles" have existence, even if they be artifacts rather than fundamental, is, at least in my opinion, a definite error. Dean L. Sinclair —Preceding unsigned comment added by Deanlsinclair (talkcontribs) 16:12, 7 April 2009 (UTC)

## Sea quark

Sea quark redirects here, so information about them (virtual quark–antiquark pairs involved in strong interaction) should be added if possible (to section "Color confinement and gluons"). Unfortunately, none of the results I find by googling for "sea quark" seem to be suitable for a reference to add an introductive sentence likely to be read by people having never heard of sea quarks. -- 12:20, 30 September 2008 (UTC)

It might make more sense to redirect it to parton (particle physics), which discusses sea partons (of which sea quarks are one type) a bit and should discuss them more. I'm not sure we have space in this article to discuss the details of scattering experiments and hadron content. -- SCZenz (talk) 12:41, 30 September 2008 (UTC)
Done. But anyway I wasn't suggesting any detailed discussion, just add to "...gluons" the phrase "and virtual pairs of quarks and antiquarks, called sea quarks [ref here]" -- 12:53, 30 September 2008 (UTC)

The current section seems to imply that the valence quarks of a hadron always stay the same, and that it is possible to determine which quarks are the valence quarks. But, if my understanding of identical particles is correct, this isn't the case – all quarks of the same flavor are equal; and all we can say is that, for example, a proton has two more up quarks than up antiquarks, and one more down quark than down antiquarks, at any one given time. Also, the word core suggests that valence quarks tend to be closer to the centre of the hadron. Can anybody with a good understanding of QCD tell if this is correct? -- 16:32, 5 October 2008 (UTC)

The valance quarks of a particular hadron are always the same three quarks in the sense that a proton is always uud; but it's utterly meaningless to ask whether the down quark at one time is the same as one at a later time. Likewise, it's meaningless to count how many sea quarks there are in a proton at any given time. You can only count what the probability of hitting a particular type of quark is if you probe it. And yes, "core" is a bad direction to go in; you really can't say where the quarks are exactly, and they certainly aren't confined to any special part of the hadron. -- SCZenz (talk) 22:13, 5 October 2008 (UTC)

## Aces

Zweig called his particles aces but Gell-Mann won the linguistic battle. Reference: Gleick, J. Richard Feynman and modern physics (1992) Little Brown and Company ISBN 0 316 903167 p. 390 Graham Colm Talk 14:16, 5 October 2008 (UTC)

Thanks. —Anonymous DissidentTalk 14:31, 5 October 2008 (UTC)

Believe me, it is not written for a physics graduate student, but I agree the lead was too heavy on terminology. I have written a new proposal at User:SCZenz/Quark#New intro. Comments from everyone appreciated. -- SCZenz (talk) 07:02, 7 October 2008 (UTC)
• The quark is a type ... --> Quarks are a type of ... ?
• most basic known building block --> most basic building block? It's "less heavy" and just as accurate.
• Only the lightest --> Only the lightests (this sentence is also very long)
• The top quark is not more massive than a gold atom, it's comparable to the mass of a tungsten atom (170 GeV = 183 or so nucleons) rather than a gold atom (200 or so nucleons).
• Also, it would probably be better to relate the mass of the up quark in terms of fractions of the proton mass, or in a multiple of electron masses. "Half a percent of the proton's masses" isn't as clear as "1200th of the mass of the proton" or "the mass of 5 electrons" or whatever the actual numbers are.
• Early universe section seems to be rather vague
• Don't forget the refs
• There should be some kinda of emphasis on quarks being elementary particles, and put in contrast with the hadrons, which are composite particles.
Headbomb {ταλκWP Physics: PotW} 07:24, 7 October 2008 (UTC)
Ok, let's see. I disagree with many of your changes, because I think they re-introduce exactly the kind of complexity that the commenters on the FAC were concerned about. Some specific comments:
• "Most basic known" is certainly more accurate; there's no special reason to believe that quarks aren't composite too. The question is whether it's worth the extra word to allow for this. I think it is; it's a little word.
• I stand corrected on the mass of gold. Nevertheless, I prefer "about as massive as a gold atom," because I think our readers are more likely to be familiar with gold than the heavy metals that are closer in mass.
• Not sure about antiquarks. Talking about antimatter adds complexity and terminology, and we have to be careful to make sure people understand that quarks aren't UNIQUE in having antiparticles, which adds more complexity and terminology still.
• The early universe section is rather vague. We'll need to write proper details later in the article.
• I am not sure the lead needs refs. Even many featured articles don't have any, and I think it's fine as long as we discuss things in more detail later and reference them then.
• Composite vs. elementary. Again, adds terminology, and expresses certainty about something that isn't really certain.
The remaining two are fine with me, in principle. Thanks for your comments! -- SCZenz (talk) 07:39, 7 October 2008 (UTC)
• About the known part, if we're going to be worried about what might be or might not be the case at every corner, then we'd have to add "known" to pretty much everything out there. Numbers of known types of quarks, number of known types of colors etc... If we must have known in there, most basic building block of atomic nucleus known is probably a better way to write it down.
• Some basic terminology needs to be retained. Things like elementary and composite are not Mandarin encrypted with a 1024-bit key to anyone with a basic grasp of english (especially with the wikilinks availible). Things need to be kept simple, I agree, but not too simple.
• I've received complaints for lack of in-line citations in the lead when I wrote the List of baryons, so I doubt this would fare well with the FAC crowd to receive a lead without in-line citations. Either way, it may not be a criteria, but they are certainly nice to have.
Headbomb {ταλκWP Physics: PotW} 07:59, 7 October 2008 (UTC)
As for gold vs tungsten, tungsten is found in the filament of incandescence light bulbs, so fewer people have never heard of it than you could believe. Also, someone who doesn't know what tungsten is is very likely to have no idea about how heavy a gold nucleus is, so using "gold" rather than "tungsten" has no significant advantage. But, OTOH, the source given uses gold as the example, so I'm not going to change it with tungsten in the article, at least for now. As for "The quark is a type ... --> Quarks are a type of", if you refer to the first sentence, I agree that the plural would be more logical for that sentence, but we would have the bold text differing from the title of the article, and we would either add /s/ at the ends of pronunciation, which would look rather weird, or we wouldn't, and then some people might be misled into believing that the plural is pronounced like that, too. And with a instead of the, as in the current version of the article, that sentence not really that awkward. -- 19:15, 17 October 2008 (UTC)
Small comment. "As a result..." in the first paragraph. This suggests to a reader that it should be obvious to him that quarks interacting through the strong interaction implies color confinement. This is all but obvious even to the field experts. It is generally agreed that QCD should explain color confinement, but to date nobody has completely proven it. (although there are good heuristic arguments that tell us it should.) (TimothyRias (talk) 09:30, 7 October 2008 (UTC))
Does it really read that way? I didn't mean to imply that it should be obvious to the reader. Obviously I did imply that QCD explains confinement, but I think it's agreed that this is true (and I'm sure I can find a source) even if it has yet to be proven mathematically. -- SCZenz (talk) 09:37, 7 October 2008 (UTC)

## Some issues

I see the article has been taken of FAC, probably rightly so. Here are some issues I have encountered in the text. (I will try to resolve some of these as I find time.)

-The "weak interaction" bit talks only about W-bosons, completely ignoring the Z-boson which also couples to the quarks. -Their should be some sort of remark on the (im)possibility of the existence of a fourth generation. -The discussion of "color charge" is on a very naive level and I have doubts about the factual accuracy.

(TimothyRias (talk) 08:41, 7 October 2008 (UTC))

Sorry that I didn't bring this up before. I had a careful read of the article this morning and I was surprised that it makes no mention of the CKM matrix. It's role in CP-violation and it the fact that allows generation changing currents seem to be quite important to mention. (TimothyRias (talk) 10:55, 12 December 2008 (UTC))

This article could/should be seriously expanded in nearly every section before it is ready for GA, let alone FA. Some points:

• History: I'd split this up into more sections, and write some more about each of the discoveries of the various quarks. Explain how they found them, possibly any controversies (I'm aware of at least one surrounding J/Psi, specifically related to Ting's name)
• Explain why there are thought to only be three generations, rather than 4
• What is expected to be found out about the quarks that is not already known? Are they actually fundamental particles, or are they made up of something?
• Rather than giving a mass range, I'd give the central mass and the error on that measurement, saying how confident that error is.
• The Pentaquark should be mentioned/discussed.

Mike Peel (talk) 21:07, 10 October 2008 (UTC)

In the Standard Model article, it says that the Up quarks have 3Mev mass and the Down Quarks have 6Mev mass. Thus A proton with 2Up + 1Down would have 12Mev and a Neutron with 1Up and 2Down would have 15Mev. Is this correct? WFPMWFPM (talk) 15:21, 16 October 2008 (UTC)
No, invariant masses aren't additive in special relativity, so the invariant mass of a system is usually greater than the sum of rest masses of particles composing it; and even massless particles, gluons in this case, can contribute to its total mass. And also, there are sea quarks... But anyway, for such questions WP:RD is usually a better place to ask than talk pages of articles. -- 13:21, 17 October 2008 (UTC)
==The May,1985 issue of National Geographics magazine has one of its customary good articles on "Worlds within the atom" in which the atom and its subcomponents (including quarks) are all discused with lots of pictures and graphics. Would make a good reference. WFPMWFPM (talk) 00:32, 24 October 2008 (UTC)

## Expected mass of the top quark

I'm replacing "around 200 times heavier than the hadron it was thought to form" with "significantly heavier than it was expected". 1/200 of the top quark mass is 856 MeV, less than a proton, so I don't think they really expected that there was any hadron as light as that still undiscovered. Richard Feynman in QED: The Strange Theory of Light and Matter says:

And now a funny particle has been found implying a new "flavor" of quark—this time it's "b," for "beauty," and it has a charge of −1/3 (see Fig. 92). Now, I want you to become high-class, fundamental theoretical physicists for a moment, and predict something: a new flavor of quark will be found, called__ (for "____"), with a charge of__, a mass of __MeV—and we certainly hope it's true that it's there!7

Figure 92 is a table like the one in the Classification section of this article, but with a blank cell instead of the top quark entry, and footnote 7 says "Since these lectures were given, some evidence has been found for the existence of a t quark with a very high mass—around 40,000 MeV." The lectures were given around 1983, and the book was published in 1985, that is ten years before the top quark was found. That was one fourth of its actual mass, but "much heavier" would suggest it's several orders of magnitude more massive. Maybe they expected a much smaller mass in 1977, but, if so, we should say "than was originally expected". Also, the source given (F. Canelli. "The Top Quark: Worth its Weight in Gold". University of Rochester. Retrieved 2008-10-24.) doesn't support that point. -- 21:05, 17 October 2008 (UTC)

## Preons

Why aren't they mentioned in this article at all? I'm not the one that should be writing about their relationship to quarks but I know it's relevant information. 68.46.139.114 (talk) 22:26, 6 November 2008 (UTC)

We don't have much reason to believe they exist. See preon. -- SCZenz (talk) 01:55, 13 December 2008 (UTC)

## Rearranging of info about strong interaction

I think I've managed to keep all the stuff about strong interaction, which is now scattered all over the article, in one place.

Since I believe that the probability of screwing something up when doing such massive changes is very close to 1, I've saved the result to User:Army1987/Quark rather than to the article. Can someone take a look at it? -- Army1987 – Deeds, not words. 00:06, 13 December 2008 (UTC)

• "There are three types of color charge a quark can carry, named blue, green and red; each of them is complemented by an anti-color: antiblue, antigreen and antired, respectively. While a quark can have red, green or blue charge, an antiquark can have antired, antigreen, or antiblue charge." Surely this can be made less verbose?
• "A quark charged with one color value will be attracted to an antiquark carrying the corresponding anticolor, while three quarks all charged with different colors will similarly be forced together. In any other case, a force of repulsion will come into effect" -- this should be clarified as a description of which color combinations are bound; I'm not sure it's true, and it's at the very least a much more subtle question, if you ask which combination are attracted together.
• "(but, for technical reasons, there are eight possible combinations, not nine)" -- remove this perenthetical note. It answers a question that nobody will ask, and can only confuse things; if people are curious they can click through to gluon.
• "despite previous observations indicating that gluons cannot exist without the 'attached' quarks" What results is this referring to? We know there aren't free quarks, but that doesn't bear on glueballs -- I guess I'm objecting to the word "despite."
• "therefore forever disallowing quarks to exist in isolation" Language is a bit cumbersome.
SCZenz (talk) 02:13, 13 December 2008 (UTC)
99% of the text in my subpage was copied and pasted from the article; all the wordings you talk about are also present in the article. I just wanted to show how the info about QCD which is now scattered all over the place could be kept together, and I didn't think I had to rewrite paragraphs to make the point. -- Army1987 – Deeds, not words. 03:12, 13 December 2008 (UTC)
OK, OK, I shouldn't be editing 'till past four in the morning (especially when I've just slept five hours the night before), 'cause my politeness goes to sleep before I do. I apologize for the arrogant wording of my comment above. But the point was that: I just wanted to show a different arranging of the information in the article. Most of your points are valid, and I'll try to address them in the article.
Which layout (ignoring content) do you like more? The current one or the one in my subpage? Anyway, if I did copy my version over to the article, I would incorporate all changes which have been made to the article meanwhile. -- Army1987 – Deeds, not words. 11:44, 13 December 2008 (UTC)

## CKM matrix

I see that Headbomb introduced a section on the CKM matrix. Good work. I do however have some comments. Lets sort these out. First of all, what is an expression like:

$|u\rangle = V_{ud} |d\rangle + V_{us} |s\rangle,$

supposed to mean? Clearly the intent cannot be to imply that the up-quark is a superposition of a down and strange quark. (that would be nonsense) But also cannot be a statement about transition probabilities between in and out states since that would involve factors of g (the weak interaction coupling constant).

The reason I ask is that I am used to a different presentation of the CKM matrix, expressing it in terms of the matrices relating mass eigenstates to weak-coupling eigenstates. That is if u'=Uuu and d'=Udd express the weak coupling eigenstates u' and d' of the up and down type quarks in terms of the mass eigenstates u and d. Than V=Uu-1Ud is the CKM matrix. It is matrix appearing the the currents coupling to the W-boson when expressed in mass-eigenstates.

I'm not sure that the present presentation is incorrect, but it certainly is different from what I'm used to. Hence my apprehension to directly change the presentation. (TimothyRias (talk) 09:52, 17 December 2008 (UTC))

Yes I can see the problems with what I've done. I'm collecting my toughts and will give a reply soon.Headbomb {ταλκκοντριβςWP Physics} 10:29, 17 December 2008 (UTC)
It appears that I've half-assed things and was sloppy in what I wrote. Granted in the end, only primes were missing in the formulas, but the physics was wrong (should've specified that these were weak eigenstates). This way is more orthodox I presume?Headbomb {ταλκκοντριβςWP Physics} 10:49, 17 December 2008 (UTC)

I added some stuff about unitarity and t quarks. Also, would it be fair to say that K and M essentially predicted the existence of the third generation of quarks with their 1973 paper? I'm also worried about my chronology. The c quark was discovered in 1974, after the KM paper, but right now I'm implying that the c quark discovery led to the development of the CKM matrix...before it was discover. So ... yeah. Headbomb {ταλκκοντριβςWP Physics} 11:50, 17 December 2008 (UTC)

Chronology problems have been resolved, although the version in CKM matrix still has them.Headbomb {ταλκκοντριβςWP Physics} 02:13, 18 December 2008 (UTC)
Yes, I think it would be correct to say that Kobayashi and Maskawa predicted the third generation - or rather, their explanation for the origin of CP breaking required it. That (and not flavor mixing in general) is why they were awarded the Nobel prize and Cabibbo was excluded (see, e.g., http://nobelprize.org/nobel_prizes/physics/laureates/2008/press.html). --Blennow (talk) 08:28, 18 December 2008 (UTC)

OK this is already better. But, in still not happy with the notation

$|u^\prime \rangle = V_{ud} | d \rangle + V_{us} | s \rangle = \cos \theta_c | d \rangle + \sin \theta_c | s \rangle$

First of all why is the ket notation used. The whole discussion is taking place on the level of the classical Lagragian in which d, u and s just represent (spinor valued) fields. Secondly, why is the linear combination of d and s denoted u'? The linear combination is still a down type field. I would suggest denoting the linear combination as d' such that the weak isospin doublet becomes (u, d')L.(TimothyRias (talk) 11:09, 18 December 2008 (UTC))

There's a discussion going on at Talk:Cabibbo–Kobayashi–Maskawa_matrix#uct_primes right now on that very topic.Headbomb {ταλκκοντριβςWP Physics} 11:13, 18 December 2008 (UTC)

### Version from Markus Poessel

In quantum theory, there is the possibility of linearly superimposing states. In everyday life, we are used to an arrow pointing in one definite direction only; in quantum physics, there can be an electron state that is a combination of an electron's spin pointing up and its spin pointing down. For quarks, there is a specific form of linear superposition of quark states that is crucial for describing weak interactions, as follows: There are two different ways of defining the usual six separate flavors of quarks (up, down, strange, charm, bottom, top). First of all, the way that quarks move and react to external forces shows that there are six separate quarks, each with a specific mass. Secondly, the way that quarks couple to each other and to the carrier-particles of the weak interaction shows that there are six separate quarks, each with a specific way of interacting.[2]

Significantly, the two sets of six quarks each thus defined are almost, but not quite the same. At best, three of the quark species coincide. Conventionally, one takes the u, c and t quarks to be the same in both definitions, but once that choice is made, it turns out that the down quark d', as defined by the weak interactions, is not quite the same as the down quark d that has a specific mass – specifically, d' is a linear superposition of d with small contributions of s and b quarks, and similarly for the s' and b' quarks. Mathematically, this linear combination can be written in terms of a matrix called the Cabibbo-Kobayashi-Maskawa matrix, as follows:

$\begin{bmatrix} \left| d^\prime \right \rangle \\ \left| s^\prime \right \rangle \\ \left| b^\prime \right \rangle \\ \end{bmatrix} = \begin{bmatrix} V_{ud} & V_{us} & V_{ub} \\ V_{cd} & V_{cs} & V_{cb} \\ V_{td} & V_{ts} & V_{tb} \end{bmatrix} \begin{bmatrix} \left| d \right \rangle \\ \left| s \right \rangle \\ \left| b \right \rangle \end{bmatrix}$

These linear superpositions directly determine which quark species can decay into which other kinds of quark in the course of weak interactions.[2]

Currently, the best experimental determination of the CKM matrix is:[3]

$\begin{bmatrix} V_{ud} & V_{us} & V_{ub} \\ V_{cd} & V_{cs} & V_{cb} \\ V_{td} & V_{ts} & V_{tb} \end{bmatrix} = \begin{bmatrix} 0.97419 & 0.2257 & 0.00359 \\ 0.2256 & 0.97334 & 0.0415 \\ 0.00874 & 0.0407 & 0.999133 \end{bmatrix}.$

I changed it to the previous version (it still needs work tho). This talk about arrows and linear superpositions is IMO even more technical than probabilities.Headbomb {ταλκκοντριβςWP Physics} 23:19, 17 December 2008 (UTC)

If you just say it's about probabilities of decay, that's selling the mechanism short, I think. After all, there are similar terms for the leptons, and nobody needs a CKM matrix for those. Not because they don't decay into each other, but because they're separated along lepton families. And my other worry with the now-restored version is that it doesn't even try to explain to someone not familiar with quantum mechanics why a sum of particles would even make sense - that's what my expanded introduction was about. If you can come up with a better one, by all means. But if you just leave it out, the CMK section will be a real break with the rest of the article's style – suddenly, reader unfamiliar with physics would find him- or herself in much deeper water, with not even an attempt to make things understandable. Markus Poessel (talk) 15:58, 19 December 2008 (UTC)
Well, there is really nothing more to the CKM matrix than a bunch of coupling constants. The equivalent matrix for leptons happens to be diagonal in the mass eigenstates. Actually it is forced to be diagonal by masslessness of neutrino's in the standard model. If neutrino masses are added the PMNS matrix is the analog of the CKM matrix.
About quantum mechanics. The CKM matrix involves no quantum mechanics at all, it is an issue the plays completely at the classical (pre-quantization) level. It just about considering linear combinations of classical fields. It doesn't have anything to do with a quantum mechanical superposition of states. It is easy to think that it does, this is why I think using a ket notation is so confusing.(TimothyRias (talk) 21:47, 19 December 2008 (UTC))
But is there a problem that rises from thinking of them as quantum states, or more precisely, that rises from a use of kets to describe them? What confusion is there when kets are used?Headbomb {ταλκκοντριβςWP Physics} 00:48, 20 December 2008 (UTC)

### CP breaking phase

The current piece on the CKM matrix only talks about the magnitude of the CKM matrix entries. Shouldn't it also mention the CP breaking complex phase? This was after all the primary motivation for KM to introduce a third generation. Does anybody have an idea how we can bring this in a not to technical way? (TimothyRias (talk) 23:46, 22 December 2008 (UTC))

## Ordering of properities subsections

Is there any particular idea behind the current ordering of the properties subsections? They seem somewhat random at the moment. May I suggest an ordering that builds up from simple basic properties like spin and mass to the more esoteric weak and strong interactions. I would suggest

1. Mass
2. Spin
3. Electric charge
4. Weak interaction
5. Flavor quantum numbers
6. Color charge
8. Table of Properties

(TimothyRias (talk) 12:48, 18 December 2008 (UTC))

In theory your idea is good, but the whole problem is that certain concepts introduced in one section are explored and referenced without explanation in later sections, in the current scheme. Were we to change it, it has real potential to leave the reader confused, since the material was written with consideration for the current structure. I think you'll also find that some of the harder topics are currently near the bottom end (cf. Flavor quantum numbers). —Anonymous DissidentTalk 13:03, 18 December 2008 (UTC)
But also the current scheme has some "below" links... (That's why I wrote User:Army1987/Quark.) -- Army1987 – Deeds, not words. 13:16, 18 December 2008 (UTC)
Army, I thank you for drafting another version, but so many recent edits have occurred on the present state that merging it back in would be impossible. Also, and as I tried to note, I think having "other properties" after "quarks in hadrons" and color confinement is introducing the complicated before the simple. Just my opinion. —Anonymous DissidentTalk
I'll try to make a compromise solution these days (but I'm not sure I'll succeed). -- Army1987 – Deeds, not words. 15:37, 19 December 2008 (UTC)

## Missing word?

"Quarks have various that are dependent on flavor, such as electrical and color charge, spin and mass." I am going to put in "properties" between various and that unless anyone has an objection. Dustybunny (talk) 14:50, 18 December 2008 (UTC)

## removed nonsense paragraph

I removed the following paragraph from the article:

If this were a valid treatment, the probabilities |V2
ud
| and |V2
us
| would add up to 1, but instead add up to 0.9999866461, indicative of the missing top quark. The missing term is |V2
ut
| = 0.0000128881. However, determining |V2
ud
| and |V2
us
| with a high-enough precision to predict the existence of the t quark was not possible at the time.

It was basically nonsense since with errors included |V2
ud
| + |V2
us
| = 1.0000 +/- 0.0009. Even with the current knowledge of the mixing matrix we wouldn't be able to predict the existence of the top quark! (TimothyRias (talk) 08:38, 19 December 2008 (UTC))

It's not 1.0000 ± 0.0009, it's 1 - (0.00359 ± 0.0016)2.Headbomb {ταλκκοντριβςWP Physics} 09:36, 19 December 2008 (UTC)
No that would be circular reasoning. (you would predict the existence of the bottom from studying the decay of hadrons containing a bottom, then assuming unitarity, concluding that the other mixing terms cannot add up to 1 and then concluding that there must be a bottom because the other terms don't add up to 1. Do you see the kind of nonsense you are proclaiming. The fact remains that direct measurements of Vub and Vuc simply provide no evidence for the existence of a third generation. (TimothyRias (talk) 10:07, 19 December 2008 (UTC))
I'm not saying that measurements that probes V_ud and V_us independently of V_ub (thanks for the correction) as-of-now-predict the existence of a non-zero V_ub, I'm saying the fact that V_ud and V_us don't add up to 1 is indicative that V_ub was not taken into account. And that back in 1963, V_ud and V_us were not known with enough accuracy to predict the existence of the third generation on their own, which is still the case, so that's not how the b/t quarks were predicted.Headbomb {ταλκκοντριβςWP Physics} 10:30, 19 December 2008 (UTC)
But that is a weird point to make. The sum of V_ud and V_us (or rather their magnitudes squared) does not significantly differ from 1 so it really isn't indicative of the existence of a third generation. The only to assert with any certainty that they don't add up to 1 is to 1) observe decays of bottom into up quarks and 2) assume that the CKM matrix is actually unitary. Using that to predict the existence of the bottom quark is turning the world upside down.(TimothyRias (talk) 22:30, 20 December 2008 (UTC))

## Conflict with charm quark and up quark/down quark

Charm quark says they were theorized by Glashow Illious and Maini in 1970. This article says they were theorized by Glashow and Bjorken in 1964. Headbomb {ταλκκοντριβςWP Physics} 02:16, 20 December 2008 (UTC)

The down and up quark pages said they were discovered in 1967, not 1968. Also the ref are dated from 1969. So why way is it?Headbomb {ταλκκοντριβςWP Physics} 10:13, 20 December 2008 (UTC)

## Question

Is the reason why the up quark is less massive than the down quark known? This always intrigued me.Headbomb {ταλκκοντριβςWP Physics} 08:13, 20 December 2008 (UTC)

I don't think so. The quark masses (or rather the coupling of the quarks to the Higgs field) are free parameters of the standard model. (TimothyRias (talk) 22:22, 20 December 2008 (UTC))

## Went through the versions from the "milestones", here are some things worth talking about

The terms:

are thrown in some way in that version. Many of them I feel shouldn't be included, but this list might be useful in determining if we covered everything that should be covered.Headbomb {ταλκκοντριβςWP Physics} 09:29, 20 December 2008 (UTC)

I've made a "See also" section with some of them, but it more than a sentence about them can be said, feel free to move such links into the text of the article. -- Army1987 – Deeds, not words. 11:08, 20 December 2008 (UTC)
Thanks for making the extensive list, but most of these are already linked in the text; and the "navigational aid" purpose is already served by the "Particles in physics" navbox at the bottom. (As for QED, I don't think that term is usually understood to refer to the study of the electroweak interaction as a whole.) -- Army1987 – Deeds, not words. 13:21, 20 December 2008 (UTC)
(Matter of fact, the navbox would serve that purpose much better if it were before the references, but see http://en.wikipedia.org/w/index.php?title=Wikipedia_talk:Layout&curid=143132&diff=259171656&oldid=259159942. -- Army1987 – Deeds, not words. 19:48, 20 December 2008 (UTC))

## What about Yuval Neʾeman in 1961?

The guy proposed SU(3) to classify hadrons. Isn't this something that should somehow be mentionned? I think Nucl. Phys. 26:222-9, 1961 is the relevant publication, but I can't find an online version.Headbomb {ταλκκοντριβςWP Physics} 10:53, 20 December 2008 (UTC)

And Gell-Man, from 1961 too.. [1]. This is all so confusing.Headbomb {ταλκκοντριβςWP Physics} 13:19, 21 December 2008 (UTC)

## flavour symmetry

Should the article mention that flavour symmetry only is a symmetry in the approximation that the involved quarks have equal mass? To this a related question, did people really ever have phenomenological success with su(4) flavour symmetry? That would be surprising to since the charm is several orders of magnitude more massive than the up and down. Then again assumption that all four are massless is not that bad for high energy processes, so maybe it is possible. (I don't have access to the hughes text quoted for section talking about su(4) flavour symmetry.)

On a relatated note is the article clear enough that the concept of flavour symmetry was flawed as a model for the strong interaction and the troubles were resolved by the introduction color su(3) symmetry? (TimothyRias (talk) 22:53, 20 December 2008 (UTC))

I haven't heard much about SU(4). I guess the mention of SU(3) is important not so much as an exact symmetry than as the reason for postulating quarks in the first place. I don't think we're mentioning much in the way of failed models for quark dynamics (the original string theory, for instance), and I'm not sure how much more detail there should be. We could mention chiral symmetry, and symmetry breaking with the pions as Goldstone bosons, which I personally always found a very neat concept. Markus Poessel (talk) 08:00, 21 December 2008 (UTC)
I don't think we need to give a complete history of failed models here (if anywhere that should discussed in the article on QCD). My worry is that the current discussion of flavour symmetry might leave readers confused. Readers can be left thinking that flavour symmetry is an actual (instead of approximate symmetry) of the quarks. Moreover, the historical link flavour symmetry --> colour symmetry is missing. (this might actually relate to headbomb's confusion about different years being cited is the year quarks were proposed). Unfortunately I will be away from my QFT textbooks for the rest of the holidays so I can't real check what they said about this. (TimothyRias (talk) 23:42, 22 December 2008 (UTC))

## Cabibbo angle and CKM matrix

I'm unclear about the mathematical notation in this section. Is it fair to say that the first equation is using bra-ket notation? If so, are the $V_{ud}$ and $V_{us}$ vector wave functions? Are the cos and sin functions supposed to be vectors or scalars? If the latter, then perhaps the use of middle dots would help to clarify it? Seems a little confusing to me. Sorry.—RJH (talk) 18:48, 2 January 2009 (UTC)

The Cabibbo angle and two generations of quarks
The Euler angles corresponding to the rotation of the strong eigenstate space into the weak eigenstate space. I am not sure if I got the angles correct.
Yes, they are kets. $V_{ud}$ and $V_{us}$ are elements of the CKM matrix.
In a two-dimensional real vector space (i.e. a plane), if you have two orthogonal unit vectors x and y, and two other orthogonal unit vectors x′ and y′, you can express the latter in terms of the former with a rotation matrix:
$\begin{pmatrix} \mathbf x' \\ \mathbf y' \end{pmatrix} = \begin{pmatrix} \cos \theta & \sin \theta \\ -\sin \theta & \cos \theta \end{pmatrix} \begin{pmatrix} \mathbf x \\ \mathbf y \end{pmatrix}$
that is, $\mathbf x' = \cos\theta \mathbf x + \sin\theta \mathbf y$ and $\mathbf y' = -\sin\theta \mathbf x + \cos\theta \mathbf y$, where $\theta$ is the angle between $\mathbf x$ and $\mathbf x'$. cos and sin are the ordinary trigonometric functions.
(See the picture beside, where x is called |d>, y is called |s>, and x′ is called |d'>.)
Now, quantum states form a complex vector space: vectors have a phase as well as a magnitude. Given two states $|a\rangle$ and $|b\rangle$, you can form a state $|c\rangle = c_a |a\rangle + c_b |b\rangle$, where $c_a$ and $c_b$ are complex numbers. A system in the state $|c\rangle$ will have a probability $|c_a|^2$ of being found in the state $|a\rangle$ and a probability $|c_b|^2$ of being found in the state $|b\rangle$, if you make a measurement in order to distinguish between the latter two states.
It turns out that, in the case of two-dimensional complex spaces (only two distinct states between which a measurement could distinguish), the fact that the space is based on complex numbers is irrelevant, as you can obtain a real rotation matrix by choosing the "right" phase of the basis vectors. Now, before the top and bottom quarks were discovered, it was believed that the state of quarks with -1/3 electric charge (let's consider only them, for simplicity) was such a 2D complex space. Imagine a point in the picture to the right (for simplicity, assume it's on the unit circle). It represents a quark state. The |d> and |s> states represent quarks "known" (so to speak) to be of the down and the strange flavor, the |d'> and |s'> states represent quarks "known" to be of the light and heavy mass. Given any point representing a state, the square of its components along the |d> and |s> axes represent the probabilities of finding that a quark in such a state is of the down/strange flavor, whereas those along |d'> and |s'> represent the probabilities of finding it with a given mass.
When you add a third quark family, you have a 3D space (imagine another blue axis perpendicular to your screen). The yellow axes should be very slightly tilted so that they aren't exactly in the plane of the screen. Now, it turns out that, with 3D complex spaces, the trick of obtaining a real rotation matrix doesn't work: the final matrix (the CKM matrix) will still need one complex phase to be specified. The fact that this phase is nonzero allows the violation of the CP symmetry (don't ask me how, I don't know the exact answer and I expect it to be a quite technical one, requiring quantum field theory to be explained).
There are surely many imprecisions in this approximate description, but I hope the general idea is clear. -- Army1987 – Deeds, not words. 20:24, 2 January 2009 (UTC)

Pretty much what Army said. |d'>, |d>, |s> are kets (vectors), and the Vud and Vus are simply coefficients (whose square corresponding to the relative probability of d and s quark decaying into u quarks). Since the probability sums up to 1 (or rather should), then you can use cosθ = Vud and sinθ = Vus. Aka the angle is simply a parameter that tells you what Vud and Vus are when you take its cosine and sine.

I've just noticed a nice peculiarity of the Cabibbo angle: it also describes the 2x2 matrix with the c quark included very well (the orthogonal state to |d'> would be |s'> on the picture above). I wonder why that is. Same for the high symmetry of the matrix. I wonder why that is. Headbomb {ταλκκοντριβςWP Physics} 22:30, 2 January 2009 (UTC)

I guess that it's because the other two angles, θ13 and θ23, are so small. -- Army1987 – Deeds, not words. 01:02, 3 January 2009 (UTC)
Well obviously. I meant the "big why". Why so near symmetry, but not quite? Why so small θ13 and θ23? But I suppose that if one why knew, a nobel prize would've been awarded for that already. Headbomb {ταλκκοντριβςWP Physics} 04:08, 3 January 2009 (UTC)

So our problem is to explain where symmetry comes from. Why is nature so nearly symmetrical? No one has any idea why. The only thing we might suggest is something like this: There is a gate in Japan, a gate in Neiko, which is sometimes called by the Japanese the most beautiful gate in all Japan; it was built in a time when there was great influence from Chinese art. This gate is very elaborate, with lots of gables and beautiful carving and lots of columns and dragon heads and princes carved into the pillars, and so on. But when one looks closely he sees that in the elaborate and complex design along one of the pillars, one of the small design elements is carved upside down; otherwise the thing is completely symmetrical. If one asks why this is, the story is that it was carved upside down so that the gods will not be jealous of the perfection of man. So they purposely put an error in there, so that the gods would not be jealous and get angry with human beings.

We might like to turn the idea around and think that the true explanation of the near symmetry of nature is this: that God made the laws only nearly symmetrical so that we should not be jealous of His perfection!

— R. P. Feynman, The Feynman Lectures on Physics, vol. 1, chapter 52 "Symmetry in Physical Laws", section 9 "Broken symmetries", last two paragraphs

-- Army1987 – Deeds, not words. 12:54, 3 January 2009 (UTC)

IOW, the answer is the same as to "why is the up quark lighter than the down quark":

Vuolsi così colà dove si puote
ciò che si vuole, e più non dimandare.

See http://math.ucr.edu/home/baez/constants.html for a list of numbers which we have no idea of where they come from. -- Army1987 – Deeds, not words. 13:02, 3 January 2009 (UTC)

These are non-answers at best. The real one probably has to do with quarks being the exited states of the same particle. Each excitation has a different mass as they would be different weak isospin excitations, and the transition rates (the Vij) given by a rule similar to Fermi's golden rule, yielding something like $V_\mathrm{ij} \propto \mathrm{e}^{-\Delta{m}}$ and selection rules such as $\Delta{T_\mathrm{z}=\pm 1}$. But that's just me pulling stuff out of my ass here and how much of it makes sense I don't know.Headbomb {ταλκκοντριβςWP Physics} 13:53, 3 January 2009 (UTC)
Neither does anyone else, probably. -- Army1987 – Deeds, not words. 14:25, 3 January 2009 (UTC)
Can someone confirm that the Euler angles have been correctly labelled in the image?Headbomb {ταλκκοντριβςWP Physics} 05:13, 19 January 2009 (UTC)Euler angles

### Arbitrary break

Okay, thanks for the lengthy response. Getting back to my original question: the current page doesn't explain the meaning of Vud and Vus. It becomes unclear then how the average reader is supposed to comprehend the mathematics. Also, as the cos and sin entries are scalars, I think it would be clearer to write that segment as:

$| \mathrm d^\prime \rangle = V_\mathrm {ud} | \mathrm d \rangle + V_\mathrm {us}| \mathrm s \rangle = | \mathrm d \rangle \cos\theta_\mathrm C + | \mathrm s \rangle \sin\theta_\mathrm C$

as I saw done in at least one google'd textbook I viewed. Thanks.—RJH (talk) 17:40, 26 January 2009 (UTC)

That way it'd be less clear that Vud is cos θC and that Vus is sin θC. What about:
$| \mathrm d^\prime \rangle = V_\mathrm {ud} | \mathrm d \rangle + V_\mathrm {us}| \mathrm s \rangle = \cos(\theta_\mathrm C)\,| \mathrm d \rangle + \sin(\theta_\mathrm C)\,| \mathrm s \rangle$? -- Army1987 – Deeds, not words. 18:00, 26 January 2009 (UTC)

## Weak Interactions

The section about weak interactions has the following phrase: "A quark can decay into a lighter quark by emitting a virtual W boson, or can absorb a virtual W boson to turn into a heavier quark". That doesn't seem entirely correct to me. I don't understand the distinction between absorption and emittion and how does that correlate with decaying or turning into a heavier quark. The distinction would make sense if the Ws were real particles, but the ptext is explicitly refering to virtual particles. —Preceding unsigned comment added by Dauto (talkcontribs) 05:29, 23 January 2009 (UTC)

Why is the text referring explicitly to virtual W bosons anyway? Surely, the W-boson in a weak interaction vertex can as real as the photon in an EM vertex. The W-boson is not stable so a real W-boson will subsequently decay most likely in a pair of leptons, but that does mean that the W-boson is virtual (i.e. off mass shell). The word virtual makes an already hard section even more confusing. (TimothyRias (talk) 13:41, 26 January 2009 (UTC))
I've removed "virtual" from that sentence. As for absorb vs emit, yes, they are essentially the same, but mentioning them both explicitly is useful for readers who aren't aware of the CPT symmetry. -- Army1987 – Deeds, not words. 14:41, 26 January 2009 (UTC)
Would it be useful to include a Feynman diagram of the interaction vertex? If needed I can probably create one. (TimothyRias (talk) 15:25, 26 January 2009 (UTC))
There already is one in the Weak interaction article, although within a larger diagram. Do you think that a similar diagram but not including the non-interacting quarks and the leptons could be useful in this article? -- Army1987 – Deeds, not words. 16:36, 26 January 2009 (UTC)
An up-type quark U can change into a down-type quark D by emitting/absorbing a W-boson. The relative strengths of these interactions is given by the CKM matrix.
I was think along the lines of this. Of course details are up for dicussion. (TimothyRias (talk) 10:35, 28 January 2009 (UTC))

## Classification

Changed: From "All quarks of the same flavor are identical particles,..." to: "All quarks of same flavor and color are identical,... - Same holds for antiquarks". Reason: Quarks of same flavor may differ in color, therfore may not be identical as formerly stated. For weak interaction, there is a difference between left-handed and right-handed quarks in addition (different weak charges). Please refer to http://www.jlab.org/qweak/ -- Is there any correlation tothe spin? Someone who knows better than me should take account for this in the article. Thanks. -- (ErnstS 13:50, 25 January 2009 (CET))

I'd consider color more like a degree of freedom like spin; you wouldn't consider a spin-up electron and a spin-down electron non-identical particles. But I think we only disagree about nomenclature, not about physics. -- Army1987 – Deeds, not words. 13:08, 25 January 2009 (UTC)
Well in a sense an up and a down spin electron are non-identical particles. If you put an spin up and spin down electron in a box (or rather make that neutrinos so that at least at tree level there is no spin-spin coupling) then they would behave as distinguishable particles the ground state would for example have lower energy than if both particles had the same spin. This is also the reason that there can be two electrons in one atomic orbital. That being said in the presences of interactions the particles could easily change spin and the picture would change.
In the end, I agree it is mostly a question of nomenclature. But to show how ambiguous this really is note that we general consider the different members of a weak SU(2) multiplet to be different particles, while most people consider the different members of a strong SU(3) multiplet to be the same particle. Of course, this has to do with the first being a broken symmetry while the second isn't. But one could definately make case for considering the different colors to be different particles. However, a very good reason not to do this, is because it would mean choosing a prefered basis of colors, which would be quite unnatural. (TimothyRias (talk) 14:08, 25 January 2009 (UTC))

## Spin.

A concerned about the accuracy of the explanation. This might be related to the theoretical Bjorken conditions that Bci2 mentions, but I never heard of Björken conditions, so maybe there's no relation. In the article it's said that the Deltas are in spin 32 config because the spins are aligned, while nucleons are in spin 32 because the spins are unaligned.

Now it's my understanding that the Deltas are in spin 32 config because the colour part of its wavefunction is antisymmetric, while the space and flavour parts are symmetric. In order for the overall wavefunction to be antisymmetrical (because of Pauli), then the spatial part of the wavefunction needs to be symmetric as well. So you count the number of symmetric spin wavefunctions possible, you end up with 4. Now we, for what I can only imaging are historical reasons, want this to be represented by a "vector" S whose projections vary by 1. Since you have 4 "projections" (Sz = +32, +12, −12, −32), you need a vector of length S = #Sz212 = 2212 = 32 to do the job. THAT is why the spin of the Deltas is 32, NOT because the spins are "aligned". They can be aligned (Sz = +32, −32), but they could also be unaligned (Sz = +12, −12). On the other hand the nucleons have a mixed spin symmetry and a mixed colour symmetry (or antisymmetry). If you count the number of mixed symmetric (or antisymmetric) wavefunctions allowed by Pauli you end up with 2 (Sz = +12, −12), meaning that S = 2212 = 12. Headbomb {ταλκκοντριβς – WP Physics} 03:31, 15 February 2009 (UTC)

Minor correction to what you said. You said that nucleons have symmetrical spatial function, mixed spin symmetry, and mixed color symmetry. The correct is symmetrical space, antisymmetrical color, mixed spin (which explains the spin=1/2), and mixed flavor symmetries (which explains why there are only two nucleon states -- the proton and the neutron). BTW, there really is a vector (as opposed to historical inertia) and the length of the vector is not S. the length is sqrt(S(S+1)). Dauto (talk) 04:23, 15 February 2009 (UTC)
Hold the phone, Headbomb; can you please quote the part of the spin section you're questioning? —Anonymous DissidentTalk
Uh yes, mixed spin/flavour + antisymmetrical colour, not mixed spin/color + antisymmetrical flavour (although if I understand things correctly, this is allowed as well), my bad. As for the vector, yes there is a vector whose length is $\scriptstyle{\hbar \sqrt{S_z(S_z+1)}}$, but that vector is not the S "vector" we're talking about, the S "vector" we're talking about has a length of $\mathbf{S} = \frac{ \mathrm{number \ of \ } S_\mathrm{z} \ \mathrm{ of \ that \ particular \ symmetry} - 1}{2} = \mathrm{max}\left(S_\mathrm{z}\right) \ \mathrm{of \ that \ particular \ symmetry}$. Since there are four symmetric spin states for the uuu, they have S = (4-1)/2) = 3/2, while the uud has four symmetric spin states (we call those the Δ+, which thus have S = (4-1)/2 = 3/2), and also two spin states (S = (2-1)/2 = 1/2) of mixed symmetry (we call those the N+ (proton)).
Here's the quote from the article:

For example, the proton and the Delta baryon are both composed of two up quarks and one down quarks: in the Δ+ their spins are all aligned in the same direction, yielding a total spin of 32, whereas in the proton one of them has the opposite direction, giving a total spin of 12.

Headbomb {ταλκκοντριβς – WP Physics} 05:31, 15 February 2009 (UTC)
After reading the text about spin I have to say that I don't see anything wrong with it. I don't know what Headbomb is complaining about. Dauto (talk) 05:33, 15 February 2009 (UTC)

If this piece of text is contentious, it can be removed without much wounding done; it is, after all, merely an example, and it is also uncited. —Anonymous DissidentTalk 05:35, 15 February 2009 (UTC)

As far as I know, there is only one vector associated with the spin, and its length is $\scriptstyle{\hbar \sqrt{S(S+1)}}$ not $\scriptstyle{\hbar \sqrt{S_z(S_z+1)}}$ as you quote. That means the spins of the three quarks in a Δ+ are indeed alined even when $S_z=1/2$. They are merely aligned in a direction which is not the z direction. Dauto (talk) 05:46, 15 February 2009 (UTC)

(edit conflict) Okay, take the Δ+ wavefunction. This state has the symmetric flavour wavefunction:
$|color \rangle = \frac{1}{\sqrt{3}} \left(| u u d \rangle + | u d u \rangle + | d u u \rangle \right)$
However, it can have any of the following four spin wavefunctions:
$|spin \rangle = | \uparrow \uparrow \uparrow \rangle$
$|spin \rangle = \frac{1}{\sqrt{3}} \left( | \uparrow \uparrow \downarrow \rangle + | \uparrow \downarrow \uparrow \rangle + | \downarrow \uparrow \uparrow \rangle \right)$
$|spin \rangle = \frac{1}{\sqrt{3}} \left( | \downarrow \downarrow \uparrow \rangle + | \downarrow \uparrow \downarrow \rangle + | \uparrow \downarrow \downarrow \rangle \right)$
$|spin \rangle = | \uparrow \uparrow \uparrow \rangle$
The Delta+ doesn't have a spin of 3/2 because it's spins are aligned, the Delta+ has a spin of 3/2 because we've labeled the states associated with the four symmetric spin wavefunction the Delta+. Since they are four of these states, we say they have S = (4-1)/2. In fact, two of the four possibilities have unaligned spins. Do you see what I'm getting at?Headbomb {ταλκκοντριβς – WP Physics} 05:49, 15 February 2009 (UTC)

Headbomb, you seem to believe that the S=3/2 is simple a matter of us chosing to label the four states you described together. It is not. even the state with $s_z=1/2$ still have an spin angular momentun with $S^2=s(s+1)$ and therefore must have its spins aligned. they are merely not aligned in the z direction. Dauto (talk) 06:04, 15 February 2009 (UTC)
(editconflict) Uh, sorry I meant $\scriptstyle{\hbar \sqrt{S(S+1)}}$, but what I'm getting at is the vector of length $\scriptstyle{\hbar \sqrt{S(S+1)}}$ cannot be the S we are talking about here because then you would have $|\mathbf{S}| = S = \hbar \sqrt{S (S + 1)}$, which is nonsense (or rather only true when S=0). Headbomb {ταλκκοντριβς – WP Physics}
(edit conflict) Just to clarify somethingelse you said earlier. The color state cannot have mixed symmetry because that would violate color confinement. Dauto (talk) 06:04, 15 February 2009 (UTC)

(unindent) Yes, but that's not forbidden by Pauli, which was what I was getting at. Headbomb {ταλκκοντριβς – WP Physics} 06:11, 15 February 2009 (UTC)

You are confusing the length of the vector S with the spin quantum number s (note the captal letter). Dauto (talk) 06:06, 15 February 2009 (UTC)
You would have no problem with $|\mathbf{L}| = L = \hbar \sqrt{l (l + 1)}$. Dauto (talk) 06:07, 15 February 2009 (UTC)
That's a possibility, but it still doesn't make any sort of sense to have three vectors that are aligned, but whose projections aren't.Headbomb {ταλκκοντριβς – WP Physics} 06:11, 15 February 2009 (UTC)
Also, aren't small S and Sz the same anyway?Headbomb {ταλκκοντριβς – WP Physics} 06:15, 15 February 2009 (UTC)
(edit conflict)The alignment isn't perfect ($3*\sqrt(s(s+1))= \sqrt(3s(3s+3)) > \sqrt(3s(3s+1))$). That allows it enough wiggle room to make it work. Dauto (talk) 06:20, 15 February 2009 (UTC)
NO, $s_z$ and s are different quantum numbers. think $s_z$ -> m, while s -> l Dauto (talk) 06:24, 15 February 2009 (UTC)
I'll look into that. However, why would, for example, say that a proton is in S = 1/2, when |S| = sqrt(s(s+1)) = sqrt(1/2(1/2+1)) = sqrt (3/4) = ~0.866  != 1/2? Headbomb {ταλκκοντριβς – WP Physics} 06:31, 15 February 2009 (UTC)
It is common to supress the subscript and replace s_z by s whenever (hopefully) there is enough context to avoid confusion. I can distinctly remember finding that confusing when I was a student. I guess people are lazy and the alfabet is too short. Dauto (talk) 06:36, 15 February 2009 (UTC)
Okay, so then what's the link between big S, small s and S_z?Headbomb {ταλκκοντριβς – WP Physics} 07:49, 15 February 2009 (UTC)

OK, lets think in terms of orbital angular momentum for a while. We can label a state as |l,m> which is simultaneously an eigenstate of the operator $L\,$ and $L_z\,$ with eigenvalues $L|l,m>=\hbar \sqrt (l(l+1))|l,m>$ and $L_z|l,m>=\hbar m|l,m>$. Now, to go to intrinsic angular momentum (spin) make the replacements $L \rightarrow S$, $L_z \rightarrow S_z$, $l \rightarrow s$, and $m \rightarrow s_z$, and get the eigenvalue equations $S|s,s_z>=\hbar \sqrt (s(s+1))|s,s_z>$ and $S_z|s,s_z>=\hbar s_z|s,s_z>$. A proton has two possible eigenstates. Both have $s=1/2\,$, while $s_z\,$ can be either +1/2 or -1/2. The states are $|1/2,1/2>\,$ and $|1/2,-1/2>\,$. A Δ+ has four possible eigenstates. All four have $s=3/2\,$ (and therefore are considered states of alignment of the spins of the constituent quarks), while $s_z\,$ can be anyone of +3/2, +1/2, -1/2, and -3/2 The states are $|3/2,3/2>\,$, $|3/2,1/2>\,$, $|3/2,-1/2>\,$, and $|3/2,-3/2>\,$. Now, since all the states associated with a particle have the same value for $s\,$ it is reasonable (once one states what particle they are talking about) to drop the $s\,$ label form the eigenfunction, which should then be labeled as $|s_z>\,$. We say the proton has spin $1/2\,$ with two eigenstates $|1/2>\,$ and $|-1/2>\,$, while the Δ+ has spin $3/2\,$ with four eigenstates $|3/2>\,$, $|1/2>\,$, $|-1/2>\,$, and $|-3/2>\,$. Now, human nature being as it is, people often drop the z subscript and simply state that the Δ+ has four spin states $s= +3/2, +1/2, -1/2, -3/2\,$ confusing as that may be.

One last point. It is quite common to use $m_s\,$ instead of $s_z\,$, so may be you are more familiar with that. Dauto (talk) 17:34, 15 February 2009 (UTC)

Okay that all makes sense, but then the "spin 3/2" we are talking about is the small s, not the big S. And the value of the small s is decided by counting the number of small s_z in the same symmetry config (since there are four symmetric configs for the delta +, then the delta + is said to be of small s = (4-1)/2 = 3/2, while the proton has two mixed symmetric config, so its said to be in a small s = (2-1)/2 = 1/2 ). Nowhere are we concered with the big S in this article. Headbomb {ταλκκοντριβς – WP Physics} 22:56, 15 February 2009 (UTC)
The big S is an operator. The little s is a quantum number used to describe the eigenvalue of the big S operator $S|s,s_z>=\hbar \sqrt(s(s+1))|s,s_z>\,$. The two come together. One makes no sense without the other. But the point I was makingn is that even the state of the Δ+ with $s_z=1/2\,$ still has $s=3/2\,$ and has the constituent quark spins aligned. Dauto (talk) 23:27, 15 February 2009 (UTC)
Yes, big S is an operator in the equation $\hat S | s , s_z \rangle> = \hbar \sqrt{ (s (s + 1 ) ) } | s , s_z \rangle$, and $S = \hbar \sqrt{ (s (s + 1 ) ) }$ is the eigenvalue of the operator. And in the sentence in article, we're saying s = 3/2 (delta) and s = 1/2 (nucleon) because spins are "aligned". What I'm saying is that s isn't 3/2 or 1/2 because the "spins are aligned", I'm saying s is 3/2 or 1/2 because of the number of spin states in a particular symmetry configuration (four in the former, leading to s = 3/2, and 2 in the later, leading to s = 1/2). The spin vector isn't physical is what I'm getting at. You're approaching from the viewpoint that what is physical is small s, which dictates the number of s_z. I'm saying it's the number of s_z that determines the small s. We first get the sz of the elementary particles from the Dirac equation (if I understand things correctly), which turns out to be +1/2 and -1/2 for elementary fermions. Then we treat the sz = +1/2 and sz = -1/2 states as any other quantum states, and we combine them in the manner discussed above. We then regroup them according to wavefunction symmetries. Then we count the number of allowed wavefunction in a type of symmetry, and only then can we say what small s is. Small s is defined to be the number of allowed wavefunction of a particular symmetry. We choose to see the various s_z as the various projections of a small s vector, with the post hoc rule that the projections of that vector must vary by 1. That is why it doesn't make any sense to speak of s_x or s_y. That is why s and s_z commute, we've defined them so they would commute. Headbomb {ταλκκοντριβς – WP Physics} 06:46, 16 February 2009 (UTC)
Am I making any sense here, or am I coming off as some kind of time-cubist? Headbomb {ταλκκοντριβς – WP Physics} 06:48, 16 February 2009 (UTC)
Sorry, but you are not making sense at all. First of all by you logic photons would be spin-1/2 particles as they have only two spin state, while we all know that photons are spin-1 particles. Anyway, (from the theorists POV) the spin of a particle is simply the representation of the Lorentz group in which it transforms. For particles with integer spin this is easy to determine because it is just the number of indices, for spin-1/2 particles it just means that they obey the dirac equation. I slightly more physical POV is to see the spin simply as the quantity that appears in the expression for the particles magnetic dipole moment. (As such we can actually measure the spin of a particle, which puts your interpretation of spin as related to the number of spin states in an odd light.) The make matters even worse is that, when we talk about the spin of a hadron (or meson) we are actually talking about the total angular momentum J+S of the bound state, not just the spin. (This is somewhat mediated by the fact that the lowest energy state will usually have zero angular momentum.) (TimothyRias (talk) 09:23, 16 February 2009 (UTC))
Headbomb, That wich you talk about is simply a book keeping device, a practical way to find out what are the representations of the Lorentz group you are dealing with. It does not make the spin vector and its eigenvalues any less physical. It is not true that we chose to see the various projections $s_z$ as part of the same representation through some ad hoc rule. They are part of the same representations because they transform amongst themselves under Lorentz transformations. One man's $s_z=1/2$ is another man's $s_z=3/2$. Dauto (talk) 13:41, 16 February 2009 (UTC)

Re to Tim: Yes, but isn't photon's spin 1 not having a 3rd state, sz = 0 state the result of the photon having something to do with the photon being a hybrid of the W0 and the B boson? What about virtual photons? Those can have sz=0 right? Also any explanation from group theory is lost on me (hence why I'm dealing with the wavefunctions; it's the only way I'm getting anywhere).Headbomb {ταλκκοντριβς – WP Physics} 23:50, 16 February 2009 (UTC)

The photon has only two spin states because of the fact that it is massless. Being a mix of the B and the W0 plays no role here. Virtual photons are not restricted to their mass shell (That is, they don't respect the equation E2=(cp)2+(mc2)2), so they don't really know they are supposed to be massless. Dauto (talk) 04:41, 18 February 2009 (UTC)
Well isn't them being the mix of the B and the W0 the reason why they don't have mass in the fix place? That to me is a pretty strong suggestion that them being the mix of B and W0 does play a role here (although what exactly that would be I don't know). Also, if virtual photons are allowed to have s_z=0, then my counting scheme does work, since you have three projections (and thus have spin s = (3-1)/2 = 1). I'm very conscious that at this point I'm sorta trying to "salvage" my "s = (number of s_z in the same symmetry config - 1) / 2" idea, but on the other hand I seem to be able to reproduce every results from this very simple idea. Which strikes me as being the hallmark of more thana simple "fluke". Headbomb {ταλκκοντριβς – WP Physics} 05:12, 18 February 2009 (UTC)
Before electroweak symmetry breaking and the mixing of the B with the W0 all four electroweak gauge bosons (the B, the W0, the W+ and the W-) have rezo mass. The mixing doesn't "give" the photon its zero mass (that's what the masses were to begin with). The Electroweak symmetry breaking gives the Z, W+, and W- their non-zero masses. But no matter. You are right (at least partially) about the book keeping method of counting states to get an idea about the spin of the particles, but that does not make the spin vector any less real. Dauto (talk) 05:56, 18 February 2009 (UTC)

## Current state of the article

Isn't it an error that nownere in the article is the fact mentioned that although the entire quark madel is elaborate and apparently self consistant, it is actually a model, a set of hypotheses? See my comment on "The opening sentence."Dean L. Sinclair

Also, and @Headbomb, I have addressed the remaining ref problems brought up by Poessel in the last FAC; how do you feel the article is looking right now? —Anonymous DissidentTalk 05:38, 15 February 2009 (UTC)

Arguing on the mathematics isn't going to help the text. If there is a problem with it, does anyone have a problem with its removal? And HB, you've not replied to my question; how do you think the article is going now? —Anonymous DissidentTalk 06:13, 15 February 2009 (UTC)

I've listed several historical concerns which were never addressed spread around the talk page. Plus some {{fact}} tags are still in the article. I haven't thoroughly reviewed the article since the last FAC so I can't comment more than this as of now. But I'll review the article over the weekend / early next week. I'd also like to include the 3-D image of the euler angles, but someone needs to confirm I got the angles right. Also that image might be more fitting for the CKM matrix article.Headbomb {ταλκκοντριβς – WP Physics} 06:30, 15 February 2009 (UTC)

## http://en.wikipedia.org/wiki/Quark#Flavor_quantum_numbers

Can someone explain to me why this section is particularly relevant? Quarks are a footnote in this section. I don't really see why it is essential to the properties section, or, indeed, the article as a whole. I understand it is important to baryons and mesons, but we have links to the articles on isospin and strangeness etc. for a reason. —Anonymous DissidentTalk 08:54, 16 February 2009 (UTC)

Some parts still have comments (2). Specifically:

A quark charged with one color value can be bound with an antiquark carrying the corresponding anticolor, while three quarks all charged with different colors will similarly be bound together. In any other case, the resulting system will be unstable.

—Forbidden by Pauli?

The connection with group theory become fully clear in 1961, when Gell-Mann and Ne'emann showed that all the proposed quantum numbers could be explained by relating the basic SU(3) triplet to the three lightest quarks: up, down and strange.[citation needed]

— But weren't the quarks introduced in 1964...

Other than that

• Classification: OK
• History:
• The source for "These two new quarks became known as truth and beauty, but over time top and bottom became the predominant use." reads like a speculation from the author's part. Can this really be considered WP:RS?
• Removed. We already mentioned earlier on that they are alternative known as truth and beauty. That's enough; colloquialisms do not require further mention. —Anonymous DissidentTalk 10:39, 1 March 2009 (UTC)
• "The top quark's discovery was quite important, because it proved to be significantly more massive than expected,[citation needed] ..."
• Etymology: OK
• "The quarks (and antiquarks) which determine the quantum numbers of hadrons are called valence quarks. Apart from these, any hadron may contain an indefinite number of virtual quarks, antiquarks and gluons which do not influence their quantum numbers.[citation needed]"
• Electric charge: OK, but I would talk about exotic nuclei here, like hypernuclei and other exotic nuclei.
• Spin: OK
• Weak interaction: OK
• CKM Matrix: OK, but a bit heavy mathematically. If someone could head over at Talk:Cabibbo–Kobayashi–Maskawa matrix and confirm that the euler angles in the 3D image are correctly labeled, then we could include the 2d and 3d images to illustrate this. And perhaps we could get rid of the matrix, and simply talk in terms of vector rotations and euler angles. We'd still mention CP violation and its implication, but we'd refer to the CKM matrix article at this point.
• Strong interaction:
• "These octets and decuplets can be viewed as constructions of a central, basic triplet;[clarification needed] the initial emptiness of this triplet, the fact that the three places were unfilled,[clarification needed] contributed to the postulation of the quark theory and the realisation that hadrons needed substructure."

(more to come) Headbomb {ταλκκοντριβς – WP Physics} 05:13, 27 February 2009 (UTC)

## Alternative approach for discussing the CKM matrix

I agree with Headbomb that the current section on the CKM matrix is not optimal. (It is OK, but just is not of the standard you would ask for this article to become featured.) The section seems to be a bit heavy on the technical details, while it somehow seems to gloss over the implications for physics.

I however do not think that discussing it in terms of mixing angles will help make things clearer. In fact, IMHO, mixing is one of the "technicalities" we could try to avoid. I propose that we in fact ignore discussing weak eigenstates altogether and discuss the CKM matrix entirely from the perspective of the mass eigenstates. (i.e. the states people normally associate with the physical particles.) From this perspective the CKM matrix is just a table of coupling constants. (normalized by the universal weak coupling) The table just indicates how strongly the different types of up-type and down-type interacts.

If we want to mention CP-violation we could even note that the the coupling for the antiparticles is given by the complex conjugate of the coupling for the normal particles. And explain that if any of the values of the matrix are complex this means that particles couple differently from anti-particles. (which violates CP) We could even mention that KM discovered that the symmetries of the theory force all values of the CKM matrix to be real if there are less than 3 generation, while for more generations a CP-violating phase is allowed. (This might however already become to technical.)

Ofcourse, this approach obscures certain properties of the CKM matrix. Such as the fact that it must in fact be a unitary matrix, conscently it is also obscured that the matrix may be (in the case of 3 generations) described by 3 real and 1 complex parameter. But these points are may be better discussed in the CKM matrix articles.

Any other thoughts on this? (TimothyRias (talk) 10:00, 2 March 2009 (UTC))

Well, not to go in circles, but doing it in terms of mixing angles would give readers a visual support to picture things. Aka 2gen-->2D space, rotations in a 2D = 1 angle. 3Gens-->3D space, rotations in 3D = 3 angles. This doesn't explain CP violation, but it does explain the couplings, or at least gives a significance to them. CP violation can then be mentionned as a consequence of the complex nature of the matrix, and refer to CKM at that point.
On a related note, I really can't visualize/understand/decipher the constraint on the CKM matrix that leads to CP violation. Developing the N=3 case in an explicitly manner would IMO, add a lot to the CKM article.Headbomb {ταλκκοντριβς – WP Physics} 10:36, 2 March 2009 (UTC)
I have only ever had an elementary understanding of this section; this goes hand-in-hand with my fairly undeveloped knowledge of mathematical matrices. All I can request and state is that what needs to happen with this section will not entail an increase in complication, but must entail more explanation that the average reader can benefit from. Any efforts towards making this happen are to be appreciated. —Anonymous DissidentTalk 10:42, 2 March 2009 (UTC)
To Headbomb. I fail to see how it helps the reader to know that the CKM matrix needs one real parameter in 2 generations and 3 in 3 generations. My point is (in some sense) that to reader wanting to know about quarks it doesn't really matter if the CKM matrix is given by 3 or 9 parameters. It is much more important to explain what the 9 entries of the matrix mean physically, and may be the significance of them being real or complex (but the later is already pushing what we should include here).
(As to deciphering the contraint on the CP-violating phases, I'll head over to the CKM article to see if I can make that a little clearer.) (TimothyRias (talk) 10:59, 2 March 2009 (UTC))
Well we first have to clarify what we mean by "reader". Aunt Jenny ain't the one we're aiming for, so I would suggest more or less undergrads in their final years as a better target. Usually at that point, you went through some QM, and applied it to (at the very least) to optical system. Projecting photons in polarized states and that sort of thing. You have a photon, which is in general represented by a linear combination of two polarization states |1> and |2>, going through a polarizer placed at some angle θ relative to |1>, which'll give you a final state of |ψ> = a |1> + b |2> = a cos θ |1> + b sin θ |2>; a rotation in 2D space (set a=b [45° lin. pol.] and you've got Cabibbo). The CKM matrix represent the same sort of thing, but in 3D. How the weak eigenspace is oriented relative to the strong eigenspace depends on the couplings, and the CKM matrix is simply the transformation matrix between the two. Simply speaking of the couplings without giving at least some context will lose pretty much everyone who doesn't already know what "coupling" means.Headbomb {ταλκκοντριβς – WP Physics} 13:24, 2 March 2009 (UTC)
Just to make things more precise, The CKM matrix relates weak (isospin) eigenstates to mass eigenstates. Both of them are strong (color) eigenstates. Dauto (talk) 13:54, 2 March 2009 (UTC)
Well, the idea of "coupling" as the strength of an interaction is a rather intuitive notion that we have to convey anyways. (I find it more than a little bothersome that the article seems to talk only about decays and pretty much ignores any other interaction.) This idea will be much easier to get across than the somewhat abstract notion of weak eigenspace, let alone how that relates to the mass eigenspace. (also note that Dauto is right in that the CKM matrix relates mass and weak eigenstates. The strong eigenstates are invariant under flavour rotations.) (TimothyRias (talk) 14:11, 2 March 2009 (UTC))
Thanks for pointing that out. I thought that "mass" was colloquial for "strong force". Headbomb {ταλκκοντριβς – WP Physics} 23:31, 2 March 2009 (UTC)

I have drafted an alternate version for the part on the weak interaction and the CKM matrix. It is a bit lighter on the mathematical technicalities and has a bit more focus on the physics. It is still far from perfect. The prose is a bit rough, and we still may need to smooth out some of the more technical parts. Also we will need some addition references, but most should be obtainable from the right pages in Peskin and Schroeder. (TimothyRias (talk) 13:13, 9 March 2009 (UTC))

Thank you for your effort, Timothy. As you say, there needs to be improvement in the prose and such, but any movement away from the mathematics is good. I'll read it more thoroughly soon, copyedit it, and we can then see if it should be substituted for the current version. —Anonymous DissidentTalk 13:40, 11 March 2009 (UTC)
Yes that is much better suited for this article than the current version. Should we give the CKM values as of Particle Review 2008?Headbomb {ταλκκοντριβς – WP Physics} 14:08, 11 March 2009 (UTC)
We could, but I'm not sure if it adds anything for the average reader. But I guess we could.
Looking back at the text, do you guys think it is clear what is meant by "exchanging a W-boson" for the average reader? If not, any ideas on how to make this clearer? (TimothyRias (talk) 16:28, 11 March 2009 (UTC))
Well it's clear to me, but I already know what we're talking about. Perhaps including picture of beta decay to illustrate? (Image:Beta Negative Decay.svg). Headbomb {ταλκκοντριβς – WP Physics} 01:59, 12 March 2009 (UTC)
• I would note that the section starts off as if to assume the reader already knows what weak interaction is; "Quarks can participate in the weak interaction in two different ways." —Anonymous DissidentTalk 06:29, 12 March 2009 (UTC)
• I have integrated a short summation of your version of the part on the CKM Matrix into the weak interaction. I personally don't see a problem with the current version of the central "weak interaction" section; it is not overly mathematical, if at all, and I think the physics is stated well. And now we've eliminated the difficult mathematics from the text relating to the matrix. Looks good. —Anonymous DissidentTalk 21:19, 15 March 2009 (UTC)
I do have some issues with the current version (which I tried to solve in my draft). First of all there is the tag on sentence A quark can also emit or absorb Z bosons. This sentence is completely pointless for pretty much any reader. It doesn't in anyway related what the significance is of Z-boson exchange. Then there is the inaccuracy that the weak interaction only effects left-handed particles, while this is true for W-bosons, Z-bosons actually also couple to right-handed particles but with a different strength (basically given by the Weinberg angle).
The current text also suggests that it is impossible for a top quark to absorb a W-boson, which is not necessarily true. Finally, the current text suggest that the entries of the CKM matrix are the relative probabilities of decay. The probability is actual only proportional to the absolute square of the enteries, and in particular is also dependent on the masses of the involved quarks. (TimothyRias (talk) 09:46, 23 March 2009 (UTC))
I believe everything is corrected, TimothyRias. —Anonymous DissidentTalk 13:52, 9 April 2009 (UTC)
I did some minor editing a couple of days ago and I think the section now strikes a good balance between being simple and correct. The issues I had with the section are resolved. Maybe it is time to try to get the article through GAN?(TimothyRias (talk) 14:16, 15 April 2009 (UTC))
I think this article is beyond that. I see no barriers to FA; it's comprehensive, well-referenced and well-written. After all, why shoot for GAN when you can't find any issues that would stop it from FAC? Unless you can think of any...? —Anonymous DissidentTalk 04:55, 21 April 2009 (UTC)
=== Weak interaction (draft) ===
{{main|Weak interaction}}

Quarks can participate in the weak interaction in two different ways. Either by exchanging a [[Z-boson]] or a [[W-boson]]. Interactions induced by exchange of a Z-boson are in many ways similar to the electromagnetic interactions induced by exchange of a photon. There are however two important distinctions. First, the Z-boson (as well as the W-boson) is a massive particle, which causes strength of interactions caused by Z-boson exchange to fall of exponentially with distance. Moreover, interactions with the Z-boson affect left-handed quarks much more strongly than right-handed quarks. The weak interaction is the only interaction that [[parity violation|violates parity]] (the symmetry that switches left and right) in this way.

[[Image:Quark decays.svg|thumb|left|A pictorial representation of the six quarks' decay modes, with mass increasing from left to right.]]

The exchange of a W-boson is again similar to the exchange of a Z-boson. The interactions violate parity and are exponentially suppressed because of the mass of the W-boson. However there is one property that makes the [[W-boson]] exchange distinct from all other interactions in the standard model – it is the only interaction that allows a quark to change flavor; by exchanging a W-boson an up-type quark can change into a down-type quark and vice versa. This is the interaction that allows the [[beta decay]] of some [[radioactive decay|radioactive]] elements. For example one of the down quarks in a neutron (composition {{SubatomicParticle|up quark}}{{SubatomicParticle|down quark}}{{SubatomicParticle|down quark}}) can change into an up quark be emitting a {{SubatomicParticle|W boson-}}-boson, transforming the neutron in a proton (composition {{SubatomicParticle|up quark}}{{SubatomicParticle|up quark}}{{SubatomicParticle|down quark}}). The {{SubatomicParticle|W boson-}} boson then decays into an electron ({{SubatomicParticle|Electron}}) and an electron antineutrino ({{SubatomicParticle|Electron antineutrino}}).<ref>
{{cite web
|title=Weak Interactions
|url=http://www2.slac.stanford.edu/vvc/theory/weakinteract.html
|accessdate=2008-09-28
|year=2008
|work=Virtual Visitor Center
|publisher=[[Stanford Linear Accelerator Center]]
|location=Menlo Park (CA)
}}</ref>

:{|
|-
|-
|-
|}

W-boson exchange can also allow quarks or hadrons to decay into completely different elementary particles through a process of [[annihiliation]]. For example, for the [[pion|pi meson]] (composition {{SubatomicParticle|Up quark}}{{SubatomicParticle|Down antiquark}}), a decay into a corresponding quark–antiquark flavor pair such as {{SubatomicParticle|Up quark}}{{SubatomicParticle|Up antiquark}} or {{SubatomicParticle|Down quark}}{{SubatomicParticle|Down antiquark}} would result in an annihilation of the quark–antiquark pair. The release of energy therein could effect the creation of the new [[lepton]]s, such as [[muon]]s or [[neutrino]]s.<ref>
{{cite book
|title=The Forces of Nature
|author=P.C.W. Davies
|year=1979
|publisher=[[CUP Archive]]
|isbn=052122523X
|page=205
}}</ref>

Any up-type quark can in principle change into any down-type quark. These transitions are however not all equally probable. The relative probabilities of are kept track of in the [[Cabibbo–Kobayashi–Maskawa matrix]] or (CKM-matrix),

:$\begin{bmatrix} V_\mathrm {ud} & V_\mathrm {us} & V_\mathrm {ub} \\ V_\mathrm {cd} & V_\mathrm {cs} & V_\mathrm {cb} \\ V_\mathrm {td} & V_\mathrm {ts} & V_\mathrm {tb} \end{bmatrix},$

where ''V''<sub>ud</sub> is related to the relative probability that an up quark changes into a down quark upon exchanging a W-boson. The entries of this matrix are constrained by various symmetries of the standard model. For example, [[weak universality]] require the matrix to be unitary (i.e. requires the inverse of the matrix to be equal to its [[hermitian conjugate]]). The similar matrix of the transitions of the antiquarks has a very simple relation to the CKM-matrix, namely ''V''<sub>{{SubatomicParticle|Down antiquark}}{{SubatomicParticle|Up antiquark}}</sub> = ''V''<sub>ud</sub><sup>*</sup>. As a result any complex entry of the CKM-matrix will cause antiparticles to behave differently from normal particles, and thus breaks the symmetry (called [[CP symmetry]]) between the two. Kobayashi and Maskawa discovered that there must be at least three generations for the matrix to have complex entries, and postulated a third generation to explain the CP violation observed at the time. For this discovery they were awarded the 2008 Nobel prize in physics.


## First sentence weak interaction section

The two versions are:

A quark of one flavor can transform into a quark of a different flavor is through the weak interaction, one of the four fundamental interactions through which particles interact with each other.


and

The only way a quark of one flavor can transform into a quark of a different flavor is through the weak interaction, one of the four fundamental interactions through which particles interact with each other.


The first one makes no grammatical sense (it has an extra is), so needs to be fixed anyway. Of course, we could fix that by just removing the is, but then we would be missing the information that this is the only way a quark can change flavor. We would be merely stating that this a way it can achieve it, and that there may be others. I think this is important information to convey. (TimothyRias (talk) 15:38, 15 April 2009 (UTC))

Problem fixed with the current wording. —Anonymous DissidentTalk 04:53, 21 April 2009 (UTC)

## A.V. Mahonar

Currently (ref 12) is "A.V. Manohar, M.B. Wise (2000). Heavy quark physics. Cambridge University Press. p. 1. ISBN 0521642418." and it is used to support the claim that there is strong evidence that there isn't more than 3 gens of quarks? The "page 1" strikes me as odd, as this is not something I would expect to see on the first page of a book (unless this is an introduction). Could someone confirm? Headbomb {ταλκκοντριβς – WP Physics} 19:17, 22 April 2009 (UTC)

IIRC, I cited that particular book (and page) because it contained the text:
"At the present time three generations of quarks and leptons have been observed. The measured width of the Z boson does not permit a fourth generation with a massless (or light) neutrino."
It was on page 1 because the author was using the preface to review the Standard Model. We may want to get another or different ref here, because this could be construed as indirect. On the other hand, we could simply bring in the argument about the Z boson, since its width is one of the reasons. What do you think? —Anonymous DissidentTalk 22:14, 22 April 2009 (UTC)
Others to look at:
Take your pick. I think the last one states it well. On a related note, it may be good idea to state why there can be no more than three gens; and these refs here give us the reasons. —Anonymous DissidentTalk 22:25, 22 April 2009 (UTC)
Well personally I would go with the PopSci article (in depth, availible online, accessible for laymen) + the original LEP paper ('cause that the original source for saying 3 gens).Headbomb {ταλκκοντριβς – WP Physics} 02:06, 23 April 2009 (UTC)

## partons

The following paragraph (from the history section) appears to suggest that the partons in de early SLAC experiments where only the up and down quarks. And also that quarks are to only partons. Now, it is known that gluons can also be partons (gluon-gluon fusion is an important creation proces for Higgs production in hadron colliders). I'm not full up on the exact details of the SLAC experiment, so it can be that no gluon partons where observed in those experiments. If not, than the paragraph needs a little tweak.(TimothyRias (talk) 08:53, 23 April 2009 (UTC))

In 1968, deep inelastic scattering experiments at the Stanford Linear Accelerator Center (SLAC) showed that the proton was not an elementary particle, but instead contained much smaller, point-like objects.[4][5][6] While this proved that hadrons indeed had a substructure, as predicted by the quark model, physicists remained reluctant to identify these smaller objects with quarks. Instead, they became known as partons (a term proposed by Richard Feynman, and supported by some experimental project reports).[7][8][9] The objects that were observed at the SLAC would later be identified as up and down quarks as the other flavors began to surface. Their discovery validated the existence of the strange quark, because it was necessary to the model Gell-Mann and Zweig had proposed.[10]

I have my doubts as to whether gluons would have been observed; they're fairly recent phenomena, I think. All that needs to be done is a tweak in wording; I'll get to that later. —Anonymous DissidentTalk 09:42, 23 April 2009 (UTC)
Wasn't the "three-jets event" in the 1970s the first solid evidence for gluons? Headbomb {ταλκκοντριβς – WP Physics} 15:14, 23 April 2009 (UTC)

## GAN or FAC

I think this article is beyond that. I see no barriers to FA; it's comprehensive, well-referenced and well-written. After all, why shoot for GAN when you can't find any issues that would stop it from FAC? Unless you can think of any...? —Anonymous DissidentTalk 04:55, 21 April 2009 (UTC)

Well, my experience is that it is usually easier to get an article through FAC if it has already passed GAN. The GAN process tends to focus more on the comprehensiveness of the article than MoS issues and the quality of the prose. By first going through GAN these discussions can thus be somewhat separated.
Furthermore, with the current state of the article I think it should pass GAN without any major problems. However, I'm not really sure of the prose is up for the mark of FA. Don't get me wrong, the article is reasonably well written, but I'm not sure it has the brilliance expected from a featured article. To put it short passing GAN is pretty much a given, passing FAC is a given.
Also, on a matter of wikipolitics. The article has 2 recent previous attempts to pass FAC, to some less motivated reviewers it might seem as we are trying to push the article in the hope it slips through on some occasion. By first putting it up for GAN before trying for FA again, we can better demonstrate the effort that went into the article. (TimothyRias (talk) 08:09, 21 April 2009 (UTC))
Okay, sure. With regard to the prose – I've given it a preliminary copyedit and it reads reasonably well. I'll go over it again soon, but I think it's of a good standard by now, for the most part. —Anonymous DissidentTalk 08:21, 21 April 2009 (UTC)
Ultimately I'll leave it up to you to decide. You have put the most work in this page and probably will do most of the work getting this article through either process (although I'll help out where I can). (TimothyRias (talk) 09:42, 21 April 2009 (UTC))
I thought I replied to this, but I was having computer problems (crashes) so it's possible my response got lost. Anyway, going to GA before FA is a waste of time IMO. This article is clearly of GA status, and the objections raised last time were not of content, but on referencing (which were fixed) and the scariness of the weak interaction/CKM matrix section (which was tweaked into a much less technical and much more readable thing). Also, there was some person who recently compiled the results of FAC and he found that GAs failed just as often as non-GAs (forget where it is, and I don't feel like looking for it either). I say we each give it a final review, fix the image below, and we go to FA3. Headbomb {ταλκκοντριβς – WP Physics} 18:04, 22 April 2009 (UTC)
headbomb gives a good argument, but I listed it for GAN before he made his point. Let's wait, say, 1 week, and if the article isn't GA-reviewed by then we'll remove the nomination and go to FAC. —Anonymous DissidentTalk 09:24, 24 April 2009 (UTC)
There are articles listed there from 13 March, so don't hold your breath. :-) --A. di M. (formerly Army1987) — Deeds, not words. 10:04, 24 April 2009 (UTC)
I say we close it now and go to FAC. I really don't see what's to be gained from the GAN and (worse) it'll be a waste of the GA reviewers' time (they already have a big enough backlog) as well as ours. Headbomb {ταλκκοντριβς – WP Physics} 15:49, 24 April 2009 (UTC)
@Headbomb: I'd be happy to do that after one final thing: see my last comment in the QCD matter section below. —Anonymous DissidentTalk 01:26, 25 April 2009 (UTC)

← Yes, I'd say let's wait for Timothy to replace the QGP section with one about QCD matter in general, and then we nominate the article for FAC. --A. di M. (formerly Army1987) — Deeds, not words. 10:57, 25 April 2009 (UTC)

## "New" discovery

I found this link recently [2], and I'm rather puzzled by the title. Seems to imply that something new was found, but I can't find anything that seems new to me. Could someone else take a look and opine?Headbomb {ταλκκοντριβς – WP Physics} 16:49, 23 April 2009 (UTC)

The "new" thing is that top quarks produced through the weak interaction (i.e. through the decay of a W-boson) have been observed. This process is much rarer than the common through strong interaction (gluon decay), so I guess the thing they are proud of is actually finding this process in the immense background. (TimothyRias (talk) 18:15, 23 April 2009 (UTC)
Ah, but how is that different from the 2006 press realease from Fermilab [3]? Should things from these two articles be incorporated into top quark (if it hasn't already been incorporated)? Headbomb {ταλκκοντριβς – WP Physics} 03:41, 24 April 2009 (UTC)
It is the same thing. The difference seems to be that in 2006 fermilab was claiming "strong evidence", and now they are claiming "discovery". Practically this means that in 2006 they had a significant signal (probably 2σ or 3σ) in one of the detectors (D0). Now three years later they have found the signal in both tevatron detectors with a greater certainty (5σ if they use the same standards for discovery as CERN.)
As for integrating it in the top article. It is already there. It also explains the difference between the 2006 and 2009 publication. (The 2006 publication indeed claimed a 3σ signal, according to that article.) (TimothyRias (talk) 07:52, 24 April 2009 (UTC))

## QCD matter

The section on QCD matter currently only really mentions quark-gluon plasma. I recent your a lot of work has been done on the conjectured color superconducting phases that might exist in neutron stars. Should these be mentioned? Maybe we should include a picture of the conjectured QCD phase diagram. (TimothyRias (talk) 09:49, 23 April 2009 (UTC))

No. I feel that mentioning all of these other theories is digressive. We have to remember that this is an article on quarks and it is already quite long for the casual reader. The section is on the quark-gluon plasma, not QCD matter; that's why it only really mentions the quark-gluon plasma. In addition to that, mention of other QCD phases wouldn't be a good idea because the subsection is in the "color confinement and gluons" supersection and talking about other phases would probably digress from that too far. —Anonymous DissidentTalk 10:06, 23 April 2009 (UTC)
We could rename the section to "QCD matter" and change it from level 3 to level 2, then. As for "already quite long for the casual reader", we're talking about the last section, so the reader who just wanted to know whatever the hell a quark is would have already left this page long before. --A. di M. (formerly Army1987) — Deeds, not words. 10:40, 23 April 2009 (UTC)
I'm not suggesting to add extensive descriptions of each phase of QCD matter; but the article currently doesn't even say what they are. No reason why QGP is so special we should include it and not even mention the others. --A. di M. (formerly Army1987) — Deeds, not words. 12:37, 23 April 2009 (UTC)
Well, I suppose a mention wouldn't be a bad idea. Since I don't really know much about QCD matter, I'd appreciate it if someone else could go about injecting that mention into the article. —Anonymous DissidentTalk 12:57, 23 April 2009 (UTC)

I don't really have a problem with including QCD matter in general, but like Anon. Diss. I have a feeling that this could be a significant digression from the topic at hand, where we're talking of individual quarks and their bound states, rather than their "group behaviour". But then again this was also my feeling with the QGP section, which is, if I understand correctly, a sub-topic of QCD matter. If that is indeed the case, then QCD matter and its phases should be tackled in this article rather than QGP, but I wouldn't go too technical here. An analogy with ordinary matter should be sufficient, along with a very concise overview of important "results/fields of researchs/topics". Headbomb {ταλκκοντριβς – WP Physics} 02:42, 25 April 2009 (UTC)

My feeling on this is that you cannot really discuss confinement (which is one phase of QCD), without at least mentioning under what conditions confinement does not occur. I'll try to dig some material on the QCD phases for references and write a short one or two paragraph piece. Maybe it is a good idea to replace the current section on QGP with a somewhat more general superficial piece on all the proposed phases of QCD. (That section needs to be updated anyway, since what it says about the search for QGP is outdated by about 10 years, as it completely ignores the progress made by RHIC in this area.) (TimothyRias (talk) 08:45, 25 April 2009 (UTC))
PS. I won't really have time for this, this weekend so it will probably happen next week. (TimothyRias (talk) 08:46, 25 April 2009 (UTC))
I have drafted a two paragraph piece on QCD matter in my sandbox. I still need to added proper references for most of the claim (although the reference lecture notes can actual cover all necessary claims, I would prefer better reference than just that.) and I need to find/create any apropriate image of the QCD phase diagram. But in the mean time please comment away.(TimothyRias (talk) 09:33, 29 April 2009 (UTC))
There is a diagram at QCD matter#Phase diagram; is it OK? --A. di M. (formerly Army1987) — Deeds, not words. 12:34, 29 April 2009 (UTC)
That one is basically OK, it contains all the information we want to convey here. There are some minor issues with it though
• It would be nice to have it as an SVG instead of PNG, allow for better scaling.
• For this article it would nice to have the temperature in Kelvin instead of MeV as I did in the draft. I think expressing temprature in MeV will throw most readers off.
• Again for this article it would be nice to have density on the x-axis, instead of the somewhat abstract baryon chemical potential.
Having said that, I/we need to decide of these objections make it worth it to make a new diagram. (TimothyRias (talk) 13:33, 29 April 2009 (UTC))
Thanks for doing this, Timothy. The new content looks good, but I'd like to copyedit it before we paste it in if you don't mind. One other thing: have you just posted the old version there for the sake of reference? —Anonymous DissidentTalk 13:11, 29 April 2009 (UTC)
Go ahead, copyedit away. As I said this is a draft, so I expect that there are plenty of typos and phrase that can be worded better. I think the current draft covers pretty much everything that should be said in this article on the subject, but is probably worded a bit technical for this article. I also need to double check some of the claims.
PS. Yes, the old section is there pure as a reference. Some of the refs there may be useful for some of the claims in the new paragraph. (TimothyRias (talk) 13:40, 29 April 2009 (UTC))

## Comments from the peanut gallery

Great article. Here are some ideas from the point of view of someone that is barely conversant in HEP. Most of my knowledge comes from seminars I attended at a university with a strong HEP department. (My research was in condensed matter though.) I will place the ideas in order from most important (in my estimation) to least important with the least important being typically easiest to 'fix' and most likely to be correct.

1. Reorganize Properties section. You have a great table at the end of the properties section that you spend a fair amount of time working toward. You do a great job explaining charge and mass etc... But then the flow is interrupted by the sections on the weak interaction and the strong interaction. I see no reason that these have to be here. They do nothing to help develop the properties of the quarks.
2. Refactor weak and strong interaction sections after properties. The two strong interaction sections (one before table of properties one after) then can be merged and reinforce each other better.
3. OKM matrices either needs a better explanation or removal. Perhaps a place to start for the explanation is by explaining the nice diagram showing the possible decay paths for the quarks. That is what the OKM is about right? As it stands, this article tells me nothing about what the OKM matrix is used for. I have no clue what quark states it is relating to which for instance. The linked article is hardly any better from my point of view.
4. Explain in a few sentences what Isospin, charmness, strangeness, etc.. are in a paragraph before the quark properties table. (The table is more or less self explanatory, but it might be useful to explain why u,d are merged to form Isospin why everything else has its own propery charmness, strangeness
5. A better short description of valence quarks (preferably before the term 'sea quark' is seen to help avoid confusion. This is a great place for an abreviated table of mesons and baryons with their valence quarks. The table alone will do more IMO then anything else to explain what a valence quark is.
6. The term hadronization is used in at least three sections without any good explanation of what it means. I think I figured it out from the context, but it hardly seems so important of a word to use so often. The concept that a 'free quark' will quickly be bound to form hadrons, if that is truly what hadronization means, seems to me to be much more important then the name. As it is the concept is being buried under the name, at least from the point of view of someone outside of the field.
7. Probably an unimportant sidenote but I remember a lot of seminars using the termed dressed and undressed with respect to the mass. There is no mention of it here.
8. I would love to see Quark Gluon Plasma expanded unless that truly fell by the wayside
9. I feel there is a bias toward the theoretical and the well established in this article. I would love to see more discussion of the experimental evidence. What are the doing today experimentally to extend, improve and test the model? There is also too much of a feeling, IMHO, that the field is fully understood. What wiggle room is there for new physics? (This is too much of a task for the short term and it isn't needed. That is why I did not put this first. On the other hand as a mid to long term goal it would really make a difference if done right, I think.)
10. (Warning this is a nit-pick!) Personally, I don't see what is gained by the Gel-Mann quote about the naming of the quark. The poem stanza before that is necessary and sufficient.
11. I love the table in the classification section. The caption needs more detail, though. At the very least it should mention that the quarks are the purple section. Mentioning that the first three columns represent the three families will also strengthen that part in the paragraph. (The sentence about the families in the paragraphs is pretty weak IMO and needs some support. See table to the right may be sufficient.)
12. History paragraph 4. From a readers point of view I would prefer if references 6 and 7 were moved to just after experiments (or possibly (SLAC)) to emphasize that these references are the results of the experiments. Reference 30 can be placed after 1968 to represent that it is a broad historical reference. I understand it may be a matter of preference so as not to break up the paragraph, but it makes it easier to understand what the references are for.
13. History paragraph 5. Two more references that are out of place from my point of view. Where it says 'In a 1970 paper,' I really want to see a reference. The same is true for after 'Makoto Kobayashi and Toshihide Maskawa'. Here at least it does not need to be placed in the middle of the sentence. That semi-colon could just as well be a period. (It is better as one IMO.)
14. More importantly, in History paragraph 5 you begged the question when you say that 'Glashow, John Iliopoulos and Luciano Maiani gave more compelling theoretical arguments' without as far as I can tell explaining what those theoretical arguments are. (As a sidenote is there anyway to highlight Glashow even though he was previously linked so that his name is not so easy to miss when everyone elses is linked?)
15. In history paragraph 5 you use the phrase 'could be explained if there were another pair of quarks' does not adequately explain if this other pair with the addition of the charm quark to form a strange/charm pair or if the new pair is the top, bottom.
16. In history paragraph 2 the term duo of physicist is used to compare two pairs of physicists where the first pair worked independently when the second pair (presumably) worked together. It is a small complaint but it was distracting to me.
17. Properties: Electric charge. Maybe it is because I am tired but all of those positive and negatives 1/3 and 2/3 and the like made my head spin. A table, is worth at least 500 words. I would love to see a table here of the quarks and antiquarks and charge. (Perhaps 3 columns (one for each family and four rows (including anti quarks). It would steal a little thunder from the final table but I think it would be worth it. Something similar to the purple section of the table in the classification section will do nicely, but with extra rows for the anti-particles.
18. No picture of George Zweig. If Zweig is to get equal credit, why does he not receive equal recognition? I mean this as a general question, not just of this article or because of a lack of a picture. Did Zweig not contribute as much or was his explanation not as good?
19. Finally, I am not quite sure if this is a problem or not, but I noticed that many of the diagrams seem not to be referred to directly in the main article. (As in 'see table to the right') This may be an issue of taste. On the other hand, on more then one occasion there was a useful figure that I glossed over because it wasn't mentioned directly. On the other other hand, I may be a bad reader or just a too tired one.

Over all this was an excellent article. I hope you can find these comments useful in improving the article even more. TStein (talk) 05:49, 28 April 2009 (UTC)

Thanks for your comments. I'll get working on them soon. I must say that I disagree with 1, though. Strong/weak interaction is a property of quarks. —Anonymous DissidentTalk 07:20, 28 April 2009 (UTC)
I am always scared when someone listens to my advice. The only thing scarier is when I edit an article myself. My suggestion to move the interaction sections from properties, while possibly being misinformed, is based solely on making the table as useful and as connected to the article as possible. It seems to me that you are right that color charge should also be included at the very least. Is there enough room to add the color charge property to the table then include 'all' (or 'yes') meaning 'all colors' for each quark? If I thought I was an expert, I would have edited it myself, though. TStein (talk) 19:36, 28 April 2009 (UTC)
As for point 3, once there was no mention of the CKM matrix in the article and people complained for that; then a detailed explanation was added, and other people complained for that; the current version which mentions it without fully explaining it is a compromise. As for point 7, AFAICT the undressed mass and the dressed mass are what the article calls "current quark mass refers to the mass of a quark by itself, while constituent quark mass refers to the current quark mass plus the mass of the gluon particle field surrounding the quark". If someone finds a source we can also add these terms. As for point 10, at some point someone tried to explain the issue of the pronunciation and the etymology of quark without using Gell-Mann's own words, but it was somewhat confusing (see RJH's point 5 in the latest peer review and my reply to it). All other points sound valid to me. --A. di M. (formerly Army1987) — Deeds, not words. 18:10, 28 April 2009 (UTC)
You can't win with some things (like CKM matrices) can you? I have no need to see the term 'dressed mass' or 'undressed mass' in the article. I have no clue how popular they are in modern terminology. They were quite popular at seminars at Kent State University 10 years ago, but things change.
Overall this article was much better then I expected it to be. An article on quarks could easily go too far technically or not near enough. This article strikes the right balance. Kudos to all the editors.
To me, though, the scariest part of your response was 'All other points sound valid to me.' I am still a novice reviewer here. I am still not quite sure whether it was a good idea for me to put my 2 cents at this time at all. I don't want my opinion to be given undue weight just because of the pressure of the review process. Nor do I want to upset the balance of opinion on contentious issues like CKM matrices. (Sometimes a solution even any solution is better then the results of trying to fix and refix the same problem over and over.) Keep up the good work. TStein (talk) 19:36, 28 April 2009 (UTC)
Comments are always welcome.(TimothyRias (talk) 21:16, 28 April 2009 (UTC))

Hi, here are some comments on the (greatly improved!) article:

A major issue that deserves to stand alone:

1. In the section "Strong interaction and color charge", the last two paragraphs mix up the gauge SU(3) with the flavour SU(3). Those two are completely different.

Other issues:

1. "Quarks are the only known elementary particles whose electric charge comes in fractions of the elementary charge." -> since readers might wonder why this charge is elementary if there are fractions of it, should this perhaps be something like the "what is usually defined as the elementary charge", or similar?
I don't really think this is a problem. "[E]lementary charge" is just a name, and I think it's clear enough. —Anonymous DissidentTalk 01:49, 9 May 2009 (UTC)
2. "and there is strong indirect evidence that more than three generations cannot exist." - I think the statement is that more than three generations do not exist in our universe - cannot could be taken to mean that more than three generations are incompatible with the very laws describing strong interactions, or something like that.
Done. —Anonymous DissidentTalk 01:50, 9 May 2009 (UTC)
3. "There are a great number of known hadrons" - shouldn't that be "There is a great number of known hadrons"? I'm never sure about these things.
Done. —Anonymous DissidentTalk 01:55, 9 May 2009 (UTC)
4. "all the reported pentaquark candidates have been established as being non-existent since." - it's hard to establish non-existence. I suppose what's meant is something like "all the data that had been taken to indicate the existence of pentaquark has found convincing alternative explanations"?
Addressed below. —Anonymous DissidentTalk 02:24, 9 May 2009 (UTC)
5. History: I think a little bit of further pre-history would be in order. After all, "up" and "down" don't make sense if you don't know about isospin. And strangeness as a quantum number was introduced to explain experimental data. This version makes it sound as if the quarks sprang fully-formed from Zweig and Gell-Mann's heads, whereas there were important developments leading up to it. Isospin makes a brief appearance later in the article as a flavour quantum number, but there's no indication in the history section that this concept predates the quark model.
Addressed below. —Anonymous DissidentTalk 02:24, 9 May 2009 (UTC)
6. "there was contention about the actual physicality of the quark concept" - "actual physicality" sounds too complicated. There was contention whether or not quarks where physical entities, as opposed to parts of a purely mathematical ordering scheme?
Improved wording. —Anonymous DissidentTalk 02:09, 9 May 2009 (UTC)
7. "a term proposed by Richard Feynman, and supported by some experimental project reports" - "supported" could be taken to imply that there was actual data involved in the decision; isn't it just "and taken up by some of those reporting on the experimental data in question"?
Fixed by someone else. —Anonymous DissidentTalk 02:16, 9 May 2009 (UTC)
8. "This was a strong indicator of the top quark's existence, because the bottom quark would have been without a partner if it had not." -> "because otherwise the bottom quark..."
Introduced different and better wording. —Anonymous DissidentTalk 02:21, 9 May 2009 (UTC)
9. "because elementary particles are believed to be point-like." - belief doesn't enter into it. The same theoretical models that describe elementary particle spin, namely quantum field theories like the standard models, are based on the notion of point-like particles.
Addressed below. —Anonymous DissidentTalk 02:24, 9 May 2009 (UTC)
10. The description of the CKM matrix should at least contain a brief sentence mentioning weak eigenstates. After all, that's the way the standard model is usually formulated, and why left-handed and right-handed particles behave differently, and so on.
Addressed below. —Anonymous DissidentTalk 02:24, 9 May 2009 (UTC)
11. "For example, a proton is composed of one d and two u quarks and has an overall mass of approximately 938 MeV/c2, of which the mass of three valence quarks contributes only 11 MeV/c2; the remainder can be attributed to the gluons' QCBE." - I remember commenting on this in the FAC. The last part of the statement is very suspect, I think. I'm pretty sure quark kinetic energy enters into this, as well. At the very least, there should be a reference for the statement that all the rest is due to gluons' QCBE. (Addendum: One of the sources I just checked for a latter paragraph of this lemma, Steinberger p. 130, attributes only about half the mass to gluons.)
Reworded to "much of". If we can;t find a cite for the kinetic energy fact, this is fine. —Anonymous DissidentTalk 07:09, 9 May 2009 (UTC)
12. "Gluons are constantly exchanged between quarks through a virtual emission and absorption process." - strange usage: sure, the gluons are virtual, and that's a well-defined statement (they're off-shell), but the "emission and absorption process"? The vertex is just like any other. Also, I'm pretty sure I commented on this before: the virtual-particle-exchange is a perturbation theory picture. What goes on in a hadron is highly non-perturbative. At the very least, one should be cautious about using perturbative language in this context.
13. "The color field carried by gluons is responsible for hadron indivisibility." - that's misleading. Hadrons are certainly divisible - if you pull at them hard enough, you'll get separate pieces. But those aren't single quarks.
Fixed. —Anonymous DissidentTalk 07:22, 9 May 2009 (UTC)
14. "These strong interactions are complicated by the fact that gluons can emit gluons and exchange gluons with other gluons." - that's not new information, though. It's an important ingredient of what was mentioned in the previous paragraphs - the rubber-band like binding. Should be re-arranged.
Rearranged. —Anonymous DissidentTalk 07:42, 9 May 2009 (UTC)
15. Sea quarks: Is the distinction as straightforward as the formulation here suggests? I'd expect that, as there is strong interaction between all the quarks and gluons within the hadron, the roles (who's on-shell, who's off-shell) change constantly. In this light, statements such as the sea quarks being much shorter-lived don't make much sense. I certainly don't find them in the references that are being quoted here (which is problematic in itself).
16. I still think the quark-gluon-plasma should mention more than just the old CERN experiments. The more modern heavy-ion experiments (RHIC, LHC) should at least get a sentence or two.

All the best, Markus Poessel (talk) 19:56, 26 April 2009 (UTC)

• Fixed #3
• #4: The sentence is about the reported pentaquarks, and these indeed have been established as being non-existent (ak the resonances were statistical oddities rather than actual resonances).
• #5 I think this is best for the up quark and down quark article. Going into isospin only to introduce the names up and down is a rather big digression. As for the "history of isopsin", again this is better treated in isospin/eightfold way than in quark, IMO.
• #6 Yes, your simplification is better.
• #9 I doubt anyone sane will read this to mean this is "mere belief". Let's not be pedantic here.
• #10 There was a mention of the weak eigenstates before, and we toyed around with the CKM section before and haven't found a way to make them accessible (eigenstate is scary word) in a reasonable ammount of space. Best left to the CKM matrix article.
• #11 Yes, good pick. I remember thinking "I thought kinetic energy played some part here?" but it slipped my mind.
• #12 Worth talking about. The perturbative "way of thinking" seems appropriate for what we're talking about here, but then again, I've never even written the propagator of anything, so what do I know?
• #13 Indeed that is misleading, fixed.
• #16 See above, we're thinking of making this about QCD matter rather than QGP
• More to come Headbomb {ταλκκοντριβς – WP Physics} 00:20, 27 April 2009 (UTC)
1. There is already a link to "Elementary charge" in case the reader wonders, but I wouldn't oppose a clarification.
2. Gonna change "cannot" to "do not" there. "Can" was intended in the "deductive" sense, as in "John can't have been there: I was with him at that time"; I hadn't noticed it was ambiguous here. Good catch.
3. If this followed the same rules as band names etc., I'd guess it's "there is a great number" in AmE and "there are a great number" in BrE. Can a native speaker confirm or deny this?
7. Well, experiments cannot support that you have to refer to a particular object as "parton" rather than as "widget" or as "thingy", so there is only one possible meaning; but if you think it can be misunderstood, I'm going to change "support" with "used".
9. Replacing "believed" with "assumed" or something like that? It's not like a prophet was told that elementary particles are pointlike by God himself, but if you can find a term implying that it's more than just a guess...
11. As for the first point, I'm going to change "mass" to "rest mass"; dunno what to do about the rest.
15. Since quarks are identical particles it makes little sense to ask which are sea and which are valence; but OTOH if there is a carbon-12 nucleus in some DNA strand in some cell of my hand, and a carbon-12 nucleus somewhere in the Imperial Palace in Japan, it makes little sense to ask which is which, either. So getting too pedantic is not very useful.
--A. di M. (formerly Army1987) — Deeds, not words. 10:59, 27 April 2009 (UTC)

Some replies:

• About #10, I personally don't think it is a good idea to talk about weak eigenstates. They are useful when you want to talk about general properties of the standard model, such as weak universality, etc. But when it comes to properties of quarks there is very little actual physics in the notion. And introducing weak eigenstates pulls open a whole new can of worms about the definition of the concept "particle" in high energy physics. (i.e. a plane wave excitation of a field in the free field limit.)
• About #12, this has actually bothered me a little as well. This article tries to formulate the physics of confinement in the perturbation theory language. However, since confinement fundamentally is a result of the break down of the validness of perturbation theory in terms of quarks at low energies (Hadrons in some sense are pseudoparticles of GCD at low energies), it is unclear to me that what is being said here is really valid.
• About #16, I agree, and am currently working on a beter replacement paragraph that also mentions other forms of GCD matter. (TimothyRias (talk) 16:00, 28 April 2009 (UTC))

Re #3, in my experience, within current English usage, the phrase "a [great, small, or no adjective] number of ..." has taken on the form of a compound adjective indicating the extent of the pluralness of the noun clause following the "of", making it parallel to "some", "many", "several", and other plural adjectives, rather than being treated as "a number" (singular) followed by a grammatically irrelevant subclause. After all, I think we'd all agree the semantic (if not syntactic) subject of the overall sentence in question is "hadrons", not "number" - are "number"s differentiated by their quark content? However, rather than wrangle further, I've rewritten the initial phrase slightly so as to completely avoid the initial "There is/are". John Darrow (talk) 20:06, 28 April 2009 (UTC)

## Good: now let's stop for a second

We seem to have restored order here. To all the regular editors of the article, let's take a step back before posting further improvements/additions/content to the article, and review what we really need to do. As far as I'm concerned, the structuring looks fairly good. The reason that "color confinement and gluons" is split off from "properties" remains: the section is quite large and has enough subsections to warrant its own two-level section. However, as noted above, there are still content additions and changes to be made. I've started a list below that anyone is free to add to; it can be used as a point of reference.

1. QCD matter section (extra content + refs; drafted by TRias).

Will add more later. I appreciate thoughts, or additions to the list. —Anonymous DissidentTalk 22:29, 30 April 2009 (UTC)

I'm wondering if we should speak of weak isospin... Headbomb {ταλκκοντριβς – WP Physics} 00:27, 1 May 2009 (UTC)

## "Forbidden by Pauli?" in Strong interaction and color charge section

Right after the sentence stating that color combinations other than RGB and X-antiX would be unstable is (along with a clarify me tag) the comment "Forbidden by Pauli?" Now, this may be betraying my layman's understanding of the subject, but wouldn't Pauli only prevent combinations actually involving two identical quarks, e.g. two red up quarks in the same particle? Pauli says nothing as far as I know about forbidding the possibility of non-identical quarks (e.g. a red quark and an antigreen quark) binding together in some combination which is not color-balanced; it is only QCD that forbids that. If I'm wrong, please let me know, but if not, that particular comment should disappear. John Darrow (talk) 07:54, 9 May 2009 (UTC)

That's what I'm trying to figure. Unstable... unstable how? Is it simply because the overall result is not white and we've observed/inferred those to be unstable? What's the decay mode? That's what I'm trying to figure out. Headbomb {ταλκκοντριβς – WP Physics} 09:21, 9 May 2009 (UTC)

## Redone "Other phases of quark matter" section

Some review would be nice. Is this the kind of information we were wanting? Is this section complete enough now? —Anonymous DissidentTalk 07:55, 10 May 2009 (UTC)

## Good Article

Someone's talk page requested that I help review this article. My first impression is this is a very good article. At my level of understanding I don't see anything wrong with it. So, I guess, once you guys get the more technical details out of the way - I vote yes for Good Article. I will read it a couple more times to see if I can contribute anything more than this.

By the way I was trying to find this (Quark) on the FA candidate list and I couldn't find it. Do you guys have a link for that? I would like to read the comments there too. Thanks. Ti-30X (talk) 02:44, 20 May 2009 (UTC)

## Ne'eman

Uhmm.. So, I was reading the article about Quarks, and I noticed there's no mention of Yuval Ne'eman. I think he had an important part at discovering the quark model. —Preceding unsigned comment added by Edenshere (talkcontribs) 10:12, 15 May 2009 (UTC)

I think it's that Ne'eman played a way in developing the Eightfold Way (a system of classification of hadrons), but not in developing the quark model (the physical reason behind the classification). That being said, I still don't exactly understand the disctinction between the work of Ne'eman and Gell-Mann or Zweig. I raised the issues many times and never got any answer. Definetively something that should be addressed. Headbomb {ταλκκοντριβς – WP Physics} 12:08, 15 May 2009 (UTC)
Headbomb, I addressed this in the last FAC. Ne'eman's role was relatively minor. We might do well to give him a sentence, but not much more, I think. —Anonymous DissidentTalk 11:07, 19 May 2009 (UTC)
I've afforded Ne'eman the said sentence. —Anonymous DissidentTalk 15:12, 21 May 2009 (UTC)

## arbitrariness comparison and coordinate axes

The following sentence was within the section Strong interaction and color charge:

Because the quark colors are not uniquely defined, the designation of which colors are which is as arbitrary of [sic] the respective designation of the axes of the Cartesian plane [sic] as x, y, z.

Originally I was just going to fix the incorrect phrase "as arbitrary of" to "as arbitrary as" but the more I looked at it, the less sense the whole thing made. Besides the issue of how do you quantify arbitrariness in order to be able to make a comparison, the sentence doesn't make clear what aspect of the designation of axes is being considered arbitrary. Is it the simple linguistic arbitrariness of picking the letters x, y, and z, as opposed to a, b, c (or some other choice)? Is it that of, starting from three given axes, picking which one is x, which is y, which is z? Is it the arbitrariness of, starting from a given space, picking some point as the origin of the coordinate system of that space, picking some line through that point and labeling it as one of the axes, and picking some other line at right angle to the first and labeling it as a second axis (at which point the standard definition of coordinate axes in a cartesian three-space (not plane!) gives us the third axis)? Furthermore, all of the above options also, under certain circumstances, cease to be totally arbitrary (e.g. within a limited area upon the surface of a rotating spheroid like Earth, it seems natural, not arbitrary, to make the direction of gravity z, and to pick a line tangent to a meridian (i.e. pointing toward the pole) as y, leaving x for the axis along the direction of rotation).

I'm not opposed to there being some comparison, as long as the comparison actually makes sense! John Darrow (talk) 23:10, 19 May 2009 (UTC)

The sentence in question is a watered-down version of
"The choice of which state represents a blue, green or red quark, respectively, is as arbitrary as the choice of three coordinate axes x,y,z in three-dimensional space. Similarly to the way one can rotate one spatial coordinate system to produce another, the different ways of choosing a quark color scheme are related by generalized rotations known as the color SU(3) symmetry group (SU(3)c)."
- which hopefully clears things up a bit. I agree that the version which you quote is misleading. It's not about choosing the letters x,y,z. It's about choosing directions in a multi-dimensional space. The one ambiguity that remains is the non-arbitrariness in certain situations (you mentioned the Earth, and a natural choice of z-axis). The statement here is about mathematical space (three-dimensional, Euclidean) or, alternatively, about empty space, where there are no objects that might dictate a certain choice of coordinate axes.
As for how to quantify arbitrariness, the mathematics behind it is quite clear, and the same in both cases: symmetry. Empty space has rotation and translation symmetry; another way of stating this is that you can choose the position of your origin and the orientation of your coordinate axes arbitrarily, and the results you get for geometrical properties of objects in that space (angles, areas, volumes, lengths...) will be the same regardless of your coordinate description. In the quark case, all the physics (the probabilities for specific reactions, but also the way you write down the mathematical description of the theory) is SU(3)_c symmetric: it doesn't change if you choose different ways of defining the three "color coordinate axes" in complex three-dimensional space. Markus Poessel (talk) 08:00, 20 May 2009 (UTC)
• Perhaps this analogy is simply too confusing? I mean, is the point really that crucial? I think not; and if it's going to cause confusion or cause distraction from the point, I think we should just leave it. —Anonymous DissidentTalk 14:16, 21 May 2009 (UTC)
• How else are you going to say what the color-SU(3) is about, then? It's either talking all technical, or using an analogy. And this one has the advantage of being a very good analogy - it's not something vague that breaks down if you look more closely, it holds right down to the mathematics of it all - SO(3) in the case of coordinate axes, SU(3) in the case of quarks. Markus Poessel (talk) 21 May 2009 (not logged in, currently) —Preceding unsigned comment added by 217.83.181.82 (talk) 14:37, 21 May 2009 (UTC)
• The analogy is already given by the "rotations of a co-ordinate system" part. —Anonymous DissidentTalk 14:51, 21 May 2009 (UTC)

So far I have read up to the CKM matrix. (I like that CKM matrix illustration by the way - excellent). The diagram showing quark decay of the neutron is excellent, too. The article thus far is an easy read and not technical. I think the general reader, with a general understanding of particle physics, will have an easy time understanding this article.

There are two things I want to mention that you may want to consider clarifying, if you think it needs it. These are:

• In the third paragraph of the introduction the article says, "For every quark flavor there is a corresponding type of antiparticle, called antiquark, that differs from the quark only in that some of its properties have the opposite sign." I am not clear as to what you mean by the antiparticle differs in that some of its properties have the opposite sign. As I have read through more of the article I have tried to see how "some of it properties" having the opposite signs is explained. Does this mean that a quark and anti-quark can differ in electric charge but have the same color properties? Or that a quark and anti-quark have different color properties but the same spin? etc., etc
• The second thing is this sentence: "While the process by which quarks transform into one-another is the same for all quarks, each quark has a certain preference to transform into the quark of its own generation. " I notice this sentence is backed up by the matrix diagram, which is good. However, it seems the phrase "certain preference to transform" does not convey the meaning of the process. I think it would be more accurate to say something like: "There is a higher probability that a quark will transform into a quark of its own generation, and a lower probability that a quark will transform into a quark of another generation." Something like that. By the way, this statement is also backed up by the CKM matrix diagram. So, what do you think?

Just trying to help :) Ti-30X (talk) 13:41, 25 May 2009 (UTC)

Concerning the first bullet, it's that the charges of the quarks are of opposed signs (colour, flavour quantum numbers, electric charge, and so on) but not properties such as mass, spin, lifetime, and so on. For the second bullet, the problem with your phrasing is that it is akward. For example, it is not true that a strange quark has a 0.222 probability of transmuting into an up quark, the exact probabilities depends on the kinematics of the situation. However, I think, but I am not sure, that you could say these are the high-energy probabilities. Headbomb {ταλκκοντριβς – WP Physics} 14:17, 25 May 2009 (UTC)
Headbomb, about you last remark: No the CKM entries can't even been seem as high energy probabilities. Actually, 'high energy' doesn't really make sense for a decay process since the center of mass frame is the rest frame of the decaying particle. Also the CKM matrix doesn't distinguish between (for example) t->b or b->t that only the former occurs is because of the kinematics (it is kenmatically impossible for a lighter particle to decay into a heavier one). It think the best you can doe is say that this is the probability of quarks transforming into each other if emerged in bath of very hot (T>> the quark masses) W-bosons. (Which I guess is in some sense the high energy limit of the decay process, but I'm not sure that that is what you meant.) (TimothyRias (talk) 12:51, 28 May 2009 (UTC))
Yes, I meant high-energy in this sense. However, I'll grant you that the possibility that I've not said it very clearly exists, since I'm not entirely sure how one would rigorously relate the CKM matrix coefficients to decay probabilities. Headbomb {ταλκκοντριβς – WP Physics} 02:21, 29 May 2009 (UTC)

## Why x, y, z?

In my opinion, including the x, y, z axes is necessary for the analogy to hold. After all, the x, y, z axes are what is analogous to the three colors red, blue, green. Talking just about a "state" of a coordinate system is rather vague - why be vague when, in this case, the analogy is quite concrete?

As for the present version:

"Because the quark colors are not uniquely defined, the designation of which colors are which is arbitrary."

- in my eyes, that is so vague as to be confusing. There are two different kinds of arbitrariness here. One is to choose color names, and to speak of red, green, and blue instead of, say, mauve, pink and peach. This sentence could be read as to refer to this particular arbitrariness - the designation of which colors are which (which is red, which is green, which is blue) is arbitrary.

But that's not what is meant here. There is further arbitrariness, and that is where to choose the axes in color space in the first space. The new blue could be, say, $1/\sqrt{2}\cdot$(green+red) - it's not about re-naming, it's about rotation.

"The differing states of quarks as represented by the three colors can be compared to the differering states of a spatial co-ordinate system as it is symmetrically rotated; such variations in quark state are related by SU(3)c."

What are the "differing states" supposed to be? Why should the rotation be dynamical? (And, for that matter, what is a symmetrical rotation supposed to be?) The ambiguity applies even if the quark is in one very concrete state. One and the same vector can be in x-direction in one coordinate system, and in y-direction in another. In the same way, one and the same quark state can be described as "red" in one system, and as a linear combination of, say, green and blue in the other. Just having states in there isn't very clear - you need to make the point that the colors correspond to a choice of coordinate axes. Markus Poessel (talk) 14:09, 25 May 2009 (UTC)

Define the term "choice". —Anonymous DissidentTalk 07:13, 26 May 2009 (UTC)
Just as you'd use it in everyday life. When faced with ordinary three-dimensional space, if you introduce any cartesian coordinate system, that involves choosing where to put the origin, and the direction of x axis and the y axis. The fact that you have a choice (that is, that the placement of the origin and of these axes isn't somehow dictated by the laws of physics) is equivalent to saying that there is a symmetry involved (in this case, rotation symmetry). Same in color space: in order to write down concrete formula, you'll need to choose a basis for color space. The fact that you do have a choice (that is, that red, blue and green aren't somehow dictated by the laws of physics) is equivalent to saying that there is a SU(3) symmetry. The fact that this still works if you choose a different convention for each point in space and time is equivalent to saying that this SU(3) symmetry is local. Markus Poessel (talk) 13:24, 26 May 2009 (UTC)
I've introduced the xyz analogy. What do you think? —Anonymous DissidentTalk 23:32, 29 May 2009 (UTC)

## Section structure

I think changing back to a section header (Gluons, asymptotic freedom and confinement) doesn't make sense. The header is now very specific; too specific for the "Other phases of quark matter" and "Sea quarks" subsection. The header should be something more general. Which is why I had chosen "interacting quarks". Markus Poessel (talk) 14:24, 29 May 2009 (UTC)

## FAC?

@Frequent contributors (user:Headbomb, User:Army1987, user:TimothyRias, user:Markus Poessel): Where are we at with this? I think pretty much everything is addressed. —Anonymous DissidentTalk 15:21, 21 May 2009 (UTC)

Currently, the "See also" section is rather repetitive – it includes a great number of wikilinks that are already part of the main text (lepton, parton etc.). I'm aware that the style guide gives editors some latitude here, but it also states that, generally, wikilinks that already appear in the main article text should not be repeated here. To me, that would indicate that the current "See also" section should probably be streamlined. It's not meant to be a complete systematic collection of all relevant wikilinks. Markus Poessel (talk) 19:48, 24 May 2009 (UTC)
I think all the major issues have been addressed. So I'd say lets go for it. (I do for see some bitching about the 'See Also' section, but it is easy to change if it is brought up.) (TimothyRias (talk) 12:40, 28 May 2009 (UTC))
Mostly, the article looks good. Still some ongoing discussion on the "Strong interaction and color charge" section (I'm still unhappy with the current form, but I'm confident we will find a good compromise), and I want to go over the Sea quarks section once more, but after that, FAC looks like the right step. Markus Poessel (talk) 16:54, 28 May 2009 (UTC)
I have a feeling that asymptotic freedom could be expanded just a wee bit. It does need to be referenced though. Original articles by Gross/Wilczek/Politzerfor the inlines, and their Nobel lectures for external links seem appropriate. Headbomb {ταλκκοντριβς – WP Physics} 02:34, 29 May 2009 (UTC)
I think the asymptotic freedom coverage is fine, especially considering the overall length of that section. To Markus: I've incorporated the xyz bit, so do you think it might be ready now? —Anonymous DissidentTalk 02:21, 30 May 2009 (UTC)
I'm just now working my way through the article once more. The xyz bit is OK - better than my version -, but there are some smaller issues I'll try to fix. Also, I haven't looked at any of the sources - some of those had be a bit of a problem earlier, I recall. Markus Poessel (talk) 17:08, 30 May 2009 (UTC)

## Last paragraph on QCD matter

AD, I see that you reverted my edit. These are some of the issues I have with the current version:

• Color superconductivity does not follow from asymptotic freedom. It is the formation of colored Cooper pairs (and the associated band gap) that causes that. (Of course, the formation of Cooper pairs is possible because of asymptotic freedom, but that is not what the article is currently saying.
• The article should mention where these conditions for color superconducting phases might occur. (i.e. in Neutron stars).
• The current text suggests that the spontaneous symmetry breaking is somehow in conflict with current theory. This not the case. Symmetry breaking is something that frequently occurs in theories (and is often associated with a phase transition.) In this case it is perfectly well understood, it is similar to how the Cooper pairs in BCS theory break the EM U(1) gauge symmetry.
• It is useful to mention that the quark Cooper pairs have color. (this is after what allows the color to flow).(TimothyRias (talk) 12:50, 27 May 2009 (UTC))
DoneAnonymous DissidentTalk 13:19, 27 May 2009 (UTC)
OK, I think this pretty much covers it. I have added a picture of the QCD phase diagram. Any comments? Maybe the text should be a little larger? (TimothyRias (talk) 14:18, 27 May 2009 (UTC))
I have updated the image a bit. (TimothyRias (talk) 12:53, 28 May 2009 (UTC))

I had another fresh read of the last paragraph and it is bit odd. The last sentence of the paragraph basically explains the 'weakly-interacting' part in the first line, this is however not really clear from the current paragraph. Could we somehow incorporate the explanation that high density leads (because of asymptotic freedom) to weak interactions, in the first part of the paragraph? (TimothyRias (talk) 08:32, 29 May 2009 (UTC))

I think that's implied, and it's certainly apparent if the reader has read the rest of the article. —Anonymous DissidentTalk 08:38, 29 May 2009 (UTC)
If that is implied then the last sentence is superfluous (and possibly confusing):

The formation of the Cooper pairs (and, by extension, the emergence of color superconductivity) is explained by the properties of asymptotic freedom: as quark matter becomes denser, the strong interaction becomes weaker and the average interaction lengths between individual quarks become shorter.

If we want to explain this, it makes much more sense at the beginning of the paragraph. As it currently sits at the end of the paragraph it sounds like it is trying to say something that is distinct of the description given above. (TimothyRias (talk) 09:16, 31 May 2009 (UTC))

Hi Headbomb, would you care to elaborate? You say that "The CKM matrix (discussed below) describes what is occurring to the left of the W boson." is helpful.

From all I can see, it's misleading. "To the left of the W boson" are three quark lines. Two of them do not change - the CKM matrix has nothing to do with them; yet the sentence implies that it does. One of them changes-the only thing this has to do with the CKM matrix is that one of its elements is non-zero. All the rest of the matrix, and in particular not the matrix as a whole, doesn't matter here. And it, in itself, certainly doesn't describe what happens - the description involves a lot of physics (Feynman rule interpretation) that is totally independent of the CKM matrix. That's why I think that the sentence implies a much greater role for the CKM matrix than is really the case - hence, misleading. Markus Poessel (talk) 22:18, 30 May 2009 (UTC)

Ah I see, well in that case yes it is a bit misleading. More precisely, I'm referring to the vertex at the left. I'm not oppose to change the wording to reflect that. Headbomb {ταλκκοντριβς – WP Physics} 23:30, 30 May 2009 (UTC)
"The CKM matrix (discussed below) encodes the probability of this and other quark decays." - or something along these lines? Markus Poessel (talk) 09:17, 31 May 2009 (UTC)
That looks a fine to me (and better than what is currently there), although tweaks are possible. We'll hammer the details later. Headbomb {ταλκκοντριβς – WP Physics} 14:36, 31 May 2009 (UTC)
OK, I've put it in. Markus Poessel (talk) 19:36, 31 May 2009 (UTC)

## Color SU(3) revisited

Hi Anonymous Dissident–please be so kind as to assume good faith: I never meant to bamboozle anyone (and I'm not at all convinced that's a fair description of what I wrote), and we can certainly work on the formulations to make them more accessible. But to replace what I wrote with something that is simply wrong (and the fact that you made the same replacement previously, and presumably all in good faith, doesn't help) is not a solution.

Specifically: a "type" of symmetry group has very specific connotations, as I mentioned in my log entry. Symmetry group classification is an important part of group theory, and defines some very specific classes or types. As I wrote when making the change: To use the same word here, but in a totally different context, is misleading. Whether or not a group is implemented as a global or local group is completely unrelated to what type (SU, SO, O, G, E) it is. If you don't like "manifestation", let's search for something different, as long as it's not "class" or "type". We need an accessible version of "A way of applying a symmetry group to physical fields".

"Its basic multiplet is a set of three colored quarks with no defined flavors" - once again, no, the SU(3) doesn't know anything about quarks. Its basic multiplet is a triplet. Quarks transform in this triplet representation. And you certainly don't multiply quarks to get, among other things, gluons. That statement only applies to the triplet representation, not to the quarks themselves. And what was wrong with tying the statement in with the previous sentence? How is the reader meant to make the connection, and realize those aren't just independent statements?

"The quark interactions prescribed by SU(3)c and the fact that SU(3)c varies with conditions—that the symmetry is "local"—require eight gluon types to act as force-carriers for the strong interaction and color charge." - where to start? The first "and" is wrong - the fact that you have local SU(3) is what prescribes the interactions and requires the gluons. That's different from saying that the local SU(3) and the prescribed interactions require eight gluons. The local SU(3) is the precondition, the two other things are consequences. Also, "vary with conditions" is very vague - that could be anything. I think we should go back to the previous formulation: "should be allowed to vary from time to time, as well as throughout space" or something similar. Markus Poessel (talk) 09:15, 31 May 2009 (UTC)

Wrong? I never realised the current version was wrong. I'm still not convinced of its inaccuracy. You are picking at very acute technicalities here. But we evidently need to do something here. Let's agree to change my version, but not to your old version. My version may be incorrect, but phrases from yours like "Mathematically speaking, the existence of these three subtypes for each quark flavor q means that quarks are part of the triplet representation of SU(3)c—the symmetry group's basic multiplet, meaning that all other members of the symmetry are fundamentally associated with this set." are too confusing to be properly understood even if their meaning is correct. I'll try and re-arrange things and change things based on what you've said, with the one exception of "vary with conditions", which I think is fine – especially considering that the alternative "should be allowed to vary from time to time, as well as throughout space" is almost as vague and twice as verbose anyway. —Anonymous DissidentTalk 09:30, 31 May 2009 (UTC)
I think I've addressed your concerns. "type" --> "kind"; SU(3)c locality --> color interactions,eight gluons; and I've eliminated the confusion about quarks being the multiplet itself. I've allowed "vary with conditions" to stay the same, as I really think it's fine. Thoughts? —Anonymous DissidentTalk 10:03, 31 May 2009 (UTC)
'vary with conditions' is very vague. I've been bold and changed it to 'vary with space and time', which is not much longer and alot more precise about what is meant. I've also clarified that it is not the group SU(3) that varies, but in fact its elements that vary with space and time, i.e. a local SU(3) transformation is a function from spacetime to SU(3). (TimothyRias (talk) 11:10, 31 May 2009 (UTC))
I am in acquiescence to your phrasing, Timothy. Looks fine. —Anonymous DissidentTalk 11:41, 31 May 2009 (UTC)
As, from my point of view, these are not technicalities at all, quite the opposite (that is, key properties of what we're talking about) I'm glad that you've nonetheless made some changes. As far as I'm concerned, we're nearly there - I'll make what I think are some small tweaks, and hopefully we'll have reached a compromise acceptable to all of us. Markus Poessel (talk) 12:21, 31 May 2009 (UTC)
After one last re-reading, the only thing I'm still uncomfortable with is the "SU(3)c was introduced after the discovery of color charge and the subsequent realisation that there are at least eighteen distinct types of quarks, three subtypes to each flavor." In the reference given (Perkins, p.4) I see no support for this statement, and it doesn't ring quite true. As far as I can see, the 18 is a red herring; what matters are the three subtypes, needed to circumvent problems with the Pauli principle (which isn't even mentioned here). This argument would still work if there was only one quark family. Markus Poessel (talk) 19:46, 31 May 2009 (UTC)
M.Y. Han is given for that, not Perkins. And Han certainly mentions it. —Anonymous DissidentTalk 21:46, 31 May 2009 (UTC)
You're right - my mistake with the Perkins. But the Han ref isn't much more illuminating - and the 18 is still a red herring. The reference should be to Appendix 5, and the statement should give a proper summary of that. It's the Pauli principle that's the key. Markus Poessel (talk) 13:34, 1 June 2009 (UTC)

## PDG Citations

Hi Headbomb, if you want to cite the PDG review of particle properties like that, please insert the correct page numbers. That was my reason for the changes - you can't cite a section and then give page numbers that refer to the whole collection. Markus Poessel (talk) 08:35, 1 June 2009 (UTC)

Alright, I'm going to the library today, I'll try to find the numbers, but the documents themselves say to cite as C.Amsler et al. (2008) Phys. Lett. B. p.1. Headbomb {ταλκκοντριβς – WP Physics} 13:33, 1 June 2009 (UTC)
Turns out I checked for J Phys G, which we don't carry, instead of Phys Lett B. I'll go back tomorrow. Headbomb {ταλκκοντριβς – WP Physics} 20:00, 1 June 2009 (UTC)
Great, thanks. You are correct in that "C. Amsler et al." is what they themselves prefer (I had already reverted changes I made to the author designation after realizing this very thing). This is really about the page numbers. Kudos to you for taking the effort of checking those! Markus Poessel (talk) 21:03, 2 June 2009 (UTC)

## Checking the references

In earlier FACs of this article, I had some beef with references that didn't support the statements they were meant to support. In my view, that is one of the worst things a wikipedia article can do–pretend to be authoritative ("Oh, it must be right, there is a reference"), and then let the reader down. I'm confident that things are much better now, but I still feel it's important to check.

If I find any more problems (I'll take it step by step), I'll add them to the bullet list below. Feel free to insert comments etc. in between. Markus Poessel (talk) 19:40, 31 May 2009 (UTC)

• Actually, the very first reference (Britannica) would appear to be a case in point. Does it even mention the weak interaction? If no, why is it referenced in support of the sentence to which it is attached? Markus Poessel (talk) 20:08, 31 May 2009 (UTC)
Seems to be a situation where the ref was better suited to the sentence prior. —Anonymous DissidentTalk 12:46, 1 June 2009 (UTC)
• Kim and Pham p. 169 is a somewhat weak reference for top/truth, bottom/beauty. Has anyone out there an introductory text that mentions the existence of different naming conventions explicitly (here, they are only an aside; possibly already introduced earlier in the text)? Markus Poessel (talk) 20:08, 31 May 2009 (UTC)
Schumm, p.117. —Anonymous DissidentTalk 12:53, 1 June 2009 (UTC)
• Can somebody please confirm that "K.A. Peacock (2008). The Quantum Revolution. Greenwood Publishing Group. p. 125. ISBN 031333448X." indeed mentions both the Pauli principle as applied to quarks, and the defining property of bosons? Markus Poessel (talk) 20:08, 31 May 2009 (UTC)
• Having two distinct references for the mere statement that the best-known baryons are protons and neutrons seems like overkill. Can we decide on which one to keep? (If we keep Munowitz, page number should only be 35). Markus Poessel (talk) 20:21, 31 May 2009 (UTC)
Kept Munowitz and amended page number. —Anonymous DissidentTalk 13:00, 1 June 2009 (UTC)
• For the statement "A great number of hadrons are known (see List of baryons and List of mesons), most of them differentiated by their quark content and the properties these constituent quarks confer.", Kim/Pham p. 169 would appear to be a bogus reference. Nothing about that there are many hadrons on that page, and nothing about the crucial and subtle statement about most (but not all) differentiated by quark content. In fact, quarks are only systematically introduced much later in that book. Markus Poessel (talk) 20:25, 31 May 2009 (UTC)
That is extremely strange. Maybe a number typo on the part of the referencer? Removed. —Anonymous DissidentTalk 13:04, 1 June 2009 (UTC)
The first use of the Kim/Pham reference was actually fine. It was just the second one that was strange. Markus Poessel (talk) 13:28, 1 June 2009 (UTC)
1. Does this mean the refs are all fine now? —Anonymous DissidentTalk 13:10, 1 June 2009 (UTC)
I haven't gotten farther than most of the History section. Will continue soon. Markus Poessel (talk) 13:28, 1 June 2009 (UTC)
• "K.W. Staley (2004). The Evidence for the Top Quark. Cambridge University Press. p. 15. ISBN 0521827108.* doesn't work as it's meant to. No mention of Zweig for the first occurrence, nothing beyond names and year for J/Psi Burton/Richter on the second. Markus Poessel (talk) 14:12, 1 June 2009 (UTC)
• I'll take your word for it and remove it. I can't comment on it because, for whatever reason, the GBooks preview is upside down for me. —Anonymous DissidentTalk 07:44, 3 June 2009 (UTC)
Looks like they scanned it the wrong way. I certainly had a very awkward time reading it with my head upside down in front of my monitor. Markus Poessel (talk) 08:27, 3 June 2009 (UTC)
• "Reasons for the top quark's extremely large mass remain unclear" - current ref doesn't seem to work for this. More generally, since when does the standard model give any reasons for quark mass values? Markus Poessel (talk) 14:16, 1 June 2009 (UTC)
• "K.M. Larsen (2007). Cosmology 101. Greenwood Publishing Group. pp. 111. ISBN 0313337314." doesn't work as it says nothing about antiquarks. Surely one pointer to the appropriate section of an introductory particle physics textbook would take care of the whole paragraph? (Splitting it into two references again looks like overkill.) Markus Poessel (talk) 14:25, 1 June 2009 (UTC)
• "The Standard Model of Particle Physics". BBC. 2002. http://www.bbc.co.uk/dna/h2g2/A666173. Retrieved on 2009-04-19. - doesn't cover direction being a degree of freedom. Markus Poessel (talk) 14:27, 1 June 2009 (UTC)
It is the only reference for that paragraph, and it comes at the very end. That usually means it's the reference for that whole paragraph. In any case, the degree of freedom is unreferenced here. Markus Poessel (talk) 08:30, 3 June 2009 (UTC)
• "F. Close (2006). The New Cosmic Onion. CRC Press. p. 81. ISBN 1584887982." gives only part of the information attributed to it: spin as a vector, and measured along given axis, are missing. Probably fixable by including a greater page range. Markus Poessel (talk) 14:32, 1 June 2009 (UTC)
• "Weak Interactions". Virtual Visitor Center. Stanford Linear Accelerator Center. 2008. http://www2.slac.stanford.edu/vvc/theory/weakinteract.html. Retrieved on 2008-09-28. - doesn't work as reference for inverse beta decay. Markus Poessel (talk) 14:42, 1 June 2009 (UTC)
• Reduced reference to inv. beta decay to a mere link because I question the correctness of the former information. I found no source mentioning the emission of a W+ boson in inv. beta decay. —Anonymous DissidentTalk 01:47, 6 June 2009 (UTC)
• Z. Maki, M.Nakagawa, S. Sakata (1962). "Remarks on the Unified Model of Elementary Particles". Progress of Theoretical Physics 28 (5): 870. doi:10.1143/PTP.28.870. http://ptp.ipap.jp/link?PTP/28/870/pdf. - while it's good to have original articles, what about Pontecorvo? Going by the name alone, the modern version stems only partly from this article, and partly from work by Pontecorvo? Is there a review article reference that covers both? Markus Poessel (talk) 14:47, 1 June 2009 (UTC)
• I think (not sure) that this is because Pontecorvo himself was not involved with the matrix, but that since the matrix "explains" neutrino oscillations, people like to give him some credit. The PMNS matrix is often simply reffered as the MNS matrix. Headbomb {ταλκκοντριβς – WP Physics} 16:12, 3 June 2009 (UTC)
• I have no idea why "M. Veltman (2003). Facts and Mysteries in Elementary Particle Physics. World Scientific. p. 41. ISBN 981238149X." is given as a reference for the QCBE contribution to the proton mass. Markus Poessel (talk) 18:07, 1 June 2009 (UTC)
• Similar to the point made above: "F. Canelli. "The Top Quark: Worth its Weight in Gold". University of Rochester. http://conferences.fnal.gov/lp2003/forthepublic/topquark/index.html. Retrieved on 2008-10-24." doesn't work for the sentence it's meant to support, namely "The masses of most quarks were within predicted ranges at the time of their discovery, with the notable exception of the top quark, which was found to have a mass approximately equal to that of a gold nucleus, significantly heavier than expected." - it could even be taken to contradict it, stating, as it does, that the standard model does not predict quark masses. Markus Poessel (talk) 18:12, 1 June 2009 (UTC)
• Removed. —Anonymous DissidentTalk 01:53, 6 June 2009 (UTC)
• Strictly speaking, the reference "P. Renton (1988). Electroweak Interactions. Cambridge University Press. p. 332. ISBN 0521366925." does the job - but only for readers who know that "gluons transform in the adjoint (8) transformation" is equivalent to saying that gluons carry a color and an anti-color. And presumably, readers who have this depth of knowledge do not need the reference. This should probably be replaced with a more explicit reference (introductory elementary particle physics textbook?). Markus Poessel (talk) 18:16, 1 June 2009 (UTC)
OK, turns out the next reference (Veltman) explicitly mentions this, so I'm removing the Renton reference. Markus Poessel (talk) 19:12, 1 June 2009 (UTC)
• "A recent estimate puts the needed temperature at 1.90±0.02×1012 K." is in need of a reference. Markus Poessel (talk) 20:55, 1 June 2009 (UTC)
Done. Note that the reference expresses the temperature in MeV instead of Kelvin, I have translated it to the more well-known (to the general audience) unit. Can we live with note having a reference for a simple change in units? Otherwise it should read 164 +/- 2 MeV. (TimothyRias (talk) 08:05, 2 June 2009 (UTC))
No, that should be OK. I don't think changing units counts as original research, even on Wikipedia. Markus Poessel (talk) 16:44, 2 June 2009 (UTC)

OK, that's all I could find. I did manage to check most of the references (in particular because so many of them were so conveniently on Google Books), but not all. Markus Poessel (talk) 21:00, 1 June 2009 (UTC)

On a more general note, I noticed that there are few references that do not follow the same conventions as the other articles. The general convention seems to be:

• Use the "cite xxx" template.
• Authors as a comma separated list in the author field. (As opposed by the ; seperated list produced by using author1, author2, ...).
• Authornames as Initials Lastname, i.e. "J. Doe".

If somebody can confirm that this is the intended convention, I'll make a general sweep of the citations, bring them inline with the convention. (TimothyRias (talk) 08:11, 2 June 2009 (UTC))

Well for this article, yes that's the format. Unspaced and dotted initials, followED by last name. I'm pretty sure they are all in line, but feel-free to double check.Headbomb {ταλκκοντριβς – WP Physics} 08:18, 2 June 2009 (UTC)
You seem to have gotten the last ones. ;) (TimothyRias (talk) 08:39, 2 June 2009 (UTC))

## Behind the curve

I suppose this is a little late, but congratulations on being considered for FA. Ti-30X (talk) 04:33, 12 June 2009 (UTC)

## Rare decays?

That picture States that the decays s->u and b->c are rare decays. That cannot be right since the first one is the only way a s quark can decay and the secon is the most common way for a b quark to decay. does anybody know how to change that picture? Dauto (talk) 19:16, 21 April 2009 (UTC)

Removed until a correction can be conjured. —Anonymous DissidentTalk 04:59, 22 April 2009 (UTC)
I guess what the image was conferring was the magnitude of the entries in the CKM matrix. These are related to the frequency of the decays, but the actual decay rate also is a function of the masses of the involved particles. Anyway, since we already have the values of the CKM matrix in the article, this image has become superfluous. Do we maybe want to add a different illustration to this section? Maybe a diagram of beta decay? (TimothyRias (talk) 07:40, 22 April 2009 (UTC))
Timothy is right. A different image would be less redundant. @headbomb: If this image is incorrect, it needs to be removed, and as quickly as can be done. It's like disinformation. —Anonymous DissidentTalk 08:34, 22 April 2009 (UTC)
I disagree that the image is superfluous. It adds a lot for the "visual" oriented people. However, "common/rare/rarer" should be replaced by words reflecting coupling strength rather than decay frequency. Something like "Strong/Weak/Weaker". BTW, I've commented the image away, so it doesn't display in this current form.Headbomb {ταλκκοντριβς – WP Physics} 08:47, 22 April 2009 (UTC)
How will we go about correcting it? —Anonymous DissidentTalk 08:49, 22 April 2009 (UTC)
I've checked the image file. Changing the text will be at most 5 mins work. We would just need to decide on something that is both correct and understandable. (TimothyRias (talk) 09:06, 22 April 2009 (UTC))
I think Headbomb's idea is a good one. Could you be the one to fix it Timothy? I for one have very little experience here. —Anonymous DissidentTalk 10:03, 22 April 2009 (UTC)
Sure. working on it...(TimothyRias (talk) 10:11, 22 April 2009 (UTC))
Done most time spent actually getting file to upload. :) (TimothyRias (talk) 10:18, 22 April 2009 (UTC))
So why is it still showing "common, rare, rarer"? —Anonymous DissidentTalk 10:21, 22 April 2009 (UTC)
Have you purged your browser cache (ctrl+reload)? (TimothyRias (talk) 10:27, 22 April 2009 (UTC))
Is it only me who also finds the new version possibly ambiguous? Could it not be that someone just seeing the picture gets the impression that d→u transition is through the strong interaction rather than the weak? I don't have a really good alternative though ... Blennow (talk) 08:19, 16 June 2009 (UTC)

## Unproven

I beg to differ. Not proven is the correct status for tetraquarks and pentaquarks. They have not been proven (this is data); therefore, they are "unproven". More detail in the classification section is not needed, and the sentence structure you reverted to was awkward. On an aside, I added "hundreds" per the request of a person at the FAC. I'm pretty sure it's correct. We need something more specific than "a great number"; what would you suggest? —Anonymous DissidentTalk 07:48, 16 June 2009 (UTC)

Unproven does not accurately summarize the situation. They were theorized, thought to be found, and those thought to be found were shown to be statistical effect. The problem is "unproven" leaves out the fact that that they were at one point thought to be found, and this was reported by several news organizations of various levels of readership. Taking two sentences to explain this is not overkill. Now concerning the counting of hadrons, it's an arbitrary endeavor. I would say that there are 56 hadrons, of which 35 can be observed, and 36 mesons, of which 25 can be observed (92 hadrons, of which 60 are observable). Others would consider excited states to be different hadrons. While it is true that hundreds of hadronic resonances have been observed, to say that this means that hundreds of hadrons is equivalent to saying that observing different excitations of hydrogen atoms means that you've observed different atoms. Headbomb {ταλκκοντριβς – WP Physics} 08:26, 16 June 2009 (UTC)
Okay. I'll contrive a way of re-inserting that, but the old phraseology was quite poor. WRT the hadrons" the problem of "a great number" still remains; there isn't a rough figure we could reasonably tack to it? —Anonymous DissidentTalk 08:31, 16 June 2009 (UTC)
Well we are pointing to the lists of baryons/mesons. That seems sufficient to me. Headbomb {ταλκκοντριβς – WP Physics} 08:38, 16 June 2009 (UTC)

## The note

Okay, I find your last revert to be pretty disingenuous AD. You've said that you wouldn't revert, then revert, then pretend I haven't explained why the note is there. So again, in great details this time:

• Several people, inside and outside of wikipedia, are stumped at the statement that mass has something to do with decay. The explanation needs to be given where people are going "WTF?", not 15 paragraphs down when they forgot about it and are reading about concepts such as color charge and strong interaction. Also removing the "thus" is removing all the physics of decay, and makes it look like mass and decay are completely unrelated. The note is no more distracting than a reference, and you can always not click it.
• In addition, the classification section does not cover anything about why there are up and down quarks around. There are implicit hints of why, but never explicit statements, and if you're good enough to decrypt the hints, you're left thinking "Why are there down quarks aren't since they have a higher mass than up quarks. Shouldn't they all have decayed by now?" The note covers this.

So there.Headbomb {ταλκκοντριβς – WP Physics} 13:31, 18 June 2009 (UTC)

I didn't revert. I removed the note and tried to integrate it into the classification section. —Anonymous DissidentTalk 02:02, 19 June 2009 (UTC)
And I'd like to know who these people are. This is the leading paragraph. People are not supposed to know everything about quarks right there. It's a summary. —Anonymous DissidentTalk 02:05, 19 June 2009 (UTC)
• Okay. Let's not lose our heads. I've trialled a new phrasing in the lede that may remove the need for the note. I think it covers all our bases with regard to particle decay, and it doesn't lose any of our meaning. What do you think? —Anonymous DissidentTalk 02:19, 19 June 2009 (UTC)

## Quarks obtain their color via gluons?

That's a strange statement. If it said that they obtain their electric charge via photons I would immediately delete it as nonsense. The analogy is not perfect, as gluons do have a color charge, but saying that quarks obtain their color via gluons sounds somewhat suspect to me. Can anyone who understands QCD tell whether that makes sense? --A. di M. (formerly Army1987) — Deeds, not words. 10:00, 23 June 2009 (UTC)

Where does the article say that? (TimothyRias (talk) 10:29, 23 June 2009 (UTC))
In the last sentence of the second paragraph of "Strong interaction and color charge". If no-one objects in 24 hours, I'm going to delete the four words "obtain their color and" from it. --A. di M. (formerly Army1987) — Deeds, not words. 20:07, 23 June 2009 (UTC)

## History before classification?

I've been reading the article a few times now and I feel the order is unnatural, that history should precede classification. Thoughts?Headbomb {ταλκκοντριβς – WP Physics} 21:08, 27 June 2009 (UTC)

My vote? Leave as is. Who knows what might change or become disjointed by a move? Realistically, it's not a big deal. On an aside, I'm sorry I've been mostly away for the past week. I'll be back by Tuesday. —Anonymous DissidentTalk 13:06, 28 June 2009 (UTC)
IIRC, months ago "History" came first, but I swapped them because someone who has never heard of quarks before (and thus is most likely to read the article sequentially, rather than jumping from the TOC to the intended section) is likely to be more interested in "Classification". --A. di M. (formerly Army1987) — Deeds, not words. 15:39, 28 June 2009 (UTC)

## minor points

• "All types of hadrons always have zero total color charge." Isn't 'all' and 'always' redundant? 86.213.119.40 (talk) 23:49, 9 July 2009 (UTC)
• Removed "always". --A. di M. (talk) 01:26, 11 July 2009 (UTC)
• Dashes are wildly and inconsistently used throughout. Needs a complete recheck. 86.213.119.40 (talk) 23:54, 9 July 2009 (UTC)
• Fixed, I believe. (Hyphens are used for compound adjectives and nouns; en dashes in compounds such as "foo–bar baz" when meaning "the baz between foo and bar", or "the baz of foo and bar", and ranges; em dashes for parenthetical phrases.) I'm not 100% sure about "spin-statistics theorem": if it is to be parsed as "the theorem about spin-statistics" (spin-statistics being a compound noun) it's a hyphen; if it's "the theorem of spin and statistics" it's a dash. I've used the former as it appears to be more common in the literature. --A. di M. (talk) 01:26, 11 July 2009 (UTC)

## The top quark "may" decay before it hadronizes

The only exception to this rule is the top quark, which may decay before it hadronizes.

The "may" seems to suggest that it doesn't have to decay before it hadronizes. But I can't find any hadron containing a top quark in either "List of baryons" or "List of mesons". Was the "may" intended to mean "we don't know whether", rather than "can but needn't" (in which case it should be clarified)? or am I missing something? --A. di M. (talk) 15:16, 13 July 2009 (UTC)

I unthinkingly used "may" – but, coming round to it, which word we use in the place of "may" is of key importance. The top quark decay has been observed once, last year, yes? Would it be too assertive to say that top quark does (which implies "always does") decay before hadronization? "may" certainly has the problem you've outlined above. Maybe we should go with the slightly longer (but possibly more cautious) "has been observed to" instead of "may"? —Anonymous DissidentTalk 15:19, 13 July 2009 (UTC)
"may" is probably accurate. Decay processes are somewhat random so it is safe to say that in some cases the top quark will first briefly form hadrons before decaying. Moreover, seeing how much trouble the tevatron people had to isolate the signal of bare top decays, there must also be lots of cases where doesn't decay before it hadronizes. (TimothyRias (talk) 15:28, 13 July 2009 (UTC))

## History of the bottom quark

In the history section, the sentence "In 1977, the bottom quark was observed by Leon Lederman and a team at Fermilab." comes as a bit unexpected and dry. (This is because what was written before is well motivated and put into perspective.) Maybe explain the significance of the bottom quark and/or how it was discovered (so as, for example, to understand why it was not discovered before).

Also, minor point, "by Leon Lederman and a team at Fermilab" is a bit ambiguous. Was it a joint work? Did Lederman work independently from the Fermilab team? Was Lederman 'leader' of the Fermilab team? 92.149.128.113 (talk) 13:47, 16 July 2009 (UTC)

• If Lederman was the leader, which I assume is the correct interpretation, I suggest "by a team at Fermilab led by Leon Lederman". --Cryptic C62 · Talk 14:41, 16 July 2009 (UTC)
Inserted that. —Anonymous DissidentTalk 14:48, 16 July 2009 (UTC)
How comes I can't find the name "Lederman" in the reference given (currently, ref. #5)? --A. di M. (talk) 15:47, 16 July 2009 (UTC)
New ref inserted. Odd that Markus missed this in his meticulous examination, but all fixed now. —Anonymous DissidentTalk 15:55, 16 July 2009 (UTC)
Great for the minor point. What about the first point (expanding the history)? 92.149.128.113 (talk) 19:16, 16 July 2009 (UTC)
There's already a sentence about Kobayashi and Maskawa proposing the third generation, in the last-but-two paragraph of the section. --A. di M. (talk) 20:07, 16 July 2009 (UTC)

## etymology

Should the article discuss the naming of the different quarks? Since the quarks have such odd names, I think many readers will wonder how they came by these names. Even if the labels are somewhat arbitrary, there still are reasons why these names were chosen. These are typically the fun factoids people try to look up in an encyclopedia. If we are going to introduce such a section we would need proper reliable sources since there is a lot of nonsense floating around on this subject. This webpage from fermmilab (physics folklore may not consitute a reliable source by itself, but the sources it cites might. Unfortunately I don't have access to any of those books. (TimothyRias (talk) 12:44, 17 July 2009 (UTC))

I disagree with an inclusion of this. The overwhelming majority of the material claims the names were almost completely arbitrary, and to claim otherwise here is almost misleading. There is no impulsion to read deeper into it. Names had to be chosen; and they were. —Anonymous DissidentTalk 12:53, 17 July 2009 (UTC)
It is not like MGM choose "up" and "down" by random selection from a dictionary. If I recall correctly his original paper he explicitly says that "up" and "down" represent the up and down component of the isospin doublet. (interesting his third particle 's' stands for (isospin) singlet.) The reasons for calling 's' "strange" are also well documented. Charm is possibly the most random of them all, showing a Glashow and Bjorken being very pleased with their idea. Top and Bottom reflecting the fact that they mirror Up and Down also is very uncontroversial. Truth and beauty are again more random, but it should noted that these names were only introduced after the particle had being introduced as t(op) and b(ottom). There is nothing misleading about explaining where particles got their names and who gave them (although the last part is sometimes hard to track down). (TimothyRias (talk) 13:05, 17 July 2009 (UTC))
It's very clear that this is all trivia. We can hardly say in an encyclopedia article, "Glashow and Bjorken were very pleased with themselves, so they called it charm." That's why I would prefer to leave it out. Reliable sources in this area are very difficult to locate as well, and it's hard to know what to believe. Remember: verifiability, not truth. —Anonymous DissidentTalk 13:10, 17 July 2009 (UTC)
Well apparently "We called our construct the 'charmed quark', for we were fascinated and pleased by the symmetry it brought to the subnuclear world." is a direct quote from Glashow, published in The Hunting of the Quark by Michael Riordan. I agree that it is a vague statement by the man, but it nicely illustrates how random that naming was. (As an interesting side note, he is actually talking about the charm quantum number, which in turn give its name to the corresponding quark.) This discussing this sort of thing will give a much better context for the current 'tag on' note about beauty and truth. (TimothyRias (talk) 13:37, 17 July 2009 (UTC))
Dunno about the original paper, but J.J. Sakurai in his QM textbook mentions the same reasons for the names "up" and "down". I would not object to adding a very short paragraph about the etymologies of flavor names in #Etymology (although I wouldn't use a wording such as "very pleased with themselves"). A rough sketch: "The names up and down represent the "up" and "down" components of the isospin doublet.[MGM][JJS] The strange quark is named after strangeness, a property of certain hadrons which was then explained as the presence of a strange quark;[3] according to Murray Gell-Mann, the symbol "s" also stands for "isospin singlet".[MGM] [Insert suitable wording for the naming of charm here.][4] Kobayashi and Maskawa originally named top and bottom quarks by analogy with up and down quarks,[KM] but the names truth and beauty, proposed by Gell-Mann, were commonly used in the past; now they have mostly fallen in disuse.[6]" (Other info about puns such as "the SM has beauty but not truth" would belong to the articles about individual flavors, if anywhere.) But that wouldn't be a vital part of the article, anyway. --A. di M. – 2009 Great Wikipedia Dramaout 13:30, 17 July 2009 (UTC)
Hmmm... that actually examplifies a lot of the misinformation out there. I don't think KM introduced the names top and bottom. Their names for the extra particles were p and λ' inline with the names used in the GIM paper (p, n, λ, p' for up, down, strange, charm). To make things worse one of the earliest uses I found of top and bottom were in a paper by MGM, who quotes Harari as having used it before. I've haven't really been able to figure out when people started using beauty and truth, but appears to be around the discovery of the b quark in 1977. (TimothyRias (talk) 13:49, 17 July 2009 (UTC))
Exactly. I implore you: leave it out. This is too wishy-washy an area. We cheapen the article and possibly introduce falsities here. The only ones we know surely and which (I think) we can source well are the top and bottom for the isospin doublets. —Anonymous DissidentTalk 13:54, 17 July 2009 (UTC)
Additional note: I've thought about this some more. I suppose including quotes from key people to illustrate the name origins is not damaging, but we must be careful. I'll get to work on it tomorrow. —Anonymous DissidentTalk 14:12, 17 July 2009 (UTC)

I've gone ahead and added a paragraph. I think it's long enough. All we need is a citation for Michael Riordan's book (the page number). I couldn't access it on GBooks. —Anonymous DissidentTalk 15:07, 17 July 2009 (UTC)

Excellent. It's short enough that someone reading "Etymology" and thinking, "Why the heck should I care?" just needs to hit "PgDown" a coupla times to get to the next section header, and yet it includes everything the more curious reader will want to know (except the pun on "beauty but not truth", but that'd be way beyond the mark). Good work. --A. di M. – 2009 Great Wikipedia Dramaout 17:49, 17 July 2009 (UTC)

## SM image.

The SM image suddenly doesn't show up anymore. Does anyone else have this problem? If I remove the 300px parameter, it shows up, but otherwise it doesn't.Headbomb {ταλκκοντριβς – WP Physics} 01:20, 18 July 2009 (UTC)

I had noticed that too, but I hadn't noticed about the removing the size param. I guess that's a (hopefully temporary) technical problem and am going to ask the Village Pump about this. --A. di M. – 2009 Great Wikipedia Dramaout 09:27, 18 July 2009 (UTC)

Here are some comments regarding the article's prose:

### Properties

#### Table of Properties

1. The paragraph above the table of properties states that J represents the total angular momentum, but the key below the table states that J represents the spin (physics). As I understand it, these are two distinct concepts.
Yes, but both are equal in this case since J = L + S and L is 0. However that should be clarified.Headbomb {ταλκκοντριβς – WP Physics} 21:48, 6 July 2009 (UTC)
Done. —Anonymous DissidentTalk 07:40, 7 July 2009 (UTC)
Alrighty. I think the parenthetical addition is a good solution, but I think it should be followed by a citation. I can't find any mention of this in either Total angular momentum or Point particle, the two places that a curious reader would search (in absence of a citation). --Cryptic C62 · Talk 15:57, 8 July 2009 (UTC)
I don't think anyone ever bothered to write something like that down. L is orbital angular momentum, and is only defined around another point (such as the center of mass, or another particle). The only logical choice of a reference frame for L would be the quark itself, but then it becomes 0 by definition... It's quite an uncontroversial statement. Headbomb {ταλκκοντριβς – WP Physics} 17:18, 8 July 2009 (UTC)
That being said, if someone has a ref for this, we might as well add it. But otherwise it's still fine.Headbomb {ταλκκοντριβς – WP Physics} 17:19, 8 July 2009 (UTC)
Would http://books.google.com/books?id=sdVrBM2w0OwC&pg=PA25&dq=total+angular+momentum+and+spin+are+same+point+particle&as_brr=3&ei=dH9VSq61BIP0kASMn6CiBw&client=safari suffice as a ref? —Anonymous DissidentTalk 05:30, 9 July 2009 (UTC)
While it's obviously implied by the whole section, I don't see any specific statement that they are the same. Was there a particular passage?Headbomb {ταλκκοντριβς – WP Physics} 14:33, 9 July 2009 (UTC)
http://books.google.com/books?id=YgkfZgFdui8C&pg=PA132&dq=total+angular+momentum+spin+point+particle&as_brr=3&ei=UnxZStjzGIjMlQSIo5yVBw&client=safari states it outright: "the total angular momentum or spin j...". —Anonymous DissidentTalk 06:07, 12 July 2009 (UTC)
Sorry, but I don't see it. That's a reference for nucleon angular momentum to be 1/2, not single elementary particle orbital angular momentum to be 0.Headbomb {ταλκκοντριβς – WP Physics} 14:22, 12 July 2009 (UTC)
I think he means that the phrase "the total angular momentum or spin" implies that the total angular momentum and the spin are the same. True, but I'd prefer a reference making this point more explicitly if there's one. --A. di M. (talk) 20:20, 12 July 2009 (UTC)
Eh, I'm lost. It's difficult to find a specifically pertinent reference for such a minor factoid. Does it really need a reference? It's one of the most uncontroversial things in the article. —Anonymous DissidentTalk 13:36, 13 July 2009 (UTC)
2. "Notation like 104+26
−34
denotes measurement uncertainty." The use of "notation like" is somewhat unencyclopedic. Suggest rewording or simply using asterisks.
Inserted daggers. —Anonymous DissidentTalk 07:37, 7 July 2009 (UTC)

### Interacting quarks

1. "and any attempt to wrench a quark from a hadron will only result in the formation of new hadrons" The use of "wrench" in this context is unencyclopedic and its meaning may not be clear to non-native English speakers.
As a non-native speaker I don't think that really is a problem. You may however be right in that it is slightly unencyclopedic. i've reformaluted the sentence to avoid this. (and avoid another possible ambiguity I noticed). (TimothyRias (talk) 09:27, 13 July 2009 (UTC))
The resulting sentence doesn't really make sense either: "The process of forming new hadrons (known as hadronization) occurs before quarks formed in a high energy collision have a chance to interact." Before they have a chance to interact? Doesn't hadronization imply that the quarks are interacting? --Cryptic C62 · Talk 16:59, 13 July 2009 (UTC)
Fixed. —Anonymous DissidentTalk 07:03, 15 July 2009 (UTC)
Better, but now the problem is here: "hadronization occurs before quarks formed in a high energy collision are able to interact in any other way. The only exception is the top quark, which may decay before it hadronizes" The first sentence discusses quarks interacting. The second sentence discusses one single quark decaying. My intuition is that a single particle decaying does not qualify as an "interaction" and is thus not an exception to the rule as stated, though I could be wrong in that regard. --Cryptic C62 · Talk 14:50, 16 July 2009 (UTC)
True enough. I've changed "interact" to "behave". How does it sound? —Anonymous DissidentTalk 14:57, 16 July 2009 (UTC)
I've reverted. 'Interact' is fine. Normally decay is considered a form of interaction. (particles that do not interact also cannot decay). Specifically, decay is an interaction process in which the initial state contains only one particle. (also note that a quark can interact with other things then quarks.) (TimothyRias (talk) 15:12, 16 July 2009 (UTC))
Okay, so "interact" is fine – but might not "behave" be better anyway? It's broader and does not have the potential for confusion that Cryptic noted. —Anonymous DissidentTalk 15:20, 16 July 2009 (UTC)
To me, behave is so vague it is essentially meaningless. What constitutes behaviour for a particle? Does moving count? The top quark will most certainly cover a little distance before decaying. Interact has a very well defined meaning in this context and I doubt anybody will be really confused by this. (TimothyRias (talk) 21:14, 16 July 2009 (UTC))
I was... --Cryptic C62 · Talk 16:54, 17 July 2009 (UTC)

#### Sea quarks

1. I strongly suggest adding a diagram to illustrate the second paragraph of this section.
I don't have the facilities to create this, and I don't think it should impact on the FAC. I promise to look into it for the future, as I agree it would be nice, but it's out of my hands for now. —Anonymous DissidentTalk 01:38, 14 July 2009 (UTC)

### References

1. I've noticed that there are instances in which a single book is used in multiple footnotes because of the different page numbers used. Instead of writing out the full citation each time, I suggest putting the books into a Bibliography section and using shorthand citations. See GRB 970508 for an example. Converting to this system is rather tedious, and I'd be willing to help if you'd like.
I'd agree if this was really common, but it's not in this article. Only a few books are used more than once or twice. I don't think it's worth the effort to overhaul the ref scheme for this. —Anonymous DissidentTalk 03:23, 21 June 2009 (UTC)
A valid point. I've actually become a big fan of the other system for three other reasons: First, it allows you to list the works alphabetically. Second, it moves the bulk of the reference information out of the prose and into the bottom sections, making it much easier to edit the prose later. Third, by having all of the reference information in one section, it allows editors to make minor changes (such as implementing ndashes) to multiple sources very easily. However, none of these features are required of an FA, so the choice is entirely up to you. It just seems to me that this system generally works better for scientific articles. --Cryptic C62 · Talk 20:10, 21 June 2009 (UTC)

All done! --Cryptic C62 · Talk 18:22, 17 June 2009 (UTC)

1. ^ http://physicsworld.com/cws/article/news/38140
2. ^ a b Section 2.4.3.2 in Burgess, Cliff; Moore, Guy (2007), The Standard Model. A Primer, Cambridge University Press, ISBN 0-521-86036-9
3. ^ C. Amsler et al. (2008). "Review of Particles Physics". Physics Letters B667: 1–1340.
4. ^ Cite error: The named reference Bloom was invoked but never defined (see the help page).
5. ^ Cite error: The named reference Breidenbach was invoked but never defined (see the help page).
6. ^ J.I. Friedman. "The Road to the Nobel Prize". Hue University. Retrieved 2008-09-29.
7. ^ R.P. Feynman (1969). "Very High-Energy Collisions of Hadrons". Physical Review Letters 23 (24): 1415–1417. doi:10.1103/PhysRevLett.23.1415.
8. ^ S. Kretzer et al. (2004). "CTEQ6 Parton Distributions with Heavy Quark Mass Effects". Physical Review D 69 (11): 114005. arXiv:0307022v1.
9. ^ D.J. Griffiths (1987). Introduction to Elementary Particles. John Wiley & Sons. p. 42. ISBN 0-471-60386-4.
10. ^ J. Schombert. "Short History of Particles". University of Oregon. Retrieved 2008-10-05.