Talk:Standard Model

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Diagram of Standard Model particles and interactions[edit]

A recent edit [1] removed the following image (below). Is this image worth restoring? Isambard Kingdom (talk) 19:23, 12 July 2015 (UTC)

Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).
It is an extremely busy diagram, and definitely should not be in the lead, where it was. The simpler diagram that is still there (File:Standard Model of Elementary_Particles.svg) is more interpretable. Without formal training I cannot even comment on the value of the removed diagram. Another diagram (File:Standard Model.svg) I find similarly inscrutable, and its value here could also be debated. —Quondum 03:35, 13 July 2015 (UTC)
The one here looks clear and correct to me (not 100% about the "left-handed" parts for the spin-1/2 particles). M∧Ŝc2ħεИτlk 10:54, 13 July 2015 (UTC)
I'm the one who removed it. It is too busy, like User:Quondum said. Also, the image is low quality Buckbill10 (talk) 13:51, 13 July 2015 (UTC)
I agree with Buckbill and Quondum. The diagram is too busy. I also find File:Standard Model.svg inscrutable. It's extremely hard to see what it's even about and I'm not even sure it's technically right. Headbomb {talk / contribs / physics / books} 14:01, 13 July 2015 (UTC)
  • For some reason, the JPG file failed to render, and I kinda figured that it was the servers that failed to create the thumbnails. So I downloaded the image, coverted it into a PNG file, uploaded it, and marked the .jpg image as superseded. Because PNG is a lossless format, thumbnails of PNG files won't appear distorted. -Mardus /talk 05:03, 24 December 2015 (UTC)

Nature on standard model[edit]

"Yet its failure to account for phenomena such as gravity and dark matter leads many physicists to think that it is merely an approximation of another description beneath." http://www.nature.com/news/lhc-signal-hints-at-cracks-in-physics-standard-model-1.18307

should this be put into the article? — Preceding unsigned comment added by Vilagarcia (talkcontribs) 15:53, 10 September 2015 (UTC)

Total particle count[edit]

Elementary Particles
Types Generations Antiparticle Colors Total
Quarks 2 3 Pair 3 36
Leptons Pair None 12
Gluons 1 1 Own 8 8
Photon Own None 1
Z Boson Own 1
W Boson Pair 2
Higgs Own 1
Total number of (known) elementary particles: 61

I removed the "total particle count" section. The table that was in it is preserved on the right in case someone wants to try to derive something useful from it, but right now I think it makes little sense. It certainly isn't true that 61 has any special status as the "correct" number of Standard Model particles. To get this number, you have to treat particles related by some exact symmetries (gauge symmetries and CPT) as distinct, and treat particles related by other exact symmetries (continuous Poincaré) as equivalent.

Here are some ways of counting particles (in the SM with neutrino mass) that seem more principled:

  • If you count degrees of freedom of the field at a point, I think the best answer is 2 · 28 + 96 = 152 (see Luboš Motl's answer here, though he points out that you can argue for other numbers).
  • [Original research; I can't find a source for this:] If you count fundamental (pre-EWSB) fields that are not equivalent under any fundamental symmetry, you get H + G + W + B + 3 · (L + ν + e + Q + u + d) = 22.
  • [Original research; I can't find a source for this:] If you count post-EWSB particles that are not equivalent under any post-EWSB symmetry (essentially counting masses, except that gluons and photons are distinct), you get H + G + W + Z + γ + 3 · (ν + ν' + e + u + d) = 20 (assuming the Majorana coupling is nonzero; 17 if it's zero).

I don't really feel that it's useful to have any of these numbers in the article. They are the sort of thing that you memorize and regurgitate when playing Trivial Pursuit, not the sort of thing that is likely to provide any insight into particle physics. -- BenRG (talk) 03:44, 15 June 2016 (UTC)

Did SM really predict the W and Z boson masses ?[edit]

History section says "The W± and Z0 bosons were discovered experimentally in 1981; and their masses were found to be as the Standard Model predicted.[citation needed]" but W_and_Z_bosons doesnt seem to confirm the prediction of boson masses. - ... (Standard_Model#Tests_and_predictions mentions the prediction but with no source.) - Rod57 (talk) 20:52, 2 September 2016 (UTC)

June 2013 comment above also queries this (says only the mass ratio was predicted) so the unsourced material was moved to that comment. - Rod57 (talk) 10:57, 6 September 2016 (UTC)

When was the Standard Model first defined and named as such[edit]

When was the Standard Model first defined and named as such ? [2] says "1974: In a summary talk for a conference, John Iliopoulos presents, for the first time in a single report, the view of physics now called the Standard Model. ... " Should we mention this in history ? - Rod57 (talk) 20:37, 2 September 2016 (UTC)

SM does not predict the number of leptons or quarks.[edit]

According to [3] "1976 : The tau lepton is discovered by Martin Perl and collaborators at SLAC. Since this lepton is the first recorded particle of the third generation, it is completely unexpected." - worth noting if verifiable with RS ? - Rod57 (talk) 20:46, 2 September 2016 (UTC)

The third generation was expected after CP violation was observed. "The Standard Model" means the model with three generations. Just 2 or more than 3 wouldn't be the SM. It is a bit tricky to talk about prediction if it is a matter of naming conventions. It is easy to extend the SM to more generations but then it is not the SM any more. --mfb (talk) 13:32, 13 June 2017 (UTC)

Tests and predictions[edit]

You would expect this section to summarise the current status of notable deviations from the Standard Model. Currently there are 2 poor attempts at summarising press releases about minor results without even mentioning their wider context. For example, the R(D*) anomaly is one of several anomalies in B decays, and BaBar isn't the only experiment to measure it. --Dukwon (talk) 14:59, 8 November 2016 (UTC)

Clearer image from CERN[edit]

I find that the current image at the top of the article could more clearly illustrate the connections between the fermions and bosons.

CERN standard model It has a more nuanced use of colour and negative space. Furthermore it more clearly associates the photon with the electron, the quarks with the gluons, and the mechanism producing neutrons with the neutrons.

In the current image these interactions are shown but they are a strain to discern for two reasons: the fact that they are forced into a single row and because of the lines being forced into the narrow space between the boxes.

The CERN charter states:

ARTICLE II : Purposes 1. The Organization shall provide for collaboration among European States in nuclear research of a pure scientific and fundamental character, and in research essentially related thereto. The Organization shall have no concern with work for military requirements and the results of its experimental and theoretical work shall be published or otherwise made generally available.

This seems to suggest that this material may be public domain. If so, we could use it directly. If not I would be happy to reproduce a similar image.

Craig Pemberton (talk) 03:34, 22 February 2017 (UTC)

Looks like a reasonable improvement in clarity, particularly in clearly presenting the underlying interactions (strong, weak, electromagnetic) that work with each elementary particle. Does it make sense to show the graviton though? The old Standard Model image used on the page did not show it, due to its hypothetical, yet-to-be-proven nature. DarthCaboose (talk) 07:50, 22 February 2017 (UTC)
That diagram seems to imply the photon and the gluon couple to the weak force. It shows that the quarks carry colour, but doesn't mention that gluons also carry colour. It also has the same problem with neutrino masses as the current diagram (quoting mass limits on the flavour eigenstates doesn't make sense). The spin and electric charge notation is inconsistent: there are zeroes on the neutrinos, but other zeroes (on the Higgs and gauge bosons) are omitted. There is no graviton in the Standard Model, so it shouldn't appear on a diagram representing the field content of the SM. Dukwon (talk) 09:21, 22 February 2017 (UTC)
There is a lot of CERN material that is not public domain, and the CERN charter is not sufficient to determine the status of that image. We can ask CERN. If we can use and modify it, I suggest the following changes to include Dukwon's points:
  • Remove the Graviton
  • Put the Higgs to the right of the Z. Change its mass to 125 GeV. Add its spin of 0. Extend the strong interaction box to the right, outside the weak interaction, and put the gluon in the new area that covers only the strong interaction.
  • The color of the gluon is indicated by the background color of the overall gluon box (in the same way the photon background matches the charge corner color), but maybe there is a better way to show this.
  • Keep the photon where it is. It couples to the W boson, that is electroweak enough to stay in the box I think. You could also call it electromagnetic, then the W has to move into the electromagnetic box. I think the current arrangement is better.
  • Make the 0 charge labels consistent, no opinion on the direction.
  • Make a conservative "<1 eV" for all three neutrinos. Yes, the flavor eigenstates are not mass eigenstates, but we know all three mass eigenstates are below 1 eV.
--mfb (talk) 15:55, 22 February 2017 (UTC)

(gravity is not an unsolved question, changed word order)[edit]

There is a recent edit with the edit summary: (gravity is not an unsolved question, changed word order). As far as I know, a theory of gravity consistent with both quantum mechanics and special relativity has not been solved. I won't revert, but someone might want to look into this. Gah4 (talk) 03:29, 9 April 2017 (UTC)

"Gravity?" is not an unsolved question - it is not even a meaningful question. "How to include gravity into QFT?" is one, but that is not the phrasing I changed. Gravity is a phenomenon not described by the SM, so I put the example of gravity next to the things not described by the SM. --mfb (talk) 13:09, 9 April 2017 (UTC)

Historical background[edit]

The historical background section is short. It does not give any context to the theory, and now the article reads as if the theory emerged for no reason in 1961. I tried to add some information on the prior development of thermodynamics and the discovery of the Big Bang theory, and how the standard model because of this has a different scope than classical mechanics. I directly quoted Lemaître's prediction of early universe high-energy particles and the context of this prediction. I also asked for a better explanation of the "theoretically self-consistent" claim. The idea of mathematical self-consistency was so harshly criticised by Kurt Gödel that I think a citation or a comment is mandated by who reverted my addition of a tag. Alternatively, we do not move into this metaphysical difficulty, but in that case the "Historical background" part will need to be renamed to "Background". Narssarssuaq (talk) 00:28, 5 November 2017 (UTC)

The Standard Model is the Standard Model of particle physics. Particle physics didn't exist at the time you want to add, and it was not the result of the events you want to add either. It was the result of lab and accelerator experiments and the study of cosmic rays. This has nothing to do with the big bang, thermodynamics, classical mechanics, or general relativity. Add these things to the cosmological standard model if you want (but leave out the classical mechanics stuff and thermodynamics please, they don't belong there either). --mfb (talk) 00:45, 5 November 2017 (UTC)
Thank you for your reply. "It was the result of lab and accelerator experiments and the study of cosmic rays" is an interesting way to put it. So they randomly figured out that they should do some random experiments based on random hypotheses and random observations and randomly came across a theory of almost everything? Not really, there was a historical and theoretical context to these observations and experiments, which in the dictionary genre may be of some relevance. I'll look more into the physics and see if I can contribute with something better than what I came up with, but it won't be now. Again, thanks for your valuable feedback. Narssarssuaq (talk) 01:13, 5 November 2017 (UTC)
No one said anything about randomness, although many discoveries were unexpected. What was driving particle physics was based on lab experiments, not based on cosmology. --mfb (talk) 01:33, 5 November 2017 (UTC)
OK, so it rests on no fundamental assumptions. That sounds like a perfect environment for circular reasoning, but I will not investigate this further now. Narssarssuaq (talk) 03:13, 5 November 2017 (UTC)
The fundamental assumption is that we can describe the world with physical laws. The rest is driven by experimental results. --mfb (talk) 02:15, 6 November 2017 (UTC)

hatnote[edit]

  I just made a mess of the initial hatnote, in correcting the way it had been confounding between IIRC the topic and the article. I can't recall the proper format for my repl't hatnote, nor look it up on this iPad 2, nor at the moment wake up the quasi-real computer, so a colleague's correction of my blunder is a consumation devoutly to be wished.
--Jerzyt 19:55, 1 December 2017 (UTC)