# Talk:Down quark

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## Quark composition

Does anyone know if there are any theories to the possibility that the Down Quark is composed of an Up Quark and an electron? I once heard that when a Proton and Electron mix it produces a neutron. So if this is true then if you mix an Up Quark and an electron it must form a down quark...I am not sure though. - BlackWidower

Please see my answer to this question on Talk:Electron. -- SCZenz 22:22, 25 October 2005 (UTC)

## Particle zoo

A good way to understand the particle zoo and its species

If you talk about the particle zoo where more and more discoveries are made each year. wouldn't there infact be a sub particle zoo within each particle of the so-called particle zoo. In other words wouldn't the structure of each particle be composed of a group of smaller particles which would be composed of a sub-group of smaller particles and so on to infinity and beyond? Can a human being visualize what an infinitesimally small particle could be like or not. In other words do we really really really know what it's all about; or just suppose. Carl Kravis

The term particle zoo refers to all the particles (and thus subparticles). There's only one zoo, although you are free to divide it how you like. The current way of describing the zoo is found in the image I gave. There are six quarks, six leptons and these are the elementary fermion (aka there is nothing "smaller"). Combine quarks in three and you have baryons. Combine quarks in quark-antiquark pairs and you have mesons. Combine baryons together and you have nucleis (exotic or not). Other combinations (the "species" of the particle zoo) have different names. Headbomb {ταλκκοντριβς – WP Physics} 15:42, 26 November 2009 (UTC)

## New Reference

if some one can get a hold of C. T. H. Davies, C. McNeile, K. Y. Wong, E. Follana, R. Horgan, K. Hornbostel, G. P. Lepage, J. Shigemitsu, H. Trottier. Precise Charm to Strange Mass Ratio and Light Quark Masses from Full Lattice QCD. Physical Review Letters, 2010; 104 (13): 132003 DOI: 10.1103/PhysRevLett.104.132003 it is purported to have refined values for both qu and qd Abyssoft (talk) 04:45, 24 May 2010 (UTC)

Mass of the Common Quark Finally Nailed Down by Adrian Cho on April 2, 2010 5:56 PM http://news.sciencemag.org/sciencenow/2010/04/mass-of-the-common-quark-finally.html which uses the above as it's source lists 4.79 +/- 0.16 MeV for d and 2.01 +/- 0.14 MeV for u Abyssoft (talk) 18:19, 20 June 2010 (UTC)

Before adopting the new value, I'd wait until the PDG adopts them or not for the 2010 review. The PDG makes a thorough independent review of all results on the subject, on basis of which they decide on a best average value. Results from a single method, may have systematic error not advertised in the relevant article. Nonetheless, I expect that the lattice QCD results for the light quark masses will lead to an adjustment of the PDG values. TimothyRias (talk) 06:29, 21 June 2010 (UTC)

2010 PDG values have been posted, http://pdg.lbl.gov/2010/2010/tables/rpp2010-sum-quarks.pdf
I will wait a few more days before making the changes to mass. If there are no objections I'll apply the changes on Friday August 06, 2010 sometime between 0700 and 2200 UTC. Abyssoft (talk) 20:26, 2 August 2010 (UTC)

2011/2012 values posted 5.0+0.7
−0.9
MeV/c2
if no objections I'll apply the changes next friday. 74.202.23.198 (talk) 00:00, 29 February 2012 (UTC) [Abyssoft not signed in]