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Lepton

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This peer review discussion has been closed.
I've listed this article for peer review because…

  • I'm not quite sure where to go from here.
  • Get feedback on what's already there.
  • And maybe even get other people to add content and to clarify what I can't.

Thanks, Headbomb {ταλκκοντριβς – WP Physics} 12:11, 17 November 2008 (UTC)[reply]

Resolved stuff
  • At present the article doesn't seem all that well developed and I think it needs a copy-edit. I feel it should be addressed more at a lay reader who is unfamiliar with particle physics, so more explanation is needed in general.—RJH (talk)
  • Well, I'm mostly trying to get the physics right and to be comprehensive in the coverage for the moment. I'm not denying that in the present state, a lay reader won't grasp everything, but this I don't think there's one subject in particle physics that a lay reader will feel comfortable in claiming that they "get it". If you have ideas about how to write things more clearly, don't be shy in sharing them.Headbomb {ταλκκοντριβς – WP Physics}
  • Perhaps the article could start off with a verbal discussion of the particles and how there were discovered? I think some history can go a long way to putting things in perspective and helping people gain a better understanding.—RJH (talk)
  • In the mass section, is Q in the Koide formula the charge from the prior section? The units don't seem to match.—RJH (talk)
  • In the 'Lepton universality' section, could you explain what 'flavor-independent' means? K and GF are also unexplained, so why not just say proportional to the mass? The 'branching ratios' needs to be clarified. Is the Γ the same as the gamma function? In the last half, does the B mean the beta function? If so, there should be two parameters. Otherwise, B is unexplained. In the first B formula, should the l− be l−?—RJH (talk)


  • No offense, but the Leptonic numbers section seems somewhat meandering and a little disorganized. The term 'weak isospin doublet' is introduced without explanation. (In this case, just providing a link doesn't seem sufficient to me. An explanation would provide clarity.) Conservation of leptonic numbers is introduced, immediately followed by a violation, thereafter with the stronger version, then back to why conservation it is relevant in most cases. I think it should be written: concept introduction, followed by the majority case, then the exceptions with an explanation.—RJH (talk)
  • I reordered things according to that scheme, it's indeed a better way to say things. As far as the weak isospin doublet goes, I'm not quite sure how to convey that in a less technical way.Headbomb {ταλκκοντριβς – WP Physics}
  • You might mention the possibility of fourth generation leptons.[1]—RJH (talk)

Here are some comments that I hope are of some use:

  • The individual sections under Properties seem too short. See, for example, paragraph 1, Wikipedia:Layout#Headings_and_sections. With regard to section titles, see bullet 5 of Wikipedia:HEAD#Section_headings. The short sections should either be expanded or merged. It might be interesting to have some information about how the values in the Properties section are determined.—RJH (talk)
  • In the mass section, something could be said about how physicists don't yet understand how the different particles are at the masses they have. (Perhaps a mention of the Higgs boson?) You could also explain why they suspect neutrinos may have mass. I'm not sure what to suggest about spin.—RJH (talk)
  • I'm, no expert, but from what I gather, the higgs is the explanation of why the W and Z bosons have mass, while the photon doesn't. I've never seen the higgs generalized as an explanation as to why all massives particles have mass, but then again, I never looked for that generalization, and again, I'm no expert. Neutrino oscillations are the reason why they suspect neutrinos have mass, and it's mentionned. But I'll try to expand that section.Headbomb {ταλκκοντριβς – WP Physics}
  • Indeed, in the standard model the Higgs mechanism gives mass to all massive elementary particles including leptons. (Note, however that it is not the source of all mass, as is often claimed in popular media. In fact, almost all mass in nature comes from QCD binding energy in hadrons.) (TimothyRias (talk) 11:15, 25 November 2008 (UTC))[reply]
  • The term 'weak isospin projection' should be clarified.—RJH (talk)
  • I'd like to see some information relating leptons to everyday experience, as well as physical phenomenon. For example, lepton decay from cosmic rays, the role of lepton formation during the big bang, and the possible contribution to dark matter. I'd also like to see some discussion of how they are detected.—RJH (talk)

Comments by TR

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  • The section "Spin, helicity, and parity" claims that the standard model contains only left handed leptons. This is wrong. The SM contains both left and right-handed charged leptons. It only doesn't contain right handed neutrinos.
  • On a related note, the same section talks about the helicity of leptons as a well defined quantity, while this is only well defined for massless particles. For massive particles, their helicity is state and observer dependent!there are two ways out of this problem:
    1. Refer to the more abstract chirality of the particle.
    2. Use that on a formal level all leptons are massless in the SM.
  • Related to the last remark. The article should mention that leptons in the SM acquire their mass for the vacuum expectation value of the higgs field.
  • Related to that it should mention that (because their are no right handed neutrinos) the lepton mass matrix does not contain off diagonal terms. (i.e. there are no transitions between leptons of different generations.) (This obviously should not be mentioned in these technical terms)
  • The table of lepton properties lists mass limits for each lepton. This doesn't quite make sense. First of all, the mass eigenstates of the neutrinos are quite probably very different from the flavor eigenstates, this what is causing neutrino oscilations. This means that an electron neutrino will not have a well defined mass. Current data consists of estimates for the total sum of masses en parameters measuring relative masses of the neutrinos. Interpretation of this data has an hierarchy ambiguity (it is unknown if there are two light and one heavy (relatively speaking) neutrinos or that there are one light and two heavy neutrinos.

I'll have a look to see if I can sort out some of these problems.(TimothyRias (talk) 13:47, 25 November 2008 (UTC))[reply]

Yeah, good idea, since this is completely beyond me.Headbomb {ταλκκοντριβς – WP Physics} 22:16, 25 November 2008 (UTC)[reply]
I have attempted to add in some of the missing info. I do however fear that the text might be a bit jargony at the moment. So it might be good to have some feedback from people that don't speak QFT for a living. (TimothyRias (talk) 10:46, 28 November 2008 (UTC))[reply]
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