Talk:Lepton

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Charge

The article states that "All known leptons have a negative or neutral charge." That statement is meaningless, as there is no fundamental reason one is a particle and the other is an antiparticle; by convention for leptons the particle is the negative one

--anon

The article no longer states this. Careful though: leptons can have positive, negative or neutral charge.

RobPlatt 11:07, 25 Oct 2004 (UTC)

IN cosmicastronomy.com IT IS WRITTEN THAT LEPTONS ARE RESPONSIBLE FOR VIRTUAL STEREO

Tau/Tauon?

Why is the Tau particle being called a Tauon throughout Wikipedia?

It's not, any more. --DannyWilde 01:57, 29 November 2005 (UTC)[reply]

Lepton numbers

This page lacks any info on lepton numbers. I'm not sure I'm qualified to add it without making mistakes :) But here's a summary:

-There are three lepton numbers: electron, muon, and tau. You can see a sumary here: http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.html#c7 That info should be probably be included in the articles table.

-Lepton numbers are conserved during decays. Apparantly this is only approximately true and there are circumstance where the conservation breaks, but I don't know much about that. :)

Good idea. Added a sentence. -- ALoan (Talk) 10:39, 10 Feb 2005 (UTC)

Lepton/Lepta?

Perhaps the plural form of Lepton should be written as Lepta (from the Greek Λεπτά).

This is never used in the particle physics communityJameskeates 12:32, 17 August 2006 (UTC)[reply]

Etymology

On the origin of the term "lepton" (from the OED, citing L. Rosenfeld Nucl. Forces p. xvii):

Following a suggestion of Prof. C. Møller, I adopt — as a pendant to "nucleon" — the denomination "lepton" (from λεπτόσ, small, thin, delicate) to denote a particle of small mass.

The Weak Doublet

There is something I don't understand in this article: what keeps the electron and the electron neutrino together? and the same question for the muon and tau and their neutrinos. - Henry Likos 22.42 09 August 2006

This is related to lepton number conservation mentioned above in the talk page. An electron and its neutrino have the same lepton number and this is conserved in all known interactions and the same for the muon and tau. A muon decaying to an electron for example must give off a muon neutrino so the muon number remains constant (as well as an electron anti-neutrino to balance the electron produced).Jameskeates 12:35, 17 August 2006 (UTC)[reply]

Neutrino Helicity

The article states that "only one helicity is observed for the neutrinos (all the neutrinos are left-handed, and all the antineutrinos are right-handed)." However, the article about neutrinos says that this is not true, since neutrinos do have a small mass, even if all neutrinos actually observed were left-handed. Maybe saying that "ALL the neutrinos ARE left-handed" is too strong a statement. Also, I believe that the sentence "The charged leptons have two possible SPIN states, while only one HELICITY is observed for the neutrinos" is confusing since it opposes two different concepts (spin and helicity) as if it were the same thing. I don't dare to fix all that (I'm still a physics undergrad, and not even a particle-oriented one), but maybe some of you could do it. - Arnoques 16.46 20 May 2007

bigger lepton

Feynman mentions observations of a larger lepton, c. 40,000 MeV he says, in a subscript to one of his books. Has this panned out? —Preceding unsigned comment added by 66.44.102.150 (talk) 03:52, 10 September 2007 (UTC)[reply]

no, it hasn't - in fact, there is experimental evidence from CERN in switzerland that the 3 known families of lepton (e,µ,tau) are all there is http://keyhole.web.cern.ch/keyhole/projects/number_of_families.html

cheers, -K —Preceding unsigned comment added by 139.18.249.104 (talk) 17:55, 30 January 2009 (UTC)[reply]

Table of leptons unclear

Below the table of leptons is some explanatory text that doesn't seem to make sense to me: "However there have been measured (indirectly based on the oscillation periods) the differences of the mass squares between the neutrinos, which have been estimated ..." - could somebody who knows what this is supposed to mean reword it?

Generally speaking: the neutrino of one falvour oscillates into other flavours. The parameters of these oscillations depends on value of (m1^2 - m2^2). The parameters of oscillations are known - that's why values of these differences are also known.

How about I change that line into "However, indirect measurements of the mass differences between the neutrinos have been made based on their oscillation periods. These oscillation periods are directly dependent on the differences of their mass squares."? SkyLined (talk) 17:23, 29 February 2008 (UTC)[reply]

It may be changed according to your suggestion.

May I suggest that you sign your messages so I know who is giving me the OK to make this change? You could be my kid-sister for all I know... SkyLined (talk) 12:22, 4 March 2008 (UTC)[reply]

Ethymology

Just above the ethymology, I found this: "The names "mu" and "tau" seem to have been selected due to their places in the Greek alphabet; mu is seven letters after epsilon (electron), whereas tau is seven letters after mu." - should that not be in the ethymogoly section? Also, this seems like an inverified assumption by an unknown person and there's no reference or source. Does anybody know what the real story is? SkyLined (talk) 20:42, 16 February 2008 (UTC)[reply]

Anomalous Magnetic Moment

Why doesn't the table of propreties of leptons include their anomalous magnetic moment? If nobody objects, I'm going to include it. Dauto (talk) 05:52, 24 February 2009 (UTC)[reply]

Sure go ahead. I suppose these anomalous ratios aren't known for quarks? Also could you review the mass of the neutrinos in the table. I'm not too sure about them.Headbomb {^ταλκ_{κοντριβς} – WP Physics} 10:52, 24 February 2009 (UTC)[reply]

Fixed lepton isodoublets figure

The lepton isodoublets figure had the leptons with the wrong isospin assignments -- every convention I've ever seen has the electric charge of the upper member of the isodoublet one unit larger than that of the lower member (in accordance with Q = T3 + Y). Apologies to Headbomb for replacing your figure. HEL (talk) 03:43, 1 April 2010 (UTC)[reply]

Incorrect diagrams

- The diagrams in 'Electromagnetic interaction' and 'Weak interaction' , showing two electrons distructing to create a photon (on the 1'st) and a Z0 (on the 2'nd) - are incorrect.

In both cases - these should be an Electron (e-) and a Positron (e+) - not as was drawn.

(94.159.221.248 (talk) 10:28, 11 October 2010 (UTC))[reply]

No. Look at the arrows. Electron in, electron out. --Michael C. Price ^talk 10:30, 11 October 2010 (UTC)[reply]

Well, actually the arrows on the lepton lines don't say much in this respect as they just indicate the flow of lepton number. Even so, the diagrams are correct if you read then as going from left-to-right. (Also, note that they are interaction vertices not full diagrams, as such it contains no assumptions about particles being on-shell.TimothyRias (talk) 10:36, 11 October 2010 (UTC)[reply]

The arrows do not all represent lepton number flow. But they are all correct, anyway. --Michael C. Price ^talk 10:46, 11 October 2010 (UTC)[reply]

- Forgive me if I'm wrong, but in the main picture for the article ("Leptons are involved in several processes such as beta decay.") shouldn't the arrow for the anti-neutrino point in the opposite direction? Currently it appears to be travelling backwards in time. Rbelsham 13:00, 29 November 2012 (GMT) — Preceding unsigned comment added by Rbelsham (talk • contribs)

Most common lepton?

Introduction says "Thus electrons are stable and the most common of leptons in the universe..."

Isn't this incorrect and neutrinos being the most common lepton by far?

IlkkaP (talk) 17:04, 5 December 2010 (UTC)[reply]

I think so, by several orders of magnitude, if there exists a cosmic neutrino background. The sentence obviously refers to electrons being the most common charged lepton. I've changed it to say so explicitly.TimothyRias (talk) 18:17, 5 December 2010 (UTC)[reply]

Unless the cosmic neutrino background contains an approximately equal number of antineutrinos. Does it? I tried looking it up at Timeline of the Big Bang, but couldn't see any mention of the neutrino dissociation event. --cheers, Michael C. Price ^talk 12:42, 6 December 2010 (UTC)[reply]

See [1] page 81 and forward, for a discussion of neutrino decoupling and the neutrino number density.TimothyRias (talk) 12:56, 6 December 2010 (UTC)[reply]

First sentence is wrong: it fails to deliver any real concise information

The first sentence in the article is completely imprecise and wrong, since it is bothmisleading and fails to distinguish leptons from other elementary particles like quarks:

“A lepton is an elementary particle and a fundamental constituent of matter.”

Leptons do include neutrinos, which are not ordinary “matter”, but leptons don't include quarks that undergo strong interactions and are present in the nucleons of every atom! I suggest that the first sentence should be replaced with:

“A lepton is a elementary particle which does not undergo strong interactions, but is subject to the Pauli exclusion principle (apart from quarks and bosons, all known particles in the universe are leptons).”

NC Photocopier (talk) 15:47, 9 November 2012 (UTC)[reply]

I have changed the first sentence to read: "A lepton is an elementary particle of matter which does not undergo strong interactions, but is subject to the Pauli exclusion principle (apart from quarks and bosons, all known particles in the universe are leptons)." This tells readers what a lepton is. The original sentence came from an encyclopedia which obfuscated.

(It's a bit like saying that a Dutchman is multicellular lifeform: this is not only a failure to distinguish between the features of different people, but it is also wrong because readers of the first sentence will come away with the idea that any multicellular organism can be described as a Dutchman. It's a very ambiguous and misleading way to describe something. What you want to know is what is specifically different about the thing you refer to, as opposed to the characteristics of other objects in the same category.)

Photocopier (talk) 15:57, 9 November 2012 (UTC)[reply]

secondary plasma field

observation ,discovery, when a secondary plasma field is generated through the interaction of particular metals, ie stainless steel mesh., and the primary plasma field, the interaction with that secondary field and steel wool ie.steel wool wrapped around secondary glass .,,then bringing a piece of stainless steel to it, causes the secondary field to increase and lite the wool on fire . a simple plasma ball with various gasses, and a mercury vapour high frequency bulb for secondary interaction. interesting to say the least. Ronald sykes.50.93.20.150 (talk) 05:37, 13 July 2013 (UTC)[reply]

Mass ratios

Can someone please find a place to add these formulas for lepton mass ratios.

Leptons	Formula	Experimental value
Muon / electron	${\frac {m_{\mu }}{m_{e}}}=\left({\frac {\alpha ^{-2}}{2\pi }}\right)^{\frac {2}{3}}{\frac {(1+2\pi {\frac {\alpha ^{2}}{2}})}{(1+{\frac {\alpha }{2}})}}=206.76828$	(206.72827)
Tau / muon	${\frac {m_{\tau }}{m_{\mu }}}=\left({\frac {\alpha ^{-1}}{2}}\right)^{\frac {2}{3}}{\frac {(1+{\frac {\alpha }{2}})}{(1-4\pi \alpha ^{2})}}=16.817$	(16.817)
Tau / electron	${\frac {m_{\tau }}{m_{e}}}=\left({\frac {\alpha ^{-3}}{4\pi }}\right)^{\frac {2}{3}}{\frac {(1+2\pi {\frac {\alpha ^{2}}{2}})}{(1-4\pi \alpha ^{2})}}=3477.2$	(3477.3)

KnowMoreThanU (talk) 15:31, 14 December 2014 (UTC)[reply]

What is the source? Something like this looks like numerology – and there are many examples in physics of formulae like this being presented that match experimental figures extraordinarily well, but that have no basis beyond that. This encyclopaedia article is not the place for such examples. —Quondum 18:24, 14 December 2014 (UTC)[reply]

Inconvenient for the Standard Model that these exist I grant you but, no, not numerology. KnowMoreThanU (talk) 21:59, 14 December 2014 (UTC)[reply]

With an answer like that, you can't expect anyone to take notice. —Quondum 22:11, 14 December 2014 (UTC)[reply]

I deleted this section. It is purely the speculative work of one person. Regardless of its possible veracity, (which has not been shown), it does not belong here, as it is not generally accepted in the physics community. LordKitchenersValet (talk) 23:15, 26 July 2022 (UTC)[reply]

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Implications of violation of lepton universality

The observed violation of lepton universality (last paragraph of section Universality) has, as of yet, not reached the level of significance usually required to claim a discovery (5 sigma deviation from expectation based on previously accepted model), so there is no reason to get all worked-up. Yet, if these observations keep holding up in further experiments, the implications are tremendous. The paper by Ciezarek et al., referenced in our article, ends with, "A confirmation of new-physics contributions in these decays would shake the foundations of our understanding of matter and trigger an intense programme of experimental and theoretical research." "New physics" refers to physics beyond the Standard Model, involving new particles and interactions. Is it worth pointing this out in the article? --Lambiam 19:34, 20 July 2017 (UTC)[reply]

I wiki-linked to new physics. I don't think it's worth spelling it out here: people can just click through to the main article. If any detail is to be added, it should be more about what the anomalies are (i.e. P5´, R(K), R(K*), R(D), R(D*)) or at least cite the experimental papers. It might be worth mentioning some of the more common proposals for new physics, such as Z´s and leptoquarks. — dukwon (talk) (contribs) 20:26, 20 July 2017 (UTC)[reply]

And what about the anti-quarks?

Why are the anti-leptons mentioned in the introduction and not the anti-quarks? — Preceding unsigned comment added by Koitus~nlwiki (talk • contribs) 23:03, 3 March 2020 (UTC)[reply]

Tgf verified L vioaltion PASSED

What could this be? 2A00:20:C001:E5D9:588A:CCCF:E982:75E (talk) 10:41, 19 November 2021 (UTC)[reply]

Who coined the term lepton?

The section Etymology ascribes the coinage to Rosenfeld, said to have "first used" it in 1948. However, Abraham Pais wrote in his book A Tale of Two Continents, referring to a paper he supposedly co-wrote with Christian Møller presented at the International Conference on Fundamental Particles and Low Temperatures held at the Cavendish Laboratory, Cambridge, UK, on 22–27 July 1946,

Nevertheless our paper, also published in the Cambridge conference Proceedings, contains a contribution that will last forever. We felt it necessary to introduce a collective name for all “light” particles, those in the electron-neutrino family. After consultation with a learned acquaintance, we settled on the name lepton (from the Greek λεπτός = small). As a result, our paper contains one footnote: “For the ‘light’ particles we propose the name ‘leptons.’”^[2]

The Conference Proceedings appeared in print in two volumes in 1947, published by Taylor & Francis under the title Report of an International Conference on Fundamental Particles and Low Temperatures. The article in question appeared in Volume 1, starting on page 184, and the quoted addition appears indeed as a footnote on page 184.^[3] Confusingly, however, the paper in question, titled "The possible existence of mass spectra of fundamental particles" and occupying a single page, page 184, lists only C. Møller as author.^[4] In any case, this appeared earlier than Rosenfeld's book. --Lambiam 20:51, 21 January 2023 (UTC)[reply]

"Electron-like lepton" vs "electron"

In the first paragraph it it says "Two main classes of leptons exist: leptons (also known as the electron-like leptons or muons), and neutral leptons". Then it says "The best known of all leptons is the electron."

This makes me (an uninformed reader) wonder if "electron-like leptons" are the same thing as "electrons" or if the electron is not in one of the two main classes of leptons. Yellowpelican (talk) 16:22, 21 September 2023 (UTC)[reply]