Questions tagged [leptons]

Leptons are elementary fermions that do not experience the strong interaction: electrons, muons, tauons, and neutrinos.

Filter by
Sorted by
Tagged with
3
votes
2answers
384 views

Decay of electron? [closed]

Have we detected any decays of electrons to an electron neutrino and $W$-boson in Fermilab or in CERN? Are neutrinos the only possible stable leptons inside an electroweak field?
0
votes
0answers
21 views

Ratio of cross-sections for muon pair production with photons from electron-positron pair

What is the ratio $\sigma(e^+e^- \rightarrow \mu^+\mu^-) : \sigma(e^+e^- \rightarrow \mu^+\mu^-\gamma) : \sigma(e^+e^- \rightarrow \mu^+\mu^-\gamma\gamma)$? My thoughts so far are that, due to $C$ ...
0
votes
0answers
55 views

Next-to-Leading Order (NLO) di-boson production cross-section at the Future Circular Collider (FCC-ee)

is there anyone who knows a reference for a paper estimating the Next-to-Leading Order (NLO) cross-section prediction for the $$e^+e^-\to W^+W^-$$ inclusive process? The centre-of-mass energy I'm ...
7
votes
2answers
1k views

What are the advantages of an electron-electron collider vs. An elec./positron one? Has one ever been built?

The current LHC is a proton-proton collider (instead of proton-antiproton) for reasons I have read about elsewhere. Why has there never been an electron-electron collider? Also, I am reading now ...
0
votes
1answer
51 views

Does lepton family number always have to be conserved?

So for example, is the following reaction possible?: $$ \mu^- \rightarrow e^- + \gamma $$ In the textbook it says this is possible, as it conserves the lepton number. However, the lepton flavour is ...
0
votes
3answers
85 views

What tells quarks, electrons, etc. to move the way they do? [closed]

I've recently had some interest piqued in physics, and this is one of the many questions that I have continuously found myself trying to figure out; what tells/told particles to go in the direction ...
2
votes
1answer
72 views

Is there a lepton anti-lepton asymmetry?

I dont know is this a stupid question or not but I wanted to ask We all familiar with the fact that there must be some more baryons w.r.t antibaryons. Since we do not observe any anti-baryons we ...
14
votes
2answers
241 views

Is there a reason, other than mass hierarchy, that we associate each quark generation with a particular lepton generation?

The Standard Model contains three generations of quarks, and three generations of leptons. We generally pair off these generations into the "light" generation ($e, \nu_e, u, d$), the "medium" ...
2
votes
1answer
80 views

Why is there no 4th generation of leptons in the standard model?

Why is there no 4th generation of leptons in the standard model? Is there any explanation, as to why they don't exist? More precisely, is there any theoretical restriction to having only 3 generations ...
2
votes
1answer
69 views

If a particle and its antiparticle annihilate upon contact, how do they form bound states?

I am reading about some old discoveries in particle physics and early collider experiments from Perkin's Introduction to High Energy Physics. However, I didn't get the answers to all my questions. If ...
0
votes
1answer
76 views

How to find theoretically the decay width of a particle-decay process? [closed]

The problem is devided into two parts: First part: There is an interaction Lagrangian for real scalar fields given by L=$\lambda_1 \phi_1 \phi_2\phi_3+\lambda_2\phi_1^2\phi_3$. I need to know how to ...
2
votes
1answer
125 views

Why is usual matter made up of $n,p$ and $e^-$?

We have six leptons and six quarks. Yet most of what we see around us is made of only neutrons, protons and electrons. For $\mu^-$ and $\tau^-$, I think the reason is that these are unstable particles ...
0
votes
0answers
34 views

Are the electron and positron doublets in any mathematical sense?

I know left handed electrons and electron neutrinos are isospin doublets. Is there any analogous way in which an electron and a positron are related? My first thought is some sort time-parity doublet.
1
vote
0answers
47 views

How $W^{\pm}$ bosons get their electric charge $\pm 1$ as opposed to $Z_0$ that have neutral electric charge?

In the 'Standard Model' book by Y. Grossman and Y. Nir, in chapter 7 (the leptonic standard model) on page 93 after defining the charge of the broken symmetry generator, i.e $Q=T_3+Y$ they say that ...
-1
votes
1answer
39 views

What is the way to work out the running of lepton masses?

If we assume the GUT unification energy is some value E, (say $10^{16}GeV$). Can we work out the running of the particle masses for example the electon, muon and tau at various energies? And will ...
0
votes
1answer
52 views

How can pure leptonic interactions be mediated by the weak force?

$\mu^+ \rightarrow e^+ + \nu_e + \bar \nu_\mu$ Consider the above decay, it is given in my lecture notes as a weak force interaction. I thought the weak force was only involved when quarks change ...
0
votes
1answer
54 views

Conservation of lepton

I was reading a bit about nuclear/particle physics when I came up to Cours et problèmes corrigés de physique nucléaire et de physique des particules by Philippe Miné in 2016 ISBN 2340011566, which is ...
2
votes
3answers
165 views

Can muonic atoms exist?

Would it be possible in the standard model to have atom like systems in which muons (or tauons) take the place of electrons? Why don't we see more of them? For instance it could be related to some ...
6
votes
2answers
931 views

Can muons decay into quarks?

Muon decays are almost always written as $$\mu^- \rightarrow e^-+ \bar\nu_e +\nu_\mu.$$ The reason given on wikipedia is that one of the product neutrinos of muon decay must be a muon-type neutrino ...
1
vote
0answers
24 views

Mass splitting for leptons and down quarks in $SU(5)$ model?

In the minimal $SU(5)$ GUT model, the masses of the leptons and the corresponding down-type quarks must be equal. i.e. $m_e=m_d$, $m_\mu=m_s$, $m_\tau=m_b$. Whereas this is approximately correct for ...
0
votes
1answer
144 views

Fierz identities and Weinberg operator

I've been told that $$ (\bar{L_i^c}\widetilde{\phi}^{\ *})(\widetilde{\phi}^\dagger L_k) = -\frac{1}{2}(\bar{\widetilde{L}}_i \vec{\sigma}L_k)(\widetilde{\phi}^\dagger \vec{\sigma} \phi) \tag1 $$ by ...
2
votes
1answer
302 views

Decay width of the tau lepton

The total decay width of a particle, $\Gamma$, is proportional to the fifth power of its mass, $m$, $$ \Gamma \propto m^5$$ We also know that the dominant decays of the tau lepton are $$\tau^- \to \...
0
votes
1answer
156 views

Feynman diagram for semileptonic decay of neutral kaon

I am unsure how to draw a feynman diagram for a reaction that occurs as follows $$ K^0 --> l^+\nu_l\pi^- $$ Any tips would be helpful.
0
votes
2answers
53 views

Possible decay modes of Pion

I am aware that the following decay mode may happen: $$\pi^- → e^-\overline\nu $$ My question is why is the following decay mode not possible $$\pi^- → e^-\nu $$
-1
votes
1answer
67 views

Muons - how are we even able to detect them? [closed]

muons have a very small half life comparable to 2.5 μs or so. But we know that it has to cover a very large distance from upper atmospheric layers to reach the particle detectors installed at earth's ...
1
vote
3answers
115 views

Half-life and muon decay

Imagine that we have a single muon. It has a life span of 2.2 microseconds on average. So normally, after that amount of time, the muon will decay. Now imagine we have two groups of muons. Group A has ...
1
vote
1answer
99 views

Can a neutron decay into a proton + muon (+ muon-neutrino)

Can a neutron, if it has enough kinetic energy, decay like: $ \hspace{0.3cm} n \rightarrow p + \mu^- + \bar{\nu}_\mu $ I assume it's not allowed since it's not on the possible decay modes on the ...
-1
votes
2answers
45 views

Naive question about lepton/quark energy states

I understand there are 3 energy states for quarks and leptons (electron, muon, tauon... Up, charm, top etc.) And we have 3 forces (not including gravity, em, strong and weak). This naively seems ...
-4
votes
1answer
72 views

Gamma Photons vs. Muons; Which is more expensive [closed]

Which one takes more energy to produce? I ask as I theorize that keeping the plasma in a fusion reactor is very expensive. Muons, while useful, are too short lived. Maybe... Keeping the plasma at ...
3
votes
2answers
102 views

Leptons during Electroweak Epoch

Prior to the electroweak force splitting, did charged leptons still carry a charge of $e$? I was under the impression that, since electromagnetism didn't exist in its current state prior to ...
3
votes
0answers
77 views

Black hole and lepton number conservation [duplicate]

Can falling of an electron into a black be treated as a process in which energy, charge, spin (angular momentum) and lepton number of the system are conserved? Imagine a small volume of space that at ...
-1
votes
1answer
50 views

Muon decay - Type of interaction

Why does weak interaction occur when a muon decays? Why can't electromagnetic interaction occur when a muon decays?
0
votes
1answer
239 views

Is this Feynman diagram possible?

I have been introduced to Feynman diagrams in a particle physics University module and I just created this diagram to practice checking conservation laws: I have been told that charge, baryon and ...
2
votes
1answer
86 views

How does Bhabha scattering imply the existence of quark/lepton substructure?

In the 1983 journal article New Tests for Quark and Lepton Substructure which covers some science and mathematics behind quark and lepton composition (theoretical). It says: Bhabha-scattering ...
1
vote
2answers
67 views

Flavour violating muon decay

Why is a muon decay into gamma and electron not possible? Where/how does it violate the lepton flavour as muon and electron both have -1? Reference: https://en.wikipedia.org/wiki/Lepton_number
0
votes
1answer
66 views

What, specifically, creates tauons?

It is hard for me to find a site/book/article explaining how, exactly, tau particles are created.
2
votes
1answer
162 views

Why do we regard ($e^{-}, \nu_{e}$) as a doublet?

To my understanding, particles in a multiplet have similar properties (similar masses and so on) and slight or symmetric differences (in mass, electric charge, spin, and so on). They can be regarded ...
0
votes
1answer
241 views

Antimuon and electron annihilation to 2 photons [closed]

An antimuon and electron may bind together via Coulombic attraction and then decay, but is the following process possible? $$(\mu^++e^-) → \gamma + \gamma$$ $\mu^+$ : antimuon $\gamma$ : ...
0
votes
0answers
36 views

Can quark-lepton mass be partially generated by Higgs?

In the Standard Model, quark-lepton masses are also generated by their couplings with the Higgs particle as the W, Z vector bosons are. Their masses are different because the Yukawwa couplings are ...
-1
votes
2answers
85 views

Can we tell something about rest mass from this plot of differential cross-section? [closed]

What we can interpret from the plots below? My aim is to find any resonance peak for di-leptons considering the the produced gamma from quarks and antiquarks can annihilate to lepton and anti ...
3
votes
1answer
306 views

Is it at least theoretically possible for an electron and an antimuon or antitauon to annihilate?

In other words, can mismatched particles and antiparticles react with each other? What about an up quark and anti-down quark?
2
votes
1answer
165 views

Why is $\mu\to e \gamma$ forbidden in the SM w/o neutrino masses?

I have some questions about the next problem: The process µ → eγ does not occur in the Standard Model in the absence of neutrino masses. a) The muon is identical to the electron except for ...
-3
votes
1answer
121 views

Is this an acceptable formula for charged lepton masses?

Looking for a formula which gives good values for the charged lepton masses and which satisfy the Koide relationship, I derived this formula (note the square): $$\{m_e, m_\mu, m_\tau\} \propto ...
2
votes
2answers
281 views

Is it possible to create anti-muons in a particle accelerator?

I love particle and nuclear physics and I'm starting to search some things about it even though I'm only a high school student. So, my doubt is: is it possible to create antimuons (positive charged ...
1
vote
1answer
53 views

How does one categorize antiparticles in flavor, family and generation?

$$\newcommand{\A}{\text{A}}\newcommand{\B}{\text{B}}\newcommand{\C}{\text{C}}\newcommand{\D}{\text{D}} \begin{array}{|c|ccc|} \hline { } & \text{1st} & \text{2nd} & \text{3rd} \\ \hline \...
3
votes
1answer
86 views

Why the $\beta^-$ decay releases $e^-+\nu_e$ and not $\tau$ or $\mu$ generations?

The $\beta^-$ decay is \begin{equation} n \rightarrow p + e^- + \bar\nu_e \tag{1} \end{equation} It can be broken down into \begin{align} d \rightarrow & \ u + W^- \tag{2}\\ W^- \rightarrow &...
-2
votes
1answer
53 views

Looking for info on the average decay energy of the Tauon

I am interested in finding the average decay energy of the Tauon. I am interested in the average net decay energy as a function of the known branching ratios of the tauon decay as well as the average ...
0
votes
1answer
153 views

How is the electron depicted in simplest string theory and how the muon and tau? Are intermediate masses excluded by the model?

I am curious to understand can string theory give the masses of electron, muon and tau. I suppose they are closed strings and vibration wavelength must be the length of the string divided by a digit $...
0
votes
1answer
93 views

How can energy in Ev of particles e.g. muons be measured in a cloud chamber?

I have a Wilson thermoelectric cloud chamber and would like to obtaine the energy of cosmic particles e.g. muons. I would greatly appreciate your answer.
2
votes
1answer
359 views

Feynman Diagram with antineutrinos and neutrinos

I just recently learned how to draw feynman diagrams by looking at an equation such as one for $\beta-$ Decay: $$n = p + e^- + \bar{v}_e$$ I was wondering in $\beta-$ why an electron-antineutrino was ...