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Questions tagged [leptons]

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

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Is there a sigma for unexplained hypothetical discoveries?

I recently read that the Koide formula relating electronic leptons rest masses is often considered to be numerologic, since unexplained, even though recent years experiment data tend to narrow the ...
olivierlambert's user avatar
2 votes
1 answer
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How does a $\mu_R^-/\mu_L^+$ decay?

While studying SM, I was taught that weak force bosons $V=\{W^\pm,Z^0\}$ do not interact with right/left-chiral fermions/antifermions. For this reason, we cannot observe right-handed neutrinos (if ...
A.M.M Elsayed 马克's user avatar
3 votes
1 answer
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How to be sure that when a muon passes a detector it is actually a muon?

The question is as follows: when you have any kind of detector for muons you just take measurements and you say, for example, the number for the muon flux but how you're sure that all particles ...
Francisco Santiago's user avatar
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2 answers
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Can Muon Catalyzed Fusion work in a Plasma?

From what I understand, muon catalyzed fusion works by injecting muons into the deuterium and tritium, which then they replace the electron shared between the hydrogen isotopes in a molecule, making ...
Barry Allen 's user avatar
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2 answers
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Would a muon placed in a confinement smaller than most electron wavelengths decay slower?

We know that between two perfect mirrors certain photon frequencies become disallowed. The casimir effect is often even described as a lack of virtual photons of certain frequencies within quantum ...
Sven Heinz's user avatar
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General formula for a $f1\to f2$ gamma processes (e.g. $\mu \longrightarrow e\gamma$), understanding the detailed calculation in the paper by Lavoura

I want to work out in detail the paper by Lavoura to get some real practice as a beginning student. I have stumbled upon several problems as I am moving along with the arguments. Firstly, I am not yet ...
Hubert John's user avatar
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What does it mean, during the Grand Unified Epoch, that matter fluctuated between lepton and baryon states?

My understanding of leptons and baryons is that leptons are an elementary particle, while baryons are a composite particle. Can someone explain to me what particles fluctuating between lepton and ...
blacktopshaman's user avatar
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Within a generation, fermion species' mass seems like it could have an effect on how many of the fundamental forces it interacts with. Is this true?

So, fermions all interact with the gravitational force and the weak force. All fermion species. Now, if you eliminate from that list, the particles that don't interact with electromagnetism, you ...
blacktopshaman's user avatar
1 vote
1 answer
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How was the tau lepton predicted?

I know the tau lepton has been predicted before it was discovered – unlike the muon. But how does our theory (SM/electroweak theory) predict the existence of a third lepton generation?
MBZL's user avatar
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Would it be possible to generate muons using neutrinos and electrons?

The decay products for a muon are an electron, a muon neutrino, and a electron antineutrino. As the decay products for a neutron (electron, proton, neutrino) can combine together to form a neutron ...
Abdur Rahman Hashmi's user avatar
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Are quarks real particles? Or only combination form of leptons inside nucleons? [duplicate]

There are not any free and independent quark in the nature. Collision of many particles inside most powerful accelerators could not produced any free and independent quark but result of collision ...
QQQ's user avatar
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Notation of small $n$ in the production of muons in cosmic rays

I came across this page in the "Cosmic rays and particle physics" by Gaisser. I cannot find any explanation to the notation of $n$ (eqn. 6.8 and forward). Intuitively it should be something ...
sasssu's user avatar
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2 votes
2 answers
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Can exchange interaction exist between electron and muon? [closed]

I'm studying about the exchange interaction and it's quite confusing. Why does it happens between same kinds of particle? How about electron and muon? Or one particle and another one which has all the ...
Song's user avatar
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7 votes
5 answers
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What happens when an anti-electron collides with a neutrino?

What happens when an anti-electron collides with a neutrino? If something does happen, is a photon released after the collision?
mr.thach's user avatar
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1 answer
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How would I estimate the partial width for the decay of upsilon meson into an electron-positron pair?

I cam across a question that stated the total decay width for the phi meson was 4300 kev and the partial decay of it into an electron-positron pair was 1.3kev. How would I estimate the partial width ...
user2279603's user avatar
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Is it possible for an electron and antimuon to neutrinos?

If i have an electron and an antimuon is it possible that they could annihilate into a electron neutrino and antimuon neutrino? Am i correct in saying both spin and charge are conserved in this ...
user2279603's user avatar
6 votes
2 answers
262 views

Electrons decaying into heavier particles

Suppose we have a system of electrons a very tightly confined space (like a tiny magnetic trap). Let's say we continually increase the degree of confinement such that the electrons are confined into ...
Jamie S's user avatar
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The muometric positioning system, how does it work exactly?

While GPS uses light signals to determine the location of a device, I just learned that something similar can be done using cosmic muons rather than light, see e.g. this paper. The idea, as I ...
Inzinity's user avatar
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Cloud Chamber Help Needed! [closed]

I was inspired by this video to attempt to create a cloud chamber without dry ice (it's very challenging to get where I live) and I have had limited success so far. This is what the design looks like: ...
Carl Davis's user avatar
1 vote
0 answers
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Time dilation - Example of Muon [duplicate]

A very common example of time dilation is given for muons i.e. how presence of large number of muons reaching earth (which were created in upper atmosphere) can be explained using time dilation. The ...
user31058's user avatar
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Could you use Muons as electricity (or rather mutricity)?

Muons and electrons are both leptons that carry charge, so could you build a circuit that uses muons instead of electrons? Do substances like copper that conduct electrons also conduct muons?
qazwsx's user avatar
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Why is the branching fraction of strange $D$ mesons to tau leptons so high?

From the PDG (https://pdg.lbl.gov/2008/listings/s031.pdf & https://pdg.lbl.gov/2010/listings/rpp2010-list-Ds-plus-minus.pdf) the branching rate for strange D mesons to tau leptons is about 3 ...
Arthur's user avatar
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17 votes
5 answers
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Does substituting electrons with muons change the atomic shell configuration?

Suppose we take an example of $\text{Be}^{2+}$ and we add two muons to it. Will they go into L shell or there will be two K shells - one each for muons and electrons? If so, the system should have ...
Jaswinder Singh Sidhu's user avatar
1 vote
2 answers
432 views

Can tau decay into a pair of charm and strange quarks?

I found on wikipedia that tau can decay to hadrons made of quarks and it seems like a tau can only decay to a pair of down and anti-up quarks. I understand that tau (1.8GeV) doesn't have enough mass ...
L L's user avatar
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0 answers
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Wilson Coefficients in the Standard Model

I'm not particularly knowledgeable in this area of physics. From my understanding as an undergraduate, Wilson coefficients are sets of parameters that arise from an effective field theory which ...
probablysid's user avatar
2 votes
0 answers
111 views

How is the $SU(2)_L$ conjugation applied?

I'm reading a paper where they introduce the lepton doublets $L$ and "their $SU(2)_L$ conjugations" $\tilde{L}$, which I'm guessing means $$ \tilde{L} = i\sigma_2L^*. $$ After $\textit{vev}$,...
Depenau's user avatar
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1 answer
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What's the difference between Lorentz transformation properties of Hermitian and Dirac adjoint lepton doublets?

If the lepton doublet transforms like a left-handed Weyl spinor under Lorentz transformations, $$ L \longrightarrow exp\left[\frac{1}{2}(i\theta_j\sigma^j - \beta_j\sigma^j)\right]L = \Lambda_{sL}L, $$...
Depenau's user avatar
  • 525
-4 votes
1 answer
188 views

What charge does muon have? [closed]

I have a simple $\mu$-meso atom model. Kernel is just one proton and on orbit there's one muon, which is 210 times heavier than electron. What charge does it have? I checked some tables about muons ...
Nikita Artemenko's user avatar
3 votes
2 answers
157 views

Are all elementary particles consequential?

Apologies if the title is misleading. Really what I'm curious about is if every elementary has a point, at least in what we know. I know the different types of quarks are important of course, as they ...
SCPirate's user avatar
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Can a positive $W$ boson and negative $W$ boson exchange a lepton, and release a charged lepton antilepton pair or neutrino antineutrino pair?

Would it be possible for two passing $W$ bosons with opposing charge to either release a neutrino and become the corresponding charged lepton and charged antilepton, or release a charged lepton, and ...
zion does math weird's user avatar
0 votes
1 answer
156 views

Chirality in muon decay

Consider the muon decay process: We assign the chirality according to the $W$ boson current: (i.e. P&S eq.(20.80)) $$J_W^{\mu+}=\frac{1}{\sqrt{2}}\bar{\nu}_{\mu L}\gamma^{\mu}\mu_L \quad J_W^{\mu-...
Daren's user avatar
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2 votes
1 answer
140 views

Clarification about the question of whether neutrinos are their own antineutrinos

There are various pages that say we can distinguish between neutrinos and antineutrinos. Why do we not know whether or not neutrinos are their own antiparticles? Why are neutrino and antineutrino ...
Maximal Ideal's user avatar
1 vote
1 answer
86 views

Flavor Oscillations, the case of leptons

In the neutrino sector neutral particle oscillation occurs which gives rise to neutrino oscillation. From my currrent understanding , the observation of the neutrino oscillation occurred because the ...
Stefano Barone's user avatar
0 votes
1 answer
142 views

What particles existed in the Planck, GUT, and electroweak epochs, respectively?

What quarks, leptons, and bosons existed in each of the individual epochs of the early universe (Planck, GUT, electroweak)? Did the quantum zoo gain or lose species during these times? Or did some of ...
blacktopshaman's user avatar
1 vote
1 answer
50 views

Why LNV for 0νββ process has odd dimensions?

I am studying a couple of papers on the subject of neutrinoless double beta decay problem, somewhere in one of these papers, they emphasize that $ΔL=2$ operators have odd dimensions. What is the ...
Ymir Saber's user avatar
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2 answers
238 views

The Dirac equation predicted the positron. Does the Dirac equation also suggest the existence of muons?

The Dirac equation is given by: $$ (i\partial \!\!\!/ - m) \psi(x) = 0$$ It famously predicted positrons by suggesting negative energy solutions. First it was solved with the 'Dirac sea' and positrons ...
bananenheld's user avatar
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5 votes
1 answer
179 views

Is the muon superfluous?

When the muon was discovered, it was so unexpected that Rabi's reaction was, "What? Who ordered that?" The muon doesn't play any obvious role in the behavior of protons, neutrons, and ...
rob's user avatar
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2 votes
2 answers
183 views

Is Lepton Flavour Universality an accidental symmetry of the Standatd Model?

Is Lepton Flavour Universality an accidental symmetry of the Standatd Model? If it is, why? How does it emerge from the Standard Model?
Abel Gutiérrez's user avatar
-3 votes
1 answer
49 views

Could the equal amounts of positive and electric charge point to equal amounts of matter and anti-matter?

The universe is electrically neutral because the electric charges of all quarks and leptons cancel. If particles are electrically charged, then there are equal amounts of positive and negative ...
MatterGauge's user avatar
1 vote
0 answers
78 views

Anomalous magnetic moment form factor of $e^-,\mu^-$ and $\tau^-$ in QED

The anomalous magnetic moment form factor $F(q^2)$ of an elementary fermion at $q^2=0$, calculated at one-loop, is $$F_2(0)=\frac{\alpha}{2\pi}.$$ At least at this order (order-$\alpha$), $F_2(0)$ ...
SRS's user avatar
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-1 votes
1 answer
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Is leptons annihilation one process of 4 particles simultaneously or two independent processes of 3 particles? [duplicate]

Why leptons annihilation is not 4-particles, and it is represented in the form of two 3-particles? If the pair of an electron and a positron has formed a positronium particle, then what is virtual ...
Imyaf's user avatar
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8 votes
3 answers
606 views

Fundamental reason for the color and flavor group to be the same?

The answer to this question might just be a straight-up "no, it's just a coincidence", but since coincidences are rarely a thing in physics, I thought I'd ask. Is there a fundamental reason ...
Mauro Giliberti's user avatar
0 votes
1 answer
87 views

Does Lepton flavour universality arise natural in the SM

I always thought LFU is stated by the SM , but I recently read that it was just assumed because measurements suggested this universality. If thats true, proving LFU violation would not automatically ...
gamma's user avatar
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0 answers
132 views

Is the electromagnetic coupling constant of the muon exactly the same value with the electron $α \approx1/137$?

I am asking because I want to know If I can use the Schwinger equation: $$a_{e}=\frac{\alpha}{2 \pi} \approx 0.0011614$$ to calculate the one-loop QED contribution to the anomalous magnetic moment of ...
Markoul11's user avatar
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2 votes
1 answer
159 views

Why do we say lepton flavour violation is against the standard model if no symmetries are associated with lepton flavour?

Or if a symmetry does exist what is it? If possible could you compare this to a symmetry that leads to a conservation?
Adrien Amour's user avatar
0 votes
1 answer
192 views

The effect of the fifth force of nature being detected?

The article https://www.sciencealert.com/physicists-may-have-discovered-new-force-of-nature-in-lhc-experiment speculates that possibly the effect of the fifth (so far unknown) force of nature has been ...
Alex's user avatar
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2 votes
0 answers
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Explanation for exact amounts ratio between up,down quarks and electrons in a universe

As I've understood in the quark era $\approx (10^{-12} - 10^{-6}) \,\text{s}$ unified interaction has decoupled into Leptons and Quarks. Given that now Hydrogen+Helium atoms accounts for $97.9\%$ of ...
Agnius Vasiliauskas's user avatar
2 votes
0 answers
87 views

Why is the hadronic $\tau$ branching ratio into 2 pions prefered?

In the PDG the $\tau$ branching ratios are listed and Br$(\tau^- \rightarrow \pi^-\pi^0 \nu_\tau)\approx 25$ %, while Br$(\tau^- \rightarrow \pi^-\nu_\tau)\approx 11$ %. How can this be since the ...
krabby patty's user avatar
2 votes
2 answers
276 views

Higgs Mechanism Confusion

I find myself confused about the Higgs mechanism, but more specifically about how the leptons get their mass. The intuitive picture I have in my head is that since the leptons are interacting with the ...
Eric David Kramer's user avatar
1 vote
0 answers
247 views

If neutrinos were Majorana fermions, then what would be the lepton number of the neutrino?

Majorana particles are their own antiparticles and the lepton number of antimatter is -1 whereas for matter is +1, so if neutrinos were Majorana fermions, then what would be the lepton number of the ...
Prvy_Monk's user avatar