The muon (; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not known to have any sub-structure – that is, it is not thought to be composed of any simpler particles.
The muon is an unstable subatomic particle with a mean lifetime of 2.2 μs, much longer than many other subatomic particles. As with the decay of the non-elementary neutron (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the weak interaction (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electron of the same charge as the muon and two types of neutrinos.
Like all elementary particles, the muon has a corresponding antiparticle of opposite charge (+1 e) but equal mass and spin: the antimuon (also called a positive muon). Muons are denoted by μ− and antimuons by μ+. Formerly, muons were called "mu mesons", but are not classified as mesons by modern particle physicists (see § History), and that name is no longer used by the physics community.
Muons have a mass of 105.66 MeV/c2, which is approximately 207 times that of the electron, me. More precisely, it is 206.7682830(46) me.Due to their greater mass, muons accelerate more slowly than electrons in electromagnetic fields, and emit less bremsstrahlung (deceleration radiation). This allows muons of a given energy to penetrate far deeper into matter because the deceleration of electrons and muons is primarily due to energy loss by the bremsstrahlung mechanism. For example, so-called "secondary muons", created by cosmic rays hitting the atmosphere, can penetrate the atmosphere and reach Earth's land surface and even into deep mines.
Because muons have a greater mass and energy than the decay energy of radioactivity, they are not produced by radioactive decay. However they are produced in great amounts in high-energy interactions in normal matter, in certain particle accelerator experiments with hadrons, and in cosmic ray interactions with matter. These interactions usually produce pi mesons initially, which almost always decay to muons.
As with the other charged leptons, the muon has an associated muon neutrino, denoted by νμ, which differs from the electron neutrino and participates in different nuclear reactions.
Hello,
The Feynman graph of muon decay is
and I asked my professor if we could also write
and he said no, because then out of nothingness an electron and an (anti)electron-neutrino would appear and send out a boson to the muon.
However, I was not very convinced, so I wanted to double...
I am trying to revise for PhD, going over MSc work. Could anyone help me with this question?
Homework Statement
A pion traveling at speed β(=v/c) decays into a muon and a neutrino, π→μ + \nu. If the neutrino emerges at 90° to the original pion direction at what angle does the muon come off...
Homework Statement
Muon with mass 80m is at rest. Muon decays into photon and particle Qm. The photon has an energy of E=60m in the +x direction. Find all of the other components.Homework Equations
Vx= Px/E
m^2=E^2-P^2
Pt=E
Ignoring the Y and Z components of the Four-Momentum as they are...
Why is it that the differential cross section for processes like Inverse Muon Decay (IMD) are always given in the CM frame? Every paper I have seen that discusses Inverse Muon Decay gives the differential cross section in CM frame. Is it very hard to calculate the differential cross section in...
I know there's a difference between how they're detected. (Cherenkov radiation cone size) They have different "flavors." (I'm not sure what that means.) There's a difference in their simbol. (Ve, Vu, Vt) And they have different masses. But that's all I know. There must be something more to the...
Homework Statement
uons are unstable subatomic particles that decay to electrons with a mean lifetime of 2.2 microseconds. They are produced when cosmic rays bombard the upper atmosphere about 12.3km above the Earth's surface, and they travel very close to the speed of light. It is known that...
I'm need some help understanding my lab concerning the muon. I'm trying to find information about the lab but I'm not find anything. I just would like to know the following:-
1.Does changing the saturated amp output change the timing of the FPGA? Does it and how?
2.What are the...
Hello,
I was looking at the quark masses and had this doubt regarding the muon decay: Why can't the muon decay into up and down quarks (plus neutrino). I know the explanation is because muon doesn't exhibit hadronic decays because its mass isn't big enough m_\mu=107MEV. But I just saw that...
Homework Statement
Taking the proton to be a uniformly charged sphere of radius 1 fm, find an
expression for the change in potential experienced by the muon as compared with that
in the case of a point-like proton. Use first order perturbation theory to calculate the
ground-state energy...
What's the dominating opinion about the issue that muon g-2 deviates from the standard model? Is this generally considered as experimental inaccuracy, incompetent theoretical calculation, or genuinely beyond the standard model?
On a related front, I'd like to ask about the experimental...
The proper mean lifetime of a muon is 2.20 µs, which is denoted as τ. Consider a muon, created in Earth's upper atmosphere, speeding toward the surface 8.00 km below, at a speed of 0.980c. What is the likelihood that the muon will survive its trip to Earth's surface before decaying? The...
Is it reasonable to expect muon decay to be slowed or stopped in electron degenerate matter like metallic hydrogen? The electron that would be the product of the decay would need to find a higher energy level. The effect may be analogous to the reason why a neutron is stable within a nucleus...
Homework Statement
5. What is the average distance traveled by a muon with an energy of 5 GeV? 500 GeV? (assume v is approximately c)
Homework Equations
The Attempt at a Solution
I wasn't really sure where to begin with this. I was under the impression that if in both...
muon decay constant/ muon flux
where can i find the decay constant of a muon (the lambda which appears in):
http://upload.wikimedia.org/math/3/f/2/3f28b1c0d4362b86a89f976d83d81070.png
thanks
edit:
oh the wiki page http://en.wikipedia.org/wiki/Exponential_decay
gives the relationship...
Homework Statement
Substitute an electron in a neutral hydrogen atom with a muon.
a) calculate the Bohr radius of the ground state for this myonic atom of atom. The answer must be right to at least 2 significant digits.
b) Calculate the fraction of the myon that is located inside the proton...
Homework Statement
Substitute an electron in a neutral hydrogen atom with a muon.
a) calculate the Bohr radius of the ground state for this myonic atom of atom. The answer must be right to at least 2 significant digits.
b) Calculate the fraction of the myon that is located inside the proton...
Hi guys, just wanted to ask a question related to muon
experiments (and all other which can be presented this
way) to get some things clearer.
Ok, here goes:
We have lots of muons traveling towards Earth. Their
mean lifetime, measured in lab conditions (at rest) is
2.2µs. Their...
In lab, my partner and I are determining muon lifetime with a scintillator. I understand that the scintillator will help us find the average lifetime by measuring the difference between the time that a particle enters the scintillator and when in decays, but I am not able to figure out why this...
Hello physics enthusiasts,
I am currently trying to estimate the effects of the muon flux on an experimental setup located overground. In particular I am interested in the angular distribution with which they are impinging.
Sofar I have had problems even finding a simple muon energy spectrum...
Homework Statement
As a lab experiment, we must try to measure and calculate the lifetime (τ) of a muon. After all data is collected, the lifetime can be calculate by using the maximum likelihood estimation.
The function on which MLE is applied...
Homework Statement
A muon of 40MeV is propagating through free space. It decays to an electron, muon neutrino, and electron antineutrino. What is the beta value of the electron?
Homework Equations
None provided
The Attempt at a Solution
I thought I could just take the total energy...
Homework Statement
Unstable, subatomic particles called muons have a rest energy of 105.7 MeV and a speed of 0.994c. If a muon were to decay and produce an electron and a photon, what would be the momentum of the electron as measured by an observer in the muon's frame? HINT: assume that the...
Homework Statement
A pion spontaneously decays into a muon and a muon antineutrino. Recent experimental evidence indicates that the mass m of the antineutrino is no larger than about 190 keV/c^2 and may be as small as zero. Assuming that the pion decays at rest in the laboratory, compute the...
Homework Statement
A muon is traveling with a speed of v = 2.995x10^8 m/s. Calculate the value of the dilated lifetime for this muon. Assume that the speed of light is c = 3.000 x 108 m/s and that the proper lifetime of the muon is 1.500 x 10-6 s.
Note: Do your calculations to 4...
Homework Statement
Particle Physicists use particle track detectors to determine the lifetime of short-lived particles. A muon has a mean lifetime of 2.2 microseconds and makes a track of 9.5 cm long before decaying into a electron and two neutrinos. What was the speed of the muon?
Homework...
Hi,
Could anyone explain to me why it is that cosmic radiation supplies slightly more positive than negative muons? I know that negative muons disappear a little faster than the positive ones as they can decay or be captured, but I don't know if this would have any impact on what I'm asking...
Given the lifetime of a muon as 2.197 microseconds, and the rest mass of 105.65MeV, and a total particle energy of 10GeV, I need to calculate how far, in the rest frame, the particle will travel before decay.Homework Equations
Beta=v/c
Gamma=1/sqrt(1-beta^2)
deltaT'=gamma*deltaT...
Homework Statement
In using the experiment where a scintillator is connected up to PMTs, and the data is then recorded on the computer... The muon has already lived outside the scintillator for a large amount of time before it decays in the scintillator, so how is it that the experiment...
Homework Statement
I have to find the Fermi Coupling Constant using my measurement of the muon lifetime. My measurement is 2.1786x10^-6s
Homework Equations
G_F=\sqrt{\frac{192.pi^{3}}{\tau.m_{\mu}}}
The Attempt at a Solution
I tried plugging in the numbers that I have and I get...
Show that the phase space factor \rho \propto p^2 dp/dE for the decay \pi\rightarrow \mu + \upsilon is
\rho \propto \frac{({m_\pi}^2 - {m_\mu}^2)^2}{{m_\pi}^3}E_\mu
where E is the total energy.I can show that p^2 = ({m_\pi}^2 - {m_\mu}^2)^2/4{m_\pi}^2
but then I get stuck, I don't know how...
Hi,
Could someone tell me please what is the scientific consensus(or some interesting theories) on why do muons decay and what is the mechanism of it? My understanding of particle decay is based on for example neutron wchich decays because a quark in it flips from down to up. But leptons, if...
I know this is basic stuff but my maths is truly terrible. I hope someone can help.
Assuming you have a muon moving at near light speed, it will generate a magnetic field due to its movement. I'm assuming there is no external magnetuc field present. How can I calculate the field produced please?
Homework Statement
A muon traveling with negligible energy loss at v = 0.996c travels past a 4730m mountain. What is the relavitistic mass of the muon given the rest mass energy of 1.69 x 10^-11 joules?
Homework Equations
The Attempt at a Solution
I think I should be using...
I have been doing an experiment on muon lifetime, and am wondering if my count rate is correct.
A little about the experiment:
I have two scintillators (plastic) set up above a lead glass absorber, and a third scintillator(plastic), under the lead glass to veto muons that do not stop in the...
Homework Statement
I'm having trouble with e-muon scattering. Tree level, no loops. (This is problem 7.26 in Griffiths Intro to Elem Particles). I get that the amplitude is as stated in the text, but I am having problems coming up with a number when the momenta and spins are added in...
Homework Statement
How far will a beam of muons with kinetic energy (a) 1 MeV, (b) 100 GeV travel in empty space before its intensity is reduced by half?
Homework Equations
See below
The Attempt at a Solution
My main problem with this is that it looks like we won't be taught the...
Homework Statement
A muon (an elementary particle) enters a region with a speed of 4.20 106 m/s and then is slowed at the rate of 1.10 1014 m/s2.
(a) How far does the muon take to stop?
________ m
Homework Equations
x(t)= initial position + final velocity * time
v(t)=...
Hello,
how do the angular distributions of Bhabha Scattering
e^+ e^- \Rightarrow e^+ e^-
and Muon pair production
e+ e- \Rightarrow \mu^+ \mu^-
differ?
Regards,
Phileas Fogg
consider two frames s and s' where s' is moving with velocity vector (0.9c,0,0) with respect to s frame. At time t=t'=0 the origin of the two frames coincide. At time t=2.2x10^-6s a muon decays at coordinates (100,0.8,1.0) meters in the s frame.
a) At what time and coordinates does the muon...
I am inquiring if anyone here is qualified to numerically calculate the following equation:
Fermi coupling constant and Muon decay lifetime: (ref. 1)
\frac{G_F}{(\hbar c)^3} = \sqrt{\frac{192 \pi^3 \hbar}{(m_{\mu} c^2)^5 \tau_{\mu}}
Muon decay lifetime: (ref. 2)
\tau_{\mu} = 2.197034 \cdot...
What is the typical efficiency (as a function of muon energy and/or rapidity) of a moun detector at an accelerator experiment?
More specifically I would like to know about the lower energy treshold: E.g. if a muon with energy of just some few GeV is produced in the collision process, what is...
Hi,
I'm starting a prac on muon lifetimes and we have been asked to calculate the range of energies suitable for the experiment...
Thinking about this, I was a bit stumped as to what we were supposed to be calculating... Is this a limitation of the detection equipment? Or do low energy...
Homework Statement
In some theory the electron neutrinos and the muon neutrinos mix like this:
\mathcal{L}_{m} &= -\frac{1}{2}m\left(\overline{ \nu^{C}_{\mu\text{R}} }\nu_{\text{eL}} + \overline{ \nu^{C}_{\text{eR}} }\nu_{\mu\text{L}}\right) + \text{h.c.}
Show that there exists a...
Homework Statement
The muon is an elementary particle that decays with a mean (rest) lifetime of 2.20E-6 s. A beam of muons has a speed of 0.600c. In the reference frame of the muon, how far does the laboratory travel in one mean lifetime? Homework Equations
L=\frac{L_o}{\gamma}
The Attempt at...
I'm doing a Monte carlo simulation of cosmic ray interactions in the atmosphere, and as part of this I need to calculate how far a decaying particle travels before it decays
In vacuum it would be simple: l_D = c \tau \gamma \beta with a probability of traveling the distance l before decay: P_D...
Homework Statement
in the decay process, \pi ^{+} -> \mu^{+} + \nu_{\mu}
show that for a neutrino of finite (but small) mass, compared with the case of the massless neutrino, the muon momentum would be reduced by the fraction:
\frac{p'}{p}= - \frac{m_{\nu}^2...
the mc^2 for a pion and muon are 139.57 MeV and 105.66 MeV respectively. Find the kinetic energy of the muon in its decay from \pi ^+ -> \mu^+ + \nu_{\mu} assuming the neutrino is massless. Here's what I did:
Since E^2=p^2c^2+m^2c^4 and that c=1, then E, p and m have same units.
E^2 = p^2...
I am trying to work out the solid angle acceptance of a muon telescope. The telescope is comprised of two aligned square detector panels (of size x squared metres) set at a distance apart of L metres. The way I was initially working it out (by using the solid angle of a pyramid of base x...