one of the four known fundamental forces of nature and the one responsible for beta-decay radioactivity. The weak interaction is very short-ranged and more weakly coupled than either the strong nuclear force or electromagnetism. At energy scales above the Z mass the weak and electromagnetic ...
6
votes
2answers
123 views
What stabilizes neutorns against beta decay in a neutron star?
Free neutrons are known to undergo beta decay with a half-life of slightly above 10 minutes. Binding with other nucleons stabilizes the neutrons in an atomic nucleus, but only if the fraction of ...
0
votes
0answers
20 views
Some basic questions about electric field & nucleus [duplicate]
I am not good in physics.You can say I am beginner in this field.
I have some basic questions.
I ju st want to know that
[1] If there is repulsive force between same charges proton-proton then why ...
3
votes
1answer
166 views
What breaks the symmetry between the electromagnetic and weak nuclear force?
I know the electromagnetic force is mediated by a photon and the weak nuclear force is mediated by two massive bosons. Are there any other insights into why the masses are so different?
0
votes
0answers
101 views
Weak isospin and types of weak charge
My understanding is that QCD has three color charges that are conserved as a result of global SU(3) invariance. What about SU(2) weak? Does it have two types of charges? What I'm getting at is:
U(1) ...
1
vote
3answers
98 views
Effective operator in four-fermion interaction
In one book, I have got the following lines which I found myself unable to understand what is effective operator? The paragraph is given below:
The weak interaction describes nuclear beta decay, ...
1
vote
0answers
68 views
Why does the electron energy distribution from muon decay peak near the kinematic maximum?
I'm trying to understand why when you have a muon decay event, the energy of the electron peaks near the maximum kinematically allowed value. Is there an intuitive explanation for why this is the case ...
2
votes
2answers
108 views
What is difference between the different 'flavours' of neutrinos?
Moreover, how-come scientist know that muon-neutrino are different from electron-neutrino when they didn't even know what the difference was? Did they interact differently with other particles?
3
votes
2answers
104 views
Playground of Forces
Why is it that the gravitational force acts on large sized objects while the strong and weak nuclear forces act at subatomic levels only? What is that stops each other to enter each others domain?
6
votes
1answer
186 views
Weinberg angle measurement methods
I was reading up on the history of $W/Z$ bosons today and I got a little puzzled. I always assumed that people measured $M_Z$ and $M_W$ and then derived the Weinberg angle. But it appears that they ...
2
votes
1answer
364 views
Jarlskog Invariant and its mathematical origin
CP violation is present in the weak interactions if
There are no degeneracies in the up-quark/down-quark matrices
The Jarlskog invariant $J=Im(V_{us} V_{cb} V_{ub}^* V_{cs}^*)$ is nonvanishing
...
0
votes
0answers
95 views
What would the universe be like if Electroweak symmetry were unbroken? [duplicate]
Possible Duplicate:
What happens to matter in a standard model with zero Higgs VEV?
What if the Higgs did not have a "Mexican hat" potential and the therefore it's vacuum expectation value ...
2
votes
1answer
202 views
4th order feynman-diagrams for $e^- + \mu^+ \to \nu_e + \bar{\nu}_\mu$
The task is to draw the two 4th-order Feynman diagrams of:
$$e^- + \mu^+ \to \nu_e + \bar{\nu}_\mu $$
I drew the first one as (time left->right):
...
12
votes
2answers
379 views
Why is the (free) neutron lifetime so long?
A neutron outside the nucleus lives for about 15 minutes and decays mainly through weak decays (beta decay). Many other weakly decaying particles decay with lifetimes between $10^{-10}$ and $10^{-12}$ ...
0
votes
1answer
154 views
Can action of the weak and strong forces be reduced to action of electromagnetic force?
It is known that electromagnetic (EM) fields action on particles is limited to the Lorentz force action. In terms of spinors and currents, the EM field:
(i) rotates the Dirac current around the ...
4
votes
1answer
345 views
CP Violation of the CKM Matrix
Considering the relation between the $SU(2)_{WEAK}$ partners of the $|u \rangle$, $|c \rangle$, and $|t \rangle$ mass eigenstates and the corrseponding downtype eigenstates
$
\left(
...
2
votes
0answers
147 views
Can the mass of longitudinal and transverse W bosons be measured separately?
Some higgsless unified models of particle physics predict that the mass of longitudinally polarized W bosons and the mass of transversely polarized W bosons are different.
In those models, a ...
3
votes
2answers
204 views
interaction at a distance: how it works
In classical physics, I know the forces due to gravity and electrostatics. I know a lot of work has been done, but don't know the status. Is there a generally accepted theory of how the force is ...
7
votes
3answers
561 views
Why does the weak force distinguish left and right handedness?
I'm wondering why the weak interaction only affects left-handed particles (and right-handed antiparticles).
Before someone says "because thats just the way nature is" :-), let me explain what I find ...
8
votes
1answer
360 views
Do color-neutral gluons exist?
If I'm correct a quark can change color by emitting a gluon. For example a blue up quark $u_b$ can change into a red up quark by emitting a gluon:
$$u_b \longrightarrow u_r + g_{b\overline{r}}$$
...
4
votes
2answers
238 views
Sterile Neutrinos as Dark Matter
There has been recent activity by astrophysicists to determine whether a fourth flavor of neutrino, a sterile neutrino, exists. It would likely be more massive than electron, muon or tau neutrinos. ...
9
votes
2answers
2k views
How come neutrons in a nucleus don't decay?
I know outside a nucleus, neutrons are unstable and they have half life of about 15 minutes. But when they are together with protons inside the nucleus, they are stable. How does that happen?
I got ...
4
votes
1answer
243 views
Why does parity violation in weak decay imply decay asymmetry?
I googled the sentence in the title of this question and found the famous experiment by
Wu et al demonstrating that electrons in weak decay are emitted ``in the direction of motion of a left-handed ...
1
vote
1answer
567 views
Quantum numbers of the helicity states of the W boson
What are the weak hypercharge and weak isospin quantum numbers of the helicity states of the $W^\pm$ and $Z^0$ bosons?
The W boson is a spin-1 massless particle. Consequently it has three helicity ...
2
votes
1answer
211 views
How much CP violation does the weak force cause?
I'm looking for the most readable quantitative explanation, with the least amount of difficult mathematics. Rather than an answer with just a number, I'd like to see the derivation from the CKM ...
6
votes
3answers
2k views
How to explain the weak force to a layman?
I'm trying to explain in simple terms what the weak interaction does, but I'm having trouble since it doesn't resemble other forces he's familiar with and I haven't been able to come up (or find on ...
1
vote
2answers
249 views
Is there a relationship between Berry-Pancharatnam phase and CP violation in quark mixing?
Berry-Pancharatnam phase is the phase that quantum systems exhibit when they pass through a sequence of states and return to their original state. It's a complex phase and it is different from the ...
3
votes
3answers
467 views
Energy of the electron-muon reaction
Lets see the reaction:
$e^- \mu^- \to e^- \pi^- \nu_\mu \;\;\;\;\;\;\;\;\;\;\; {(1)}$
I suppose, that this reaction occurs as follows
$e^- \mu^- \to e^- \mu^- \pi^+ \pi^- \to e^- \pi^- \nu_\mu$
Is ...
