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 ...

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4
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3answers
101 views

If neutrons aren't affected by electromagnetic force, what causes it to bounce off matter?

Say a neutron is heading for a mountain, what would cause it to bounce off said amalgamation of matter? Electromagnetism is ruled out, gravity is too weak, (if I'm not mistaken) nuclear strong force ...
1
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1answer
46 views

The charges of the forces

I am trying to establish a simplified understanding of the fundamental forces to explain them to a young audience. If we say that gravity has one charge (attractive), electromagnetism has two charges ...
1
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0answers
31 views

Where does the square root of two in the conversion between the Fermi constant and the weak coupling constant come from?

As in the title, where does the square root of two in the conversion $$ G_{F}=\frac{\sqrt{2}g^{2}}{8m_{W}^{2}} $$ between the Fermi constant and the weak coupling constant come from? I was able to ...
3
votes
1answer
30 views

How to determine if interaction is allowed?

I'm trying to determine if the reaction $$n\rightarrow p\pi^-$$ is allowed. First of, this doesn't list this as one of the decay modes of the neutron, so I suspect that it should not be allowed. ...
2
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3answers
62 views

How is each neutrino associated with a specific charged lepton?

For instance, why is an electron neutrino called that and what is its relationship with an electron?
1
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2answers
93 views

How is an electron “recycled” in a neutron?

A proton is made up, they say, by 2 up and 1 down quark, drowned in a sea of virual paricles: when an electron is captured this process thereby changes a nuclear proton to a neutron and ...
0
votes
1answer
35 views

Direct vs. indirect CP violation: theoretical foundations

I know very little about the difference between direct and indirect CP violation. I've been studying QFT from Peskin and Schroeder's "An Introduction to QFT", and they don't seem to address this ...
3
votes
1answer
83 views

Neutrinos and DNA

This is a question which bridges the gap between biology and physics... but I thought this was the best place to ask it. I remember reading a while ago that it is thought that neutrinos may play a ...
2
votes
0answers
64 views

Fermi's theory of beta decay - Does Fermi's Hamiltonian have the wrong transformation properties?

I'm studying the theory of beta decays as proposed by Fermi in the 30's, and I found an inconsistency between the transformation properties that he claims for his Hamiltonian and the transformation ...
10
votes
2answers
768 views

Why couldn't the decay $\pi^- \to e^- + \bar\nu_e$ occur if electrons were massless?

If we assume that electrons (just like neutrinos) are massless, why can’t the decay $\pi^- \rightarrow e^- + \bar{\nu}_e$ occur under the weak interaction?
4
votes
1answer
129 views

SU(2) confinement picture

Preamble: In section 2 of these lecture notes (Gerard 't Hooft, 1998) an alternative interpretation of the weak interaction is presented, in which the weak force is confined, much like the strong ...
0
votes
0answers
18 views

Mass difference in particle oscillation from weak lagrangian

Looking for an answer to how an expression to $\Delta M = M_2 - M_1$ arise in QFT I have found the approximation \begin{equation} \Delta M_K \approx \frac{G_F^2}{4\pi} m_K f_K^2 \sum_{q=u,c,t} m_q^2 ...
0
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1answer
84 views

Strangeness of elementary particles

What is the property, whose violation led to the assumption of strangeness? Prior to the discovery of strangeness was it assumed that particles that are produced by strong interactions can decay only ...
0
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1answer
38 views

Is dark matter particle affected by weak interaction too?

Neutrino is affected by weak subatomic force and gravitational force and just like dark matter they don't easily interact with matter, if dark matter cannot be affected by the weak interaction how ...
2
votes
0answers
115 views

Feynman amplitude for electron-positron annihilation and $W^{\pm}$ production

I'm working with this interaction Hamiltonian density $$ H_{int}(x) = ig\bar{\Psi}_{\nu_e}(x)\gamma^\rho P_L \Psi_e(x)V_\rho(x) + igV^\dagger_\rho(x)\bar{\Psi}_e(x)\gamma^\rho P_L \Psi_{\nu_e} $$ ...
4
votes
1answer
498 views

Are there weak force waves?

In the same way as there are electromagnetic and gravitational waves that update the information on their respective field, is there an analogue for the weak and strong forces?
0
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1answer
68 views

Leptonic Decay of Muon and Tau

So the question asks: (a) Draw the Feynman diagrams showing the dominant leptonic decay mode of the $\mu^-$ and the $\tau^-$. (b) Assuming $m_\tau \gg m_\mu \gg m_e$, estimate the ratio of the rate ...
1
vote
1answer
26 views

Is the Electroweak theory chiral regardless of temperature?

Is the electroweak theory a chiral theory regardless of whether one is above the electroweak symmetry breaking temperature or not?
5
votes
1answer
69 views

Why is the $D^0$ oscillation so different from the $K^0$ and $B^0$?

I have looked for this answer into many articles and books but I am not able to figure out why $D^0\to\bar{D}^0$ is so highly suppressed if compared to the $B^0 \to \bar{B}^0$ and $K^0 \to \bar{K}^0$ ...
0
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1answer
41 views

Wu experiment beta decay

maybe it's a stupid question. But in Wu experiment she showed that parity in not conserved in beta decay. So how to say on general that this is true for any weak force interaction?
0
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1answer
43 views

Do neutrinos ever turn back to something less ghostly?

The most notable source of neutrinos seems to be the Sun. Obviously, the neutrinos are created from something else. Now as I think of it, they can just fly away through the solar system and be gone. ...
0
votes
1answer
58 views

Why should we expect dark matter with weak scale masses?

The WIMP "miracle" is often used to motivate WIMPs: that a WIMP with a weak-scale mass naturally freezes out of thermal equilibrium after the big bang with the right relic abundance. I understand the ...
0
votes
4answers
73 views

Change in the half-life of a neutron

What would happen if the half-life of a neutron was much more less than it is now? How could this affect the nuclei?
5
votes
0answers
73 views

Distinguishing between left-handed and right-handed weak coupling from electron-neutrino scattering

This question comes from Schwartz's QFT book, exercise 13.6. In it we consider a coupling between fermions (neutrinos and electrons in this particular case) and the Z boson of the form $g_V \bar{\psi} ...
2
votes
1answer
48 views

What is the product of low energy neutrino annihilation?

Since neutrinos are only subjected to weak interaction(ignore gravitation), thus the interaction of neutrinos are only governed by Z bosons, and photon is unlikely produced. If two neutrinos ...
3
votes
1answer
69 views

Why does virtual negative W boson decay mainly into antiup and down quarks during weak decays of lambda, Xi, omega and other baryons

Virtual $W^-$ boson may decay into $\bar{u}$ and $d$ quarks, $\bar{c}$ and $s$ quarks, $e$ and $\bar{\nu}_e$, $\mu$ and $\bar{\nu}_{\mu}$, $\tau$ and $\bar{\nu}_{\tau}$. Decay into $\bar{u}$ and $s$, ...
6
votes
1answer
143 views

Why does an interaction see the proton instead the quark mass?

When an interaction goes deep in the nucleus, should we have some way to interpolate between the proton mass and the quark mass which is going to be the ultimate destination of the interaction? For ...
1
vote
1answer
151 views

Why we unified electromagnetic and weak force?

We have unified electromagnetic and weak force into one single force called Electroweak force. I mean we can use these different forces within their respective domains like weak interaction for short ...
2
votes
1answer
147 views

How can we calculate pion decay constant in Chiral Perturbation Theory ?

Above diagram is an one-loop contribution to the Pion decay constant $f_\pi$. For example in this paper (Eq.7) they have written down the pion decay constant to one loop, but the calculation is not ...
2
votes
1answer
35 views

Is the mass of the Z due to mixing with the photon “precursor” B or to interaction with the Higgs?

I want to get something clear that I do not seem to understand. I used to read that the photon A and the Z boson are (different) linear combinations between the W^0 (neutral weak boson before SU(2) ...
2
votes
1answer
102 views

How do neutrons escape nuclei?

How do neutrons ejected from a nucleus gain kinetic energy if the they don't repel electrically and the nuclear force only attracts? Does it have something to do with the weak force?
2
votes
1answer
37 views

Gluon have colour-anticolour; what about weak bosons?

Gluons can be red-antiblue, or green-antired, etc. What about weak interaction bosons? (Say before symmetry breaking, to make matters simpler.) Is there a similar "weak charge" structure of ...
0
votes
1answer
57 views

Role of SU(2) group in isospin and in the weak interaction

I know that the SU(2) group describes internal symmetries such as isospin and the weak interaction. But isospin and weak interactions are quite different, so more precise what is the role of SU(2) in ...
2
votes
1answer
67 views

Why are bare mass terms for W-bosons forbidden, but coupling terms to Higgs doublets allowed?

The $W$ bosons live in the adjoint rep of $SU(2)$, which is three dimensional. The standard model Higgs lives in a $SU(2)$ doublet, i.e. the two dimensional rep. The $W$ bosons get their mass ...
1
vote
1answer
92 views

Experimental evidence of two neutrinos in muon decay?

We know that the pion decays into a lepton/neutrino pair while the muon decays into a muon neutrino, electron and electron neutrino. How do we distinguish them experimentally? Would the muon decay ...
8
votes
2answers
1k views

Is half-life a statistical average of variable decay times?

Is the half life of a material only accurate as long as you are still in a macroscopic regime? If I had 8 particles in a box would I observe a fluctuation in half lives, and what would occur within ...
0
votes
0answers
22 views

What is the entropy of strong and weak nuclear forces? [duplicate]

Can we determine the entropy of strong and weak nuclear forces? If so, what will be the formula to determine the strong and weak force entropy? Thank you :)
3
votes
0answers
145 views

Is there a relationship between force and entropy?

Is there any relation between force and entropy? If any, I would like to know what the equation of this relation will be. What is the entropy of strong and weak nuclear force? Can we determine it? If ...
3
votes
0answers
56 views

Matrix elements of four-quark operators [closed]

In weak interaction phenomenology, especially in strangeness changing processes, effective four-quark operators are used. Such as $Q_1 = (\bar{s}_\alpha \gamma_\mu (1-\gamma_5) d_\alpha) ...
2
votes
2answers
55 views

Ambiguity with reaction equations

I understand that if two particles are on the left hand side of a reaction equation they are said to "interact". For example, $p+e^{-}\rightarrow n+v_e$ is a proton and electron interacting (electron ...
1
vote
1answer
343 views

How to tell if a particle interaction is strong/weak?

Problem: Prove that the reaction $p+p\rightarrow p+K^+$ is impossible, where $p=\text{proton}$, $K^+=\text{kaon}$. (Side question: Is there a specific name for a positive Kaon, just like a "positive ...
0
votes
1answer
63 views

What does “interact via strong force” mean?

I was just wondering if the words "strong force" and "strong interaction" are interchangeable? Also, these are referring to "strong nuclear force", correct? Then what does it mean for particles to ...
3
votes
1answer
128 views

Could the 4 Forces Split Off or “Decay” into Other Forces in the Distant Future? [duplicate]

From my basic understanding of popular-level physics articles and books and such, the 4 forces (Electromagnetism, Gravity, Strong and Weak Force) used to be 1 force in the early universe, then split ...
1
vote
0answers
131 views

About generator of $SU(2)$ flavor symmetry group

I am reading the textbook, "weak interactions" by Howard Georgi which can be founded in his homepage. Here i am trying to solve the problem 1b-2. The problem is given as follows. Consider the ...
1
vote
1answer
33 views

Mass dimensions and weak interaction

The Fermi constant has a mass dimension of $-2$ and a value of $10^{-5}GeV^{-2}$. How can I infer from this information that the mass scale of the weak interaction is about $10^2 GeV$?
3
votes
1answer
56 views

Decay Feynman diagram

$$D^0 \to K^+ +\pi^- + \pi^0 + \pi^0$$ cannot occur by first order weak interactions. Could anybody help me confirm this? What I currently have is that the initial charm goes to anti-strange and the ...
0
votes
1answer
212 views

What are the equations for the weak and strong forces?

What are the equations for the strong and weak force, like how for the Electrostatics the equation is $F_c= k*Q*q/(r*r)$. I understand to an extend what the strong and weak forces are. However, I ...
1
vote
1answer
77 views

What are the quantum numbers of Majorana neutrinos?

I have a question about majorana neutrinos. Majorana particles are particles that are their own antiparticle. From this I would argue that they need to have all quantum numbers equal to zero. My ...
0
votes
2answers
37 views

What would happen if weak bosons wouldn't interact with higgs field?

I have a silly question - what would happen if weak bosons wouldn't interact with higgs field? What would happen to weak interactions? How it would affect mass of other particles?
3
votes
2answers
451 views

$\mathrm{\rho^0}$ meson decay via the weak interaction?

Of course, the $\mathrm{\rho^0}$ meson can decay in $\mathrm{\pi^{+}\ \pi^{-}}$ through the strong interaction. Using Feynman diagrams, I cannot understand why the same decay couldn't happen through ...