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Questions tagged [weak-interaction]

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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New weakly interacting particles and resonance

I am wondering if there might be a new type of particles that interact with known physical particles so weakly that they elude our observation, but which may influence certain physical systems in a ...
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What happens during a weak interaction?

For e.g. during $\beta^-$ decay a $W^- $ boson is emitted changing an up quark to a down quark. This seems very weird to me as it looks like that up quark is not interacting with some other particle ...
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What are the other components of the weak isospin?

Sorry for a lazy question, I was just looking this up on the internet for a basic grasp of Standard Model. However, I couldn’t find anything on Wikipedia or just somehow managed to miss it on my ...
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Why Majorana neutrinos is a solution for the existence of only LH neutrinos?

At lesson my teacher stated that the possible reason for why only LH neutrinos are observed are that either: neutrinos are Dirac fermion but the RH neutrinos are not interacting weakly or that they ...
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Why does the weak nuclear interaction have a shorter range than strong nuclear interaction?

My textbook says: "Weak nuclear interaction acts on protons, neutrons, electrons and neutrinos in order to bring about beta decay. It has very short range (10-18m)" "Strong nuclear interaction ...
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Weak force field strength tensors

How do you calculate the values of the field strength tensors in weak nuclear field theory. If you could show an example it would be appreciated.
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Half-life of $W$ and $Z$ bosons

$W$ and $Z$ bosons should decay through weak interaction. But their half-life is around $\tau = 10^{-25} s$ which is a typical value for particles decaying through strong force (instead of a $10^{-12}-...
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Could anyone explain how energy and momentum are conserved when an isolated neutron decays into a beta-minus particle?

I am not able to get to a reasonable explanation as to how momentum and energy are conserved when an electron, a proton, and a neutrino are created.
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Rule of thumb for identifying dominant quark contribution in loop calculations

I am trying to understand some calculations of $B$ meson decays and just stumbled upon the low energy effective weak Hamiltonian describing $\Delta S = 1$ $B$ decays: $$\mathcal{H}_\text{eff} = \...
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Polarisation 4 Vector and Spin Density Matrix

I'm looking at calculating cross sections of weak processes with polarised outgoing particles. I think I have a good understanding of the polarisation vector but quite a few of the papers I've seen ...
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Antimatter: weak and strong forces

Antimatter is known to have equal mass to matter and opposite charge sign. Positron has the same mass as electron and opposite sign of charge, anti-proton has the same mass as proton and opposite sign ...
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A place of space-time where the only fundamental interaction will be the gravitational forces: does make sense?

We know that there are four (fundamental forces) fundamental interactions of nature, this Wikipedia. I'm curious about if we can speculate that there exists a place of the space-time in which, after ...
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About the electroweak force

So, I'm struggling to understand how the electromagnetic and the weak force were connected. Separately, I know pretty much how the two forces work and interact with the environment. I read a few about,...
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Universality of the Z interactions

In the SM the interaction of leptons and quarks with the Z boson are universal, and the way to see it is to start with the covariant derivatives which lead to terms of the form $$ \delta_{ij}\bar{\psi}...
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Equality of positron and proton charge problem statement

When I hear that the equality of positron and proton charge is an unsolved problem I assume that we are putting the electric charge by hand in the electroweak section of the SM Lagrangian. Is this ...
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Could the electron count as a force-carrying particle?

Pretty straight-forward this one. If we're going to get a bit more nit-picky about this relatively straight-forward question I'd like to first of all point out that yes, I have considered that ...
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Electroweak Force Capabilities

I understand that Electroweak force is the unification of Weak force and electromagnetism, but that are the actual effects or capabilities of this fundamental force? or at the very lease, what are the ...
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Measuring characteristic time of strong and weak interaction using cross section

Consider a scattering between two particles a and b that produces two particles c and d: d is stable, while c decays in two other different particles e and f. The first interaction is by strong ...
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Neutral Kaon Decays to positively/negatively charged Pions

$K^{0}$ meson consists of a $d$ quark and an $\bar{s}$ antiquark. Its antiparticle $\bar{K^{0}}$ consists of an $s$ quark and a $d$ antidown quark. $$|K^{0}\rangle=|d\bar{s}\rangle$$ $$|\bar{K}^{0}\...
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Feynman amplitude and tensor 4-vector multiplication (muon neutrino-electron scattering)

In the calculation of the Feynman Amplitude for the muon neutrino-electron scattering (in the Charged Current way from W boson), or $e + \nu_\mu \rightarrow \nu_e + \mu$ (considering the 4-momentum ...
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Parity in Madame Wu experiment

To see the effects of parity violation it's necessary to consider an observable that is non-invariant under parity, was chosen the projection of the electron momentum ($p_e$) on the polarization ...
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What gives mass to dark matter particles?

Assuming that dark matter is not made of WIMPs (weakly interacting massive particles), but interacts only gravitationally, what would be the possible mechanism giving mass to dark matter particles? If ...
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Well colour me surprised$.$

I was reading Scharf's Quantum Gauge Theories: A True Ghost Story when I stumbled upon the following paragraph (p. 118): The standard example of a gauge theory with massless gauge fields is the ...
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Weak interaction of $(\nu^c)_R$ fields of the SM and $N_R$ fields in type-I seesaw extension of the SM

The antiparticle of $\nu_L$ is given by its charge conjugated field i.e., $(\nu_L)^c$ which is equal to $(\nu^c)_R$. Both $\nu_L$ and $(\nu^c)_R$ are part of the Standard Model (SM) of massless ...
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A proton's weak charge is .0719. Is this dimensionless? A ratio?

A recent piece of major news in the physics world is that the proton's weak-force charge was measured to be .0719. Is that a ratio? A dimensionless number, with no units? The articles I read ...
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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?
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Is it possible for the reaction $\pi^+ \, \pi^- \rightarrow \nu_e \, \bar{\nu}_e$ to occur? If so, how would this happen?

The reaction doesn't violate any conservation laws that came to my mind - however I am having trouble thinking of how it might occur.
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How are neutrino energy eigenstates different to the momentum eigenstates?

Neutrino flavour eigenstates can be expressed (approximately) in terms of their mass eigenstates, leading to neutrino oscillations. $|\nu_e\rangle = \cos \theta |\nu_1\rangle - \sin \theta |\nu_2\...
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1answer
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How to derive the decay rate from the Lagrangian of an interaction?

For instance, in Fermi theory of beta decay, the lagrangian is shown in the fig. How do we derive the decay rate and the distribution of kinetic energy from that?
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Question about nuclear reation

In Landau and Liftshitz Volume 5 page 318, it talks about nuclear reaction in high density, where proton reacts with electron and becomes neutron and neutrino: $$A_z+e^- = A_{Z-1}+\nu$$ where $A_z$ ...
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No global monopoles in QCD

If a global symmetry gets both spontaneously and explicitly broken, the explicit symmetry breaking pattern is crucial for understanding the formation of topological defects. For example, in the axion ...
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1answer
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Why is the Beta-Decay of a Neutron asymmetric?

The Wu-experiment, which originally showed the parity violation of Beta-Decay experimentally, is often used to give an intuitive explanation for the asymmetry of the decay: $${}^{60}_{27}\text{Co} \...
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What is the reason for emission of anti-neutrino during beta emission?

My book says that "Later on, to keep the number of particles either odd or even on both sides another particle called anti neutrino, was also assumed to be emitted along with the beta particle. ...
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Does the field (force-carrying) of a gluon or boson have a magnetic-like shape? Not spherical

The challenge of force-carrying boson is that many experiments generate results that are not consistent. Hence, quantum statistics. It is established that things like 'strong nuclear interaction/...
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Interaction of the leptons before the electroweak phase transition

This question is related to this one: Form of Coulomb’s law before the electroweak phase transition. Given that the electromagnetic and weak forces were united before the electroweak phase transition ...
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1answer
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Why is the Fermi coupling $G_F$ is measured from muon decay?

The decay rate of all weak processes, calculated from the $V$-$A$ theory will contain a factor of $G_F$, the Fermi coupling constant. However, $G_F$ is usually measured from $\mu^-$ decay which is in ...
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What are the Feynman diagrams for neutrino oscillations?

Which Feynman diagrams are at the basis of neutrino oscillations? I find no clear explanation via Google.
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Corrections from violation of P-symmetry for chemistry, biochemistry, life?

Imagine a mirror image of a biological cell: all molecules replaced with their symmetric versions (enantiomers). At least in theory, we should be able to synthesize it (Wikipedia), for example for ...
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1answer
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Weak isospin 1/2 vector bosons

The weak vector bosons are spacetime vectors (spin 1) and also incidentally weak isospin vector components (-1, 0, +1). I understand why that is required from nucleon beta decay and other weak ...
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Calculation of the weak coupling constant

There are two ways to calculate the coupling constant of the weak interaction $g$. 1) From the electromagnetic coupling constant and the weak mixing angle, using the relation $${\sf e} = g\sin(\...
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What is the direction of the weak force between electrons and protons?

Is the weak force between electrons and protons repulsive or attractive? Does it affect somehow the electron shells of atoms?
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Why can increasing energy, the weak force and the EM-force become a similar force?

When the heat of the universe was much higher it seems that the weak force and the EM-force was combined into the electro weak force. For a layman the EM-force and the weak force look quite different,...
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If Baryons are subject to the strong nuclear force, how are they involved in Beta decay?

The question is really in the title with this one, I just need a little bit of clarity, consider beta-minus decay, which is an interaction governed by the weak nuclear force, $$n\to p^+ +e^- +\bar v_e$...
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Should some neutral particle electromagnetic decays also involve the weak force?

Take, for example, the neutral pion, π0. 98.823% of the time, it decays electromagnetically, into two photons: π0 → 2γ On its face, this process does not violate any flavor quantum numbers: the ...
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Why is $|\bar{K}^0\rangle=\mathscr{CP}|K^0\rangle$ and not $|\bar{K}^0\rangle=\mathscr{C}|K^0\rangle$?

If the charge conjugation operator $\mathscr{C}$ changes a particle state into the corresponding anti-particle state then we must write $|\bar{K}^0\rangle=\mathscr{C}|K^0\rangle$. But instead, we ...
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Is the weak force conservative?

Does it make sense to talk about "conservative" potentials and forces in (quantum) field theory? If yes, to what extent? Is (for example) the weak force conservative and what would it mean ...
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Why doesn't the Higgs give mass to neutrino? [duplicate]

We learn that elementary particles acquire mass through the weak interactions with the Higgs field. The photon and gluons do not interact weakly, do not coupe with the Higgs field and for this reason ...
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Dark matter mass and weak interactions

If dark matter forms halos around galaxies, it must have invariant mass. In the Standard Model, elementary particles acquire mass usually through the weak interactions with the Higgs field. Does this ...
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Why are the masses $m_{W}/m_{Z}$ and the coupling constants $e/g$ related in electroweak unification?

Gottfried and Weisskopf write in their book, in the chapter on electroweak theory, that $\frac{m_W}{m_Z} + \left(\frac{e}{g}\right)^2 = 1$ In this expression, $m_W$ and $m_Z$ are the masses of the $...
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Conservation of Strangeness

The above image is considered to be a reaction that can occur practically. However, isn't the strangeness of $\Xi^-$ -2, and $\Lambda^0$ -1? This would leave a net -1 value on the left side of the ...