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 interactions are unified (that is subject to a unified mathematical treatment).

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Question about the parity violation of weak interaction Lagrangian

In the textbook of A. Zee, Quantum Field Theory in a Nutshell, the author states that the following Lagrangian: $$ \mathcal{L} = G (\overline{\psi}_{1L} \gamma^\mu \psi_{2L})(\overline{\psi}_{3L} \...
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Is there a law stating why a quark never decays weakly into a quark of the same weak-isospin ($T_3$)?

So I read multiple articles on weak isospin and one of them stated that "a quark never decays weakly into a quark of the same $T_3$". If this is true, can someone please explain what law ...
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Where does the Energy for $W$ and $Z$ Boson Emission come from?

I understand that the Weak interaction is mediated by the $W$ and $Z$ bosons, and that their huge masses are the reason for the Weak interaction's short range. However, I cannot find an explanation ...
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Translating Parameter Estimation Principles of Quantum Weak Measurement to a Classical Problem

I am not an expert in quantum theory. I want to carry out some parameter estimation on a set of data I have. I have a model for the data with the parameter(s) of interest as variable(s). The data ...
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Charged current $e^-e^+$ weak interaction Feynman diagram

I am new to the weak interactions and in particular to the interactions given by charged current interaction lagrangian $$ \mathcal{L}_{int}^{CC} = \frac{g}{2\sqrt{2}}\left[J^{\mu}W^{+}_{\mu}+J^{\mu \...
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Has there been experimental confirmation of electron capture being a neutrino source?

Detecting nuetrinos is not easy of course but it seems that there are several interesting ways of playing with neutrinos using radioactive sources that can only decay by electron capture. For example, ...
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Can someone clarify this quote about weak interactions causing neutron-to-proton ratio to go to zero if equilibrium were possible?

I'm self-studying Modern Cosmology by Dodelson and Schmidt 2nd edition, and I've found a certain passage in Section 4.2.1 particularly interesting. It says, Therefore, at high temperatures, there ...
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Electroweak theory Landau pole

It is known that non-asymptotically free theories like Quantum Electrodynamics or Scalar field with quartic interactions ($\phi^4$) have a landau pole which mainly investigated through lattice ...
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Why can't neutral pion decay to two neutrino's

I know neutral pions mostly decay electromagnetically to two photons, but I don't understand why the decay to two neutrino's is not possible. Perhaps they violate parity, but someone at the link https:...
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Is this an allowed interaction?

I am looking to understand whether this reaction is allowed: $$e^+ + e^- \rightarrow K^0 + \pi^0.$$ Baryon number is conserved Charge is conserved Total intrinsic spin of underlying particles is ...
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Antiparticle from the weak charge

For the electromagnetic charge and the colour charge, every particle carrying these charge has an antiparticle having the opposite charge. Why are there no antiparticle from the weak charge?
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Working through the solution of the Ozma problem

I’m trying to work through the Ozma problem and the Wu experiment to get a better handle on parity and I’m being tripped up by something which is almost certainly trivial. I can explain negative ...
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Chirality vs Helicity in Top Quark Decay

I still have not had a good explanation of how a Right Handed Top Quark decays. As I understand it, helicity and chirality are both a part of spin. Does this mean that if either is left handed, the ...
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How is C-symmetry violated?

I see how P-symmetry and CP-symmetry are violated, but no one is talking about experiments related to C-symmetry. How did people prove that C-symmetry is violated?
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Do cold neutrons produce radioactive elements?

As far as I have understood neutron nuclear reactions, if a fast neutron gets captured by a nucleus, since the kinetic energy has to go somewhere, the newly formed nucleus is radioactive and must ...
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Nuclear Physics - Meaning of Terms in Beta Decay Hamiltonian

I am new to nuclear and particle physics, but am familiar with the concept of a Hamiltonian and nonrelativistic quantum physics. In this paper by Yang and Lee on parity conservation in weak ...
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Why do $Z$ or $H$ bosons can decay to a pair of quarks $t^+t^−$ with mass larger than boson in the inertial reference frame of boson?

The masses of $Z$ or $H$ bosons is less than the sum of the mass of two $t$ quarks. Why do $Z$ or $H$ bosons decay to a pair of quarks $t^+t^−$ with mass larger than boson in the inertial reference ...
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Can Top quarks change their spin direction?

Since we know there are right handed quarks, and that the Weak Force does not interact with Right Handed particles, if a quark cannot change its spin direction, how does the Top quark decay? If the ...
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Mass difference of $B^0$, $\overline{B^0}$-states

It is known that $B^0$, $\overline{B^0}$ or $K^0$, $\overline{K^0}$ particles have different masses and that they oscillate in 'an equivalent' way to neutrino oscillations. Is it theoretically ...
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Where are the right-handed leptons?

So the weak force only works on left-handed leptons and quarks. Does this mean there are no right-handed leptons and quarks? If there are, why don't we see an abundance of right-handed particles that ...
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Kaon decay parity if pion parity is redefined as +1

I am reading in Neeman’s book, The particle hunter, second edition, page 169, about the “theta-tau riddle.” He writes that You might suggest that we define the parity of the pion as $+1$, but this ...
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Handedness over the current terms in Feynman diagrams

This is a question about the Feynman diagrams: imagine I want to calculate the following process: $$\nu_{e, L} + e^-_R \rightarrow \nu_{e, L} + e^-_R$$ I can have a t-channel diagram with $e^-_R e^-...
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How long can an unstable particle live? Is there a theoretical upper limit?

Somehow, in all my years of studying and reading, I have never come across an answer to this question.... Is there a fundamental limit to the lifetime of even the shortest-lived subatomic particles, ...
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Fermi's theory and left-handed anti-neutrino

I calculated the $\mu \rightarrow e^- + \nu_{\mu} + \bar{\nu}_{e}$ both in Fermi's theory (V-A) and Intermediate Vector Boson theory and IVB at first order seems to match with Fermi's theory which is ...
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Can interactions be both Cabibbo suppressed and allowed?

Concerning the decay of the $K^+$ meson as shown in picture. I am restricting the analysis to the first two generations of quarks. As far as I understand, Cabibbo suppressed decays occur at $W$-...
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What would happen in a hypothetical universe without the other forces other than gravity? [closed]

What would be the rules of a hypothetical universe where there is only gravitational force, and weak strong and EM force do not exist? What would be the consequences of that?
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Quick question about $\nu_{\mu} + e^{-} \rightarrow \nu_{e} + \mu^{-}$ scattering in intermediate vector boson theory

Below I added a diagram representing the $\nu_{\mu} + e^{-} \rightarrow \nu_{e} + \mu^{-}$ process and the corresponding Feynman amplitude: Please ignore the typo $k^2 = t^2$. It is $k^2 = t$ I know ...
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Does stimulated emission also occur under the weak force?

Q: is stimulated emission only relevant for electromagnetic interactions through photons, or is it also valid for beta-decay? Example: Imagine an amount of tritium decaying in a strong beam of anti-...
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Nuclear FISSION origin

Neutrons and protons consist of quarks, and when a neutron and a proton are squeezed tightly enough together, the quarks in each begin to interact and cause them to attract one another. The resulting ...
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What, exactly, is the Fermi Constant? What is its value? And what is the difference between $G_f$ and $G_f^0$?

There is no Wikipedia page for Fermi's Constant, and the page they DO have is confusing. From Fermi's Interaction: How can $G_f^0$ not be equal to $G_f$? What is the difference? And when they give ...
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Deep Ineslastic Scattering for neutron and proton in weak-interaction

I'm studing Deep Inelastic Sacttering theory to study the parton model. I have studied the scattering $$e+q \to e+ q$$ And the structures functions $$F_1 = \frac{1}{2} \sum_q e_q^2 \cdot q(x)$$ and $...
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Can weak measurement principles of Quantum mechanics be used in similar questions in classical estimation problems?

This is a surface level question and I don't want to go into detail. Imagine an algorithm which when used with a sensor output gives the statistical moments of a variable in nature (for example mean ...
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Does the weak interaction conserve both weak hypercharge and electric charge?

And if so whats the motivation for the introduction of hypercharge?
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If a weak eigenstate (such as a $d'$ or a neutrino) interacts with a gravitational field do the mass eigenstates interact on their own?

Weak interaction eigenstates don't correspond with mass eigenstates. I was wondering how such a superposition of mass eigenstates would interact in a gravitational field. I assumed they would do so ...
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Can the weak interaction be studied without bothering the electromagnetic one?

It is well known that the electroweak interaction can be studied as a $SU(2)_L \otimes U(1)_Y$ gauge theory. It is also known that the electromagnetic interaction is a $U(1)$ gauge theory, and it ...
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Are chiral fermions and chiral bosons equivalent in a chiral Lagrangian?

Is it equivalent to talk about a chiral theory in terms of 1. chiral fermions which are differently coupled to the gauge field or 2. fermions coupled to a "vector minus axial" gauge boson? ...
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Flavor-changing neutral currents (FCNC) and leptons oscillations

I have some confusion regarding flavor-changing neutral currents (FCNC) processes and relative meson-antimeson oscillations. If the question has already been asked, I'm sorry, I didn't find what I was ...
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Why is positron in the Feynman Diagram for β+ decay directed towards the W+?

From https://en.wikipedia.org/wiki/Beta_decay In $β^+$ decay, or positron emission, the weak interaction converts an atomic nucleus into a nucleus with atomic number decreased by one, while emitting ...
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Why does S-V or T-A couplings in Fermi weak interaction model produce electron oscillations?

In Fermi interaction model, vector bilinears were originally included in the interaction Lagrangian but since these couldn't explain nuclear spin changes other combinations were considered. However V-...
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Does the weak force get transmitted at speeds less than $c$?

The force carrier of EM is the photon (or off-shell photons at least). These are massless field disturbances. However the force carriers in Weak interactions are the $W$ and $Z$ bosons. Having mass, ...
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What are the weak force and strong force and higgs constants?

We use the SI System of measurement which is a human made system. In order to accurately describe forces/fields in nature we need to use certain experimentally determined constants to "scale"...
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How do the strong and weak forces relate to nuclear fission and fusion?

Fission and fusion are due to the strong and weak forces, but it is unclear to me which is responsible for which.
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Why can't I assume the quarks inside a hadron move together?

Looking at the following Feynman diagram: Using conservation of energy, we can see that in the rest frame of $D^0$, the energy of $K^-$ is higher than its rest energy. Meaning, it is in motion. I ...
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Distinguishing right/left hand by aliens

If we are in some way contacting aliens, and we want to tell them how to use nuclear $\beta$ -decay to tell clockwise from counterclockwise. For this, we will need to figure out how to relate the L in ...
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If magnetic monopoles exist would magnetic charge contribute to weak hypercharge similar to how electric charge does?

Electromagnetism and the weak force are intertwined as two parts of the electroweak force and some links still exist even at low energy levels one of the being weak hypercharge which is determined by ...
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Why does beta decay of a free neutron not violate conservation of energy?

I apologize for gaps in my knowledge that may make this obvious, but shouldn't the emission of a W boson from a neutron violate conservation of energy? The mass of a neutron is 939.565 MeV/$c^2$, so ...
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Are massless antineutrinos in the Standard Model right-handed or right-chiral?

For massless fermions, their chirality (determining under which representation of the Lorentz group they transform) and their helicity (projection of spin onto three-momentum) eigenvalues are the same....
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Are weak vector bosons produced in atomic transitions?

In another question, I asked if gravitons could be produced in atomic transitions (an electron decaying to smaller energy orbitals). The energy taken away is astronomically small though. Can the same ...
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Why does the weak interaction ineract solely with left handed particles?

So let me elaborate, my problem is that I don't fully understand why the weak interaction is a chiral theory - I would like an answer with the Lagrange density and the Higgs field. I also want to know ...
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How is this Yukawa coupling term invariant?

I have the seen the following term used to describe Yukawa coupling for the lepton and Higgs field: $$ \epsilon_{ij}\phi^{i}\bar{e}_{R}f_{L}^{j} $$ Under $SU(2) \otimes U(1)$ and so expected the ...
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