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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In Madame Wu’s experiment, why don’t we say the electrons are emitted opposite to applied magnetic field instead of saying opposite to their spin?
My understanding of the experiment is that if the magnetic field for example, is applied away from me, and so the orientation of the spins will also be away from me aligned to the magnetic field. Now ...
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If neutrinos have non-zero mass, and hence are not in a pure chiral state, couldn't the sterile neutrinos still interact with the Weak Force?
I was reading this article on neutrino physics, and there's one point in the Seesaw mechanism I didn't understand:
If neutrinos have mass, the mass eigenstates need to have an admixture of left-handed ...
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Neutrino oscillation via some unknown interaction mechanism
My query is based on this post. Similar to the Feynman diagram proposed in the problem, why don't we consider a similar mechanism in beyond standard model to explain the neutrino oscillation? It would ...
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Fermion Charges and Intermediate $B-L$ Charge in Trinification
We have a Trinification Model, $$SU(3)_C \times SU(3)_L \times SU(3)_R.$$ The first group is the colour group, the second is the Left Weak force and the third is the Right Weak force. There are 27 ...
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How parity violation in weak interaction relate to electromagnetism?
https://en.wikipedia.org/wiki/Electroweak_interaction
After the Wu experiment in 1956 discovered parity violation in the
weak interaction, a search began for a way to relate the weak and
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Does $K_L^0 →π^+π^−$ violate strangeness and/or parity?
The long-lived neutral Kaon $K_L^0$ is a superposition of $K^0$ and its antiparticle $\overline{K^0}$. Thus, I would say the strangeness is 0 on both sides. However, if we draw the corresponding ...
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Does the weak force hold electric charges together in the way that virtual photons do?
If two electric charges of opposite sign are within 10^-18 metres of each other does the weak force help attract them together just as virtual photons from the electric force do?
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A question about Wu's parity check experiment
It is known that the Co-60 nucleus are polarized by an external magnetic field.
Is the magnetic field on when the data collecting starts? Or is it off?
I notice that the horizontal axis is time in her ...
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What are the known or hypothesized pathways for the $\Lambda^0 \rightarrow n + \pi^0$ reaction?
Note to the Gentle Reader
I have found over the years that the moderators herein often offer negative marks, but when doing so they seldom offer helpful commentary. I am genuine in my desire to learn ...
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Does $\Lambda^0 \rightarrow p^+ + \pi^-$ reaction involve strong or weak force?
Since $\Lambda^0$ has strangeness equal to +1, a proton has strangeness equal to 0, and a pion has strangeness equal to 0, can I therefore conclude that the reaction
$$\Lambda^0 \rightarrow p^+ + \...
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What is the associated charge for the weak neutral current?
So for the strong force, there's color charge; for electromagnetism, there's electric charge; and for weak charged current, there's weak isospin. How about the weak neutral current? Is there an ...
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How can a virtual $W$ boson turn into an electron and electron antineutrino?
This is specifically with regard to beta decay. My current understanding is that in one type of beta decay, a neutron turns into a proton, an electron, and an electron antineutrino. In order to change ...
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What does it mean for the electron to be absorbed in electron capture?
In electron capture, when looking at the Feynmann diagram, I'd interpret the interaction as the electron emitting a W boson which interacts with the proton and turning into a neutrino. However, as the ...
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Why do heavy bosons have less range?
Why is it that there's a precise relationship between the mass of a mediator particle and its range? Because mass shouldn't directly affect decay time, right?
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How does a $\mu_R^-/\mu_L^+$ decay?
While studying SM, I was taught that weak force bosons $V=\{W^\pm,Z^0\}$ do not interact with right/left-chiral fermions/antifermions. For this reason, we cannot observe right-handed neutrinos (if ...
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Fermi theory cutoff from unitarity bound
Tree-level cross sections for processes described by Fermi theory behave like $\sigma $ $\sim$ $G_{F}^2 \cdot s$, where $G_{F}$ is the Fermi constant and $\sqrt s$ is the energy entering in the ...
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Elastic vs inelastic scattering in particle physics
Does elastic scattering occur via the Z boson and inelastic scattering via the W boson? If so, why? Does it have something to do with the fact that interactions via the Z boson don't change quark ...
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$Z$ bosons coupling to other $Z$ bosons
I'm learning about Higgs boson production at the moment. One way that it's produced is by 'vector boson associated production' or VH, which has this Feynman diagram:
What I'm wondering is: how can $Z$...
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Average kinetic energy of a non-relativistic electron in beta decay
I am trying to show that (a bird told me), in a beta decay, the average kinetic energy carried off by a non-relativistic electron is $E_0 / 3$. I have derived that, for the states, a distribution
$$dN ...
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How does crossing symmetry affect the value of an electroweak vertex (e.g. $u+W^-\to d$ vs. $W^-\to\pi^-$)?
Two of the weak charged current vertices I often encounter in my first foray into particle physics are $u+W^-\to d$ and $W^-\to\pi^-$, shown in the following Feynman diagrams:
These feel like the ...
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Can $W^\pm$ bosons act by changing the weak isospin state of particles?
From what I understand, the weak isospin part of the symmetry-unbroken electroweak interaction consists of the $\mathfrak{su}(2)$ valued gauge field $\hat W_\mu = \sum_i^3W^i_\mu \hat T^i$, where $\{\...
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Is electron capture the exchange of a virtual $W$-boson?
Betaplus: an upquark emits a $W^+$-boson which turns it into a downquark and then decays into a positron and electron neutrino.
Electron capture: an upquark emits a $W^+$-boson which is absorbed by a ...
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Asimov's nuclear intensifiers
Well, it is fiction: in Isaac Asimov's stories there are "nuclear amplifiers" that magically (fiction without even an attempt of explanation) produce a beam of W-bosons, thus amplifying the (...
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Kinematics in the pion decay
If a charged pion decays via a charged current $W$, the $W$ boson is much heavier than the pions. How is this not a problem? Could the processes be off-shell in such a drastic manner?
It is tempting ...
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Determining force of interaction from a decay equation
I have the decay equation
$$p + π^− → n + K^− + π^+.$$
I have been told the force of interaction in this is the weak nuclear force, but I was looking for an explanation of how you can work that out ...
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General matrix element in weak interaction
During my studies on weak interactions and $\beta$-decay, I've to study how theory and experimental results bring us to achieve the V-A structure of weak vertices. My doubts regard the theory.
Suppose ...
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Neutrinos and Weak interaction
As a beginner in particle physics I have a small doubt. Do we get neutrinos as a product in any process involving weak interaction? Is emission of a neutrino signature of weak interaction? OR there is ...
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Does the kaon participate in the weak interaction?
I'm looking at a physics textbook for A-level and in the book it states that kaons are only affected by the strong force and the electromagnetic force.
Isn't this incorrect?
Aren't kaons affected by ...
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Do the WI coupling constants change sign under $C$?
I am trying to understand discrete symmetries in the SM, and I have some troubles in understanding why the CC interaction violates CP. In my (badly written) notes it's said that, taken two fermonic ...
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Interpretation of Gargamelle Experiment Photos
I have been trying to understand the Gargamelle experiment, but would like some clarification.
I understand the apparatus is designed to cause charged particles to generate bubbles which are visible ...
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Gauge invariance of simplified weak interaction
I am having difficulties with a homework set. We are given the following lagrangian for a simplified weak interaction between an electron $\psi$, neutrino $\chi$, and a massive (complex) vector-boson $...
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Mass of different isospin baryons
Why are the masses of baryons (of same quark content) with different isospin, different? - Is there a physical intuition/explanation to this? Does higher isospin baryons always higher mass than lower ...
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Why is the decay of the positive Kaon into two Pion more likely than decay of the positive Kaon into three Pion?
I was wondering if someone could explain me (or introduce me a reference) about my following question:
Why is the decay of the positive Kaon into two Pion more likely than decay of the positive Kaon ...
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Feynmann diagram for $W$ boson decay
So a $W^{-}$ boson decays into right-handed antineutrino and left-handed lepton with "wrong" helicity. I found that textbook explanation of that process involves lots of handwaving.
I am ...
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Why is the fermionic sector of Standard Model the way it is? [closed]
"Because it works!" will be considered too broad an answer. I want to precisely know which experiments forced to consider the model construction the way it is. For example, I can see Wu's ...
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Why is the vacuum state $|0\rangle$ invariant under parity?
I was studying the leptonic pion decay $\pi\rightarrow l\nu_{l}$, and usually the amplitude is computed by
$$\mathcal{M}(\pi\rightarrow l\nu_{l})=-i\frac{G_{F}}{\sqrt{2}}V^{*}_{ud}\langle0|\bar{d}\...
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How Fast Can Toponium Form?
I understand that Toponium is only theoretical because the T quark decays too quickly.
My question is this, would a right handed T quark live long enough to form a meson? If not, how long would it ...
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How is the chirality for the weak interaction conserved for non-relativistic neutrinos?
In this article, one can read that the neutrinos in the cosmic neutrino background have a speed of about 1/50 of the speed of light, which is clearly non-relativistic.
From the viewpoint of, say, ...
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Electroweak Interaction and SSB
I read that above unification energy, on the order of 100 GeV, electromagnetic force and weak force would merge into a single electroweak force.
I do not really understand how and when exactly two ...
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Gamma Ray Emission in the Wu Experiment
In the classic Wu experiment (https://doi.org/10.1103/PhysRev.105.1413) parity violation was discovered in the weak interaction through the asymmetry in the distribution of electrons in the beta decay ...
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How does parity conservation follow from the Wu experiment?
The Wu experiment shows how parity symmetry does not hold for the weak force. However, how does this proof that parity conservation also doesn't hold?
If my understanding is correct, the absence of ...
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Why are there no particles that ONLY interact via the strong force?
The title speaks for itself really: I noted everywhere I learned about fundamental interactions that there are particles that interact ONLY via the Weak Force (and gravity, if it counts)(e.g. ...
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Is this Why a Neutron can Decay Into a Proton, Electron and Electron Antineutrino?
A neutron is udd, then an u-anti-u starts to exist close to the neutron. Then the one d and u change places forming an uud (proton) and anti-ud which decays to an electron and electron-antineutrino. ...
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Calculation of the decay rate of the $W$ boson
I am trying to calculate the decay rate of the $W^-$ boson to a charged lepton and the corresponding antineutrino.
I denote the four momentum of the $W$ boson with $q = (M_W, \vec{0})$. The momenta of ...
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Two Possible States for Weak Interactions?
Layperson trying to learn particle physics here. For strong interactions, there are three colors (and corresponding anti-colors) which define the possible states of a particle (i.e. quark) for the ...
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Improved estimate of density of free neutrons in solar core
In an answer to this question:
Free neutrons in the sun's core?
I made a very rough attempt to estimate the density of free neutrons in the solar core. There is some non-zero rate for production ...
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Isn't weak interactions necessarily violate strangeness?
The electron-proton elastic scattering process $$e^-+p^+\to e^-+p^+$$ can take place either via a photon exchange (electromagnetic interaction) or via $Z^0$ exchange (weak interaction). But isn't weak ...
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How is this equation about pion decay derived?
I'm reading Peskin's Concepts of Elementary Particle Physics and these equations confuse me.
What are the $\pi^1$ and $\pi^2$ in (15.49) and why $\pi^-$ equals to this?
I don't understand the ...
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How do we prove that hypercharge is different for singlets and doublets?
I am trying to teach myself about the standard model and I am stumped by this point.
I understand that:
When picking an U(1) generator for SU(2)xU(1), any multiple of the identity will do ($YI_n$)
...
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$\beta^{+}$ and $\beta^{-}$ decay processes
We know that electron cannot exist inside the nucleus for various reasons like its energy, angular momentum violation and etc. But these $\beta^{+}$ and $\beta^{-}$ processes occurs inside the nuclei ...
