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

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Energy release from beta decay

It is difficult for me to understand how beta decay releases energy. The neutron is more massive than a proton, electron and antineutrino combined. Would this not imply that energy is being ...
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How can neutron be converted to proton and electron?

Since a neutron and a proton are made up of quarks and an electron is a lepton, how can a neutron yield an electron?
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A bilinear form or a dot product $X \cdot Y$ of emission X and absorpion Y of a vector boson W in the context of transformation of quark flavors

The reason for this question is related to the fact that I think something is missing when an absorpion and emission of a (intermediate) vector boson $W$ in the context of transformation of quark ...
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How does meson exchange work within large nuclei?

I read the Wikipedia page on Mesons and it mentioned that there both charged and uncharged Mesons that decay into neutrino/electrons and photons, respectively. Unfortunately it didn't elaborate on ...
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Why is $\Delta^0$ not decaying weakly?

Given the lower decay I wonder why it happens this way. Wouldn't it be possible to decay via a weak process as well?
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How does the introduction of the charm quark suppress FCNC?

I did some reading on the GIM mechanism today, and simply fail to understand how it works. I understand how the CKM-matrix can be used to do the basic calculation of the probability of, say, observing ...
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Weak interaction and charge conjugation $C$

Does the weak interaction always change the charge of all participating particles? And in this context, what does $C$-violation do then?
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$K\to \pi \gamma$ decay

I was asked the following question in an exercise sheet: The decay $K \to \pi\gamma$ is absolutely forbidden by a certain conservation law, which is believed to hold exactly. Which conservation ...
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67 views

When a Z boson decays into a particle/antiparticle pair, do those particles instantly annihilate each other?

If you look at a Feynman diagram of neutrino-electron scattering, there is the mediation of force by means of a virtual Z boson, and the product of this interaction is just the neutrino and electron ...
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Decay process of pions

$\pi^+$ and $\pi^-$ decay into muon(or electron) and neutrino and $\pi^0$ decays into photons. So there is a weak interaction in the decay process of $\pi^+$ and $\pi^-$. But the mean lifetime of $\...
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How does the weak interaction sense the instability of a nucleus?

To reduce the disruptive energy, the weak interaction allows the number of neutrons to exceed that of protons (...) (via nasa.gov). How did it know it needs to reduce the disruptive energy? Example: ...
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Confused about the anapole (toroidal) moment

I am a bit confused about the existence of the anapole moment. As far as I understand, in order to fully describe a charge-current distribution, one needs, beside the normal electric and magnetic ...
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What kind of interaction phototelectric effect is?

All standard-elementary books which discuss modern physics quote the value of time of interaction for phototelectric effect to be less than $10^{-8}$ seconds. If the phenomenon takes about this time, ...
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Is the Weak Force really a force?

My definition/understanding of a force still carries largely over from classical physics which is something that tends to change the motion of an object (a push, pull). Gravity and electromagnetism ...
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Is there a radiation equivalent in the strong and weak forces?

I know that light is electromagnetic radiation (sourced by accelerating charge) and gravitational waves are gravitational radiation (sourced by accelerating mass). Is there equivalent radiation for ...
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How are length and time scales for the different kinds of interactions (strong, weak, electroweak) determined?

I was recently asked what the length scale of the strong interaction is and found my self a bit lost at the question. A quick Google search revealed a result of $10^{-15}\,\text{m}\approx 1\,\text{GeV}...
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Pion decay as a point-particle

The $\pi^-$ meson is a composite particle of $\bar{u}d$ quarks, but for many practical purposes it can be treated as a point particle with an effective interaction. The vertex responsible for the $\pi^...
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Below which energy would the weak interaction become confining?

Claudson et al considered an alternative formulation of the standard model where the SU(2) interaction was strengthened to become confining below ≈ 300 GeV, above the electroweak scale. Consider if ...
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What processes conserve (and don't conserve) GUT $X$-charge?

I've been Wikipedia-ing the weak interaction and GUTs and I came across 2 seemingly conflicting pieces of information. In the page for Weak Hypercharge it says this: one of the interactions is with ...
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How do we know that the $W$ and $Z$ bosons aren't composite?

Background to my reasoning: When the strong force was first discovered, it was considered to be the force that interacts between nucleons to keep the nucleus together and that the mediator bosons of ...
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Strangeness Conservation

I am stuck as to how to prove that strangeness is conserved in electromagnetic and strong interactions, while it is not conserved in weak interactions. I know that this can be shown by studying the ...
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Could $\nu_e+p\rightarrow e^-+\pi^++p$ occur via the weak interaction? If so, how would be the Feynman diagram?

I checked if the reaction conservate baryon number, charge and leptonic number and it seems like it does. But I tried to draw the Feynman diagram and I don't understand how the proton interact, so ...
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What is the difference between the differents lennard-jones parameters

I know different lennard jones potentials 12-6, 9-6, 9-3. I think the difference between them is the way they describe long-range interactions,but when I use each of them? Thank you in advance
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How can pure leptonic interactions be mediated by the weak force?

$\mu^+ \rightarrow e^+ + \nu_e + \bar \nu_\mu$ Consider the above decay, it is given in my lecture notes as a weak force interaction. I thought the weak force was only involved when quarks change ...
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The difference between a neutron's and muon's decay lifetime

Both neutrons and muons decay via the weak force/a weak interaction, with the neutron having a mean lifetime of around 900 seconds, and the muon having a lifetime of around 2.2$\mu$s, i.e., a factor ...
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Masssive mediator boson, a game changer, so is the weak force fundamentally different from the other forces?

I have read this question: How it is possible to mediate a weak interactions by very heavy particle such as Boson? How can a pion have a mass, given it's a "field mediator" and ...
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Is there an equation for the weak force?

I have read this question: Is there an equation for the strong nuclear force? Weak force: attractive or repulsive? And yes, I have read the comment, where is says that the weak and the strong ...
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Does the weak force have an attractive/repulsive force observable in everyday life like the other forces?

After the correct comments, this question is not here to compare gravity's and EM's long range forces' energetics and amplitudes to microscopic scattering amplitudes of such forces as weak and strong. ...
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How can weak interactions not conserve strangeness if the SM always conserves energy?

I have read these questions: Weak Interaction and Strangeness transformation Weak decay iff or if strangeness changes? Understanding type of force interaction in particle decays The decay of the ...
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$\tau \rightarrow \nu_{\tau} e^- \bar{\nu}_e$ decay. Where is my mistake?

I want to calculate $\tau \rightarrow \nu_{\tau} e^- \bar{\nu}_e$ decay rate $\Gamma$, with the effective four fermion interaction to leading order. $$\mathcal{L}_{eff} = -\frac{G_F}{\sqrt{2}} [e^+\...
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Weak Interaction and Strangeness transformation

Is there any processes involving weak interaction that preserve the strangeness for $S \neq 0$? I can't find an answer to it on net or anywhere else, generally it is true that weak interaction ...
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Why Neutrino is a ghost particle?

why neutrinos are called ghost particle.why it is not affected by strong magnetic field. why it does not interact with matter. why it does not interact with gravitational field? I am unable to ...
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Spectrum of beta decay

I have a very simple question regarding the emission spectrum of a beta decay: Why does the $\beta^+$-spectrum start at $0$ but the $\beta^-$ doesn't? This would mean that there are a bunch of ...
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When can you simplify the $W$ boson propagator?

I have seen in several sources that the propagator of the $W$ boson is: $$\frac{- i \left( g^{\mu\nu} - \frac{P^\mu P^\nu}{m_W^2} \right)}{p^2 - m_W^2} . $$ But then in some calculations (usually ...
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What would a universe with a long range weak force look like?

If the W's and Z bosons were massless at low energies (i.e. no Higgs interaction), what would the universe look like? Would there be "weak bound states" ? How would electromagnetic theory differ with ...
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Left Handed / Right Handed Particles and the Weak Force

Good Afternoon, I am a 50-year-old guy who was never a scientist or physics student. Just a person who loves to read books on particle physics. I have a question on the Weak Force and particles. (...
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Muon neutrino interacting with nucleon's quarks

I'm considering the muon neutrino/anti-quark interaction with the nucleons of ice in the IceCube experiment. The purpose is to decide which antiquarks are $\bar{q}$ and $\bar{q}'$. I have the ...
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Muon neutrino and down quark interaction diagram

My questions concerns the IceCube experiment, in particular, the interaction between muon neutrino and the down quark. I've drawn the following Feynman diagrams: Are both diagrams correct? Can I say ...
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Unitarity violation: sign inconsistency in Quigg

In Gauge Theories of the Strong, Weak, and Electromagnetic Interactions, C. Quigg explains how the process $\nu \overline{\nu} \rightarrow W^+ W^-$ violates unitarity at high energy unless we add the $...
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Constraints on RH component of fermion triplet under $SU(2)_L$

Consider a fermion $\chi$ whose left-handed part is in a triplet representation of $SU(2)_L$: $$ \chi_{L} = (\chi^1,\chi^2,\chi^3)_L^{\ \ \text{T}}. $$ The charged current of $\chi_L$ (i.e. its ...
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Charged and neutral current in Feynman diagrams

I am stuck on finding the 'right' mediator in weak interactions. Consider the following reactions. 1: $$\mu^+\rightarrow \bar{\nu}_\mu + e^+ +\nu_e$$ This is mediated by the vector boson $W^+$. 2: ...
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Weak interaction, parity violation, and the observer-dependence of helicity

It is said that the Weak Interaction only couples to left-handed particles which a negative spin (left-handed). However some sources say that spin or helicity is dependent on the observer's position ...
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Energy difference between enantiomers (matter/antimatter)

I am aware of the fact that enantiomers have different energies, for example L-amino acids have different energy than D-amino acids. The difference is not significant and is most usually about $10^{-...
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Muon decay - Type of interaction

Why does weak interaction occur when a muon decays? Why can't electromagnetic interaction occur when a muon decays?
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Does the weak force obey the CPT symmetry? How?

I have read that the weak force does not obey the charge symmetry, the parity symmetry, and the time reversal symmetry. Then how does it obey the CPT symmetry?
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Why is the muon decay a Flavor Changing Charged Current (FCCC) process?

One way of understanding why the muon decay $$\mu^-\to e^-+\bar{\nu}_e+\nu_\mu\tag{1}$$ is a Charged Current (CC) process is to write the intermediate step through which the decay (1) proceeds i.e., $$...
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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 ...