39 votes
Accepted

Can neutrinos "hit" electrons?

Yes, neutrinos "hit" electrons all the time inside the sun, on their way to getting out, which results into the resonant conversion of their flavor, predicated on the changing effective index of ...
Cosmas Zachos's user avatar
27 votes
Accepted

How can K (kaon) and Σ (sigma particle) be created quickly via the strong interaction and decay slowly via the weak interaction?

Kaons and sigmas contain strange quarks, so the "ground state" particles must decay by changing quark flavour. The strong and electromagnetic interactions cannot change flavour, but the weak ...
dukwon's user avatar
  • 2,044
26 votes

Can neutrinos "hit" electrons?

Can neutrinos “hit” electrons? Yes, e.g., Image credit
Alfred Centauri's user avatar
26 votes
Accepted

What gives mass to dark matter particles?

I think this question contains a misconception unfortunately caused by popular science descriptions of the Standard Model. The question seems to assume there needs to be some concrete source that ...
knzhou's user avatar
  • 102k
22 votes

Why must the speed of light be the universal speed limit for all the fundamental forces of nature?

$c$ is not first and foremost the speed of light. It is first and foremost the universal speed limit of a cause-effect relationship - if $A$ influences $B$ (in the same inertial frame) causally, and ...
Selene Routley's user avatar
22 votes

What exactly does the weak force do?

The weak force is one of the fundamental forces, but it doesn't have a strong attractive or repulsive effect on particles, and the term "weak interaction" is often preferred. For details on ...
PM 2Ring's user avatar
  • 12.1k
17 votes
Accepted

How many kinds of "weak charges" exist?

The problem with "weak charges" is that electroweak symmetry is spontaneously broken. Before the symmetry breaking, electroweak symmetry is described by an $SU(2)_L \times U(1)_Y$ gauge group.This ...
Bosoneando's user avatar
  • 5,644
17 votes
Accepted

What exactly does the weak force do?

Some background As it seems that you aren't terribly familiar with the nitty-gritty mathematics of quantum mechanics (and believe me, I'm not either), perhaps I can bridge your curiosity to a more ...
Graviton's user avatar
  • 690
16 votes
Accepted

Are electroweak particles stable?

It's isn't terribly meaningful to say that Photons made of the electromagnetic force or that the W and Z bosons made of the weak force, though it's certainly true that these particles are the gauge ...
John Rennie's user avatar
15 votes
Accepted

Standard Model Proton Decay Rate

Electroweak instantons violate baryon number (and lepton number) by three units (all three generations participate in the 't Hooft vertex). This is explained in 't Hooft's original paper. As a result, ...
Thomas's user avatar
  • 18.7k
12 votes

How many kinds of "weak charges" exist?

You're mixing a few things up here. When you say "three" for the strong force, you're counting the number of colors of quarks, but when you guess "three" for the weak force, you're counting the number ...
knzhou's user avatar
  • 102k
12 votes

Why are there no particles that ONLY interact via the strong force?

You forgot the gluons (the bosons mediating the strong interaction). They interact only via the strong force, i.e. with quarks and other gluons.
Thomas Fritsch's user avatar
11 votes
Accepted

Why can't matter anihilate with itself?

One has to realize that words in physics have a definite meaning. This meaning, for words used in physics, is dependent on the specific mathematical model that uses it. The mathematical model for ...
anna v's user avatar
  • 234k
11 votes
Accepted

Has the weak force ever been measured as a force?

If by "force" you mean a change of energy and momentum but not the type or number of particles involved, then weak neutral currents would be the answer. These were predicted by Salam, Glashow & ...
user1998586's user avatar
11 votes
Accepted

Are massless antineutrinos in the Standard Model right-handed or right-chiral?

There are lots of questions on this site about chirality versus helicity, but you can clear them all up by just remembering that helicity is a property of particles (since it's defined in terms of a ...
knzhou's user avatar
  • 102k
11 votes
Accepted

Do cold neutrons produce radioactive elements?

Every neutron capture causes a nuclear transmutation. The “neutron separation energy” of the daughter nucleus is generally released promptly, usually as a cascade of gamma rays. The ground states of ...
rob's user avatar
  • 89.9k
11 votes

Antimuon-electron interaction

This diagram can do it, satisfying lepton number conservation at each vertex:
Martino's user avatar
  • 977
10 votes
Accepted

What are the Feynman diagrams for neutrino oscillations?

There are none, and the question isn't really even sensible. Neutrino oscillation is not mediated by force carrying particles any more than any other change of quantum basis is. This is similar to ...
dmckee --- ex-moderator kitten's user avatar
10 votes
Accepted

A proton's weak charge is .0719. Is this dimensionless? A ratio?

You haven't linked to any of the articles that you've read, but the value that you've quoted seems to come from this Nature paper that was published this week. Note that the news there is the ...
rob's user avatar
  • 89.9k
10 votes
Accepted

How does meson exchange work within large nuclei?

Your question is founded on misunderstandings. The theory of what goes on inside the nucleus is neither simple nor intuitive. "Meson" is simply a name for any particle that is a bound state of a ...
ACuriousMind's user avatar
  • 125k
9 votes
Accepted

Are there Planck units for weak or strong "charge", similar to the electromagnetic Planck charge $\sqrt{4~\pi~\epsilon_0~\hbar~c}~$?

All couplings in QFT are measured in Lorentz-Heaviside rationalized natural units. That is, for instance, for the electric charge, $$ \alpha = \frac{e^2}{4\pi\varepsilon_0\hbar c} \approx 1/137 . $$...
Cosmas Zachos's user avatar
9 votes
Accepted

Can you shoot a neutrino through Earth?

The cosmic rays consist of all sorts of particles ranging from heavy protons to little to no mass neutrinos. There are trillions of trillions of neutrinos passing through the earth at any given time. ...
Yashas's user avatar
  • 7,173
9 votes
Accepted

What happens during a weak interaction?

The Universe is permeated by a bunch of quantum fields. These are fermionic (like the electron field, or the quark field) or bosonic, like the electromagnetic field $A^{\mu}$ (the "photon"), or the ...
SuperCiocia's user avatar
  • 24.7k
9 votes
Accepted

Does the weak force have an attractive/repulsive force observable in everyday life like the other forces?

In everyday life? Like in your kitchen? No. Or if yes, totally not in the way that you're thinking. If you insist on thinking of the fundamental interactions in terms of attraction and repulsion, ...
rob's user avatar
  • 89.9k
9 votes

Do cold neutrons produce radioactive elements?

Actually the neutron capture cross section is typically higher for slower neutrons (that's why you need a moderator in a nuclear reactor that slows down the hot neutrons released in the fission ...
Sebastian Riese's user avatar
8 votes
Accepted

Neutrinos and DNA

Short answer: mostly no. Slightly longer answer: the interaction of neutrinos with the molecules of your body take several forms, but they all come down to ionizing dose. However, there are many ...
dmckee --- ex-moderator kitten's user avatar
8 votes
Accepted

Where does the electron come from when a free neutron transforms?

Here's an analogy that might help. When an electron jumps from a higher orbital to a lower one, it produces a photon which carries away both energy and angular momentum. This is the energy ...
David Elm's user avatar
  • 1,911
8 votes
Accepted

Can the weak interaction be studied without bothering the electromagnetic one?

There is no gauge theory describing the weak interaction after electroweak breaking. The meaning of symmetry breaking, after all, is that the resulting effective theory no longer has all the ...
ACuriousMind's user avatar
  • 125k
7 votes

How many kinds of "weak charges" exist?

I would say two, which is pleasantly consistent with the $SU(2)$ structure of the weak force. One is the coupling strength with the $Z$ boson, and one is the weak isospin which is raised and lowered ...
rob's user avatar
  • 89.9k
7 votes
Accepted

How it is possible to mediate a weak interactions by very heavy particle such as Boson?

When e.g. a neutron decays, there is no "real" W-boson inside, in the sense that it could be detected at every point. Instead, the decay of the neutron involves a "virtual" W-boson, a W-boson that ...
Luboš Motl's user avatar

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