# Thread: weak force

1. Could anyone give me a link where I can find an answer :
is it an attractive or repulsive force?
what is its formula ?
is it an inverse square law or what?
what's its strength?
what produces it?

Thanks a lot

2.

3.

4. Originally Posted by Neverfly
Thanks, but why just for fun?
It seems that weak force does not obey the inverse square law?
isn't there a formula such as for Coulomb's law?
is it repulsive ?

5. Originally Posted by monalisa
Thanks, but why just for fun?
For posting a recent news article rather than a text book definition.
Originally Posted by monalisa
It seems that weak force does not obey the inverse square law?
Correct.
Originally Posted by monalisa
isn't there a formula such as for Coulomb's law?
Coulomb's law - Wikipedia, the free encyclopedia
Originally Posted by monalisa
is it repulsive ?
Is what repulsive? The Weak Force?
It depends on the charges involved to determine if there is attraction or repulsion.

6. Originally Posted by Neverfly
Is what repulsive? The Weak Force?
It depends on the charges involved to determine if there is attraction or repulsion.
Is it like the electric force : opposite attract themselves?
and what about neutrinos they have no charge, what happens?
Is it not dependent on distance at all? what is its strength?
What generates it? (probably this is a mystery)

7. Originally Posted by monalisa
and what about neutrinos they have no charge, what happens?
Yes.

Originally Posted by monalisa
Is it not dependent on distance at all?
It is. But it does not follow the inverse square law. I'm sorry... But have you done any reading on the links provided?
Originally Posted by monalisa
what is its strength?
Oh, I don't know... But googling revealed this:
How strong is the weak force? New measurement of the muon lifetime

Originally Posted by monalisa
What generates it? (probably this is a mystery)
Yup.

8. Originally Posted by monalisa
Could anyone give me a link where I can find an answer :
is it an attractive or repulsive force?
what is its formula ?
is it an inverse square law or what?
what's its strength?
what produces it?

Thanks a lot
Hey bro,

weak "force" isnt really a good name. I know its widely used but its not a force in common sense. Weak interaction is better. Some processes of weak interaction are simple scatterings either attractive or repulsive depending on electric charge, some act in different way. There are three force carriers that mediate weak force. That is Z, W+ and W- bosons.

The Z boson is massive vector field without electric charge. In very simplistic way one can think of that as nothing else than massive photon. These act naturaly almost as photons. They mediate things like electron-electron scattering at high energies. Electron flyes close to other electron, they "exchange" Z boson which changes their momenta and they fly further but these work only at very high energies.

The real fun begins with charged vector bosons W+ and W-. These are the ones that govern beta decay among others. Since they are charged they change electric charge of their "emittor" and "recipient". They change flavours of quarks (probabilities of which are given by CKM mixing matrix), they can change lepton (electron, muon, tauon) into its respective neutrino and their decay creates lepton + neutrino pairs. Since they change flavours and part of interaction may be neutrino these are responsible for violating various conservation laws and CP symmetry.

Originally Posted by monalisa
what is its formula ?
Well thay would be weak force lagrangian but without some serious knowledge of quantum field theory this wont tell you anything. And its long.

Originally Posted by monalisa
is it an inverse square law or what?
Well for scatterings you can get Born amplitude from Feynman diagram and Fourier transformation of that will give you potential in coordinate space but again this wont tell you anything without some serious knowledge of scattering in quantum mechanics.

Originally Posted by monalisa
what's its strength?
Thats interesting question. For decays and such strengh is of course meaningless word but for scatterings its not. The thing here is that coupling constant (like electric charge in electromagnetism) is actually dependent on energy of interaction. This is principle known as running coupling constant. Thats as far as I will go with this.

Originally Posted by monalisa
what produces it?
I dont think I understand your question but weak interaction is mediated by Z, W+ and W- massive vector bosons. Same as electromagnetism has its electromagnetic field this interaction has these three fields. Interesting thing is that I read somewhere that weak force actually isnt necessary (as only one of four forces) for active universe (eg. stars, planets, supernovaes and such). I dont know where probably wikipedia but interesting thought.

9. Originally Posted by Neverfly
Oh, I don't know... But googling revealed this:
How strong is the weak force? New measurement of the muon lifetime
.
I read most of the quoted links before starting the thread as I did not find any answer, even in this link they give only the lifetime and not the strength.

In a proton or neutron we have both positive and negative quarks, how does weak force interacts with them? how can a force interacts echanging particles?
Particles interact through the weak force by exchanging force-carrier particles known as the W and Z particles.

10. Originally Posted by Gere
weak "force" isnt really a good name. I know its widely used but its not a force in common sense. Weak interaction is better. Some processes of weak interaction are simple scatterings either attractive or repulsive depending on electric charge, some act in different way. There are three force carriers that mediate weak force. That is Z, W+ and W- bosons.
Hi Gere, thanks for your enlightening post, that is cool information indeed.
Terminology is vital and here it is really misleading. Can you give me a link where I can find evidence of the W bosons?

I posed some questions in the other thread, hope you can give an answer!

11. Originally Posted by monalisa
I read most of the quoted links before starting the thread as I did not find any answer, even in this link they give only the lifetime and not the strength.
That is because the concept of "strength" does not really make sense if used in connection with the weak interaction.

how can a force interacts echanging particles?
All forces are mediated by the exchange of particles - that's one of the core concepts of quantum field theory.

12. Originally Posted by monalisa
how can a force interacts echanging particles?
Thats just result of perturbative expansion of S matrix. Simply convenient formalism. There arent photons flying from one electron to other and such just an easy way to imagine and draw (Feynman diagrams) interaction and calculate its amplitude without the need for explicit full expansion of S matrix.

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