# W- boson

1. May 4, 2010

### billbray

does the w- (or w+) boson actually possess a negative charge? i.e., would it deflect in a magnetic field like an electron? or does it just carry a negative charge?

i'm trying to come to grips with a boson possessing charge at all. if that were the case, an infinite number of negative charges could occupy the same point in space.

2. May 4, 2010

### humanino

Yes they do possess a charge and would be deflected if they were long lived enough. Please note that the direct coupling photon-W is in the terms

from wikipedia

Also, please note that this is not the sole example : the gluon possesses a color charge and gluons do accumulate over volumes in which the strong force acts ... strongly.

Last edited: May 4, 2010
3. May 4, 2010

### tom.stoer

Similar to an electron. Similar because the coupling depends on the g-factor which is different.

No particle can carry charge w/o coupling to an electric or magnetic field

The Pauli principle does not forbid electrons to occupy one single state because of their charge but because of their spin. Charged bosons will not occupy one single point in space, but this has nothing to do with the Pauli principle or the spin, but it is a result of the (repulsive) electric force. This force is present w/ and w/o spin. The Pauli principle does not act like a force.

4. May 4, 2010

### billbray

b.e.a. utiful gentlemen, thanks

5. May 4, 2010

### billbray

p.s. - am i to understand from the above equation that thw w+/- boson couples to a photon? or does the photon couple to a magnetic field?

6. May 4, 2010

### tom.stoer

Now it becomes difficult. You are mixing classical an quantum mechanical reasoning.

Talking about coupling of electrons to magnetic field one treats the electron as a quantum particle, whereas the magnetic field is treated as classical field. The same context applies to my answer regadrding the coupling of a W-boson to a magnetic field.

But of course we know that photons are the quanta of the electromagnetic field. So when you are talking about the coupling of a photon to a magnetic field then in principle one must get rid of the concept of classical fields and talk about coupling of photons to photons.

In electromagnetism and in QED photons do not couple to photons directly. That means a photon is a neutral particle and does not feel the presence of another photon. But due to quantum corrections which are suppressed and hardly measurable photons can couple indirectly to other photons.

From the two interaction terms of the electro-weak Lagrangian you can read off the direct coupling: you have to multiply out all terms and check all terms containing at least one photon field. The first Lagrangian contains third powers of the gauge fields, the second Lagrangian contains forth powers. All terms containing at least one photon plus two or three other fields indicate that the photon couples to these other fields.

So the first interaction term (with third powers) contains terms where one photon field couples to a pair of W-bosons. In the second term it looks like if there are terms with fourth powers of the photon field, but if everything is right these terms should cancel. That means that photons do never couple directly to photons alone but only together with other gauge fields.