Gauge Bosons.

trv

Quick question. If particles that mediate interactions are called gauge bosons, why isn't Pion considered a gauge boson. I'm pretty sure I've come across a few interactions mediated by it.

hamster143

I think you could say that pion is a gauge boson of chiral symmetry.

malawi_glenn

yeah, but it has nothing to do with gauge there - rather you would say that it is a goldstone boson.

blechman

gauge bosons also have spin 1, while the goldstone boson is spin 0.

it's not right to think of gauge bosons as "particles that mediate interactions" - all particles can "mediate interactions" of a sort. It's called a gauge boson because the field has a "gauge symmetry" (just like the electromagnetic field).

trv

Just realised that the pion is a meson. So I assume now that the two aren't mutually exclusive. I.e. a meson can also be a boson, or at least a goldstone boson.

malawi_glenn

You are mixing things up..

Boson is the opposite to fermion, a boson has integer spin, a fermion has half-integer spin.

Meson means that it is a strongly interacting particle with two valence quarks (one quark, and one anit-quark)

All Mesons are bosons, but not all bosons are mesons ...

kuon

If I remember correctly, pions are the pseudo-goldstone bosons when chiral symmetry is broken.

Bob_for_short

I am sure I do not remember it correctly, but it seemed to me that pions were the gauge bosons of the isotopic symmetry group (Yang-Mills fields).

Bob_for_short.

blechman

No, that's wrong. The (strong) isospin symmetry group is a global symmetry, so there are no gauge bosons.

The pions are (pseudo) Nambu-Goldstone bosons of the strong isospin group.

Definitely not Yang-Mills.