[DoctorBeaver (OP)]

Reading about Yakawa couplings and the article http://en.wikipedia.org/wiki/Yukawa_model states that "...the Yukawa particle has spin zero and even spin always results in an attractive potential."

Is it only even spin that results in an attractive potetial?
Does odd spin result in repulsive potential?

[Vern]

I don't think you could say that it is only even spin that results in attractive force since the electron is spin 1/2; I have trouble making that an even number[] Maybe it is and it just doesn't click. The photon is spin 1 and it is supposed to be charge neutral.

[DoctorBeaver (OP)]

Do you not need to add the spin of the interacting particles together? Take 2 electrons of spin 1/2 and you get 1: repulsion?

I can't answer your point about the photon without a little thinkipoos.

[Vern]

Do you not need to add the spin of the interacting particles together? Take 2 electrons of spin 1/2 and you get 1: repulsion?

I can't answer your point about the photon without a little thinkipoos.

Ok; that makes sense.

[JP]

Actually, I think it might be a bit different.  From that article, the Yukawa particle seems to be talking about the particles that make up the strong force's field, just like photons make up the electromagnetic field.  The Yukawa particles are spin 0, which from the article, means that the field is attractive only (gravitons are believed to be spin 2, and gravity is also an attraction-only field). Photons are spin 1, and electromagnetism is attractive or repulsive.   

[DoctorBeaver (OP)]

jpetruccelli - that sounds eminently feasible.