What changes under charge conjugation

[FredMadison]

Hi!

Which quantum numbers change under the charge conjugation operation?

Electric charge - yes
Spin - no
Isospin - ?
z-component of isospin - ?
Hypercharge - ?
Parity - ?

 

[Meir Achuz]

Magnitude of Ispin is the same.
I_z is tricky. It's C dependence is governed by the connection betwen charge and I_z.
Hypercharge changes sign.
Parity for bosons doesn't change.
The relative parity for p and pbar is negative so the p-pbar S state has odd parity.

 

[FredMadison]

I'm specifically looking for the parity of the antiproton. Can't find it anywhere! Anyone knows?

 

[Meir Achuz]

The antiproton does not have a parity by itself. There is a relative parity of the antiproton and the proton. That is, the proton-antiproton state has negative intrinsic parity. This is predicted by the Dirac equation, and has been measured by the angular asymmetry in the process p+pbar--> pi+pi. The combination also is negative under charge conjugation. These properties were listed at one time in the PDG data summary, but have been left out recently. They mave thought it was too obvious, which it isn't.

 

[FredMadison]

Aha, I see. Thanks a lot clem!