# Do anti-particles have opposite parity?

Hi,

I understand that anti-particles have the opposite charge to particles.

Do anti-particles have the opposite parity to particles as well?

John

Anti-particles have not only charge, but all their conservation numbers, among them charge and parity, opposite to their "normal" particles.

Thanks!

Actually, is that right?

I looked on hyperphysics and it said only the "internal" quantum numbers are reversed under charge conjugation not the spatial coordinates.

John

I looked on hyperphysics and it said only the "internal" quantum numbers are reversed under charge conjugation not the spatial coordinates.
Sure! You're right. I gave too quick answer...
Parity of compound particle (e.g. hadrons) is composed (multiplicatively) of internal parities of quarks and the parity of their relative geometry. The last do not differ from particle to anti-particle.
So both mesons and their anti-mesons have same parity ($-1^{spin+1}$). Baryons, as composed of 3 quarks, have parity +1, while their counterparts have -1.

Bill_K
So both mesons and their anti-mesons have same parity (−1)spin+1
Still too quick. There are plenty of mesons that obey this rule, and plenty more that do not. The spin-parity of a meson includes contributions from both the intrinsic properties of the quarks and the orbital wavefunction as well. Take a look at a list of the charmonium and bottomonium states.

Meir Achuz
Homework Helper
Gold Member
The parity of meson considered as q-qbar bound states is (-1)^L+1.
The spin of the meson equals L if the q-qbar are in a spin zero state, but can be different if the q-qbar are in a spin 1 state. Gauge bosons have negative intrinsic parity.
The parity of a boson antiparticle is the same as the particle.

Meir Achuz
Homework Helper
Gold Member
Fermions have only relative parity. For instance, the intrinsic relative parity of the proton and antiproton is negative.

So, when in texts it refers to applying charge conjuction (C) as replacing a particle with its antiparticle... this isn't strictly true? As particles whose antiparticle has opposite parity, would need you to apply CP to the particle to get the antiparticle?

Meir Achuz