I What is the weak isospin of hadrons?

[Ron Paul]

What are the weak isospins (T₃ values) of various hadrons, including the proton, neutron, mesons, hyperons and other hadrons? How is the weak isospin calculated for any hadron?

Published sources provide T₃ only for fundamental fermions, that is, quarks and leptons. In the fundamental bosonic sector, the photon's T₃ is (0, 1), the gluon's is 0, the Higgs boson's is -1/2, the Z boson's is 0 and the charged weak bosons' is ±1. No such information appears for composite particles.

One could calculate this using Q=T₃+Y_W/2. However, the weak hypercharge (Y_W) values for hadrons are also not available.

Supposedly, it is possible that the weak isospin of all hadrons is 0, since the weak interaction does not operate on the hadron as such, only on its constituent quarks. Is this the case?

Thanks in advance.

 

[Vanadium 50]

Weak isospin is not a conserved quantum number so the question has no answer.

 

[Ron Paul]

Weak isospin is not a conserved quantum number so the question has no answer.

Thank you.

I interpret your answer as follows: weak isospin is a quantum number that can exist only for fundamental particles. This, because composite particles (hadrons) are the result of an interaction which does not conserve weak isospin.

Hence, my assumption that "the weak interaction does not operate on the hadron as such, only on its constituent quarks" is correct.

You say that "the question has no answer"; however, is it not possible to simply say that the weak isospin of every hadron is 0?

 

[Vanadium 50]

I interpret your answer as follows:

I said precisely none of that. Weak isospin is not a conserved quantum number so the question has no answer.