Heavy Quark-Antiquark Annihilations

[Naeem Anwar]

Does Charm-Anticharm (in relative S-wave with spin-1) annihilates to a single photon? How does this vertex look like in QCD?

 

[Orodruin]

That would violate total 4-momentum conservation.

 

[vanhees71]

It can, however, got to a "virtual photon", i.e., a "dilepton" which is an $e^+ e^-$ or $\mu^+ \mu^-$ pair. This lead to the discovery of the $J/\psi$ ("The November Revolution") and thus the discovery of charm (expected from the GIM mechanism in electroweak theory):

https://en.wikipedia.org/wiki/J/psi_meson