[Physics] How many subatomic particles can absorb/emit photons

electronsparticle-physicsphotonsquantum-field-theorysubatomic

Is the electron the only subatomic particle that can absorb and emit a photon?

Best Answer

The photon couples to all particles with electric charge or magnetic moment. This includes all of the quarks, the charged leptons $e,\mu,\tau$, and their antiparticles. It also includes particles composed of quarks and charged leptons: the proton and neutron (though the neutron only magnetically), the charged mesons, etc. Many electrically neutral mesons, like the $\pi^0$, decay to states of only photons.

I'm not sure whether there is a good limit on the magnetic moment of the neutrino; I think it's connected to the question of whether the neutrino-antineutrino relationship is as described by Dirac, like the charged leptons and quarks, or as suggested by Majorana, with the neutrino and antineutrino the same particle.