Why Are Photons Emitted in Neutral Particle Annihilations?

[Ruslan_Sharipov]

It is well known that photon is a quant of electromagnetic field. It is also well known that the electromagnetic field is produced by charged particles. Assume that some neutral particle annihilates with its antiparticle. Why a photon is emitted as a resuilt, not a quant of some other field?

 

[Meir Achuz]

Neutral particles (like the neutron-antineutron) that annihilate are usually hadrons, and annihilate to mesons. Annihilation of hadrons to pure photons is rare.

 

[topsquark]

It is well known that photon is a quant of electromagnetic field. It is also well known that the electromagnetic field is produced by charged particles. Assume that some neutral particle annihilates with its antiparticle. Why a photon is emitted as a resuilt, not a quant of some other field?

It isn't just photons. The branching ratio depends on many things, but you can get electron-positron pairs as well. And just about anything else you want provided your available energy due to the collision is large enough. The branching ratio for photons is pretty high at low energies because there isn't enough energy to produce more "exotic" particles.

-Dan