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human
When an electron and positron annihilate, they give off two gamma rays - is it always exactly two? Might it be more?

And what if a proton and an antiproton annihilate? Will that also usually be two gamma rays?
gpt
>When an electron and positron annihilate, they give off two gamma rays - is it always exactly two? Might it be more?

It's *at least* two, but it can be more, with small probability.

>And what if a proton and an antiproton annihilate? Will that also usually be two gamma rays?

With protons and antiprotons, there are more channels open even at zero relative kinetic energy. So you don't have to get gamma rays, you can, for example get various mesons. Those mesons then decay to leptons, photons, etc. So proton-antiproton annihilation is more complicated than electron-positron annihilation.