Quite a simple query really, The question wants me to draw a Feynman diagram for a number of particle interactions, some are not possible, some are. This interaction: proton + antiproton ----> 3 gamma This would require each quark (uud) to annihilate with its anti matter counter part. This is fine, but this produces gluons not photons. I know these gluons can decay into particles, and they could then maybe annihilate into photons. Is this interaction, as it's stated, possible to be demonstrated using Feynman diagrams?