Hi, I'm new. I read aboot how an electron, and a positron colliding is supposed to produce two seperate gamma rays in completely opposite directions 180 deg away from each other. I understand that the gamma rays are supposed to correspond perfectly to the mass of the particles involved. I am wondering aboot any information regarding this. Especially if sometimes more or less than two gamma rays are produced?...That the two gamma rays are only one possible decay mode? Or maybe that sometimes they give off lesser particles plus electromagnetic radiation?