Answer to Question #90990 in Physics for Oded Kristianpoller

Question

An electron which has a kinetic energy 1000 MeV collides with a stationary positron.
In the collision both particles annihilate each other.
can the collision preduce only one photon?

Answer 1

It is possible in the presence of a third charged particle to which the excess momentum can be transferred by a virtual photon from the electron or positron.