How much photon energy would be required to produce a proton-antiproton pair? Give the answer in SI units.
The Attempt at a Solution
I seem to be confused I know the KE would be zero I also know this would not exist in real life but I need to find the min energy so KE of the photon pairs is 0. I am not sure if the equation has to do with the mass of a photon or the momentum of the photons. In either case I don't know what the mass of a photon would be. I read it was zero but can't figure out how to use this formula then.