1. The problem statement, all variables and given/known data Show that the energy momentum conservation forbids the reaction (gamma)-> positron + electron, Gamma is a photon, which is chargeless and massless 2. Relevant equations E(photon)=hf p(photon)=hf/c Conservation of Energy Conservation of Momentum 4-momentum 3. The attempt at a solution My intuition is just to state that a massless and chargeless particle cannot create two particles with mass and charge. Is this correct?