High energy photon production in nuclear collisions

High energy photons may be produced in nuclear reactions by several mechanisms, including bremsstrahlung from the potential field or from nucleon-nucleon collisions. Using infinite and semi-infinite nuclear matter approximations, we obtain simple expressions for the rates. Nucleon-nucleon collisions provide the more important mechanism for both proton-induced and heavy-ion induced reactions, except for the highest energy photons. The photon cross section calculated with a zero range np interaction agrees well with measurements on proton-induced reactions. For heavy-ion reactions, the initial np collisions only account for a third of the measured cross section. The disagreement may be due to an inadequacy of the infinite matter or the zero range approximations, or it may be that multiple collisions are important.