Very energetic photons from heavy-ion collisions

Single photons with energies up to 6 times the beam energy have been measured in a heavy-ion reaction for the first time. The reaction studied was Kr+Ni at 60 AMeV. In the nucleon-nucleon center of mass system the spectra exhibit an exponential shape with an inverse slope parameter Eo=20 MeV. Bremsstrahlung in individual NN collisions is the origin of the highest energy photons, as for the lower energy ones. (author) 7 refs., 3 figs