High-energy gamma-ray production in light-ion induced reactions

Abstract

Results are presented for high-energy gamma-ray production in light-ion induced reactions. Energy spectra and angular distributions were measured for high-energy gamma rays (${E}_{\ensuremath{\gamma}}$>20 MeV) from the reactions $^{2}\mathrm{H}$ on C, Zn, and Pb at E/A=53 MeV, and $^{4}\mathrm{He}$ on C, Zn, and Pb at E/A=25 and 53 MeV. The gamma-ray energy spectra are roughly exponential, and for $^{2}\mathrm{H}$ at E/A=53 MeV extend out to the full available energy (\ensuremath{\sim}100 MeV). The angular distributions of the gamma rays are slightly forward peaked in the laboratory frame, but are symmetric about 90\ifmmode^\circ\else\textdegree\fi{} when transformed to the nucleon-nucleon center-of-mass frame. For the carbon target data the angular distribution in the nucleon-nucleon frame shows a substantial dipole component. This suggests that the major high-energy gamma-ray production mechanism is bremsstrahlung from first collisions of projectile and target nucleons.