HE-3 AND HE-4 PRODUCTION BY 800 MEV PROTONS FROM C-12, TI, AND PB AT FORWARD ANGLES

The doubly differential cross section for the production of He-3 and He-4 by 800 MeV protons from C-12, Ti, and Pb has been measured at laboratory angles of 6-degrees and 15-degrees. The momentum of the detected helium nuclei varied from 1 to 2 GeV/c, the maximum being well above the incident proton momentum of 1.46 GeV/c. The cross sections were found to increase with increasing target mass and decrease with increasing momentum and scattering angle. In our momentum region, the He-3 production cross section is 1.5-10 times larger than He-4 depending on the target and the momentum. The data are consistent with the hypothesis that the dominant reaction mechanism is a direct process where the initial nucleon-nucleon scattering is followed by a sequential pickup of neutrons.