Light-fragment yield ratios from heavy-ion-induced fragmentation in atmospheric collisions of cosmic-ray primary nuclei

Abstract

A statistical nuclear-fragmentation model is used to calculate the total inclusive cross sections and yield ratios of light fragments (p, d, 3H, and 3He) from 800 MeV/nucleon mass-symmetric and mass-asymmetric collision systems. Comparison with available data reveal good correspondence between the observed total cross sections and fragment-yield ratios, and the calculated ones. The model is also used to calculate the 4He/3He ratio from CNO + CNO collisions at 1 GeV/nucleon. Averaging over the mass numberof the CNO collision system, we calculate a ratio of 5.76 ± 0.52 ± 12%. A mass-independent thermal-model formula gives a ratio of only ≈ 1.5. The appreciable calculated production of 4He relative to 3He, as fragmentation products in atmospheric CNO collisions with 1 GeV/nucleon cosmic-ray primary CNO nuclei, has important implications for studies of atmospheric secondaries as background sources for space-based and balloon-borne light-fragment observations.