Integrated simulation of fragmentation, evaporation, and gamma-decay processes in the interaction of cosmic-ray heavy ions with the atmosphere using PHITS

Ogawa, Tatsuhiko   ; Hashimoto, Shintaro  ; Sato, Tatsuhiko   ; Niita, Koji*; Kamae, Tsuneyoshi*

In the reactions of cosmic-ray heavy ions producing high-energy gamma-rays, heavy ions are directed to the ground therefore prompt gamma-rays from projectile fragments are boosted by Doppler effect and observed on the ground. Recently, a lot of experiments pay attention to such high energy gamma-rays. In order to simulate such high-energy gammas, event-by-event simulation of fragmentation reaction which determines the excitation energy and angular momentum of the produced fragment, and de-excitation simulation based on the nuclear structure data. Such models are available in the general-purpose radiation transport simulation code PHITS. JAERI Quantum Molecular Dynamics model was recently updated to accurately simulate charge and mass distribution of fragments. EBITEM, which was released recently, can simulate gamma deexcitation after evaporation based on the excitation energy and angular momentum. Thus latest PHITS can accurately simulate production of -rays attributed to cosmic-ray heavy ions. This study shows a new approach to reproduce -rays by cosmic-ray heavy ions.