Analysis of angular distribution of fragments in relativistic heavy-ion collisions by quantum molecular dynamics

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

Accurate prediction of fragment angular distribution in nucleus-nucleus collisions is essential for theoretical studies on nuclei and applications of particle beam. Quantum molecular dynamics is one of the approaches often adopted in general purpose radiation transport simulation codes to simulate formation of fragments, however, it is suggested that they tend to overestimate the width of fragment distribution angle. It is true for JQMD, the nucleus-nucleus reaction event generator incorporated to PHITS. By revising the description of peripheral collisions prediction of fragments angular distribution has been improved. First, spurious disintegration of nuclei before interaction is inhibited by introducing relativistic-covariant kinematics. By this improvement, one can distinguish nucleus spuriously disintegrated and nuclei interacted with other nuclei. Second, nucleon-nucleon scattering cross sections were increased by the suppression of Pauli blocking effect in the nucleus outer region to take into account for the increase in nucleon-nucleon scattering cross section. As a result, revised JQMD (RJQMD) predicts fragment angular distribution of fragments better than JQMD.