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

Tatsuhiko Ogawa,Shintaro Hashimoto,Koji Niita,Tatsuhiko Sato,V Greco,M La Cognata,C Spitaleri,S Pirrone,F Rizzo

doi:10.1051/epjconf/201611703011

Abstract

To predict angular distribution of fragments produced in nucleusnucleus collisions, JAERI quantum molecular dynamics model (JQMD) was improved. Because JQMD underestimated fragments in the forward angle, which were mainly produced by peripheral collisions, JQMD was revised so as to simulate peripheral collisions accurately. Density-dependent in-medium effect and relativistic effect on nucleonnucleon interactions were incorporated for this purpose. The revised version of JQMD coupled with a statistical decay model was used to calculate differential fragment production cross sections measured in earlier studies. Comparison of the measured data and calculation by the revised and old JQMD showed that the revised JQMD can predict fragment angular distribution better than old JQMD. Particularly, agreement of fragment yield in the forward angle is substantially improved.

Highlights

The angular distribution of the fragments produced in nucleus-nucleus collisions is essential for cosmic ray physics, radiation safety of space exploration, and dosimetry in heavy-ion cancer therapy.Among the microscopic reaction models developed to simulate fragment production in nucleus-nucleus reactions, quantum molecular dynamics (QMD) models are generally adopted in general-purpose radiation transport simulation codes [1, 2] and used in various applications
To evaluate the effect of the revisions, fragment production cross sections calculated by JQMD-2.0 were compared with measured data
The fragment yields calculated by JQMD have a peak at about 7 degrees and the yields are smaller at 4 degrees because peripheral collisions are disregarded by the impact parameter cut-off

Summary

Introduction

The angular distribution of the fragments produced in nucleus-nucleus collisions is essential for cosmic ray physics, radiation safety of space exploration, and dosimetry in heavy-ion cancer therapy.Among the microscopic reaction models developed to simulate fragment production in nucleus-nucleus reactions, quantum molecular dynamics (QMD) models are generally adopted in general-purpose radiation transport simulation codes [1, 2] and used in various applications. One of the QMD models, JAERI-QMD (JQMD) [3] was developed as an event generator for general purpose radiation transport code PHITS (Particle and Heavy Ion Transport code System) [4] and widely used to simulate nucleus-nucleus collision (e.g., [5,6]). It was suggested that QMD models overestimated the width of the fragment angular distributions [7, 8] and underestimated production at the forward angle. This trend was probably attributed to inaccurate treatment of peripheral collisions, in which projectiles are little deflected and fragments are ejected in the forward angle. We revise JQMD to simulate the fragment angular distribution by accurate treatment of peripheral collisions

Methods

Results

Conclusion