Eur. Phys. J. A (2016) 52: 207
https://doi.org/10.1140/epja/i2016-16207-x

Regular Article - Theoretical Physics

Effects of in-medium nucleon-nucleon cross sections on stopping observable and ratio of free protons in heavy-ion collisions at 400 MeV/nucleon

¹ Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-sen University, 519082, Zhuhai, China
² Department of Physics, Yuncheng University, 044000, Yuncheng, China
³ Institute of Modern Physics, Chinese Academy of Sciences, 730000, Lanzhou, China
⁴ The Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, 100875, Beijing, China
⁵ Beijing Radiation Center, 100875, Beijing, China
⁶ Center of Theoretical Nuclear Physics, National Laboratory of Heavy Ion Accelerator of Lanzhou, 730000, Lanzhou, China

^* e-mail: sujun3@mail.sysu.edu.cn

Received: 25 February 2016
Accepted: 28 June 2016
Published online: 27 July 2016

Abstract

The effects of in-medium nucleon-nucleon cross sections on the stopping observable and ratio of free protons in heavy-ion collisions at 400MeV/nucleon have been investigated within the framework of the IQMD+GEMINI model. Five kinds of in-medium corrections of nucleon-nucleon cross sections, which are considerably different in the referred energy and density, have been used in the model. It has been found that calculations of the stopping decrease when the in-medium cross sections decrease. Moreover, the ratio of free protons R_p depends not only on the value of the in-medium factors but also on its isospin dependence. In order to investigate the isospin effect of in-medium factors on the ratio of free protons R_p, the isospin dependence of in-medium factors has been adjusted and used in the model. The calculations have shown that the isospin dependence of in-medium factors does not impact the stopping, but impacts the ratio of free protons R_p. When the in-medium factors relation f _nn ^med > f _pp ^med is used in the model, the calculated values of R_p are larger than those in the f _nn ^med < f _pp ^med case.