Nuclear medium effect on nuclear modification factor of protons and pions in intermediate-energy heavy ion collisions

TL;DR

This study investigates the nuclear medium effects on the nuclear modification factor of protons and pions in intermediate-energy heavy ion collisions using IQMD simulations, revealing different medium effects and the importance of pion absorption.

Contribution

It introduces a detailed analysis of medium effects on $R_{cp}$ for protons and pions, highlighting the role of pion absorption and in-medium cross sections in heavy ion collisions.

Findings

$R_{cp}$ of protons increases with extit{p}_T due to radial flow and Cronin effect.

Pion absorption significantly affects $R_{cp}$ of pions, making it close to unity.

In-medium nucleon-nucleon cross section strongly influences proton $R_{cp}$.

Abstract

Nuclear modification factor ($R_{cp}$) of protons and pions are investigated by simulating Au + Au collisions from 0.8 to 1.8$A$ GeV in a framework of an isospin-dependent quantum molecular dynamics (IQMD) model. $R_{cp}$ of protons rises with the increase of \pt~ at different beam energies owing to radial flow and Cronin effect. The rate of increase of \rcp~ is suppressed at higher beam energies. The significant difference of $R_{cp}$ between protons and pions indicates different medium effects between protons and pions. By changing the in-medium nucleon-nucleon cross section, the $R_{cp}$ of protons changes a lot, while the $R_{cp}$ of pions does not. Taking the pion absorption into account, the $R_{cp}$ of pions becomes close to unity without $p_{T}$ dependence after deactivating the reaction $\pi N \rightarrow \Delta$, while there is nearly no change on proton. This suggests that the pion absorption plays a dominant role on pion dynamics and have slight effect for proton dynamics.