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

Abstract

Nuclear modification factor (Rcp) of protons and pions are investigated by simulating Au + Au collisions from 0.8 to 1.8A GeV in a framework of an isospin-dependent quantum molecular dynamics (IQMD) model. Rcp 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 Rcp between protons and pions indicates different medium effects between protons and pions. By changing the in-medium nucleon-nucleon cross section, the Rcp of protons changes a lot, while the Rcp of pions does not. Taking the pion absorption into account, the Rcp of pions becomes close to unity without pT dependence after deactivating the reaction πN → ∆, 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.

Nucleon-number scalings of anisotropic flows and nuclear modification factor for light nuclei in the squeeze-out region

“…We noticed that similar results of R cp were obtained in Refs. [46,28] due to the multiple nucleon-nucleon scattering effect or/and the radial flow effect.…”

“…The nuclear modification factor R cp is a probe to study the nuclear medium effect in nucleus-nucleus collisions, it is defined as a ratio of the particle yield in central collisions to that in peripheral collisions [24,28,29], i.e.…”

“…However, the similar NN scaling behavior of NMF is not yet examined in intermediate energy heavy ion collisions. In this energy domain, the isospin-dependent quantum molecular dynamics (IQMD) model [25,26,27] is very successful for studying reaction dynamics, such as for spectra analysis, flow analysis as well as the nuclear modification factor analysis [28]. Therefore it will be of great interest to test if the R cp of light nuclei can be scaled by the number of nucleon scaling.…”

Azimuthal-sensitive three-dimensional HBT radius in Au-Au collisions at $E_{beam} = 1.23$$A$ GeV by the IQMD model

“…[66] that the pion yield in this reaction can be described with a reduced nucleon-nucleon inelastic cross section in medium. However, introducing in-medium corrections of the nucleon-nucleon cross section has little impact on the pion spectrum and its nuclear modification factor [67]. The reason might be that the cross section for pion interaction has no significant change while the in-medium correction for nucleonnucleon cross section changes.…”

Pion production and absorption in heavy-ion collisions

“…However most of the them can be absorbed into ∆ resonances because of the inelastic πN collisions, and then may decay into pions frequently, i.e. scattering process [21][22][23]. The detail of the scattering process plays * Electronic address: gaoyuan@impcas.ac.cn an important role for extracting the information of the symmetry energy at different densities.…”