Revisiting the centrality definition and observable centrality dependence of relativistic heavy-ion collisions in PACIAE model

• Published in: Computer physics communications 2023-03, Vol.284, p.108615, Article 108615
• Main Authors: Yan, Yu-Liang, Zhou, Dai-Mei, Lei, An-Ke, Li, Xiao-Mei, Zhang, Xiao-Ming, Zheng, Liang, Chen, Gang, Cai, Xu, Sa, Ben-Hao
• Format: Article
• Language: English
• Subjects: PACIAE model; PYTHIA model; Relativistic nuclear collision; Transport (cascade) model
• ISSN: 0010-4655; 1879-2944
• DOI: 10.1016/j.cpc.2022.108615

We improve the centrality definition in impact parameter in PACIAE model responding the fact reported by the ALICE, ATLAS, and CMS collaborations that the maximum impact parameter in heavy ion collisions should be extended to 20 fm. Meanwhile the PACIAE program is updated to a new version of PACIAE 2.2.2 with convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version. The new impact parameter definition together with the optical Glauber model calculated impact parameter bin, Npart, and Ncoll in proton-nucleus and nucleus-nucleus collisions at relativistic energies are consistent with the improved MC-Glauber model ones within the error bar. The charged-particle pseudorapidity and the transverse momentum distributions in Pb-Pb collisions at sNN=5.02 TeV simulated by PACIAE 2.2.2 well reproduce the ALICE experimental data. Program Title: PACIAE version 2.2.2 CPC Library link to program files:https://doi.org/10.17632/w3g68dj4d9.4 Licensing provisions: CC By 4.0 Programming language: FORTRAN Journal reference of previous version: Comput. Phys. Commun. 224 (2018) 417 Does the new version supersede the previous version?: Yes Reasons for the new version: Recently ALICE, ATLAS and CMS collaborations reported that the maximum impact parameter bmax should be extended to 20 fm in the nuclear-nuclear collisions at relativistic energies. The impact parameter formula in PACIAE model has to be improved correspondingly. Meanwhile the PACIAE model is updated to PACIAE 2.2.2 with the convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in one unified program version. Summary of revisions: The impact parameter b in PACIAE model is calculated by geometrical model ofb=c×bmax, where c refers to the centrality percentile and bmax is assumed to bebmax=RA+RB+f×d. In above equation RA (RB) is the radius of nuclear A (B), d=0.546 fm describes the tail of the nuclear density profile. Originally, the coefficient f is set to be equal to 2 and 1 for nucleus-nucleus and proton-nucleus collisions, respectively. Now they are assumed to be equal to 4 and 2, respectively. Meanwhile, the PACIAE model is updated to the version of PACIAE 2.2.2 with the convenience of studying the elementary nuclear collisions, proton-nucleus collisions, and the nucleus-nucleus collisions in a unified program version. Nature of problem: The ALICE, ATLAS a