PACIAE 2.0: An updated parton and hadron cascade model (program) for the relativistic nuclear collisions

We have updated the parton and hadron cascade model PACIAE for the relativistic nuclear collisions, from based on JETSET 6.4 and PYTHIA 5.7 to based on PYTHIA 6.4, and renamed as PACIAE 2.0. The main physics concerning the stages of the parton initiation, parton rescattering, hadronization, and hadron rescattering were discussed. The structures of the programs were briefly explained. In addition, some calculated examples were compared with the experimental data. It turns out that this model (program) works well.Program summaryProgram title: PACIAE version 2.0Catalogue identifier: AEKI_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEKI_v1_0.htmlProgram obtainable from: CPC Program Library, Queenʼs University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 297 523No. of bytes in distributed program, including test data, etc.: 2 051 274Distribution format: tar.gzProgramming language: FORTRAN 77Computer: DELL Studio XPS and others with a FORTRAN 77 or GFORTRAN compilerOperating system: Unix/LinuxRAM: 1 G wordsWord size: 64 bitsClassification: 11.2Nature of problem:   The Monte Carlo simulation of hadron transport (cascade) model is successful in studying the observables at final state in the relativistic nuclear collisions. However the high pTpT suppression, the jet quenching (energy loss), and the eccentricity scaling of v2v2 etc., observed in high energy nuclear collisions, indicates the important effect of the initial partonic state on the final hadronic state. Therefore better parton and hadron transport (cascade) models for the relativistic nuclear collisions are highly required.Solution method: The parton and hadron cascade model PACIAE is originally based on the JETSET 7.4 and PYTHIA 5.7. The PYTHIA model has been updated to PYTHIA 6.4 with the additions of new physics, the improvements in existing physics, and the embedding of the JETSET model, etc. Therefore we update the PACIAE model to the new version of PACIAE 2.0 based on the PYTHIA 6.4 in this paper. In addition, some improvements in physics have been introduced in this new version.Restrictions: Depends on the problem studied.Running time:
• Running 1000 events for inelastic pp collisions at s=200 GeV by program PACIAE 2.0a to reproduce PHOBOS data of rapidity density at mid-rapidity, dNch/dy=2.25−0.30+0.37 [1], takes ≈3 minutes.
• Running 0–6% most central Au + Au collision at sNN=200 GeV by program PACIAE 2.0b and PACIAE 2.0c to reproduce PHOBOS data of charged multiplicity of 5060 [2] takes ≈13 seconds/event and ≈265 seconds/event, respectively.References:[1]B. Alver, et al., PHOBOS Collab., Phys. Rev. C 83 (2011) 024913, arXiv:1011.1940v1.[2]B.B. Back, et al., PHOBUS Collab., Phys. Rev. Lett. 91 (2003) 052303.

► PACIAE 2.0 is a parton and hadron cascade model for relativistic nuclear collisions.
► It is updated from based on JETSET 6.4 and PYTHIA 5.7 to based on PYTHIA 6.4.
► PACIAE 2.0 is composed of four stages.
► They are initiation, parton rescattering, hadronization, and hadron rescattering.
► It is special in studying the effects of parton rescattering and hadron rescattering.