Using a hadron and string cascade model, JPCIAE, the energy and centrality dependences of charged particle pseudorapidity density in relativistic nuclear collisions were studied. Within the framework of this model, both the relativistic experimental data and the PHOBOS and PHENIX Au+Au data at GeV could be reproduced fairly well without retuning the model parameters. The predictions for full RHIC energy Au+Au collisions and for Pb+Pb collisions at the ALICE energy were also given. We computed participant nucleon distributions using different methods. It was found that the number of participant nucleons is not a well defined variable both experimentally and theoretically. Therefore, it may be inappropriate to use the charged particle pseudorapidity density per participant pair as a function of the number of participant nucleons for distinguishing various theoretical models.
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Acknowledgements
The financial support from NSFC (19975075, 10135030, 10075035) in China and from DOE in USA is acknowledged.
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.
No. of lines in distributed program, including test data, etc.: 297 523
No. of bytes in distributed program, including test data, etc.: 2 051 274
Distribution format: tar.gz
Programming language: FORTRAN 77
Computer: DELL Studio XPS and others with a FORTRAN 77 or GFORTRAN compiler
Operating system: Unix/Linux
RAM: 1 G words
Word size: 64 bits
Classification: 11.2
Nature 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 suppression, the jet quenching (energy loss), and the eccentricity scaling of 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:
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Running 1000 events for inelastic pp collisions at by program PACIAE 2.0a to reproduce PHOBOS data of rapidity density at mid-rapidity, [1], takes ≈3 minutes.
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Running 0–6% most central Au + Au collision at 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.
The evaluator presents in this publication spectroscopic data and level schemes from radioactive decay and nuclear reactions for all nuclei with mass number A = 232.
Highlights from this evaluation include the discovery of a new isotope of francium, 232Fr, and the study of its β− decay to levels in 232Ra (2004Pe17,1990Me13). Also, it includes the first observation of spontaneous fission in 232Th and 232U, as well as the measurement of their respective partial half-lives of 1.2 (4) × 1021y (1995Bo18) and 2.6 (5) × 1015y (2000Bo46) for this type of decay.