Programs in Physics & Physical Chemistry
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|Manuscript Title: ZPC 1.0.1: A parton cascade for ultrarelativistic heavy ion collisions. See erratum Comp. Phys. Commun. 111(1998)276.|
|Authors: B. Zhang|
|Program title: ZPC 1.0.1|
|Catalogue identifier: ADHS_v1_0|
Distribution format: tar.gz
|Journal reference: Comput. Phys. Commun. 109(1998)193|
|Programming language: Fortran.|
|Computer: SPARC stations.|
|Operating system: SunOS 4.1.3, AIX 1, OSF1 V4.0.|
|RAM: 2K words|
|Word size: 32|
|Keywords: Particle physics, Elementary, Ultrarelativistic, Heavy ion collisions, Partons, Boltzmann equation, Screening mass, Parton cascade, Schemes cascade, Collision frame, Ordering frame, Ordering time, Event simulation.|
Nature of problem:
In ultrarelativistic heavy ion collisions, perturbative QCD predicts the production of a large number of minijet gluons. The gluon system produced near central rapidity can be considered as an almost longitudinal boost invariant and baryon free system. Gluons inside this hot matter will interact among themselves before hadronization. The effect of the final parton interaction on the global variables should be studied to match the experimental observables to the pQCD predictions.
The space time evolution of final state partons can be approximated by a Boltzmann equation. To solve the Boltzmann equation, we employ the cascade method in which two partons scatter when their closest distance in a specified frame is less than the interaction length. Gluon scattering cross section is regulated by a medium generated screening mass. Space cell division is made to speed up the calculation. Options to do the cascade with and without space cell division are provided to check the applicability of the optimization.
The running time depends on the density of partons and the scattering cross section. For 3 dimensional expansion, when the initial density in the local rest frame is ~ 50/fm**3 (at proper time 0.1 fm/c, with transverse radius 5 fm), and the parton-parton scattering cross section is 3.5 mb, with space cell division, it takes around 6 minutes to finish 1 event (~ 7000 binary collisions) on SPARC20, and 30 seconds on Alpha Personal Workstation.
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