General description

This file describes shortly a simulation packet based mainly on the HIJING 1.35 routines. It is intended to provide MC data needed to test efficiency of the PHOBOS detector. As an extension to standard HIJING it includes also a simple plasma source.  I am going to include, in the near future, other new physical effects which would be relevant to our understanding of physics at RHIC energies.

The simulation packet includes:

  1. main.f - main program to run HIJING routines
  2. hijing1.35.f - HIJING source
  3. hipyset1.35.f - modified PYTHIA  and JETSET source
  4. hijing.dat - control file described below
  5. Readme.html - this file
  6. Makefile

The program is intended to compile and run on   Linux system with Portland compiler - pgf77, which is installed at RCF. It may also work with g77 or egcs compiler after some modifications. To compile just  type 'make'.

Control file

File 'hijing.dat' provides the main parameters of a collision.
These are:

  1. energy per nucleon of the collision in the CM frame (default 200. GeV)
  2. number of nucleons in the projectile (197)
  3. number of protons in the projectile (79)
  4. number of nucleons in the target (197)
  5. number of protons in the target (79)
  6. minimal and maximal impact parameter, for central collision choose both zero

    In addition there are also two parameters which control the parameters of the plasma source
  7. temperature of the source (0.17 GeV)
  8. percent of pions produced from plasma source, to switch off the source choose it zero.

    The last parameter 
  9. nevent is the number of  events generated in a single run.

    The number of run is given as a command line parameter. You can specify up to 30 runs. Note that the random number generator is initialized using current date and run number.

    For the purpose of simulation at the RCF farm the program accepts the environment variable  INPUT0, which sets the alternative name of the input file.

 

Output file

The results are put in the file 'hijing_yyyymmdd_#' , where yyyymmdd stands for date and # is the current number of run. The output contains header information which describes main parameters of the run and event. The lines in the output file, which describe produced particles begin with 'P' and contain GEANT parameters: ID of a particle, total momentum, theta and phi angles. The name of the output file can be changed by setting the environment variable OUTPUT0.

Plasma source

In high energy collisions it is expected that some fraction of particles is produced directly from a plasma fireball. We decide to simulate this effect by random replacement of charged pions generated by HIJING by pions produced from thermal source. The main parameters are: temperature of the source T, which is estimated to be around 170 MeV, and probability pp of replacement of a pion. If pp=0 then we recover the pure HIJING results, on the other limit (pp=1.) we get the pure plasma source.

The total momentum of pions produced from plasma are distributed according to Boltzmann i.e.

n(p)/n(p')= (p^2/p'^2)*exp[ ( -E(p) + E(p') )/T ], 

where n(p) is the number of particles produced with total momentum p.
Production of  pions is assumed to be isotropic.

Obviously this model of plasma has several restrictions and it will be a subject of further improvements.



If you have any comments contact:

Dr. Pawel Sawicki
High Energy Physics Lab
Institute of Nuclear Physics
ul. Kawiory 26a
30-055 Krakow
Poland

email : pawel.sawicki@ifj.edu.pl
tel. +12-48-6333366 (secr.)
fax. +12-48-6333884