urqmd-afterburner

UrQMD, tailored for use a hadronic afterburner in hybrid hydro+cascade models.

Attribution

UrQMD is a large, complex model written by many contributors. Please see the UrQMD website http://urqmd.org and the included license file for more information.

Usage

This repository contains

• The latest public version of UrQMD (3.4), not including the large equation of state tables, which are only used for UrQMD's built-in hydro mode.
• The OSCAR to UrQMD converter (osc2u) written by Steffen A. Bass.
• A simple wrapper script, afterburner, that runs osc2u and urqmd in sequence.

Compile and install:

mkdir build && cd build
cmake .. [-DCMAKE_INSTALL_PREFIX=<prefix>]
make install

This will place the compiled binaries and wrapper script in <prefix>/bin:

Invoke the afterburner with two arguments:

afterburner input_file output_file

where input_file contains particle data (presumably produced by a Cooper-Frye hypersurface sampler) in the format described below and output_file is the desired filename for the final particle data.

Note: Several intermediate files are created and left in the working directory:

• urqmd.conf - UrQMD configuration file
• urqmd_input.dat - the intermediate data file between osc2u and urqmd
• tables.dat - binary cache file generated by urqmd

If running the afterburner multiple times, it is recommended to reuse the same working directory so that tables.dat can be reused.

Input format

Input files contain particle data for one or more events; multiple events are concatenated together. Each event must begin with a commented header line containing the number of particles in the event

# nparticles

The first characters of the line is ignored and the next field is read as an integer. After the header line, the next nparticles lines must contain particle data fields

ID t x y z E px py pz

i.e. the particle's PDG ID, then its position and momentum four-vectors.

Files are read using Fortran list-directed input so the format is fairly flexible. Numbers may be in any valid format, separated by spaces or commas.

Output format

The default output format is easy to parse and contains only the necessary information for computing standard event-by-event observables (charged-particle multiplicity, flow cumulants, etc).

Similar to the input format, files contain one or more events concatenated together, each beginning with a commented header line and followed by particle lines. The header contains the event number and total number of particles in the event:

# event n particles m

Then, particle lines have columns:

ID charge pT ET mT phi y eta

where

• ID is the PDG Monte Carlo particle ID
• charge is the electric charge
• pT is the magnitude of transverse momentum
• ET is the transverse energy (ET = E sin(θ) = E pT/p)
• mT is the transverse mass (mT² = m² + pT²)
• phi is the azimuthal angle of transverse momentum
• y is the rapidity
• eta is the pseudorapidity