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United Generators
Introduction
The United Generators project was launched by the Virtual Institute 146 VI-SIM in September 2005
following a proposal of Herbert Ströbele. The goal was to facilitate comparison between
various models (see below) and/or various experiments (HADES, FOPI, CERES, NA49, CBM). The package
at present allows to convert output of various event generators to a generic root format. Common
analysis operations like boosting from CMS to LAB, adding two-particle correlations, decaying the
particles, smearing of momenta or acceptance cuts etc. are implemented as tasks in the analysis
chain and affect the content of an event but keep its structure unchanged. This means they can
be applied any number of times and in any order. The events can be subsequently translated to
the experimental data format of the individual experiments (beyond the scope of United Generators),
or used as the input to the detector simulation, or a simple physics analysis can be done
directly. The figure below depicts the data flow. The colored blobs are the ones for which
the implementation already exists.
Download
To get the first feeling have a look at small samples of pp events at 158 GeV converted to
the United Generators format:
ampt.root
epos.root
hsd.root
pluto.root
urqmd.root
venus.root
Download one of them, start root, and type e.g.
TFile::Open("ampt.root","read");
events->Draw("fParticles.fT:fParticles.fZ");
events->Draw("fParticles.fY:fParticles.fX","fParticles.fPx>0.5");
To use the full functionality of the UNIGEN classes, or to convert your event generator
data to UNIGEN format, please download the complete package. The current linux version can be
obtained directly from the Subversion repository by typing
svn co https://subversion.gsi.de/trunk unigen
For Git users, a clone of the Subversion repository can be found
on GitHub. Note that at
present this repository is NOT automatically synchronised with
Subversion; when in doubt, use svn.
The version 2.1 of UNIGEN is available
here.
To build the library please prepare the root environment by setting ROOTSYS and adding
$ROOTSYS/bin to the PATH and $ROOTSYS/lib to LD_LIBRARY_PATH (or by calling your favorite
rootlogin script). Prepare the unigen environment by sourcing config/unigenlogin or
config/unigenlogin.tcsh. Then type make. See README for details.
Implementation
The "converters" (urqmd2u, venus2u, hsd2u, etc.) are standalone programs which read output files
of event generators and produce root files with events in the common root format. Each root file
contains one URun object and one tree; the tree consists of UEvents; a UEvent contains
UParticles. A UEvent represents a snapshot of an event. In most cases this is the freeze-out
state. Sometimes one is interested in the temporal development of a collision; in this case
several subsequent UEvents will represent snapshots taken at different times. These are called
"event steps"; the members fNes and fStepNr of UEvent allow to recognize this case.
The documentation of URun, UEvent, UParticle and of other classes as well as some examples
can be found here .
Development
The internal stuff like minutes of the meetings is in
this wiki page .
From 2005 till mid 2010 the UNIGEN software was managed by
Dima Kresan.
At present, it is managed by
Marek Szuba.
This webpage is maintained by
Dariusz Miskowiec.
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