Difference: MySimulationPackage ( vs. 1)

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META TOPICPARENT name="RasmusMackeprang"
How to simulate heavy stable particles in Atlas using Geant4

This page is intended as a simple manual to use the Athena package I have developed on some of the heavy stable hadrons that appear in extensions to the Standard Model such as R-hadrons and KK-gluons in hadrons.


I will assume that you are acquainted with running single-particle simulations in Athena. If this is not the case a number of tutorials are available on the web covering the subject. You will need to have a runtime environment set up. The following examples assume that your username is mackepr, that you are running release 12.0.0 on a CERN machine, and that you have set up your release in /scratch/mackepr/cmtwork/12.0.0.

You need to get the simulation package. Please download the latest version below:

Set up your installation directory:

cd /scratch/mackepr/cmtwork/12.0.0
mkdir Simulation
mkdir Simulation/G4Utilities
cd Simulation/G4Utilities
Unpack the archive in your G4Utilities directory and do the usual cmt config / source setup.sh / make

Now set up your rundir and runtime environment:

cd /scratch/mackepr/cmtwork/12.0.0
mkdir run
cd run
ln -s /afs/cern.ch/atlas/software/builds/AtlasOffline/12.0.0/AtlasOfflineRunTime/cmt/setup.sh setup.sh
. setup.sh

Next get all files from the share directory of the Particles package and look at them:


This file contains the particle definition data in the format

<PDG> <Mass (GeV)> # <Name>
Note that the heavy spectator must be the first particle in the list. The first few lines of the default file containing gluino hadron definitions are:
      1000021   300.000   # ~g
      1000993   300.700   # ~g_glueball
      1009213   300.650   # ~g_rho+
      1009313   300.825   # ~g_K*0
      1009323   300.825   # ~g_K*+
      1009113   300.650   # ~g_rho0


This file contains the list of all possible processes for your custom particles. Processes are defined using particle names in the format:

<Incident> # <Target> # <Out1> # <Out2> (# <Out3>)

A couple of lines from the gluino hadron case:

~g_rho+ # neutron # ~g_Delta0 # pi+
~g_rho0 # neutron # ~g_Delta- # pi+
~g_rho+ # proton # ~g_rho+ # proton # pi0
~g_rho0 # proton # ~g_rho0 # proton # pi0


This file allows for setting some physics switches. These are:

  • Resonant Enables / disables a cross section resonance
  • ResonanceEnergy Determines at which lab-frame kinetic energy the resonance occurs
  • Gamma The width of the resonance in CMS (A bit confusing, I know)
  • Amplitude The height of the resonance in millibarn
  • ReggeSuppression A charge suppression switch. 0 means no suppresion. 1 is full suppression.

Defaults are:

Resonant = 0.
ResonanceEnergy = 200.
Gamma = 0.1
Amplitude = 100.
ReggeSuppression = 0.


This file must be present for just about any Athena job to run. It needs to be modified to know the particles contained in customparticles_full.txt. The format is fairly self explanatory.


This is a simple set of single particle joboptions. Note that they are set to use ATLAS-DC3-05 as default geometry tag in conformance with release 12.0.0

Running the simulation

Running athena jo.py will leave a sim-file named test.root in your rundir. This file may be passed on tho the digitization. Remember to pass along the PDGTABLE.MeV. It is needed at all stages in the chain.

Changing physics scenario

I have made a set of configuration files for running on stop hadrons. The usual arguments for stability applies, and any oscillation is disregarded for now.

Moving these files into your rundir and changing the PDG code in jo.py should be enough to have you running on stop hadron in stead of gluino hadrons.

-- RasmusMackeprang - 19 Jun 2006

META FILEATTACHMENT attr="" comment="Latest version of the code" date="1150723084" name="Particles-19-06-2006.tgz" path="Particles-19-06-2006.tgz" size="81266" user="mackepr" version="1.2"
META FILEATTACHMENT attr="" comment="Stop hadron configuration" date="1150726038" name="StopFiles.tgz" path="StopFiles.tgz" size="7625" user="mackepr" version="1.1"
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