Geant4 Based Simulations
for Combined Beam Test of EMEC and HEC

	Simulations environment and output data format
	Simulated data
	Simulation code
	LArG4/LArG4TB packages

Simulations

Combined beam test of EMEC and HEC modules, which took place at CERN in 2002, simulation code for the GEANT4 is available. The code is based on the package used for the simulation of HEC stand-alone beam tests. This version allows to simulate response in the following detectors (the same as in Geant3 version):

• EMEC module with a presampler (1/8-th of EMEC wheels)
• three HEC1 (front) modules
• two HEC2 (rear) modules
• "leakage detectors" (see a drawnings)
• MWPCs
• scintillator counters F1 and F2

Simulations are done within the stand-alone package, only the GEANT4 framework and ROOT package is used.

Output of simulations is saved in ROOT TTree structure, described here. There is possibility to store either all hits, or only sum per readout channel

The following properties are fixed in the code:

• "pencil-like" beam (no vertex smearing at all)
• charge collection in EMEC: switched off
• beam angle is computed according user parameter: Y-table position

The following properties and parameter settings is possible to change via the command files:

• X position of the cryostat, and Y position of table (and consequently beam)
• particle type and energy
• random number generator initial seed
• switch for summing or not the hits within the readout channel
• switch for choosing the PhysicsList (for the moment LHEP and QGSP)
• secondaries production cut for GEANT4

Relative longitudinal position of calorimeter modules (presampler, EMEC, HEC) is kept as it is foreseen in the ATLAS detector. Position of the set of modules inside cryostat is characterized by the following.

• X: symmetrical position with respect to X cryostat=0
• Y: beam at Y=0 enters modules at the point 172 cm below the module axis (= beam line in ATLAS)
• Z: front face of the EMEC envelope is 38.6 cm from the inner cryostat wall (engineering drawings)

• EMEC and HEC modules are shifted in Y by -2.75 cm
• Presampler is shifted in Y by -1.45 cm
• Presampler is also shifted in X by -1.30 cm

Output data format

• The run information is stored in the TBCOMBRun class, and info from each event in the TBCOMBEvent class. The more detailed description of variables stored in the TTree is also available.
• The energy deposits within one event can be either summed for each readout channel, and in this case the stored "address" for energy depositions in LAr and absorber is the readout channel (according standard TB mapping),
• or all hits are stored separatelly, and then the stored address is a specially packed hit address.
• If the energy depositions are summed, the cells in EMEC not connected to readout is stored according special scheme.
• Hit address for EMEC corresponds to LArG4Identifier, for HEC to the volume id.
• The leakage detectors have also its own id scheme.

Available simulated data

The following five standard impact points are used in simulations (corresponds to standard points used in data taking):

So far available data (the tables are updated with new data, once they will be ready). The pions and electrons are simulated with statistics 5000 events per run, muons with 20000 events per run.

• negative pions
  

  Energy [GeV]:	200.	180.	150.	120.	100.	80.	60.	50.	40.	30.	20.	10.
  LHEP Physics list, Point:	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.
  QGSP Physics list, Point:	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.
  FTFP Physics list, Point:	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.

• electrons
  

  Energy [GeV]:	147.8	119.1	100.	80.	60.	50.	40.	30.	20.	10.	6.
  LHEP Physics list, Point:	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.
  QGSP Physics list, Point:			J.	J.  I.	J.  I.	J.  I.	J.  I.	J.	J.  I.	J.  I.	J.  I.
  FTFP Physics list, Point:	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.	J.  I.

• muons
  

  Energy [GeV]:	180.	150.	120.
  LHEP Physics list, Point:	J.  I.	J.  I.	J.  I.
  QGSP Physics list, Point:	J.  I.	J.  I.	J.  I.
  FTFP Physics list, Point:	J.  I.	J.  I.	J.  I.

• Y scan with 150 GeV muons, X = 70 mm, 10000 ev. (with all hits stored, suitable for checking the HV problems)
  

  Y [mm]:	-180.	-170.	-160.	-150.	-140.	-130.	-120.	-110.	-100.	-90.	-80.	-70.	-60.	-50.	-40.	-30.	-20.	-10.	0.
  Y [mm]:	10.	20.	30.	40.	50.	60.	70.	80.	90.	100.

  (or see the directory, naming convention g4_x_y_energy_particle.root)
• X scan with 200 GeV pions, Y = 0 mm, 2000 ev. (with all hits stored, suitable for checking the HV problems)
  

  X [mm]:	-260.	-240.	-220.	-200.	-180.	-160.	-140.	-120.	-100.	-80.	-60.	-40.	-20.	0.

  (or see directory, with naming convention as above)

There are available some data with nominal calorimeters positions (i.e. without shifts here.

Simulation code

The actual code, version 3, is available for download and also on afs:
/afs/cern.ch/user/p/pavol/public/simul/geant4/tb_comb/tbcomb_v3.tgz
Please consult the README.install file for installation and running the code.
There is an update for some files, which allows also storing the energy deposits in the EMEC absorber.
If there is any problem with installing, or running, please contact me.

The run parameters are read from two macros, whose names should be the two command line parameters when invoking the compiled binary.
The first one (with default name prerun.g4mac) contains apart from standard (non obligatory) G4 commands:

• beam origin (default 0. 0. -2160. cm)
• beam direction (if Y-table differs from 0, it is computed accordingly)
• beam energy
• beam particle
• number of events to simulate

• X position of the cryostat
• Y position of the movable table
• output file name
• G4 production cut
• seeds for the random number generators
• store - switch on/off the storing of hits. If off, hits are summed in readout channel
• trigg - switch on/off the checking of trigger. If off, all events are stored in file, if on only those with good trigger
• stepprint - switch on/off the printing in each G4 step
• phlist - switch the physics lists. The current available possibilities are LHEP, QGSP, NONE, STANDARD, where STANDARD is lists used in standalone HEC TB G4 simulations before the 4.1 version of G4

The example of analysis macro for ROOT, which produce the distribution of summed energy in one HEC layer.

to the MPI-HEC-Simulation page