PANDORA_PYTHIA

PANDORA_PYTHIA interfaces the PANDORA Monte Carlo to the PYTHIA version 6.2 program. PYTHIA is used to simulate gluon showering and fragmentation of final-state quarks. To decay tau leptons, TAUOLA is used with including the polarization effects. Events are output in STDHEP format.
Current version of the PANDORA_PYTHIA is 3.3 (Mar. 03 2003) which is for PANDORA version 2.3.

In order to use the interface, you need to have:

• PANDORA
  Current version (3.3) PANDORA_PYTHIA is for the PANDORA V2.3. Please refer to the PANDORA documentation to obtain the PANDORA.
  Note:: You can put the PANDORA wherever you like. PANDORA_PYTHIA uses source files in PANDORA.
  
  
• PYTHIA and STDHEP
  You must use PYTHIA version 6.20 or higher and STDHEP version 4.7 or higher.
  PYTHIA and STDHEP are included in CERNLIB.
  ( CERNLIB 2002 contains PYTHIA 6.205 and STDHEP 4.07)
  Or, you can get original PYTHIA and/or STDHEP.

PANDORA_PYTHIA installation

• The *.tar.gz file for current PANDORA_PYTHIA (V3.3) can be found here.
• After unpack the PANDORA_PYTHIA, you have 6 directories:
  bld: Makefiles to make libraries of PANDORA, TAUOLA, and pandpyth
  lib: libraries (At first this directory is empty)
  tauola: source files of TAUOLA version 2.6.
  pandpyth_src  pandpyth_inc: src and include files for pandora_pythia main files
  pythia: Makefile to make libPythia.a (option)
  examples: example programs to generate, and make an output file,

• Go to bld directory, and modify Makefile.setup. Then you can make libraries in lib directory by typing 'gmake' (or make).
• You need to link these libraries to your main program to generate. The example programs and Makefiles are in example directory.
• The default PANDORA_PYTHIA uses PYTHIA in CERNLIB. If you want to use another version PYTHIA, please copy original pythia62**.f (** = version number) from PYTHIA home page under pythia directory, and make a library.
  Note::  Final-state showering routine PYSHOW has been significantly modified to improve the heavy-quark radiation, from version 6.154.
• For the detail, Please see the README file

How to run

• In example subdirectory, there are several example main files. Please refer and make your min program. In order to make the executable for your main program. modify Makefile.setup, and Makefile.

          To make the executable, type

gmake (or make)

• Once binary can be created you can run by typing

binary_name #events  output_file_name (seed for PANDORA) (seed for PYTHIA)

Here seed numbers for PANDORA and PYTHIA are option. If you don't input them, you'll use the default values, 1 and 19518503 for PANDORA and PYTHIA, respectively. If you don't provide the optput file name, there will be no STDHEP output file.

For example, if you have a binary, named gen_eetottbar, which generate e+e- --> ttbar, and type

gen_eetottbar 1000

you can generate 1000 e+e- --> tt-bar events but don't have any output file.

If you type

gen_eetottbar 1000 output.dat 

you can generate 1000 e+e- --> tt-bar events and have an output file of "output.dat".

Or if you type

gen_eetottbar 1000 output.dat 30298

you can generate 1000 e+e- --> tt-bar events with PANDORA initial seed of 30298, and have an output file of "output.dat". (In this case PYTHIA initial seed --> default value)

The output file is HEPEVT binary file.

Important Note for experimentalist

Some detector simulators decay V0 particles during the detector simulation. If you use such simulator, you must not allow the decay of such particles in the generator level. For example, if you want to use GISMO, you must not decay L0(Pythia particle code 3122), K0-short(310), K0-long(130), S-(3112), S+(3222), X0(3322), X-(3312), W-(3334) particles in the generator level. (But If you want to use LCD FastMC, you need to decay them. Because LCD FastMC does not decay any particles.)

In PANDORA_PYTHIA, you can turn on/off the decays using

• PartDecayOn(input PYTHIA particle code) or 
• PartDecayOff(input PYTHIA particle code) 

respectively.

History

Last Modified: 13 Jan 2004 12:37 by M. Iwasaki