CalcHEP 2.5: new features for event generation and interface with MC generators

         Alexander Pukhov(pukhov@sinp.msu.ru), Alexander Belyaev(belyaev@pa.msu.edu)

           




  "New facilities in CalcHEP 2.5" talk at MC4BSM, Princeton, 2007

  The source code for CalcHEP-PYTHIA interface

version v02
the location of this file
http://www.hep.phys.soton.ac.uk/~belyaev/comphep/calchep_pyth/

see also talk at MC4BSM
http://www.hep.phys.soton.ac.uk/~belyaev/proj/intro_to_hep_tools/talks/mc4bsm_calchep.pdf

1.download calc_pyth.zip
  from http://hep.pa.msu.edu/people/belyaev/comphep/calchep_pyth/calc_pyth.zip
  and 'unzip' it --
  you will get
  event2pyth.c , event_mixer.f, call_pyth_mix.f
  files.
  See page6 of the talk  above

2.To connect production and decay process
  you need to generate both -- production and decay using  "subproc_cycle".

3.
a)Then you run  'link_event_mixer'
  which does
  'f77 -o event_mixer  event_mixer.f event2pyth.c -lm'
  and
  creates "event_mixer" executable.
 
b) Run  event_mixer will
  mix generted events and automatically connect production and decay events
  and will redirect final events into file
 
  When it asks
  "Enter the name of the directory with the events to mix"
  please input  dir name in quotes like "dir_name" 
 
  The executable will produce
 
   'event_mixer.lhe' or  'event_mixer.out'
 
  depending on you reply  (y/n) on
 
  "Would you like events in LHA format? (y/n)"
 
  question. LHA format now became universal
  for latest PYTHIA versions and other MC generators
 
  In case of "n" answer event_mixer.out
  will be created. It contains events in ascii format
  and can be used for creating an ntuple. See 6.
  for the explanation.
 

4.download latest  PYTHIA version (6.4.15 or later)

5.create 
  call_pyth_mix executable
  via
  f77 -o call_pyth_mix call_pyth_mix.f pythia64xx.o
  ( link_pythia_mix)
  Then run
 "call_pyth_mix"
  this  read mixed events from file into PYTHIA
 
6. there is also an option to create ntuple file
   from event_mixer.out
  
a) to create ntuple from "event_mixer.out" file
   one should create "nt_maker" executable by running
   "./link_nt_maker"
   or
   "sh link_nt_maker"
  
   Before running "./link_nt_maker"
   user should edit this script and
   define the correct path to CERN directory.
   Once the correct path to CERN libraries is defined,
   user should run "sh link_nt_maker"
   which supposed to produce "nt_maker" executable
  
b) once "nt_maker" is ready,
   user is in position to produce ntuple.
   The "nt_maker" always reads "event_mixedr.out"
   as a default input file.
    
   At the next step, you just run
   "./nt_maker"
  
   It will produce
   event_mixer_*.nt
  
   ntuple files splitting your events by 50k
   and putting them into ntuple;
   "*" means ntuple number
   
====================================================================
UPDATE NOTES
28.06.2008
 
 -- CalcHEP-MC Interface works now together with
    batch interface (Neil Christensen) -- see latest
    CalcHEP update notes to it
   
 -- 'qNumbers' output in non-empty if user specifies
     non-zero valid PID code in the CalcHEP particle table.
    'qNumbers' output is unique for the model and does not depend
    on particular process, i.e. all new, non-SM particles
    with  non-zero valid PID code from model used will be in 'qNumbers'
 

10.03.2008
 
 -- Calchep-MC Interface uses 'qNumbers' output from latest CalcHEP version
    and transfer it into header of LHE file
 
 -- Information about finite intermediate particle with is stored not in LHE file,
    so long living particles and respective displacement vertex are properly
    reflected in LHE output now
    
======================================================================