Event generators

EvtGen

Default script

Script Generation/GenExamples/scripts/runevtgen.py generates Aurora script to run EvtGen. This script is added to the path and can be invoked from any place:

 runevtgen.py  

This string generates the default script ctaugen.py and produces the default output file output.root. This file contains 1000 events of inclusive psi(3770) decays in the SCT edm format.

One can run

ctaurun ctaugen.py

to invoke generator again.

Configuration

The file ctaugen.py contains two lines:

from GenWrappers.EvtGenTools import generateEvtGen
generateEvtGen(dec="",root="psi(3770)",ecms=0.0,nevt=1000,ip=[0.01, 0.01, 0.5],ofile="{CWD}/output.root"),

where ${CWD} is the path from where runevtgen.py was called.

generateEvtGen function has the following parameters:

• dec - EvtGen users decay file. It can be one of the included in Aurora files or absolute path to your own decay file. Inclusive MC generation does not require user decay file
• root - root particle for EvtGen. vpho (virtual photon) should be used for non-resonant processes
  • Acceptable root particles: vpho, J/psi, psi(2S), psi(3770), psi(4040), psi(4160), psi(4415). For more details see Generation/GenTools/GenWrappers/python/EvtGenTools.py in Aurora.
• ecms - Total center-of-mass energy. This parameter should be set for virtual photon. This parameter is ignored for if root particle is a resonance (it's mass is the center-of-mass energy)
• nevt - number if events to be gnerated
• ip - uniform 3D smearing (in mm) for the primary vertex
• ofile - output file name

One can change these parameters to change behaviour of EvtGen and to produce arbitrary MC sample.

Examples

Use dec file:

generateEvtGen(dec="dkpi.dec",root="psi(3770)",ecms=0,nevt=1000,ip=[0.01, 0.01, 0.5],ofile="/gcf/stark/home/razuvaev/workarea3/run/output.root")

Some example dec files available within aurora are listed below.

File name	Decay chain
cont.dec
denu.dec	e+e- -> psi(3770) -> [D+ -> e+ nu] D- + c.c.
dhh.dec	e+e- -> psi(3770) -> [D0 -> h+ h-] [anti-D0 -> h+ h-]
dk3pi.dec	e+e- -> psi(3770) -> [D0 -> K- [pi pi pi]+] anti-D0 + c.c.
tautau.dec	e+e- -> gamma* -> tau+ tau-
xic0.dec	e+e- -> gamma* -> Xi_c0 anti-Xi_c0
taumugamma.dec	e+e- -> [tau+ -> mu+ gamma] [tau- -> X] (and c.c.)
lambdac.dec	e+e- -> gamma* -> Lambda_c+ anti-Lambda_c-

All example dec files are stored in Generation/GenExamples/share/dec folder of Aurora.

An alternative approach is to invoke runevtgen.py script with command line arguments. Here is the code snippet of the parameters defined:

usage = 'evtgen.py [options]'
parser = OptionParser(usage=usage)
parser.add_option('-w', '--wdir',   dest='workdir',      default='.')
parser.add_option('-s', '--scr',    dest='scrfile',      default='ctaugen.py')
parser.add_option('-d', '--dec',    dest='decfile',      default=)
parser.add_option('-r', '--root',   dest='rootParticle', default='psi(3770)')
parser.add_option('-o', '--out',    dest='outfile',      default='output.root')
parser.add_option('-n', '--numevt', dest='nevt',         default=1000)
parser.add_option('-e', '--energy', dest='energy',       default=0.)

I hope the meaning of parameters is self-evident.

--V.S.Vorobev (talk) 15:00, 5 August 2019 (+07)