== info ==

this directory contains the event geenrator for Timelike Compton Scattering (TCS) in electroproduction
It is actaully a event generator for Bethe_Heitler process which used for TCS estimation

The photonproduction of BH crossection is based on formula Eur.Phys.J.C23:675-689,2002
Then virtual photon flux is calculated by equivalent photon approximation (EPA) by using formula 3 of
http://lss.fnal.gov/archive/other/lpc-94-35.pdf 

events are generated eveenly within available Eg, Q2 and t phase space. the phase space factors is in output

== code ==

main generator code is GenTCS.cc which calls other code as lib

To compile
setup root env
make

to run 
setup root env
setenv LD_LIBRARY_PATH ./:${LD_LIBRARY_PATH}
./GenTCS.exe Eb(GeV) Eg_min(GeV) Q'2min(GeV2) Q'2max(GeV2) Q2max(GeV2) tmin(GeV2) Ep(GeV) l(cm) Nsim

typical SoLID choice
double Eb=11.,Eg_min=4.2,Q'2min=4,Q'2max=9,Q2max=0.05,tmin=3.2,Ep=0.,l=15;
./GenTCS.exe 11 4.2 4 9 0.05 3.2 0. 15 1e6

GenTCS_Eb11_Egmin4.2_Qp2min4_Qp2max9_Q2max0.05_tmin3.2_Ep0_l15_1e6.root

choose Ep=0 and l=non-0 for fixed target (jlab 12GeV)
choose Ep=non-0 and l=0 for collider (EIC)

The output tree is in GenTCS.root

anaTCS.C can be used to analyze the output tree
It's too slow to run as script, better run as binary
in root
.x anaTCS.C+("GenTCS.root","SoLID",true)
choose the root file by GenTCS
choose SoLID or CLAS12 detector
use "true" or "false" to turn off momentum smearing

root file with acceptance histogram is needed for anaTCS.C to work
download
acceptance_solid_CLEO_JPsi_negative_target300_output.root
clas12_acceptance.root
from
http://hallaweb.jlab.org/12GeV/SoLID/download/sim/acceptance/