MB.in

##################################################
# MEMinBias Matrix Element
##################################################

# MPI model settings

## Report the correct cross section
# (as advised e.g. in https://herwig.hepforge.org/trac/browser/Tests/Rivet/SppS-900-UE.in)
cd /Herwig/Generators
create Herwig::MPIXSecReweighter MPIXSecReweighter
insert EventGenerator:EventHandler:PostSubProcessHandlers 0 MPIXSecReweighter
set EventGenerator:EventHandler:CascadeHandler NULL

clear EventGenerator:EventHandler:SubProcessHandlers[0]

##################################################
# Create separate SubProcessHandler for MinBias
##################################################
cd /Herwig/MatrixElements/
cp SubProcess QCDMinBias

set QCDMinBias:CascadeHandler /Herwig/Shower/ShowerHandler
set QCDMinBias:CascadeHandler:MPIHandler /Herwig/UnderlyingEvent/MPIHandler
set QCDMinBias:DecayHandler /Herwig/Decays/DecayHandler

# Due to numerics the pomeron could be seen as timelike.
set /Herwig/Shower/ShowerHandler:SplitHardProcess No
set /Herwig/DipoleShower/DipoleShowerHandler:SplitHardProcess No

insert QCDMinBias:MatrixElements[0] MEMinBias

cd /Herwig/Generators
# MinBias parameters used for the new kinematics of soft MPI
set /Herwig/Cuts/MinBiasCuts:X1Min 0.01
set /Herwig/Cuts/MinBiasCuts:X2Min 0.01

# Needed to get the correct fraction of diffractive events
set /Herwig/MatrixElements/MEMinBias:csNorm 4.5584

set EventGenerator:EventHandler:Cuts /Herwig/Cuts/MinBiasCuts

cd /Herwig/MatrixElements/
insert /Herwig/Generators/EventGenerator:EventHandler:SubProcessHandlers[0] QCDMinBias