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LHC.in
sidsule (Siddharth Sule)
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sidsule
May 15 2025, 12:42 PM
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LHC.in
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# -*- ThePEG-repository -*-
##################################################
# Herwig Tutorial
# usage: Herwig read LHC.in
##################################################
##################################################
# Step 1: Generating the Hard Subprocess
#
# To start off, we will generate the process
#
# p(q) p(qbar) -> Z/Gamma -> e+ e-
#
# To do this, we need to tell Herwig a few things:
# - This is a proton-proton collision
# - We want sqrt(s) = 13000 GeV
# - We want to generate Drell-Yan Z/gamma
# - We just want e+ e- (no other pairs)
# - Any cuts on the events we want to generate
##################################################
# This is a proton-proton collision
read snippets/PPCollider.in
# We want sqrt(s) = 13000 GeV
cd /Herwig/Generators
set EventGenerator:EventHandler:LuminosityFunction:Energy 13000.0
# We want to generate the Drell-Yan /gamma
cd /Herwig/MatrixElements/
insert SubProcess:MatrixElements[0] MEqq2gZ2ff
# We just want p p -> Z -> e+ e- (no photon, or other pairs)
set MEqq2gZ2ff:Process Electron
set MEqq2gZ2ff:GammaZ Z
# Any cuts on the events we want to generate
cd /Herwig/Cuts/
insert Cuts:TwoCuts 0 LeptonPairMassCut
set LeptonPairMassCut:MinMass 60*GeV
set LeptonPairMassCut:MaxMass 120*GeV
# Run this process for 1, 10, 100, 1000, 10000, 100000 events
# and see how the results change and the cross section converges
##################################################
# Step 2: Emissions and the Parton Shower
#
# Herwig offers two models of parton showers:
#
# - Angular-ordered parton shower
# - This is the default parton shower. The
# emissions are ordered by the angle
# created between the emitter and the
# emitted parton.
#
# - Dipole parton shower
# - This is the alternative parton shower.
# The emissions now involve a third
# spectator parton. The emissions are
# ordered by the transverse momentum of
# the emitted parton.
##################################################
# Comment/Delete these lines to start Step 2
cd /Herwig/EventHandlers
set EventHandler:CascadeHandler NULL
# Uncomment these lines for the Angular-ordered parton shower
# cd /Herwig/EventHandlers
# set EventHandler:CascadeHandler /Herwig/Shower/ShowerHandler
# set /Herwig/Shower/ShowerHandler:Interactions QCD
# Uncomment these lines for the Dipole parton shower
# cd /Herwig/EventHandlers
# set EventHandler:CascadeHandler /Herwig/DipoleShower/DipoleShowerHandler
# read snippets/DipoleShowerFiveFlavours.in
##################################################
# MPI will not be used in this tutorial
# see tutorial 3
##################################################
# Leave this as it is
cd /Herwig/EventHandlers
set /Herwig/Shower/ShowerHandler:MPIHandler NULL
set /Herwig/DipoleShower/DipoleShowerHandler:MPIHandler NULL
##################################################
# Step 3: Hadronisation
#
# The Hadronisation process converts the partons
# into hadrons. In Herwig, this is done using the
# cluster model. The cluster model involves
# breaking all gluons into quark-antiquark pairs.
# Then, quarks and antiquarks are combined into a
# colourless pseudoparticle called a cluster.
# The clusters decay into hadrons.
##################################################
# Comment/Delete these lines to enable Hadronisation and Decays
cd /Herwig/EventHandlers
set EventHandler:HadronizationHandler NULL
set EventHandler:DecayHandler NULL
##################################################
# Analysis and Output Settings - No need to change
##################################################
cd /Herwig/Analysis
set Basics:CheckQuark No
cd /Herwig/Generators
read snippets/Rivet.in
insert /Herwig/Analysis/Rivet:Analyses 0 MC_ZINC
insert /Herwig/Analysis/Rivet:Analyses 0 MC_ZJETS
cd /Herwig/Generators
saverun LHC EventGenerator

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