Second run: LHC-Z+jet events
This is the simulation of a P + P -> Z + jet production event at the LHC for 7 TeV center-of-mass energy, using the ATLAS_2011_I945498 and MC_ZINC Rivet plugins for data analysis.
Please download the following input file and move it to your work directory:
Input file:
Alternatively, you can use the following command-line codes:
mkdir LHC-Z+jet cd LHC-Z+jet wget https://phab-files.hepforge.org/file/data/n36vm5xhxosaddw7xe4x/PHID-FILE-etk5vfa3ii64fngxon2w/LHC-Z_jet.in
Before running this event, let us take a look at the input file
vi LHC-Z+jet.in
As you can see, the process selection section has been completely deactivated. This is because for a process like P + P -> Z + jet, Herwig needs to use the external matrix element (ME) providers. However, the use of these tools in the docker/VM would be problematic. In an installed version of the Herwig, one can easily use these external ME providers by selecting the hard-process in the Process selection and choosing the ME providers from Matrix element library selection.
################################################## ## Process selection ################################################## ## Model assumptions # read Matchbox/StandardModelLike.in # read Matchbox/DiagonalCKM.in ## Set the order of the couplings # cd /Herwig/MatrixElements/Matchbox # set Factory:OrderInAlphaS 1 # set Factory:OrderInAlphaEW 1 ## Select the process # do Factory:Process p p -> Z0 j ################################################## ## Matrix element library selection ################################################## ## Select a generic tree/loop combination or a ## specialized NLO package # read Matchbox/MadGraph-GoSam.in # read Matchbox/MadGraph-MadGraph.in # read Matchbox/MadGraph-NJet.in # read Matchbox/MadGraph-OpenLoops.in
Fortunately, Herwig comes equipped with a set of Pre-calculated ME (you can see the complete list of these at Herwig_directory/share/Herwig/LHC.in):
################################################## # Pre-calculated ME for hadron-hadron collisions ################################################## cd /Herwig/MatrixElements/ # Z+jet insert SubProcess:MatrixElements[0] MEZJet
Now, we can run the Z+jet event using
Herwig read LHC-Z+jet.in Herwig run LHC-Z+jet.run -N 10000
and plot the results by
rivet-mkhtml LHC-Z+jet.yoda
Please change the name of the produced yoda files
mv LHC-Z+jet.yoda Z+jet_MCNLO.yoda
and take a look at the parton shower selection section
################################################## ## Matching and shower selection ################################################## read Matchbox/MCatNLO-DefaultShower.in # read Matchbox/Powheg-DefaultShower.in ## use for strict LO/NLO comparisons # read Matchbox/MCatLO-DefaultShower.in ## use for improved LO showering # read Matchbox/LO-DefaultShower.in # read Matchbox/MCatNLO-DipoleShower.in # read Matchbox/Powheg-DipoleShower.in ## use for strict LO/NLO comparisons # read Matchbox/MCatLO-DipoleShower.in ## use for improved LO showering # read Matchbox/LO-DipoleShower.in # read Matchbox/NLO-NoShower.in # read Matchbox/LO-NoShower.in
The "read Matchbox/MCatNLO-DefaultShower.in" option is chosen by default, activating an MC@NLO matched angular ordered parton shower. Please choose the "read Matchbox/MCatLO-DefaultShower.in" option, to choose the MC@LO and try running the event again:
Herwig read LHC-Z+jet.in Herwig run LHC-Z+jet.run -N 10000 mv LHC-Z+jet.yoda Z+jet_MCLO.yoda
Repeat this process again, this time with "read Matchbox/LO-NoShower.in" option and rename the yoda file as
mv LHC-Z+jet.yoda Z+jet_NOPS.yoda
At this point, you are in the position of 3 separate Z+jet production events, each with different parton shower settings. You can compare your findings by plotting these yoda files altogether:
rivet-mkhtml Z+jet_MCNLO.yoda:MC_NLO Z+jet_MCLO.yoda:MC_LO Z+jet_NOPS.yoda:NO_PS
and check out your result by
firefox rivet-plots/index.html
Switching things on and off
At this point, we are going to modify our copy of the LHC-Z+jet.in input file and make a few more runs.
These commands control the major modules of the event generator. You can switch them on and off, rerun the event and observe the produced effects of the results.
################################################## ## ShowerHandler(s) ################################################## cd /Herwig/EventHandlers set EventHandler:CascadeHandler:MPIHandler NULL # set EventHandler:DecayHandler NULL # set EventHandler:HadronizationHandler NULL set /Herwig/Shower/ShowerHandler:Interactions QCDandQED
- The Multy Particle Interaction (MPIHandler) is switched off by default. Turn it on and off, and run the event in each state and see what changes in the results.
- You can change the type of parton shoer by changing the value in
set /Herwig/Shower/ShowerHandler:Interactions QCDandQED
The options are QCDandQED, QCD and QED. Try to check out the difference they make in the event.
Your choice for the scale of the hard-process is made in this section. The primary option for a Z+jet production event, "the fixed scale option", is pre-selected here. You can choose other options and/or change the value of the fixed scale and see the effect.
################################################## ## Scale choice ################################################## cd /Herwig/MatrixElements/Matchbox/ ## Fixed scale set Factory:ScaleChoice Scales/FixedScale set Scales/FixedScale:FixedScale 91.1876*GeV ## The transverse momenta of coloured particles # set Factory:ScaleChoice Scales/HTScale ## The transverse momenta of all outgoing non-jet particles # set Factory:ScaleChoice Scales/HTPrimeScale ## For processes involving a pair of final-state leptons # set Factory:ScaleChoice Scales/LeptonPairMassScale ## The transverse component of the momentum of the lepton pair # set Factory:ScaleChoice Scales/LeptonPairPtScale ## The transverse momentum of the hardest jet # set Factory:ScaleChoice Scales/MaxJetPtScale ## The partonic centre-of-mass energy # set Factory:ScaleChoice Scales/SHatScale ## For processes involving the production of a t-tbar pair # set Factory:ScaleChoice Scales/TopPairMassScale ## The transverse mass of the t-tbar pair # set Factory:ScaleChoice Scales/TopMTScale
You can impose any constraint that you want on your event. To find out the compete list of cuts and how to use them, see Herwig documentaion on cuts.
################################################## ## Cut selection ## See the documentation for more options ################################################## cd /Herwig/Cuts/ ## cuts on jets # read Matchbox/DefaultPPJets.in # insert JetCuts:JetRegions 0 FirstJet # insert JetCuts:JetRegions 1 SecondJet # set /Herwig/Cuts/JetFinder:Variant Kt # set /Herwig/Cuts/JetFinder:ConeRadius 0.4 # set /Herwig/Cuts/FirstJet:PtMin 20.*GeV # do /Herwig/Cuts/FirstJet:YRange -5.0 5.0
- Last Author
- aidin
- Last Edited
- Jul 25 2019, 2:57 PM