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MadGraph5_aMC@NLO for Muon Colliders

A collection of references and tips for using MadGraph5_aMC@NLO to generate collision events at a Muon Collider.

This is not a tutorial on using MadGraph5_aMC@NLO. Other excellent resources exist.

Resources

Setting Up Software

Standalone aMC@NLO works out of the box on the cluster computers. Start aMC@NLO and install the necessary tools.

git clone git@github.com:mg5amcnlo/mg5amcnlo.git
cd mg5amcnlo
git checkout -b v3.5.4 v3.5.4
export ROOTSYS=/usr
./bin/mg5_aMC
install pythia8
install Delphes

Then to start MadGraph in the future, run the following inside the mg5amcnlo directory.

export ROOTSYS=/usr
./bin/mg5_aMC

Example

The following commands will generate events for Higgs production via W scaterring.

generate mu+ mu- > h vl vl~
output PROC_mumuWWh
launch

Hit <enter> when asked about post-processsing programs. Then use option 2 to edit the run_card.dat. Ensure that the following fields are set. The lpp# value of 0 disables PDFs and ebeam# sets the energy of each beam. The following corresponds to a 10 TeV muon collider.

0        = lpp1    ! beam 1 type 
0        = lpp2    ! beam 2 type
5000.0     = ebeam1  ! beam 1 total energy in GeV
5000.0     = ebeam2  ! beam 2 total energy in GeV

Close the editor and hit <enter> to continue.

Example with EW PDFs

It should be possible to use EW PDFs to generate events. This is appropriate for VBF processes where one parametrizes the probabilty of a muon to emit a vector boson. Similarly to how one parametrizes the hadronic content of a proton. However I haven't managed to get the following to run.

set group_subprocesses false
generate w+ w- > h
output PROC_WWh
launch

Hit <enter> when asked about post-processsing programs. Then use option 2 to edit the run_card.dat. Ensure that the following fields are set. The |lpp#| value of 4 sets colliding beams to be muons and ebeam# sets the energy of each beam. The following corresponds to a 10 TeV muon collider.

-4        = lpp1    ! beam 1 type 
4        = lpp2    ! beam 2 type
5000.0     = ebeam1  ! beam 1 total energy in GeV
5000.0     = ebeam2  ! beam 2 total energy in GeV

eva    = pdlabel     ! PDF set Effective W/Z/A Approx

Close the editor and hit <enter> to continue.

This results in a crash with the following error.

DiscreteSampler:: Error, no point could be picked with random variable 0.2365935444831848 using upper bound found of NaN.