Applying parton cuts
Dear Olivier,
I am generating some SM background processes for my analysis. Firstly, I tried to have all inclusive runs (with no parton cuts in MG5, I only applied cuts during analysis) and in most cases I was able to generate enough events with my laptop, but in some cases (because of the large cross section) I would have to generate > 700 mio events for sufficient statistics, so my adviser suggested me to apply cuts already in MG5 to suppress cross section but now I have some problems.
My signal should have 2 leptons (I am restricting to electrons) and 4 jets in final state and after the analysis of the signal and background which I was able to generate, I decided to make two cuts on lepton pT-s for the rest background processes. From the analysis, it was clear that the signal (from BSM) could easily be extracted with lepton pT cuts - pT(l1) > 150 GeV and pT(l2) > 25 GeV and I saw that in MG5, I am able to include those two cuts via ptl1min and ptl2min command in run_card. The problem is that when I do this, it says that the cross section is equal to 0 and one of the reasons could be too strong cuts, but I lower them and the error stayed the same. My backup plan was the ordinary ptl and then also the ptj cut, but it turned out that although the process 'went through' the cross section was still high (actually it stayed the same) even when applying abnormal cuts like ptl = 10000 and ptj = 100000. I have the problems with following processes:
p p > t t~ @0, p p > t t~ j @1, p p > t t~ j j @2 , cs = 1152 pb,
p p > V @0, p p > V j @1, p p > V j j @2, cs = 2.5e+05 pb ,
p p > V V @0, p p > V V j @1, p p > V V j j @2 , cs = 674.93 pb,
where V = w+ w- z.
Here is an example of my script:
generate p p > t t~ @0
add process p p > t t~ j @1
add process p p > t t~ j j @2
output simulations/
launch
# Param card:
shower = Pythia8
detector = Delphes
analysis = OFF
# Run card:
set nevents 1000
set pdlabel lhapdf
set lhaid 21250
# Cuts:
set ptl1min 100.0
set ptl2min 10.0
or
set ptl 100.0
set ptj 20.0
Am I missing something?
Thank you in advance, looking forward to hearing from you,
Blaž
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- Olivier Mattelaer
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