MadGraph5_aMC@NLO

MadAnalysis: Cuts depending on number of jets

Asked by Jory Sonneveld

I am trying to use MadAnalysis to see the impact of cuts on my event number. For this, I want to implement cuts depending on the number of jets. This is because in the ma_card.dat of MadAnalysis it is written:
''
# 4. For all the 'min' cuts, an event will be thrown away if the particle *
# does not exist. On the other hand, for all the 'max' cuts the cut *
# will be ignored if the particle does not exist *
# (Only dRij is an exception, for which it is the other way around) *
''
Then in the case of e.g.
p_T1 > 100GeV and p_Ti > 50GeV for 2 =< i <= number of jets
I do not want my event thrown away if there is merely 1 jet; in that case I would want only p_T1 > 100GeV.

The same holds for
delta_phimin 1 3 4 1 0.2d0 # cut between transverse momentum of ith jet and missing transverse momentum vector - single, dijet, and trijet.
If there is only one jet, the event should not be thrown away but merely a cut for only the first jet should be made (the above states 'for the first three particles of class 1 - and for me class one is the one of jets, pdg 21).

Perhaps I misunderstood the way ma_card.dat works?

Thank you in advance,

Jory

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Rikkert Frederix
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Rikkert Frederix (frederix) said : 		#1

Dear Jory,

Unfortunately for you, the way MadAnalysis was designed is indeed the way it's written in the ma_card.dat. If you ask for pT(j1)>100 and pT(j2)>50 GeV, and the event has only one jet, the 2nd requirement (pT(j2)>50 GeV) is not met, and the event is considered as not passing the cuts. There is no easy way for fixing this.

A way around it, is running MadAnalysis several times, each with different ma_card to consider all possibilities. Of course, this is far from optimal if you have many cuts to consider.

Another option would be to use MadAnalysis5 ( http://madanalysis.irmp.ucl.ac.be/ ), which gives the user a lot more freedom in choosing cuts and all that, but has also a bit more overhead. For example it needs ROOT to be installed on your computer. I'm not at all an expert on MA5, but I'm sure the authors can help you out if the manual does give you any hints towards the solution for your case.

All the best,
Rikkert

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Jory Sonneveld (jory) said : 		#2

Hi Rikkert,

Thank you for your answer. I will try to get MadAnalysis5 running on my computer. In the mean time, I would still like to know if in the current version of MadAnalysis in MadGraph5 the following works for an arbitrary number of jets:

delta_phimin 1 3 4 1 0.2d0

in other words, the first three particles of the first class should have minimal delta_phi of 0.2. If in this case there are only 2 jets, will the event be thrown away?

Thanks again,
Jory

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Best Rikkert Frederix (frederix) said : 		#3

Dear Jory,

If a condition is not met, the event does not pass the cuts. Hence, also for the delta_phimin of your example. All the events that pass that cut need to have at least three jets.

Kind regards,
Rikkert

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Jory Sonneveld (jory) said : 		#4

Thanks Rikkert Frederix, that solved my question.