MadAnalysis 5

missing particle after fastjet reconstruction

Asked by Eleni Vryonidou

Hi Benj,

I have the following problem...

I have imported a hepmc file into madanalysis5 and used fastjet to get a lhe reconstructed file. I was following the discussion here:

https://answers.launchpad.net/madanalysis5/+question/268922

so I am already using version 1.2_beta

In my process, I have a mediator (pdg 9000008), decaying into two stable DM particles, with pdg numbers +/-9000007. By importing the hepmc file that I get from pythia8 into madanalysis, I plotted the invariant mass of the DM pair using the hepmc file, and it looks fine.

I then tried to do the same with the lhe file that I get after running fastjet within madanalysis, but I realised that in the lhe output file, there is nowhere the PDG +/-9000007 and I get nothing in the plot. I only see the pdg number of my mediator in every event.

Do you have any idea where my DM particles went?

I suspect that I have the same problem as here:

https://answers.launchpad.net/madanalysis5/+question/264162

But I would like to keep my final state DM to plot missing ET etc...

Thanks a lot,

Eleni

Question information

Language:
English Edit question
Status:
Solved
For:
MadAnalysis 5 Edit question
Assignee:
Benjamin Fuks Edit question
Solved by:
Benjamin Fuks
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Benjamin Fuks (fuks) said : 		#1

Hi Eleni,

You need to indicate to madanalysis that your particles are invisible. To this aim, please type
  define invisible = invisible 9000007 -9000007
before submitting the job. Then it should work.

Cheers,

Benj

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Eleni Vryonidou (evryonidou) said : 		#2

Hi Benj,

Ok. That works, thanks. But I have one other question.

In the header of the reconstructed lhe file I see this:

# - particle with a PDG code = 12: the missing transverse energy. #
# The missing transverse energy is computed as opposite to the sum of the #
# four-momenta of all jets, electrons, muons and hadronic taus. #

But I realised that in fact this is the sum of the invisible particles momenta, as computed from the hepmc file. This is not affected by the ptmin I set for the jets, i.e. with 10 and 25 GeV ptmin I get exactly the same MET in contrast from what I would expect from the header description. The jet multiplicities and jet distributions change of course.

Is this normal?

Thanks,

Eleni

Revision history for this message
Best Benjamin Fuks (fuks) said : 		#3

Hi Eleni,

> In the header of the reconstructed lhe file I see this:
>
> # - particle with a PDG code = 12: the missing transverse energy. #
> # The missing transverse energy is computed as opposite to the sum of the #
> # four-momenta of all jets, electrons, muons and hadronic taus. #
>
> But I realised that in fact this is the sum of the invisible particles
> momenta, as computed from the hepmc file. This is not affected by the
> ptmin I set for the jets, i.e. with 10 and 25 GeV ptmin I get exactly
> the same MET in contrast from what I would expect from the header
> description. The jet multiplicities and jet distributions change of
> course
This is the sum of the visible particles included in the hepmc file, whatever are their momenta. Those guys leave tracks, even if they are nor identified as anything.

Cheers,

B>

Revision history for this message
Eleni Vryonidou (evryonidou) said : 		#4

Thanks Benjamin Fuks, that solved my question.