Delphes detector simulation

Asked by JamesB on 2018-01-18

Hello,

I have used Madanalysis to run fastjet on a .hep from Madgraph/PYTHIA. The output is a simplified LHE file. Next I have run Delphes in Madanalysis on this file, with the following syntax:

set main.fastsim.package = delphes
set main.fastsim.detector = atlas
set main.fastsim.pileup = none
set main.outputfile = higgs_delhes.lhe
import ~/higgs_lvjj_200/higgs.lhe
submit

My issue is that the particle information before and after Delphes has run seems incompatible: momenta and energy are completely different, lepton flavour changes, etc. I expected Delphes just to blur the energies and momenta somewhat. Is there a flaw in my understanding, or am I doing something wrong?

Thank you,
James

Question information

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MadAnalysis 5 Edit question
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Last query:
2018-01-18
Last reply:
2018-01-18
Benjamin Fuks (fuks) said : #1

The input for delphes must be an event file after parton-showering and hadronization. This is not the case here. This may explain the weird results you got.

Regards,

Benjamin

JamesB (jamesb8) said : #2

Thanks Benjamin,

I thought PYTHIA performed parton-showering and hadronization?
The procedure I am following is Madgraph with PYTHIA -> Fastjet for constructing jets -> Delphes to model detector response.

James

JamesB (jamesb8) said : #3

Hi,

I understand your point I think - the lhe output is not appropriate for Delphes; it should be a hep file?

So in that case how does one perform jet clustering and then dectector simulation with Fastjet and Delphes correctly?

Thank you,
James

Benjamin Fuks (fuks) said : #4

Hi,

> I understand your point I think - the lhe output is not appropriate for Delphes; it should be a hep file?
Exactly.

> So in that case how does one perform jet clustering and then dectector simulation with Fastjet and Delphes correctly?
Delphes takes care of running fastjet as configured in the delphes card.

Regards,

Benjamin

JamesB (jamesb8) said : #5

Hello,

Apologies for my ignorance - I'm unsure how running Delphes will perform jet clustering.
At the moment this is what I specify in madanalysis:

set main.fastsim.package = delphes
set main.fastsim.detector = atlas
set main.fastsim.pileup = none
set main.outputfile = higgs_after_detector.lhe
import ~/higgs_lvjj_200/higgs.hep (this file is from madgraph/PYTHIA)
submit

What do I need to include to ensure jet clustering is done as I want?

Thank you,
James

Benjamin Fuks (fuks) said : #6

Hi,

In order to learn how to edit the delphes card (and to setup the jet clustering as you need), I recommend you to have a look to the delphes manual. Concerning the output file, maybe would you prefer dealing with the root output of delphes directly?

Cheers,

Bemjamin

> On 18 Jan 2018, at 18:31 , JamesB <email address hidden> wrote:
>
> Question #663228 on MadAnalysis 5 changed:
> https://answers.launchpad.net/madanalysis5/+question/663228
>
> Status: Answered => Open
>
> JamesB is still having a problem:
> Hello,
>
> Apologies for my ignorance - I'm unsure how running Delphes will perform jet clustering.
> At the moment this is what I specify in madanalysis:
>
> set main.fastsim.package = delphes
> set main.fastsim.detector = atlas
> set main.fastsim.pileup = none
> set main.outputfile = higgs_after_detector.lhe
> import ~/higgs_lvjj_200/higgs.hep (this file is from madgraph/PYTHIA)
> submit
>
> What do I need to include to ensure jet clustering is done as I want?
>
> Thank you,
> James
>
> --
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