How to prevent certain particles from participating in jet clustering ?

[Haqiqat]

I'm studying a process with some leptons and jets in its final state. I would like to remove two most energetic leptons from the array which is used as input to FastJet, so that the removed leptons don't participate in jet clustering. Can you please advice if there is any way to do this ?

Many thanks in advance

[Michele Selvaggi]

yes, you can apply a filter to the collection given to FastJetFinder. Something like:

​https://github.com/delphes/delphes/blob/master/cards/delphes_card_CMS.tcl#L387-L397

note that here the module KEEPS all electrons and removes the rest. Instead you want to set the flag Invert to false to remove all electrons. Also remember to call the module in the ExecutionPath at the beginning of the card.

[Haqiqat]

Replying to mselvaggi:

yes, you can apply a filter to the collection given to FastJetFinder. Something like:

​https://github.com/delphes/delphes/blob/master/cards/delphes_card_CMS.tcl#L387-L397

note that here the module KEEPS all electrons and removes the rest. Instead you want to set the flag Invert to false to remove all electrons. Also remember to call the module in the ExecutionPath at the beginning of the card.

Dear mselvaggi

Thanks for your fast reply. Filtering electrons by pdg code results in removing all of the electrons from the array given to FastJetFinder. However, I need to remove only two of the electrons, not all of them. I would like to remove two most energetic electrons and keep the rest. Is it possible ?

Thanks a lot

[Michele Selvaggi]

You cannot exactly filter for the top two but you can apply a pT threshold eg:

set PTMin 25

If not you can always modify the PdgCodeFilter module:

​https://github.com/delphes/delphes/blob/master/modules/PdgCodeFilter.cc

This said keep in mind that if you are using one of the default cards where the UniqueObjectFinder is called at the end of the sequence, the Jet objects containing isolated leptons will be vetoed. If not, this is always something you can do at the analysis level with DR matching.

to suit you needs. You'll have to recompile afterwards.

[Haqiqat]

Replying to mselvaggi:

You cannot exactly filter for the top two but you can apply a pT threshold eg:

set PTMin 25

If not you can always modify the PdgCodeFilter module:

​https://github.com/delphes/delphes/blob/master/modules/PdgCodeFilter.cc

This said keep in mind that if you are using one of the default cards where the UniqueObjectFinder is called at the end of the sequence, the Jet objects containing isolated leptons will be vetoed. If not, this is always something you can do at the analysis level with DR matching.

to suit you needs. You'll have to recompile afterwards.

I see. Thanks. Suppose a jet has many constituents and only one of them is an isolated lepton. Does UniqueObjectFinder veto such a jet ?

[Michele Selvaggi]

Yes ,it is sufficient that one consitituent of the jet is an isolated lepton and the jet is vetoed.