Adding an absolute isolation criterion option

[Daschm]

Hello,

we are trying to reproduce ATLAS analyses which often use the following isolation criterion for muons: The scalar sum of all tracks not associated to the muon in a cone dR<0.2 around the muon should be less than 1.8 GeV. [see e.g. ​http://cds.cern.ch/record/1493486/files/ATLAS-CONF-2012-147.pdf ]

For electrons, the criterion usually sets an upper limit on the relative value (total pT around candidate)/(candidate's pT) and this is the (only) way the isolation module works in Delphes.

However, for the above cases it would be nice if the isolation module not only had a PTRatioMax but also a PTMax to set limits on the absolute surrounding pT. An alternative could be to just add a flag `absLimit that deterines whether the limit corresponds to an absolute upper bound or a limit relative to the candidate's pT.

Would it be possible to add a feature like that in one of the following releases?

Sincerly,
Daniel

[Michele Selvaggi]

Hi Daniel,

we will think about your proposition.
Meanwhile, you can simply replace in modules/Isolation.cc

if(ratio > fPTRatioMax) continue;
by
if(sumPT > fPTRatioMax) continue;

Also, in the atlas card you should set PTRatioMax = 1.8
Don't forget to recompile by typing make.

Is this what you had in mind?

Michele

[Daschm]

Thank you very much for your quick reply!

Yes, this is exactly what I had in mind and I could have done it myself, but a) I wanted to avoid having to manually edit the module source every time I update Delphes, and b) I thought it would be nice to have it globally included for other people, who at some point might run into the same problem. Especially since it seems to be common in many ATLAS analyses to have this absolute muon isolation criterion.

Daniel

[Pavel Demin]

Two new parameters UsePTSum and PTSumMax for the Isolation module are available in new release 3.0.10.

To use an absolute isolation criterion, set the UsePTSum parameters to true, and set the PTSumMax parameter to a desired value.