Reconstruction of tracks - long lived charged particles

[Archana]

Hello,

I have a follow-up to my recent question on Ticket #138. I have been reading the Delphes manual, 1307.6346 and now have an idea of why Delphes may not be reconstructing these long lived charged particles as tracks. Section 2.3 of the manual says that by construction, Ntrk <= Ncalo. (Ncale = hits in the calorimeter; Ntrk = hits in the tracker).

In the scenarios where a long lived charged particle decays before it reaches the calorimeter, Ncalo = 0, but Ntrk > Ncalo. Would the construction be problematic to such scenarios? What does Delphes do in this case?

Thanks,
Archana

[Michele Selvaggi]

Dear Archana,

the problem is that long lived charged particles (LLCP) are not considered as stable. Therefore Delphes does not create tracks for such particles. You will only be able to see in the Delphes output their decay products. In order to properly treat such particles, one should create a track from the production vertex to the displaced decay vertex.

Currently, the easiest solution for you would be to directly go the Particle branch in the Delphes output tree, find the relevant LLCP, and extract its kinematic parameters.

Cheers,

Michele