Duplicate Tracks in Jets

[Samuel Alipour-fard]

Dear Delphes Team,

I have been looking through the output of Delphes for a variety of processes and events, and it appears that there is double counting of Track objects in Jets.

In particular, I have generated events through Madgraph, and fed them through Pythia and Delphes. Focusing now on a specific event in the .root file output by Delphes, I loop over the constituents of each Jet and create a list containing pointers to all constituent Track objects in the event. In this list, I find that there are often two (Track *) objects which point to the same address; further investigation reveals that the Track objects to which they point have the same physical properties (e.g. vertex where the Track originates, PT, D0, etc.). I am seeing this naive evidence of double counting in both the instance where the two objects come from the same Jet and in the instance where both Track objects are constituents of different Jets.

Thus, I am concerned that there may be double counting of tracks in the Jet constituents both within a single Jet (in the case where a single Jet has two constituents with the same address and physical parameters) and also between Jets (in the case where two or more distinct Jets have Track constituents with the same address and parameters). According to my code, which I am more than happy to share if it can help, this occurs for a variety of event topologies including the fairly simple process "p p > j j" with all default parameters in Madgraph, Pythia, and Delphes. I would love to understand how to interpret and fix this issue.

Thanks very much,
Sam