Previously, I discovered that there are a lot of generated (particle-level) tracks -- particularly those with [IdEnd = 0 && IdVtx > 1] -- that have a pT of -999.  See this post:

https://drupal.star.bnl.gov/STAR/blog/dmawxc/update-01132020-understanding-tracking-efficiencies-decays-vs

Why is this so?  I did some digging, and I found out that the 'StMuDstMaker' class (the official STAR one) assigns a 'pT' of -999 to all MC tracks which have a 'pT' of less than 0.001 GeV/c.  This can be seen here:

So all the particles which have 'pTmc = -999' are super soft particles.  As I saw in the last post, these are overwhelmingly things like electrons, positrons, etc.  Thus likely these are things produced (via geant) by the detector response.  We don't want to incorporate those particles into our tracking efficiency, jet-matching efficiency, etc. calculations.

I took the liberty to output information about different sets of generated particles for the 'pTparton = 25 - 35' GeV/c bin (RFF configuration) of the embedding for different for certain combinations of [IdVtx > 1] and 'pTmc < 0' or 'pTmc > 0' GeV/c.  Those are attached and their file names describe the different combinations.

The two things I took away from looking at the output is:

1. All the tracks with [IdVtx > 1] and 'pTmc > 0' GeV/c are pions, kaons, and protons (and maybe an errant Xi or something)...
2. Overwhelmingly, the matched tracks with [IdVtx > 1] and 'pTmc < 0' GeV/c (i.e. 'pTmc = -999') are pions and protons.  There are a few electrons, positrons, muons, and such.