[Color_transp] Multiple particle tracking efficiency estimate

[John Matter]

Hi all

I'm trying to replicate the model described in this PDF.
https://hallcweb.jlab.org/DocDB/0000/000023/001/hms_tracking.pdf

The overall tracking efficiency is observed to be rate-dependent. The model
supposes that the tracking efficiencies for 1-electron events and
2-electron events are rate-independent. The origin of the overall rate
dependence is taken to be track pileup during the DC gate window. This
model suggests two interesting studies:

   1. Does the overall efficiency actually depend linearly on gate width?
   Looking at their data, the answer is yes. I'm working on this analysis for
   our data.
   2. Is the 2-electron efficiency independent of rate? This is where I'm
   stuck.

To isolate 2-electron events, the paper uses calorimeter energy deposition.
One way to do this would be to select events with normalized track energy
deposition (H.cal.etotnorm, which normalizes to spectrometer central
momentum rather than track energy) approximately equal to 2. Here's where
I'm stuck in applying this to our data:

   - In the HMS, our 3/4 rates are all ~1 kHz and below so we don't have a
   sample of 2-electron events in any of our kinematics. So I'm not sure I can
   do a 1-to-1 comparison with the paper's results.
   - In the SHMS, I'm not sure what a useful "2-proton" calorimeter cut
   would be.

Any suggestions are welcome. Thanks!

- John
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