sPHENIX tracking discussion

[Jamie Nagle <jamie.nagle AT colorado.edu>]

Hello Tracking Experts,

I have been only somewhat following the progress on understanding track distortions, corrections, and momentum resolution and its relation to the TPOT proposal.    In looking back through recent presentations, I am missing part of the big picture -- which is certainly my fault.

I thought I would ask a few questions to see what quantitative answers exist.

* As a starting point, until September 2020,  the sPHENIX plan  was to have 150 kHz of AuAu  minimum bias collisions - a large fraction which would be outside the z  vertex, i.e. |z| < 10 cm.   For pp collisions the highest rates were 10 MHz or more, and now with the  plan only having pp 200 GeV and a crossing angle this is down to ~ 2 MHz.

* Only in September 2020 with  the new sPHENIX Beam Use Proposal did we give up  these high rates for calorimeter measurements only, and settle that the highest AuAu minimum bias rates would be approximately 50 kHz or so.  

* What was the original performance spec for the TPC to handle distortions at and achieve the benchmark Upsilon mass resolution?    

* Some of the current momentum resolution / upsilon resolution plots look like that program is lost (or never was).    It is possible to produce a figure of (1) charged particle momentum resolution versus p up to 50 GeV, and (2) upsilon 3-state mass resolution for the following equivalent rates: 1 kHz, 10 kHz, 25 kHz, 50 kHz.     At what rate do the effects of degraded resolution  really kick in?

* How much of the issue  with fluctuations in IBF and corrections is CPU time versus simply a  loss of information (i.e. impossible to recover)?     Where do the outer MMGs come into play here in both cases?

Some of this information may be critical in potentially re-thinking the run plan to make sure a "good" data set, though smaller, can be assured, while testing at higher rates.   Also, I thought there were ideas with regards to how small in radius we have active in the TPC that influences things -- is that now set in stone or still being discussed?    Same with the gain and gas question.

Thanks for any  help in this direction.

Sincerely,

Jamie

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|| James L. Nagle   
|| Professor of Physics, University of Colorado Boulder

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