sPHENIX MAPS tracker discussion

[Ming Liu <ming AT bnl.gov>]

Hi Jamie and all, cc’d Russ and MVTX folks,

 

I didn’t realize that we have new projections for pp and AuAu collision rates, I do remember we discussed an idea not long ago to use beam crossing angles to minimize

the overall rates but keep the physics luminosities more or less the same within |z| <10cm.

 

These lower rate numbers in general help to reduce the overall occupancies for MVTX too, this is good.

AuAu : 150kHz - >50kHz

pp: 10MHz -> 2MHz

 

My question is – do these changes come with significant beam crossing angles?

If so, I hope the latest beam-pipe design has already taken them into account properly,  Russ, is that true?  

 

Cheers,

Ming    

 

 

 

---	Dr. Ming Xiong Liu P-3, MS H846 Physics Division   Office: 505.667.7125 Mobile: 505.412.7396 Los Alamos National Laboratory lanl.gov

 

 

From: sPHENIX-tracking-l <sphenix-tracking-l-bounces AT lists.bnl.gov> on behalf of Jamie Nagle <jamie.nagle AT colorado.edu>
Date: Monday, February 8, 2021 at 7:40 PM
To: sPHENIX-tracking-l <sphenix-tracking-l AT lists.bnl.gov>
Subject: [Sphenix-tracking-l] Questions from a place of ignorance

 

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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