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[Anthony Frawley <afrawley AT fsu.edu>]

Hello Ross,

Your summary is correct. In the case where we do not have triggered data, we do not know which crossing the cluster is associated with. Then the TPC z position depends on both start time and actual position.

Once we match the TPC track to the silicon track stub, we will be able to identify the bunch crossing. But that matching will be hard with fully distorted TPC tracks.

Tony

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From: Ross Corliss <ross.corliss AT stonybrook.edu>
Sent: Monday, October 25, 2021 11:50 PM
To: Anthony Frawley <afrawley AT fsu.edu>
Cc: sphenix calibrations <sphenix-calibration-l AT lists.bnl.gov>
Subject: Re: [Sphenix-calibration-l] TPC Distortions meeting, Tuesday, 11AM Eastern

 

Hi Tony,

To make sure I understand:  Assuming we have at our disposal a known-exactly-correct map of the static distortions, in a world unbounded by computation cost, each TPC hit is actually a path through the TPC, giving (xyz) as a function of (t).  

In the real world, we must make a preliminary estimate of the z position of a particle in order to correct its xyz position, since we can't hand a tracker the curved drift trajectories.   

The largest distortions will occur near z=zmax, since that's where the magnetic field diverges, so it is probably reasonable to make a crude assumption about the primary vertex z (or does the TPC track seed z mean something else?).  I will need to think more on how to measure the effect of this assumption, but I think it's doable with the data we have.

-Ross

==========
Dr. Ross Corliss

If it's work hours, and I'm not in a meeting, feel free to look for me in my virtual office:
https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09

On Oct 25, 2021, at 11:18 PM, Anthony Frawley via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov> wrote:

Hello Ross,

It would be useful to have a discussion about how precisely we need to know the z position of a TPC cluster to make a decent preliminary static distortion correction. This is prompted by starting to think about how to handle streamed data containing many bunch crossings, where we do not know the z position at all. 

Can we make a useful preliminary​ static distortion correction by arbitrarily moving the TPC track seed to z=0, which gets us within +/- 10 cm worst case?

Tony

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From: sPHENIX-calibration-l <sphenix-calibration-l-bounces AT lists.bnl.gov> on behalf of Ross Corliss via sPHENIX-calibration-l <sphenix-calibration-l AT lists.bnl.gov>
Sent: Monday, October 25, 2021 10:41 PM
To: sphenix calibrations <sphenix-calibration-l AT lists.bnl.gov>
Subject: [Sphenix-calibration-l] TPC Distortions meeting, Tuesday, 11AM Eastern

 

Dear Distortions Folks,

A reminder that the distortion meeting will take place tomorrow at the usual coordinates and time, 11AM EDT.  If you let me know in advance, I will add a slot to the agenda for you, but impromptu updates are also welcome.

https://stonybrook.zoom.us/j/94081538941?pwd=Y256N3ptUC9zV2M4cjNtUGgyWnJYdz09

https://indico.bnl.gov/event/12844/

-Ross

==========
Dr. Ross Corliss
Research Assistant Professor
Center for Frontiers in Nuclear Science
Stony Brook University
ross.corliss AT stonybrook.edu

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