sPHENIX tracking discussion

["Osborn, Joseph" <josborn1 AT bnl.gov>]

Hi Derek,

 

Thanks for putting these slides together, I took a look through them and here are my conclusions (feel free to correct me if I'm wrong).

 

1. Slide 5 is very interesting - there is clearly some higher likelihood that a TPC only track on or near a sector boundary is poorly reconstructed. This might be a result of our clusterizer not properly identifying the location of the clusters when there is charge shared between pads. Christof can correct me if I'm wrong, but since the real TPC geometry was implemented I don't think we have made any changes to improve the position resolution at the boundaries when charge is shared between sectors.

 

2. By all metrics it seems that the tracks with silicon seeds that are poorly reconstructed look completely fine in all of these variables _except_ pT, which is really weird. It seems like Acts fits the track perfectly fine except in momentum. What we may need to do is play around the input seed covariance to see if somehow the fit is being restricted from determining the correct momentum because the covariance is either too small or too big. What is weird is that if this was really the problem, I would have expected it to be for some certain range in pT, but slide 4 bottom right plot suggests it is basically flat in pT (maybe there is a slight preference to pT < ~6 GeV as shown in the 2D plot?). I may ask the developers to see if they have any thoughts.

 

3. Looking at page 10, it would be interesting to see the ratio of weird tracks to all tracks and normal tracks to all tracks as a function of quality. By eye you can tell that the percentage of weird tracks to all tracks is much higher at larger quality, so it would be good to see if we made a cut at some value X quality what that means for percentage of good tracks to weird tracks is in the sample. For analyses that need really good track samples, we may just have to make strong cuts on chi2/ndf. Related to this, it would be good to see what the tracking efficiency looks like as a function of the quality cut one uses.

 

 

___________________________

Joe Osborn, Ph.D

Physics Department

Brookhaven National Laboratory

josborn1 AT bnl.gov

 

 

From: sPHENIX-tracking-l <sphenix-tracking-l-bounces AT lists.bnl.gov> on behalf of Anderson, Derek [PHYSA] via sPHENIX-tracking-l <sphenix-tracking-l AT lists.bnl.gov>
Date: Thursday, January 26, 2023 at 4:43 PM
To: sphenix-tracking-l AT lists.bnl.gov <sphenix-tracking-l AT lists.bnl.gov>
Subject: [Sphenix-tracking-l] Weird Track Update

Hi all,

 

Apologies for the delay in preparing these! But here are some slides looking at some of the differences between crazy tracks with silicon tracks vs. without. There seem to be distinct differences between the two, particularly in their phi distribution and transverse DCA...

 

 -- Derek