Residuals from iTPC Era

 This study got initiated by the track residuals observed while looking at the global vertex T0 correction for the FXT runs.

Below are the plots for the residuals for the FXT runs.

Glossary to read the plots:
 NF = No Fix (Meaning before the epd-based T0 fix was applied)
G = Global Tracks
P = Primary Tracks
eOFF = tracks reconstructed only from TPC hits from west side
wOFF = tracks reconstructed only from TPC hits from east side

FXT2019 = RUn 19 FXT
7p3 = 7.3 GeV beam energy run

You can find all the plots for all the FXT energies here:

What the plots above show is followinig:

  • residuals along Z in FXT2018 are negligible whereas in FXT2019 are substantial.
  • Residuals along Z after the fix for the tracks reconstructed from hits in entire TPC are improving - FIX works
  • Residuals along Z from hits from only east or west side of  TPC are not affected by the epd-based vertex/T0 fix - as it should be
  • Above point indicates that those residuals exist due to other effects (see below)

I also looked at the residuals for the AuAu 19.6 GeV run, this would show if this effect is only in FXT runs or not.

Below is the look for FXT2019 7.3 GeV run track residuals sliced in Z direction. This shows us that the split persists thought the Z therefor indicates that it is a T0 issue between inner and outer sectors

It was decided that we rerun the alignment based on Run-19 Cosmic data (while cleaning cosmic data from noisy runs due to GG and some other runs that are not actually cosmics). The results of residuals after the alignment is shown below:

FXT2019 3.85 GeV

FXT2019 7.3 GeV

AuAu 2019 19.6 GeV [with OPr13 - wrongly]

AuAu 2019 19.6 GeV [with OPr40 - properly]

UPDATE: January 22, 2021
One more time re-checking that Z of the inner sectors need to be corrected. Below are two plots: one with pre-correction of inner sector parameters based on 2019 cosmic data and another after correction (I retested this correction and have shown that Z shift hold always exactly the same, X and Y are more free to flow though).