This page is documentary purpose.

 

 Motivation:

1. Charge identification comes from the momentum reconstruction. So the charge identification ability is related to the momentum resolution.

2. Global tracks include the hit point in the detector (TPC or FTPC in this case). While primary tracks include both the hits and the primary vertex from the all track fit. The momentum would and charge may change from global to primary tracks.

For MC after GEANT simulation results, see drupal.star.bnl.gov/STAR/blog/yili/dau-ridge-charge-identification-mc-after-geant-global-vs-primary-tracks-charge-pt-phi-ftpc-tpc.

Method:

Global and primary track Px, Py,|Pz|, Pt,Charge, φ and η  relationship within the same track for TPC, FTPC-Au, FTPC-d.

 

Data set:

Run3

|Vz| < 50 cm
nHitsFit > 25 points for TPC, 5 points for FTPC
nHitsFit/nHitsPoss >= 51%
globa dca < 3 cm
|eta|<1 for TPC, 2.8<|eta|<3.8 for FTPC

Results:

1. Px

2. Py

3. Pt

4. |Pz|

Px, Py, |Pz| and Pt are also studied upon their charge (requiring both global and primary track to be positive or negative). No significant difference is found for charnge.

5. Charge

 
 

 

6. φ

When requring both global and primary to be Positive:

When requring both global and primary to be Negative:

When requring Primary to be Negative and Global to be Positive:

When requring Primary to be Positive and Global to be Negative:

Very few TPC tracks change sign / large φ difference.

Large number of FTPC tracks have large φ change from global to primary, which corresponding to the charge sign change.

7. η

See file attachements to download of the plots.

Conclusion:

TPC: There are strong primary and global momentum correlation tracks.
Few tracks change their charge. 
 φ is positive correlated.

FTPC: The positive correlation is in pT < 0.3 GeV/c. 
Nearly half tracks charges change.
 φ is positive correlated.