This page is documentary purpose.

 Motivation:

Follow the d+Au Ridge - FTPC charge identification dicussion, www.star.bnl.gov/protected/bulkcorr/yili/dAuRidge/1stGPC.html

If there is artificial effect leading to the ftpc positive and negative difference, it may also have similar influence on BField.

Method:

1. Positive and negative distribution ratio in FTPC

2. TPC-FTPC dihadron correlation with ZDC centrality ReservedFullField vs FullField. 

Data set:

Run3

|Vz| < 50 cm
primary track for both TPC and FTPC
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. Positive/Negative single particle distribution in FTPC vs pT
 

FF	RF

2. TPC-FTPC dihadron correlation 
Note: All the dihadron correlations magnitude below needs scaled by 1/2. (I forgot.)

FF	RF

Large fluctuation issues resolved, also see drupal.star.bnl.gov/STAR/blog/yili/dau-ridge-fluctuation-tpc-ftpc-au-side-dihadron-correlation

Conclusion: 

1. Pos/Neg ratio: RF doesn't drop to 1 as FF. RF is closer to Hijing simulation than FF.

2. Dihadron correlation: large fluctuations present in the both RF and FF.
As what we learn from this RF vs FF, I don't have a conclusion now. Run 8 data will give us more statistics. However, if we don't understand the FTPC charge identification issue in Run 3, it may also affect Run 8 interpretation.