This page is documentary purpose.

 Motivation:

28M Run 8 events compared with 4M Run3 minbias events may give more information for d+Au ridge study.

For more details on Run3 result, see drupal.star.bnl.gov/STAR/blog/yili/gpc-item-ii-response-ridge-dau-global-vs-primary-track-charge-identification

Run8 trigger page: www.star.bnl.gov/protected/common/common2008/trigger2008/triggers2008.html
some discussion on centrality: www.star.bnl.gov/protected/lfspectra/cjena/run8_dAu200GeV/dAu_centrality/documentation/centrality_run8_dAu200GeV.html
several methods for pile-up cuts: drupal.star.bnl.gov/STAR/blog/yili/effort-remove-dau-run-8-pileup

Run3 trigger page: www.star.bnl.gov/public/all/trigger2003/index.html

Method:

Dihadron correlation

The trigger in TPC and associate particles in FTPC, global/primary track .The dihadron correlation below shown is ZYAM substracted. 

For Run8, TPC particle BEMC matching is used.

Data set:

Run3

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

Run8

|Vz| < 50 cm
vertex ranking >= -2.5 for pileup cut
BEMC matching for TPC track
nHitsFit > 25 points for TPC
nHitsFit > 5 points for FTPC
nHitsFit/nHitsPoss >= 51%
globa dca < 3 cm
|eta|<1 for TPC
2.8<|eta|<3.8 for FTPC
1<pT<3 GeV/c

Results:

1. Centrality
 

Run3	Run8

ZDC centrality selection:

 
Run8 has some loss of efficiency in peripheral events.

More details: drupal.star.bnl.gov/STAR/blog/yili/dau-run8-ftpc-east-refmult-and-zdc-east-adc-distribution

2. Pile-up

Pile-up has been an issue for Run8 data.

The basic pileup has been applied, i.e. vertex ranking >= -2.5.

For TPC-TPC correlation, the pile-up gives the 'W' shape along η, some discussion here drupal.star.bnl.gov/STAR/blog/yili/effort-remove-dau-run-8-pileup.

For TPC-FTPC correlation, the pile-up affects the overall magnitude (ZYAM) and may also affect the correlated yield (not clear how).  (ZYAM value affects the v₂ value.)

By studying the shape of TPC-TPC correlation, BEMC matching is found the effective way to remove pileup for TPC tracks, indicating by the disappearance of 'W' shape. Below shows the comparison of the correlations before (left) and after (right) BEMC matching.

However, for FTPC tracks, there is no effective way to remove the pileup. So they will present in the result.

3. Dihadron correlations

TPC-FTPC Au

	Run3	Run8
Global track
Primary track