Motivation:

It is observed that the near-side jet peak distribution differs from central and peripheral d+Au collisions.

Here the jet centrality difference is studied for their pT dependence

Method

Dihadron correlations are projected on Δη for near-side (Δφ~0) and away-side (Δφ~π) separately. The near-side distribution is fitted with a Gaussian + Pedestal.

The fit parameters are: Gaussian area Y, Gaussian width σ, Pedestal C.

Run 3 data used.

Both trigger and associate particles are global tracks in TPC. The associate particles transverse momentum are 0.15-3 GeV/c. The trigger particle pT are varies.

The dihadron correlation below shown is ZYAM subtracted.

Data set:

Run3

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

Associate particle 0.15< pT < 3 GeV/c

Results:

1. Near-side Correlation Fit Result

  Trigger pT depedence:

	0.3<pT<0.5	0.5<pT<1	1<pT<1.5	1.5<pT<2	2<pT<3	3<pT<4	4<pT<6
0-20%
40-100%

2. Fit Parameter Trigger pT Depedence

Gaussian Area	Gaussian Width	Pedestal

Ratio of central and peripheral:

Difference between central and peripheral:

Red line in Y difference is a fit to constant.

χ²/Ndf:

For Hijing simulation, see drupal.star.bnl.gov/STAR/blog/yili/dau-hijing-multiplicity-jet-bias

Discussion

Reply to Helen's quesiton on
How is the peripheral fit if fix Gaussin width to be same as central collisions? 

40-100%

1. Near-side Correlation Fit Result

	0.3<pT<0.5	0.5<pT<1	1<pT<1.5	1.5<pT<2	2<pT<3	3<pT<4	4<pT<6
40-100%

2. Fit Parameter Trigger pT Depedence Change

The difference between fit paramters of fix Gaussian width σ and the original fit for 40-100%

Gassian area Y increases after fix width σ to be the same as central, but still less the central collision one.
Pedestal C decreases after fix σ for fit.

χ²/Ndf: Larger when fix σ to be the central one.

Compare central and the fix σ peripheral:

Ratio:

Difference: