Ilya Selyuzhenkov November 21, 2008

Data sets:

• pp2006 - STAR 2006 pp longitudinal data (~ 3.164 pb^1)
  after applying gamma-jet isolation cuts (no R_cluster cut applied for this study).
• gamma-jet[gamma-filtered] - data-driven Prompt Photon [p6410EemcGammaFilter] events.
  Partonic pt range 2-25 GeV.
• QCD jets[gamma-filtered] - data-driven QCD [p6410EemcGammaFilter] events.
  Partonic pt range 2-25 GeV.

2x1, 2x2, and 3x3 clusters definition:

• 3x3 cluster: tower energy sum for 3x3 patch around highest tower
• 2x2 cluster: tower energy sum for 2x2 patch
  which are closest to 3x3 tower patch centroid.
  3x3 tower patch centroid is defined based
  on tower energies weighted wrt tower centers:
  centroid = sum{E_tow * r_tow} / sum{E_tow}.
  Here r_tow=(x_tow, y_tow) denotes tower center.
• 2x1 cluster: tower energy sum for high tower plus second highest tower in 3x3 patch
• r=0.7 energy is calculated based on towers
  within a radius of 0.7 (in delta phi and eta) from high tower

Cuts applied

all gamma-jet candidate selection cuts except 3x3/r=0.7 energy isolation cut

Results

There are two sets of figures in links below:

• Number of counts for a given energy fraction
• Yield above given energy fraction
  [figures with right integral in the caption]
  

  Yield is defined as the integral above given energy fraction
  up to the maximum value of 1

Gamma candidate detector eta < 1.5
(eta region where we do have most of the TPC tracking):

1. Cluster energy fraction in 0.7 radius
2. 2x1 and 2x2 cluster energy fraction in 3x3 patch

Gamma candidate detector eta > 1.5:
(smaller tower size)

1. Cluster energy fraction in 0.7 radius
2. 2x1 and 2x2 cluster energy fraction in 3x3 patch

Some observation

• For pre1>0 condition (contains most of events)
  yield in Monte-Carlo for eta > 1.5 case
  is about factor of two different than that from pp2006 data,
  while for eta < 1.5 Monte-Carlo yield agrees with data within 10-15%.
  This could be due to trigger effect?
• For pre1=0 case yiled for both eta > 1.5 and eta < 1.5 are different in data and MC
  This could be due to migration of counts from pre1=0 to pre1>0
  in pp2006 data due to more material budget than it is Monte-Carlo
• For pre1=0 condition pp2006 data shapes are not reproduced by gamma-jet Monte-Carlo.
  With a larger cluster size (2x1 -> 3x3) the pp2006 and MC gamma-jet shapes
  are getting closer to each other.
• For pre1>0 condition (with statistics available),
  pp2006 data shapes are consistent with QCD Monte-Carlo.