# 2008.11.18 Cluster isolation cuts: 2x1 vs. 2x2 vs. 3x3

Ilya Selyuzhenkov *November 18, 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 for 2x1, 2x2, and 3x3 clusters

- Energy fraction in NxN cluster in r=0.7 radius

2x1, 2x2, 3x3 patch to jet radius of 0.7 energy ratios - Yield vs. NxN cluster energy fraction in r=0.7

For a given cluster energy fraction yield is defined as an integral on the right - Efficiency vs. NxN cluster energy fraction in r=0.7

For a given cluster energy fraction

efficiency is defined as the yield (on the right)

normalized by the total integral (total yield)

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