# 2009.02.06 Pre-shower energy distribution Run6 vs. Run8 geometry

Ilya Selyuzhenkov *February 06, 2009*

### Data sets

**pp2006**- STAR 2006 pp longitudinal data (~ 3.164 pb^1)

Trigger: eemc-http-mb-L2gamma [id:137641]**mc2006: gamma-jet+QCD jets [p6410EemcGammaFilter]**events.**pp2008**- STAR 2008 pp data

Trigger: etot-mb-l2 [id:7]

Partonic pt range 2-25 GeV.

**Cuts applied**

- Di-jet events
- Require to reconstruct photon momentum (no gamma-jet isolation cuts)
- Gamma pt > 7GeV, jet pt > 7GeV
- L2gamma emulation in Monte-Carlo
- L2gamma triggered for pp2006 and pp2008 events
- cos (phi_jet - phi_gamma) < -0.8
- detector |eta_jet|< 0.8
- |v_z| < 100

### Figures

Each figure has:

- All pre-shower conditions combined, No pre-shower cuts
**Red circles**show pp2006 data**Black triangles**show pp2008 data

Data scaled to match the integraled yield from pp2006 data**Green line**shows MC sum: QCD + gamma-jet

Monte-Carlo results for QCD and gamma-jet samples are first

scaled to 3.164 pb^-1 according to Pythia luminosity,

added together, and then an additional**fudge factor of 1.24**applied.

Fudge factor is defined as pp2006 to Monte-Carlo sum ratio

for pt_jet>7GeV and pt_gamma>7 candidates

### Observations

- Pre-shower energy distributions from pp2008 data set

are narrower than that for pp2006 data.

This corresponds to smaller amount of material budget in y2008 STAR geometry. - Pre-shower energy distribution from Monte-Carlo with y2006 geometry

closer follows the distribution from pp2008 data set, rather than that from pp2006 data.

This indicates the lack of material budget in y2006 Monte-Carlo.

**Note**: There is a "pre-shower sector 10 problem" for pp2008 data,

which results in migration of small fraction of events with pre-shower>0 into

pre-shower=0 bin (first zero bins in Fig.1 and 2. below).

For pre-shower>0 case this **only affects overall normalization of pp2008 data**,

but not the shape of pre-shower energy distributions.

I'm running jet-finder+my software to get more statistics from pp2008 data set,

and after more QA will produce list of runs with "pre-shower sector 10 problem",

so to exclude them in the next iteration of my plots.

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