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Physics Prospects from PMD in d+Au collisions at RHIC

Photon Multiplicity distribution Longitudinal Scaling in asymmetric collisionsReference data for photon production in Au+Au collisions

Like to address the following physics issues :

Photon-Charged hadron Azimuthal Angle Correlations Similar rapidity range and forward-backward High ADC/Energy photon cluster triggered correlation with mid-rapidity charged hadrons Mid-rapidity charged hadron triggered correlation with photon clusters in PMD

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What we learn’t from the Photon Multiplicity Distribution in Au+Au Collisions

Scaling energy independent for both photons and charged hadronsScaling centrality independent for photons and dependent for charged hadronsDifference due to baryons

STAR : PRL 95 (2005) 062301

Longitudinal Scaling

STAR : PRC 73 (2006) 034906

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Want to see how the scaling works for d+Au data

Given : Scaling centrality independent for photons and dependent for charged hadrons

How does d+Au photon distribution fit into the picture of longitudinal scaling ?

PHOBOS : PRC (2005)

Already studied for charged hadrons in d+Au collisions by PHOBOS

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d+Au photon data a reference for Au+Au

Reference data to understand the mechanism of photon production in high energy collisions

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Expected Multiplicity, Feasibility, Events required

Feasibility : We have reconstructed such multiplicity in Cu+Cu and peripheral Au+Au collisions

In PMD coverage

Events required : For a statistical error of 1%, we require 300 K useable PMD events with minimum bias trigger

d+Au Collisions at 200 GeV Minimum bias HIJING Simulation

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Photon-Charged hadron correlation

Majority of the photons are from 0 decay

Physics issues : To understand correlation between charged

hadron and photon production in d+Au collisions.

Charged hadron - Photon correlations in forward-backward can help understand effects of short and long range correlations.

Two points to keep in mind : The energy deposited by photons in the detector (Cluster ADC)

roughly proportional to photon energy. HIJINGPMD-FTPC same coverage

HIJINGPMD-FTPC (west)Reference studies in STAR for Au+Au :

http://www.star.bnl.gov/protected/ebye/tjt/LRC_Paper/lrc.html http://www.star.bnl.gov/protected/ebye/sunil/correlation/charge-neutral_corr.html

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Motivation for triggered photon-charged hadron correlation

Taking high pT 0 in forward rapidity - allows probing high-x valence quark correlations with low -x gluons : A probe of low-x gluons

Kharzeev, Levin, McLerran NPA748, 627

pd p

Au

q

g ENxqp xgp

EN

€

Q2 ~ pT2

s = 2EN

η = −ln(tan(θ2

))

xq ≈ xF / z

€

xF ≈ 2Eπs

z = EπEq

xg ≈ pTse−η g

STAR : PRL 97 (2006) 152302

Signature of CGC

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Triggered photon cluster in PMD - charged hadron correlation

STAR : PRL 97 (2006) 152302

Want to investigate correlations with triggered high ADC/Energy photon cluster in PMD coverage and mid rapidity charged hadrons. Note PMD is on the Au going side

HIJING Simulations are underway for such a study. Preliminary estimate shows for a correlation signal of 1% Level above background we need of the order of 1 million events

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Triggered mid-rapidity charged hadron - photon cluster in PMD correlation - d+Au collisions

Want to investigate correlations similar to those carried out below with FTPC-TPC

|trig|<1, 2.7<|assoc|<3.9

Jet correlation dAu at forward rapiditiesNot a simple recombination (Hwa, Yang, nucl-th/0605037) Hierarchy in the away side yields: CGC?

Trigger part. : 3<pTtrig<4 GeV/c

Assoc. FTPC: 0.2<pTassoc< 2 GeV/c

Assoc. MTPC: 0.2<pTassoc< 3 GeV/c

Away-side correlations arevery similar in MTPC and FTPC!

Reference : L. Molnar - QM2006