Gießen 2007 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 5: Physik mit schweren Ionen

HK 5.3: Talk

Monday, March 12, 2007, 18:30–18:45, F

High-pT neutral pion and direct photon measurements in STAR — •Andre Mischke — (for the STAR collaboration) Institute for Subatomic Physics, Utrecht University, The Netherlands

The strong suppression of high-pT hadron yields and azimuthal correlations measured in central Au+Au collisions at the Relativistic Heavy Ion Collider reveals strong evidence for significant final state parton energy loss in the hot, dense medium produced in the collisions. Direct photons are a very clean probe since they leave the medium without additional interactions and therefore allow studying the earliest stages of the collision. Direct photon production in p+p interaction is a precision test of perturbative QCD and it can be used in d+Au collisions to study initial state effects in the gold nucleus. Both are essential to interpret results in Au+Au collisions at RHIC.

The STAR electro-magnetic calorimeter has very good high-pT capabilities due to its large acceptance coverage at mid-rapidity (0<eta<1 and full azimuth) combined with the very good tracking and collision vertex determination capabilities of the TPC. Neutral pions are the main source of decay photons and have to be measured with high precision.

We will present the current status of neutral pion and direct photon measurements at high-pT in STAR. The measurements will be compared to perturbative QCD calculations.