Modified Fragmentation Function in Heavy Ion Collisions at RHIC via Direct photon-Jet Measurements

Abstract

The presented results are the first measurements at RHIC for direct $\gamma$-charged hadron azimuthal correlations in heavy ion collisions. We use these correlations to study the color charge density of the medium through the medium-induced modification of high-p${}_T$ parton fragmentation. Azimuthal correlations of direct photons at high transverse energy (8 $<$ p${}_T$ $<$ 16 GeV) with away-side charged hadrons of transverse momentum (3 $<$ p${}_T$ $<$ 6 GeV/c) have been measured over a broad range of centrality for $Au+Au$ collisions and $p+p$ collisions at $\sqrt{s_{NN}}$ = 200 GeV in the STAR experiment. A transverse shower shape analysis in the STAR Barrel Electromagnetic Calorimeter Shower Maximum Detector is used to discriminate between the direct photons and photons from the decays of high p${}_T$ ${\pi }^0$. The per-trigger away-side yield of direct $\gamma$ is smaller than from ${\pi }^0$ trigger at the same centrality class. Within the current uncertainty the I${}_{CP}$ of direct $\gamma$ and ${\pi }^0$ are similar.

5 pages, 4 figures, 3rd International Conference on Hard and Electro- Magnetic Probes of High-Energy Nuclear Collisions

References in corpus (23)

• Experimental and Theoretical Challenges in the Search for the Quark Gluon Plasma: The STAR Collaboration's Critical Assessment of the Evidence from RHIC Collisions
• Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX collaboration
• Viscosity in Strongly Interacting Quantum Field Theories from Black Hole Physics
• Quark Gluon Plasma an Color Glass Condensate at RHIC? The perspective from the BRAHMS experiment
• The PHOBOS Perspective on Discoveries at RHIC
• Shear viscosity of strongly coupled N=4 supersymmetric Yang-Mills plasma
• Evidence from d+Au measurements for final-state suppression of high $p_T$ hadrons in Au+Au collisions at RHIC
• The Effect of Shear Viscosity on Spectra, Elliptic Flow, and HBT Radii
• Erratum: Transverse momentum and centrality dependence of high-\pt\ non-photonic electron suppression in Au+Au collisions at \sqrtsNN\ = 200 GeV
• Absence of Suppression in Particle Production at Large Transverse Momentum in sqrt(s_NN) = 200 GeV d+Au Collisions
• Early thermalization at RHIC
• Identified baryon and meson distributions at large transverse momenta from Au+Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV
• Jet Quenching in the Opposite Direction of a Tagged Photon in High-Energy Heavy-Ion Collisions
• Leading-particle suppression in high energy nucleus-nucleus collisions
• The Fragility of High-pT Hadron Spectra as a Hard Probe
• Direct observation of dijets in central Au+Au collisions at sqrt(s_NN) = 200 GeV
• Energy dependence of charged pion, proton and anti-proton transverse momentum spectra for Au+Au collisions at \sqrt{s_NN} = 62.4 and 200 GeV
• Dihadron Tomography of High-Energy Nuclear Collisions in NLO pQCD
• High-$p_T$ Hadron Spectra, Azimuthal Anisotropy and Back-to-Back Correlations in High-energy Heavy-ion Collisions
• Phenomenology of Jet Quenching in Heavy Ion Collisions
• Medium induced jet absorption at relativistic heavy ion collisions
• A comparative study of Jet-quenching Schemes
• High $p_T$ correlations of $\gamma$ and charged hadrons at RHIC

Cited by in corpus (3)

• Gamma-Jet Tomography of Quark-Gluon Plasma in High-Energy Nuclear Collisions
• Azimuthal correlations between charged hadrons and direct photons at high-p${}_t$ in $p+p$ and $Au+Au$ collisions at $\sqrt{s_{NN}}$ = 200 GeV
• A Four Component Picture for Jet Induced Correlations in Heavy Ion Collisions?