Parton energy loss in heavy-ion collisions via direct-photon and charged-particle Azimuthal Correlations

Abstract

Charged-particle spectra associated with direct photon (γdir ) and π0 are measured in p+p and Au+Au collisions at center-of-mass energy √sNN=200 GeV with the STAR detector at RHIC. A hower-shape analysis is used to partially discriminate between γdir and π0. Assuming no associated charged particles in the γdir direction (near side) and small contribution from fragmentation photons (γfrag), the associated charged-particle yields opposite to γdir (away side) are extracted. At mid-rapidity (|η|