Exploration of jet energy loss via direct γ-charged particle azimuthal correlation measurements

Abstract

The multiplicities of charged particles azimuthally associated with direct photons and π 0 have been measured for Au+Au, p+p, and d+Au collisions at s N N = 200 GeV in the STAR experiment. Charged particles with transverse momentum 0.5 < p T h ± < 16 GeV/c for p+p and d+Au, and 3 < p T h ± < 16 GeV/c for Au+Au and pseudorapidity | η | ⩽ 1.5 in coincidence with direct photons and π 0 of high transverse momentum 8 < p T γ , π 0 < 16 GeV/c at | η | ⩽ 0.9 have been used for this analysis. Within the considered range of kinematics, the observed suppressions of the associated yields per direct γ in central Au+Au relative to p+p and d+Au are similar and constant with direct photon fractional energy z T ( z T = p T h ± / p T γ ) . The measured suppressions of the associated yields with direct γ are comparable to those with π 0 . The data are compared to theoretical predictions.