Measurement of two-particle correlations with respect to second- and third-order event planes in Au+Au collisions at √sNN = 200 GeV

Abstract

We present measurements of azimuthal correlations of charged hadron pairs in √sNN = 200 GeV Au + Au collisions for the trigger and associated particle transverse-momentum ranges of 1 < pt T < 10 GeV/c and 0.5 < pa T < 10 GeV/c. After subtraction of an underlying event using a model that includes higher-order azimuthal anisotropy v2, v3, and v4, the away-side yield of the highest trigger-pT (pt T > 4 GeV/c) correlations is suppressed compared with that of correlations measured in p + p collisions. At the lowest associated particle pT (0.5 < pa T < 1 GeV/c), the away-side shape and yield are modified relative to those in p + p collisions. These observations are consistent with the scenario of radiative-jet energy loss. For the low-pT trigger correlations (2 < pt T < 4 GeV/c), a finite away-side yield exists and we explore the dependence of the shape of the away-side within the context of an underlying-event model. Correlations are also studied differentially versus event-plane angle 2 and 3. The angular correlations show an asymmetry when selecting the sign of the difference between the triggerparticle azimuthal angle and the 2 event plane. This asymmetry and the measured suppression of the pair yield out-of-plane is consistent with a path-length-dependent energy loss. No 3 dependence can be resolved within experimental uncertainties.