Event-plane dependent dihadron correlations with harmonic $v_n$ subtraction in Au+Au Collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV

Abstract

STAR measurements of dihadron azimuthal correlations ($\hat{I}”\ddot{I}•$) are reported in mid-central (20-60\%) Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV as a function of the trigger particle's azimuthal angle relative to the event plane, $\ddot{I}{•}_s=|\ddot{I}{•}_t-\ddot{I}{ˆ}_{\mathrm{EP}}|$. The elliptic ($v_2$), triangular ($v_3$), and quadratic ($v_4$) flow harmonic backgrounds are subtracted using the Zero Yield At Minimum (ZYAM) method. The results are compared to minimum-bias d+Au collisions. It is found that a finite near-side ($|\hat{I}”\ddot{I}•|<\ddot{I}€/2$) long-range pseudorapidity correlation (ridge) is present in the in-plane direction ($\ddot{I}{•}_s\sim 0$). The away-side ($|\hat{I}”\ddot{I}•|>\ddot{I}€/2$) correlation shows a modification from d+Au data, varying with $\ddot{I}{•}_s$. The modification may be a consequence of pathlength-dependent jet-quenching and may lead to a better understanding of high-density QCD.

8 pages, 3 figures. Accepted by Phys.Rev.C Rapid Communications