"fig6_top_right_7" of "Jet-hadron correlations with respect to the event plane in $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV Au+Au collisions in STAR"

Angular distributions of charged particles relative to jet axes are studied in $\sqrt{s_{NN}} = 200$ GeV Au+Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with $15 < p_{T, jet} <$ 20 and $20 < p_{T, jet} <$ 40 GeV\c were reconstructed with the anti-$k_T$ algorithm with radius parameter setting of $R=0.4$ in the 20-50% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields and widths of jet-associated charged-hadron distributions are extracted in three angular bins between the jet axis and the event plane. The event-plane (EP) dependence is further quantified by ratios of the associated yields in different EP bins. No dependence on orientation of the jet axis with respect to the event plane is seen within the uncertainties in the kinematic regime studied. This finding is consistent with a similar experimental observation by ALICE in $\sqrt{s_{NN}} = 2.76$ TeV Pb+Pb collision data.本研究针对质心系能量√s_NN=200 GeV的金金（Au+Au）碰撞过程，探究了带电粒子相对于喷注轴线的角分布随喷注相对于事件平面（event plane）取向的变化规律。此项差分研究旨在检验硬散射部分子穿过重离子碰撞中形成的高温致密介质时，其能量损失所预期的路径长度依赖特性。分析过程中采用二阶事件平面，作为由碰撞参数与束流方向所构成的反应平面（reaction plane）的实验估计量。在20%-50%的中心度区间内，针对横向动量范围为15 < p_{T, jet} < 20 GeV以及20 < p_{T, jet} < 40 GeV/c的带电粒子喷注，采用半径参数R=0.4的anti-k_T算法进行重建，以最大化相互作用区域的初始态偏心率。相较于此前的研究方法，本研究采用反应平面拟合方法，以更高精度去除流调制背景。在喷注轴线与事件平面之间的三个角度区间内，提取喷注关联带电强子分布的产额与宽度。通过不同事件平面区间内关联产额的比值，进一步量化了事件平面依赖特性。在所研究的运动学区域内，基于现有不确定性，未观测到喷注轴线相对于事件平面的取向依赖效应。该发现与ALICE实验在√s_NN=2.76 TeV铅铅（Pb+Pb）碰撞数据中得到的类似实验观测结果一致。