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

TL;DR

This study investigates how jet-related particle distributions vary with respect to the event plane in gold-gold collisions at 200 GeV, finding no significant dependence, which informs understanding of parton energy loss in quark-gluon plasma.

Contribution

It provides a differential analysis of jet-hadron correlations relative to the event plane, using improved background subtraction methods in heavy-ion collisions.

Findings

No observed dependence of jet-associated yields on event plane orientation.

Consistent results with previous measurements at higher energies by ALICE.

Enhanced background removal technique improves measurement precision.

Abstract

Angular distributions of charged particles relative to jet axes are studied in $\sqrt{s_{\mathrm{NN}}}$ = 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 $15 < p_{\rm T, jet} <$ 20 and $20 < p_{\rm T, jet} <$ 40 GeV/$c$ were reconstructed with the anti-$k_{\rm T}$ 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 $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV Pb+Pb collision data.