Measurement of two-particle correlations with respect to second- and third-order event planes in Au + Au collisions at $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV

07 May 2019

Abstract: We present measurements of azimuthal correlations of charged hadron pairs in $\sqrt{{s}_{\mathrm{NN}}}=200$ GeV $\mathrm{Au}+\mathrm{Au}$ collisions for the trigger and associated particle transverse-momentum ranges of $1<{p}_{T}^{t}<10\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$ and $0.5<{p}_{T}^{a}<10\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$. After subtraction of an underlying event using a model that includes higher-order azimuthal anisotropy ${v}_{2},{v}_{3}$, and ${v}_{4}$, the away-side yield of the highest trigger-${p}_{T}$(${p}_{T}^{t}>4\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$) correlations is suppressed compared with that of correlations measured in $p+p$ collisions. At the lowest associated particle ${p}_{T}$($0.5<{p}_{T}^{a}<1\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$), 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-${p}_{T}$ trigger correlations ($2<{p}_{T}^{t}<4\phantom{\rule{4pt}{0ex}}\mathrm{GeV}/c$), 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 ${\Psi }_{2}$ and ${\Psi }_{3}$. The angular correlations show an asymmetry when selecting the sign of the difference between the trigger-particle azimuthal angle and the ${\Psi }_{2}$ 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 ${\Psi }_{3}$ dependence can be resolved within experimental uncertainties.

Published in: Physical Review C 99 (2019)