Measurements of the suppression and correlations of dijets in Pb+Pb collisions at $\sqrt{s_{{}_{\text{NN}}}}$ = 5.02 TeV

Abstract

Studies of the correlations of the two highest transverse momentum (leading) jets in individual Pb+Pb collision events can provide information about the mechanism of jet quenching by the hot and dense matter created in such collisions. In Pb+Pb and pp collisions at $\sqrt{s_{{}_{\text{NN}}}}$ = 5.02 TeV, measurements of the leading dijet transverse momentum ($p_{\mathrm{T}}$) correlations are presented. Additionally, measurements in Pb+Pb collisions of the dijet pair nuclear modification factors projected along leading and subleading jet $p_{\mathrm{T}}$ are made. The measurements are performed using the ATLAS detector at the LHC with 260 pb${}^{-1}$ of pp data collected in 2017 and 2.2 nb${}^{-1}$ of Pb+Pb data collected in 2015 and 2018. An unfolding procedure is applied to the two-dimensional leading and subleading jet $p_{\mathrm{T}}$ distributions to account for experimental effects in the measurement of both jets. Results are provided for dijets with leading jet $p_{\mathrm{T}}$ greater than 100 GeV. Measurements of the dijet-yield-normalized $x_{\mathrm{J}}$ distributions in Pb+Pb collisions show an increased fraction of imbalanced jets compared to pp collisions; these measurements are in agreement with previous measurements of the same quantity at 2.76 TeV in the overlapping kinematic range. Measurements of the absolutely-normalized dijet rate in Pb+Pb and pp collisions are also presented, and show that balanced dijets are significantly more suppressed than imbalanced dijets in Pb+Pb collisions. It is observed in the measurements of the pair nuclear modification factors that the subleading jets are significantly suppressed relative to leading jets with $p_{\mathrm{T}}$ between 100 and 316 GeV for all centralities in Pb+Pb collisions.

49 pages in total, author list starting page 32, 18 figures, 1 table, published in Physical Review C. All figures including auxillary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2019-02/ This version includes modifications described in the erratum that can be found at https://doi.org/10.1103/PhysRevC.109.029901

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• Jet-like correlations with respect to K${}_{\mathrm{S}}^0$ and $\Lambda$ ($\bar{\Lambda }$) in pp and central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
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