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 $\sqrt{s_{NN}}=5.02\mathrm{TeV}$, 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 ${\mathrm{pb}}^{-1}$ of $pp$ data collected in 2017 and 2.2 ${\mathrm{nb}}^{-1}$ 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 $\mathrm{GeV}$. 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 $\mathrm{TeV}$ 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 $\mathrm{GeV}$ for all centralities in Pb+Pb collisions.

• Received 3 May 2022
• Accepted 6 July 2022

DOI:https://doi.org/10.1103/PhysRevC.107.054908

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