Measurements of the suppression and correlations of dijets in Pb-Pb collisions at √sNN =5.02 TeV

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 𝑝⁢𝑝 collisions at √𝑠_𝑁⁢𝑁 = 5.02TeV, measurements of the leading dijet transverse momentum (𝑝_T) correlations are presented. Additionally, measurements in Pb+Pb collisions of the dijet pair nuclear modification factors projected along leading and subleading jet 𝑝_T are made. The measurements are performed using the ATLAS detector at the LHC with 260 pb⁻¹ of 𝑝⁢𝑝 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_T distributions to account for experimental effects in the measurement of both jets. Results are provided for dijets with leading jet 𝑝_T greater than 100 GeV. Measurements of the dijet-yield-normalized 𝑥_J distributions in Pb+Pb collisions show an increased fraction of imbalanced jets compared to 𝑝⁢𝑝 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 𝑝⁢𝑝 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^T between 100 and 316 GeV for all centralities in Pb+Pb collisions.