Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in Pb+Pb Collisions at √s N⁢N =5.02 TeV with the ATLAS Detector

This letter presents a measurement of the nuclear modification factor of large-radius jets in √s N⁢N =5.02 TeV Pb+Pb collisions by the ATLAS experiment. The measurement is performed using 1.72 nb −1 and 257 pb −1 of Pb+Pb and p⁢p data, respectively. The large-radius jets are reconstructed with the anti-k t algorithm using a radius parameter of R=1.0, by reclustering anti-k t R=0.2 jets, and are measured over the transverse momentum (p T ) kinematic range of 158<p T <1000 GeV and absolute pseudorapidity |y|<2.0. The large-radius jet constituents are further reclustered using the kt algorithm in order to obtain the splitting parameters, √d 12 and Δ⁢R 12 , which characterize the transverse momentum scale and angular separation for the hardest splitting in the jet, respectively. The nuclear modification factor, R A⁢A , obtained by comparing the Pb+Pb jet yields to those in p⁢p collisions, is measured as a function of jet transverse momentum (p T ) and √d 12 or Δ⁢R 12 . A significant difference in the quenching of large-radius jets having single subjet and those with more complex substructure is observed. Systematic comparison of jet suppression in terms of R A⁢A for different jet definitions is also provided. Presented results support the hypothesis that jets with hard internal splittings lose more energy through quenching and provide a new perspective for understanding the role of jet structure in jet suppression.