Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in $\mathrm{Pb}+\mathrm{Pb}$ Collisions at $\sqrt{{s}_{NN}}=5.02\text{ }\text{ }\mathrm{TeV}$ with the ATLAS Detector

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Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in $Pb + Pb$ Collisions at $\sqrt{s_{N N}} = 5.02 TeV$ with the ATLAS Detector

G. Aad et al. (ATLAS Collaboration)

Phys. Rev. Lett. 131, 172301 – Published 23 October 2023

Abstract

This letter presents a measurement of the nuclear modification factor of large-radius jets in $\sqrt{s_{N N}} = 5.02 TeV$ $Pb + Pb$ 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 $k_{t}$ algorithm in order to obtain the splitting parameters, $\sqrt{d_{12}}$ 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 $\sqrt{d_{12}}$ 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.

Received 16 January 2023
Revised 11 May 2023
Accepted 18 September 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.172301

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.