Measurement of Suppression of Large-Radius Jets and Its Dependence on Substructure in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Pb</mml:mi><mml:mo>+</mml:mo><mml:mi>Pb</mml:mi></mml:mrow></mml:math> Collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi>s</mml:mi></mml:mrow><mml:mrow><mml:mi>N</mml:mi><mml:mi>N</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>5.02</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math> with the ATLAS Detector

This letter presents a measurement of the nuclear modification factor of large-radius jets in $\sqrt{{s}_{NN}}=5.02\text{ }\text{ }\mathrm{TeV}$ $\mathrm{Pb}+\mathrm{Pb}$ collisions by the ATLAS experiment. The measurement is performed using $1.72\text{ }\text{ }{\mathrm{nb}}^{\ensuremath{-}1}$ and $257\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$ of $\mathrm{Pb}+\mathrm{Pb}$ and $pp$ 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 $158<{p}_{T}<1000\text{ }\text{ }\mathrm{GeV}$ 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 $\mathrm{\ensuremath{\Delta}}{R}_{12}$, which characterize the transverse momentum scale and angular separation for the hardest splitting in the jet, respectively. The nuclear modification factor, ${R}_{AA}$, obtained by comparing the $\mathrm{Pb}+\mathrm{Pb}$ jet yields to those in $pp$ collisions, is measured as a function of jet transverse momentum (${p}_{T}$) and $\sqrt{{d}_{12}}$ or $\mathrm{\ensuremath{\Delta}}{R}_{12}$. 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 ${R}_{AA}$ 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.

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