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
G. Aad, B. Abbott, K. Abeling, S. H. Abidi, A. Aboulhorma, H. Abramowicz, H. Abreu, Y. Abulaiti, A. C. Abusleme Hoffman, B. S. Acharya, C. Adam Bourdarios, L. Adamczyk, L. Adámek, S. V. Addepalli, J. Adelman, A. Adiguzel, S. Adorni, T. Adye, A. A. Affolder, Y. Afik, M. N. Agaras, J. Agarwala, A. Aggarwal, C. Agheorghiesei, J. A. Aguilar–Saavedra, A. Ahmad, F. Ahmadov, W. S. Ahmed, S. Ahuja, X. Ai, G. Aielli, M. Ait Tamlihat, B. Aitbenchikh, I. Aizenberg, M. Akbiyik, T. P. A. Åkesson, A. V. Akimov, K. Al Khoury, G. L. Alberghi, J. Albert, P. Albicocco, S. Alderweireldt, M. Aleksa, I. N. Aleksandrov, C. Alexa, T. Alexopoulos, A. Alfonsi, F. Alfonsi, M. Alhroob, B. Ali, S. Ali, M. Aliev, G. Alimonti, W. Alkakhi, C. Allaire, B. M. M. Allbrooke, C. Flores, P. P. Allport, A. Aloisio, F. Alonso, C. Alpigiani, M. Alvarez Estevez, A. Álvarez Fernández, M. G. Alviggi, M. Aly, Y. Amaral Coutinho, A. Ambler, C. Amelung, M. Amerl, C. G. Ames, D Amidei, S. P. Amor Dos Santos, K. R. Amos, V. Ananiev, C. Anastopoulos, T. Andeen, J. K. Anders, S. Y. Andrean, A. Andreazza, S Angelidakis, A. Angerami, A. V. Anisenkov, A. Annovi, C. Antel, M. T. Anthony, E. Antipov, M. Antonelli, D. J. A. Antrim, F. Anulli, M. Aoki, T. Aoki, J. A. Aparisi Pozo, M. A. Aparo, L. Aperio Bella, C. Appelt, N. Aranzabal, V. Araujo Ferraz, C. Arcangeletti, A. T. H. Arce, E. Arena
Abstract
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.