Measurement of charged jet suppression in Pb-Pb collisions at √s NN = 2.76 TeV

Abelev, B. and Adam, J. and Adamová, D. and Aggarwal, M. M. and Rinella, G. A. and Agnello, M. and Agócs, András and Agostinelli, A. and Agrawal, N. and Ahammed, Z. and Ahmad, N. and Masoodi, A. A. and Ahmed, I. and Ahn, S. U. and Ahn, S. A. and Aimo, I. and Aiola, S. and Ajaz, M. and Akindinov, A. and Aleksandrov, D. and Alessandro, B. and Alexandre, D. and Alici, A. and Alkin, A. and Alme, J. and Alt, T. and Altini, V. and Altinpinar, S. and Altsybeev, I. and Prado, C. A. G. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Lévai, Péter and Molnár, Levente and Oláh, László and Pochybova, Sona (2014) Measurement of charged jet suppression in Pb-Pb collisions at √s NN = 2.76 TeV. JOURNAL OF HIGH ENERGY PHYSICS (3). ISSN 1126-6708

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Abstract

A measurement of the transverse momentum spectra of jets in Pb-Pb collisions at sNN−−−√=2.76 TeV is reported. Jets are reconstructed from charged particles using the anti-kT jet algorithm with jet resolution parameters R of 0.2 and 0.3 in pseudo-rapidity |η|<0.5. The transverse momentum pT of charged particles is measured down to 0.15 GeV/c which gives access to the low pT fragments of the jet. Jets found in heavy-ion collisions are corrected event-by-event for average background density and on an inclusive basis (via unfolding) for residual background fluctuations and detector effects. A strong suppression of jet production in central events with respect to peripheral events is observed. The suppression is found to be similar to the suppression of charged hadrons, which suggests that substantial energy is radiated at angles larger than the jet resolution parameter R=0.3 considered in the analysis. The fragmentation bias introduced by selecting jets with a high pT leading particle, which rejects jets with a soft fragmentation pattern, has a similar effect on the jet yield for central and peripheral events. The ratio of jet spectra with R=0.2 and R=0.3 is found to be similar in Pb-Pb and simulated PYTHIA pp events, indicating no strong broadening of the radial jet structure in the reconstructed jets with R<0.3.

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