Observation of a Centrality-Dependent Dijet Asymmetry in Lead-Lead Collisions at √<i>s</i><sub>NN</sub>=2.76 TeV with the ATLAS Detector at the LHC


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Aad G., Abbott B., Abdallah J., Abdelalim A., Abdesselam A., Abdinov O., ...More

PHYSICAL REVIEW LETTERS, no.25, 2010 (SCI-Expanded) identifier identifier identifier identifier

Abstract

By using the ATLAS detector, observations have been made of a centrality-dependent dijet asymmetry in the collisions of lead ions at the Large Hadron Collider. In a sample of lead-lead events with a per-nucleon center of mass energy of 2.76 TeV, selected with a minimum bias trigger, jets are reconstructed in fine-grained, longitudinally segmented electromagnetic and hadronic calorimeters. The transverse energies of dijets in opposite hemispheres are observed to become systematically more unbalanced with increasing event centrality leading to a large number of events which contain highly asymmetric dijets. This is the first observation of an enhancement of events with such large dijet asymmetries, not observed in proton-proton collisions, which may point to an interpretation in terms of strong jet energy loss in a hot, dense medium.