Abstract
Abstract Jet shape measurements are important for many applications. When measured in pp collisions they can be used to constrain generator and showering settings. When measured in PbPb collisions they can be used to probe for distortions from interactions with the hot and dense medium. Fully unfolded jet shape measurements are presented and compared with generator expectations in 7 TeV pp collisions, corresponding to an integrated luminosity of 36 p b − 1 . In addition, first measurement of jet shapes in heavy-ion (PbPb) collisions are presented and compared with observations in 2.76 TeV pp collisions to probe if the jet structure is modified in the medium due to parton energy loss. The PbPb data set collected in 2011 is analyzed, corresponding to an integrated luminosity of 129 μ b − 1 . The jets are reconstructed with the anti-kT clustering algorithm by utilizing particle-flow objects.
Highlights
The jet transverse momentum profile [1, 2] is sensitive to multiple parton emissions from the primary outgoing parton and provides a powerful test of the parton showering approximation of quantum chromodynamics (QCD), the theory of strong interactions
First measurement of jet shapes in heavy-ion (PbPb) collisions are presented and compared with observations in 2.76 TeV pp collisions to probe if the jet structure is modified in the medium due to parton energy loss
Jet shapes have been measured in pp collisions at the LHC [3, 4], in pp collisions at the Tevatron [5, 6], and in ep collisions at HERA [7]
Summary
The jet transverse momentum profile (shape) [1, 2] is sensitive to multiple parton emissions from the primary outgoing parton and provides a powerful test of the parton showering approximation of quantum chromodynamics (QCD), the theory of strong interactions. Measurements of jet shapes have never been performed in heavy ion collisions. High transverse momentum partons produced in heavy ion collisions are expected to lose energy while traversing the hot and dense medium created in these collisions [8]. At RHIC, indirect measurements of energy loss in the medium (“jet quenching”) have been made by studying high momentum jet fragmentation products [9]. In this note we present a new measurement to test the effects of the medium using jet shapes. In this document we present the first experimental test of this theory
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