Jet-hadron correlations relative to the event plane at the LHC with ALICE

Abstract

In ultra relativistic heavy-ion collisions at the Large Hadron Collider (LHC), conditions are met to produce a hot, denseand strongly interacting medium known as the Quark Gluon Plasma (QGP). Quarks and gluons from incoming nucleicollide to produce partons at high momenta early in the collisions. By fragmenting into collimated sprays of hadrons,these partons form ‘jets’. The outgoing partons scatter and interact with the medium, leading to a manifestation ofmedium modifications of jets in the final state, known as jet quenching. Within the framework of perturbative QCD,jet production is well understood in pp collisions. We use jets measured in pp interactions as a baseline referencefor comparing to heavy-ion collision systems to detect and study jet quenching. The jet quenching mechanism can bestudied through the angular correlations of jets with charged hadrons and is examined in transverse momentum (pT) binsof the jets, pTbins of the associated hadrons, and as a function of collision centrality. A robust and precise backgroundsubtraction method is used in this analysis to remove the complex, flow dominated, heavy-ion background. The analysisof angular correlations for different orientations of the jet relative to the event plane allows for the study of the path-length dependence of medium modifications to jets. The event plane dependence of azimuthal angular correlations ofcharged hadrons with respect to the axis of an R=0.2 reconstructed full (charged + neutral) jet in Pb–Pb collisions at√sNN=2.76 TeV in ALICE is presented. Results are compared for three angular bins of the jet relative to the eventplane in mid-peripheral events. The yields relative to the event plane are presented and then quantified through yieldratio calculations. The results show no significant path-length dependence on the medium modifications.