Event activity-dependence of jet production in p–Pb collisions at [formula omitted] measured with semi-inclusive hadron+jet correlations by ALICE

Filip Krizek

doi:10.1016/j.nuclphysa.2017.06.050

Abstract

We report measurement of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum (pT) hadron trigger, for p–Pb collisions at sNN=5.02 TeV, in p–Pb classified by event activity. This observable has been measured in pp and Pb–Pb collisions at the LHC, providing a new probe to measure quenching. Jets are reconstructed from charged particle tracks using anti-kt with R=0.4 and low IR cutoff of jet constituents (pT,track>0.15 GeV/c). The complex uncorrelated jet background is corrected by a data-driven approach. Recoil jet distributions are reported for 15<pT,jetch<50 GeV/c. Events are classified by signal in the ALICE V0A detector, which measures forward multiplicity, and ZNA, which measures the number of neutrons at zero degrees. This self-normalized observable does not require scaling of reference distributions by 〈TpA〉, thereby avoiding the need for geometric modeling. We compare the trigger-normalized recoil jet yield for p–Pb collisions with different event activity to measure the effects of jet quenching in small systems at the LHC.

Highlights

The high energy densities and temperatures achieved in collisions of heavy nuclei at the LHC and RHIC generate a Quark-Gluon Plasma (QGP), characterized by collective flow of soft particles and the quenching of hard jets [1]
The average distance traversed by a parton through the hot medium created in a p–Pb collision will be shorter than in Pb–Pb collisions
According to [4], energy density affects the magnitude of the transport parameter qwhich appears in the BDMPS formula [5] for medium-induced parton energy loss

Summary

Introduction

The high energy densities and temperatures achieved in collisions of heavy nuclei at the LHC and RHIC generate a Quark-Gluon Plasma (QGP), characterized by collective flow of soft particles and the quenching of hard jets [1]. Using semi-inclusive had√ron+jet correlations, the ALICE Collaboration assessed that in central Pb–Pb collisions at sNN = 2.76 TeV, charged jets lose energy of about (8 ± 2) GeV/c in a form of charged particles which are radiated outside of a resolution parameter R = 0.5 cone [3]. PHENIX√ has shown that inclusive jet production is not suppressed in minimum bias d–Au collisions at sNN = 200 GeV.

Results

Conclusion