Jet overlap in heavy ion collisions at LHC energies and its consequences on jet shape

Abstract

Central lead-lead collisions at the LHC energies may pose a particular challenge for jet identification as multiple jets are produced per each collision event. We simulate the jet evolution in central Pb-Pb events at $\sqrt{s_{\mathrm{NN}}}=2.76$ GeV collision energy with EPOS3 initial state, which typically contains multiple hard scatterings in each event. Therefore the partons from different jets have a significant chance to overlap in momentum space. We find that 30% of the jets with $p_{\perp }>50$ GeV, identified by the standard anti-$k_{\perp }$ jet finding algorithm with jet cone size R=0.3, contain `intruder' particles from overlapping generator-level jets. This fraction increases with increasing beam energy and increasing R. The reconstructed momentum of the jet differs from that of the modelled jet by the loss due to jet partons which are outside of the jet cone and by the gain due to intruder partons. The sum of both may be positive or negative. These intruder partons particularly affect the radial jet momentum distribution because they contribute mostly at large angles $\Delta r$ with respect to the jet centre. The study stresses the importance of the jet overlap effect emerging in central lead-lead collisions at the LHC energies, while being negligible in peripheral PbPb or $p$Pb/$pp$ collisions.

arXiv comment7 pages, 10 figures; version accepted for Physical Review C

References in corpus (21)

• The anti-k_t jet clustering algorithm
• FastJet user manual
• Better Jet Clustering Algorithms
• Parton-Based Gribov-Regge Theory
• Event-by-Event Simulation of the Three-Dimensional Hydrodynamic Evolution from Flux Tube Initial Conditions in Ultrarelativistic Heavy Ion Collisions
• Core-Corona Separation in Ultra-Relativistic Heavy Ion Collisions
• Analysing radial flow features in p-Pb and p-p collisions at several TeV by studying identified particle production in EPOS3
• Measurement of jet suppression in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions
• Full jet in quark-gluon plasma with hydrodynamic medium response
• Measurement of inclusive jet cross sections in pp and PbPb collisions at sqrt(s[NN]) = 2.76 TeV
• Interplaying mechanisms behind single inclusive jet suppression in heavy-ion collisions
• Centrality dependence of hadronization and chemical freeze-out conditions in heavy ion collisions at \sqrt s_{NN} = 2.76 TeV
• First measurement of jet mass in Pb-Pb and p-Pb collisions at the LHC
• Predictions for Boson-Jet Observables and Fragmentation Function Ratios from a Hybrid Strong/Weak Coupling Model for Jet Quenching
• A Comparison of p-p, p-Pb, Pb-Pb Collisions in the Thermal Model: Multiplicity Dependence of Thermal Parameters
• Observation of medium induced modifications of jet fragmentation in PbPb collisions at $\sqrt{s_{\mathrm{NN}}}=$ 5.02 TeV using isolated-photon-tagged jets
• Medium modification of the shape of small-radius jets in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$
• Measurement of angular and momentum distributions of charged particles within and around jets in Pb+Pb and $pp$ collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV with the ATLAS detector
• Measurement of jet radial profiles in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Discrimination of effective radiative and collisional in-medium energy-loss models by their effects on angular jet structure