Jet shapes in pp and Pb-Pb collisions at ALICE

Abstract

The aim of this work is to explore possible medium modifications to the substructure of inclusive charged jets in Pb-Pb relative to proton-proton collisions by measuring a set of jet shapes. The set of shapes includes the radial moment, $g$, and the momentum dispersion $p_{\mathrm{T}}$D. They provide complementary information on the fragmentation and can help to discriminate between two different scenarios: intra-jet broadening or collimation as a result of jet quenching. \noindent The shapes are measured in Pb--Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with a constituent cutoff of 0.15 GeV/c and jet resolution $R=$ 0.2. New techniques for background subtraction are applied and a two-dimensional unfolding is performed to correct the shapes to particle level. The corrected jet shapes for jet $p_{\mathrm{T}}$ $40\le p_{\mathrm{T},\mathrm{jet}}\le 60$ GeV/c are presented and discussed. The observed jet shape modifications suggest that the in-medium fragmentation is harder and more collimated than vacuum fragmentation as obtained by a PYTHIA calculation. The PYTHIA calculation is validated with proton-proton data at 7 TeV.

4 pages, 3 figures, to appear in the proceedings of Quark Matter 2015, KOBE, Japan

References in corpus (3)

• Pileup subtraction using jet areas
• Pileup subtraction for jet shapes
• Jet Fragmentation and Jet Shapes in JEWEL and Q-PYTHIA

Cited by in corpus (11)

• Review of Jet Measurements in Heavy Ion Collisions
• Medium response in JEWEL and its impact on jet shape observables in heavy ion collisions
• An overview of experimental results from ultra-relativistic heavy-ion collisions at the CERN LHC: hard probes
• Novel subjet observables for jet quenching in heavy-ion collisions
• Exploring jet substructure with jet shapes in ALICE
• Jet structure modifications in heavy-ion collisions with JEWEL
• Measurements of jets in heavy ion collisions
• Jet Production at RHIC and LHC
• Exploring system size dependence of jet modification in heavy-ion collisions
• Medium modification of jet shape observables in Pb-Pb collisions at $\sqrt{s_{NN}}$= 2.76 TeV using EPOS and JEWEL event generators
• Study of medium modified jet shape observables in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV using EPOS and JEWEL event generators