A1 Journal article (refereed)
First measurements of N-subjettiness in central Pb-Pb collisions at √sNN = 2.76 TeV (2021)

ALICE collaboration. (2021). First measurements of N-subjettiness in central Pb-Pb collisions at √sNN = 2.76 TeV. Journal of High Energy Physics, 2021(10), Article 3. https://doi.org/10.1007/JHEP10(2021)003

JYU authors or editors

Publication details

All authors or editors: ALICE collaboration

Journal or series: Journal of High Energy Physics

ISSN: 1126-6708

eISSN: 1029-8479

Publication year: 2021

Volume: 2021

Issue number: 10

Article number: 3

Publisher: Springer

Publication country: Germany

Publication language: English

DOI: https://doi.org/10.1007/JHEP10(2021)003

Publication open access: Openly available

Publication channel open access: Open Access channel

Publication is parallel published (JYX): https://jyx.jyu.fi/handle/123456789/78614

Web address of parallel published publication (pre-print): https://arxiv.org/abs/2105.04936

Abstract

The ALICE Collaboration reports the first fully-corrected measurements of the N-subjettiness observable for track-based jets in heavy-ion collisions. This study is performed using data recorded in pp and Pb-Pb collisions at centre-of-mass energies of √s = 7 TeV and √sNN = 2.76 TeV, respectively. In particular the ratio of 2-subjettiness to 1-subjettiness, τ2/τ1, which is sensitive to the rate of two-pronged jet substructure, is presented. Energy loss of jets traversing the strongly interacting medium in heavy-ion collisions is expected to change the rate of two-pronged substructure relative to vacuum. The results are presented for jets with a resolution parameter of R = 0.4 and charged jet transverse momentum of 40 ≤ pT,jet ≤ 60 GeV/c, which constitute a larger jet resolution and lower jet transverse momentum interval than previous measurements in heavy-ion collisions. This has been achieved by utilising a semi-inclusive hadron-jet coincidence technique to suppress the larger jet combinatorial background in this kinematic region. No significant modification of the τ2/τ1 observable for track-based jets in Pb-Pb collisions is observed relative to vacuum PYTHIA6 and PYTHIA8 references at the same collision energy. The measurements of τ2/τ1, together with the splitting aperture angle ∆R, are also performed in pp collisions at √s = 7 TeV for inclusive jets. These results are compared with PYTHIA calculations at √s = 7 TeV, in order to validate the model as a vacuum reference for the Pb-Pb centre-of-mass energy. The PYTHIA references for τ2/τ1 are shifted to larger values compared to the measurement in pp collisions. This hints at a reduction in the rate of two-pronged jets in Pb-Pb collisions compared to pp collisions.

Keywords: particle physics

Contributing organizations

Ministry reporting: Yes

Reporting Year: 2021

JUFO rating: 2