The global geometrical property of jet events in high-energy nuclear collisions
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Regular Article - Theoretical Physics
The global geometrical property of jet events in high-energy nuclear collisions Shi-Yong Chen1, Wei Dai2,a , Shan-Liang Zhang1, Qing Zhang1, Ben-Wei Zhang1,3,b 1
Key Laboratory of Quark and Lepton Physics (MOE) and Institute of Particle Physics, Central China Normal University, Wuhan 430079, China School of Mathematics and Physics, China University of Geosciences, Wuhan 430074, China 3 Institute of Quantum Matter, South China Normal University, Guangzhou 510006, China
2
Received: 10 May 2020 / Accepted: 8 September 2020 © The Author(s) 2020
Abstract We present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse sphericity (S⊥ ) distribution of jet events with parton energy loss in relativistic heavy-ion collisions. In our investigation, POWHEG + PYTHIA is employed to make an accurate description of transverse sphericity in the p + p baseline, which combines the next-to-leading order (NLO) pQCD calculations with the matched parton shower (PS). The Linear Boltzmann Transport (LBT) model of the parton energy loss is implemented to simulate the in-medium evolution of jets. We calculate the event normalized transverse sphericity distribution in central Pb + Pb collisions at the LHC, and give its medium modifications. An enhancement of transverse sphericity distribution at small S⊥ region but a suppression at large S⊥ region are observed in A + A collisions as compared to their p + p references, which indicates that in overall the geometry of jet events in Pb + Pb becomes more pencil-like. We demonstrate that for events with 2 jets in the final-state of heavy-ion collisions, the jet quenching makes the geometry more sphere-like with medium-induced gluon radiation. However, for events with ≥ 3 jets, parton energy loss in the QCD medium leads to the events more pencil-like due to jet number reduction, where less energetic jets may lose their energies and then fall off the jet selection kinematic cut. These two effects offset each other and in the end result in more jetty events in heavy-ion collisions relative to that in p + p. 1 Introduction Heavy ion collision experiments performed at the RHIC and the LHC are designed to study the properties of the deconfined Quark Gluon Plasma (QGP) which created shortly a e-mail:
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b e-mail:
[email protected] (corresponding author)
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after these collisions [1–7]. Energetic partons produced at the initial collision will traverse through this hot and dense medium and lose their energies by interacting with such medium, it is referred as jet quenching effect [8–10]. This phenomenon can be quantified by various observables, from h [11–18] to the single hadron production suppression RAA observables within the productions of full jets such as inclujet sive jets RAA , dijets momentum imbalance A J , and tagged jets momentum imbalance z J , the angular correlations of the leading two jets 12 etc. The available of these full jets observables are due to
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