Hard gluon evolution in the last stage of the bottom-up thermalization

Journal of Physics G Nuclear and Particle Physics ◽

10.1088/1361-6471/ac427d ◽

2021 ◽

Author(s):

F. G. Ben ◽

Magno V. T. Machado

Keyword(s):

Weak Coupling ◽

Heavy Ion ◽

High Energy ◽

Low Energy ◽

Thermal Bath ◽

Parton Energy Loss ◽

Bottom Up ◽

Ion Collisions ◽

Hard Gluon ◽

Last Stage

Abstract The study of how fast thermalization in heavy ion collisions occurs has been one of the central topics in the heavy ion community. In the weak coupling picture this thermalization occurs from “the bottom up”: high energy partons, formed early in the collision, radiate low energy gluons which then proceed to equilibrate among themselves, forming a thermal bath that brings the high energy sector to equilibrium. In this scheme we apply a model on parton energy loss to discuss the eﬀects of medium expansion on the thermalization problem and estimate the average transverse momentum diﬀusivity for thermalization in a Bjorken expanding medium.

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Hard gluon evolution in warming medium

The European Physical Journal C ◽

10.1140/epjc/s10052-022-10000-0 ◽

2022 ◽

Vol 82 (1) ◽

Author(s):

F. G. Ben ◽

M. V. T. Machado

Keyword(s):

Heavy Ion ◽

Gluon Plasma ◽

High Energy ◽

Entropy Density ◽

Local Thermal Equilibrium ◽

Thermal Bath ◽

Perturbative Approach ◽

Average Temperature ◽

Ion Collisions ◽

Hard Gluon

AbstractWe describe the energy distribution of hard gluons travelling through a dense quark–gluon plasma whose temperature increases linearly with time, within a probabilistic perturbative approach. The results were applied to the thermalization problem in heavy ion collisions. In the weak coupling picture this thermalization occurs from “the bottom up”: high energy partons, formed early in the collision, radiate low energy gluons which then proceed to equilibrate among themselves, forming a thermal bath that brings the high energy sector to equilibrium. We see that, in this scenario, the dynamic we describe must set in around $$t \sim 0.5$$ t ∼ 0.5 fm/c after the collision in order to reach a fully thermalized state at $$t \sim 1$$ t ∼ 1 fm/c. We then look at the entropy density and average temperature of the soft thermal bath, as the system approaches (local) thermal equilibrium.

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The global geometrical property of jet events in high-energy nuclear collisions

The European Physical Journal C ◽

10.1140/epjc/s10052-020-08452-3 ◽

2020 ◽

Vol 80 (9) ◽

Author(s):

Shi-Yong Chen ◽

Wei Dai ◽

Shan-Liang Zhang ◽

Qing Zhang ◽

Ben-Wei Zhang

Keyword(s):

Energy Loss ◽

Heavy Ion Collisions ◽

Heavy Ion ◽

High Energy ◽

Jet Quenching ◽

Relativistic Heavy Ion Collisions ◽

Parton Energy Loss ◽

Boltzmann Transport ◽

Ion Collisions ◽

Medium Modifications

AbstractWe present the first theoretical study of medium modifications of the global geometrical pattern, i.e., transverse sphericity ($$S_{\perp }$$ 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 $$S_{\perp }$$ S ⊥ region but a suppression at large $$S_{\perp }$$ 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 $$\ge 3$$ ≥ 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.

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Jet tomography in high-energy nuclear collisions

EPJ Web of Conferences ◽

10.1051/epjconf/201920604004 ◽

2019 ◽

Vol 206 ◽

pp. 04004 ◽

Cited By ~ 2

Author(s):

Ben-Wei Zhang ◽

Guo-Yang Ma ◽

Wei Dai ◽

Sa Wang ◽

Shan-Liang Zhang

Keyword(s):

Energy Loss ◽

Heavy Ion ◽

High Energy ◽

Jet Quenching ◽

Parton Energy Loss ◽

Matrix Elements ◽

Leading Order ◽

Nuclear Collisions ◽

Ion Collisions ◽

Jet Observables

When an energetic parton traversing the QCD medium, it may suffer multiple scatterings and lose energy. This jet quenching phenomenon may lead to the suppression of leading hadron productions as well as medium modifications of full jet observables in heavy-ion collisions. In this talk we discuss the nuclear modificationfactors and yield ratios of identified meson such as η, ρ0, φ, ω, and $ K_{\rm{S}}^0 $ as well as π meson at large pT in A+A collisions at the next to-leading order (NLO) with high-twist approach of parton energy loss. Then we discuss a newly developed formalism of combing NLO matrix elements and parton shower (PS) for initial hard production with parton energy loss in the QGP, and its application in investigating massivegauge boson(Z0/W±)tagged jet productions and b $ \bar {b} $ dijet correlations in Pb+Pb at the LHC.

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A Description of Pseudorapidity Distributions of Charged Particles Produced in Au+Au Collisions at RHIC Energies

Advances in High Energy Physics ◽

10.1155/2018/1369098 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8

Author(s):

Z. J. Jiang ◽

Dongfang Xu ◽

Yan Huang

Keyword(s):

Phase Transition ◽

Heavy Ion Collisions ◽

Charged Particles ◽

Dense Matter ◽

Heavy Ion ◽

High Energy ◽

Low Energy ◽

Ion Collisions ◽

Rapidity Distributions ◽

Pseudorapidity Distributions

In heavy ion collisions, charged particles come from two parts: the hot and dense matter and the leading particles. In this paper, the hot and dense matter is assumed to expand according to the hydrodynamic model including phase transition and decouples into particles via the prescription of Cooper-Frye. The leading particles are as usual supposed to have Gaussian rapidity distributions with the number equaling that of participants. The investigations of this paper show that, unlike low energy situations, the leading particles are essential in describing the pseudorapidity distributions of charged particles produced in high energy heavy ion collisions. This might be due to the different transparencies of nuclei at different energies.

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Jet quenching in high-energy heavy-ion collisions

International Journal of Modern Physics E ◽

10.1142/s0218301315300143 ◽

2015 ◽

Vol 24 (11) ◽

pp. 1530014 ◽

Cited By ~ 97

Author(s):

Guang-You Qin ◽

Xin-Nian Wang

Keyword(s):

Energy Loss ◽

Quark Gluon Plasma ◽

Heavy Ion Collisions ◽

Heavy Ion ◽

Gluon Plasma ◽

High Energy ◽

Jet Quenching ◽

Parton Energy Loss ◽

Ion Collisions ◽

Phenomenological Studies

Jet quenching in high-energy heavy-ion collisions can be used to probe properties of hot and dense quark–gluon plasma. We provide a brief introduction to the concept and framework for the study of jet quenching. Different approaches and implementation of multiple scattering and parton energy loss are discussed. Recent progresses in the theoretical and phenomenological studies of jet quenching in heavy-ion collisions at RHIC and LHC are reviewed.

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