Minijets, created by perturbative hard QCD collisions at moderate energies, can represent a significant portion of the total multiplicity of a heavy-ion collision event. Since their transverse momenta are initially larger than the typical saturation scale describing the bulk of the equilibrating quark-gluon plasma (QGP), they ought to be described through the physics of parton energy loss. Indeed, their typical stopping distances are larger than the usual hydrodynamization time, so they do not in general hydrodynamize at the same pace than the bulk of the collision. Therefore, in general minijets cannot be described solely by a unique preequilibrium stage that bridges the initial, overoccupied glasma state, with the hydrodynamical evolution. In this work we make use of a new concurrent minijet+hydrodynamic framework in which the properties of the hydrodynamically evolving QGP are modified due to the injection of energy and momentum from the minijets. We study the system for different choices of the minimum transverse momentum associated with minijet production. In order to achieve a realistic description of charged particle multiplicity, the amount of entropy associated to the low- x initial state needs to be reduced. Moreover, the fact that the injected momentum from the randomly oriented minijets is not correlated with the spatial gradients of the system reduces overall flow, and the value of the QGP transport coefficients needs to be reduced accordingly in order to describe the measured flow coefficients in experiments. They are, in effect, an important new source of fluctuations, resulting in a spikier, notably modified hydrodynamical evolution when compared to the scenario in which the presence of minijets is ignored. We avow that their abundance makes it necessary to include their physics in holistic descriptions of heavy-ion collisions. We discuss the impact of the minijets on a number of observables, such as pT spectra and pT-differential flow vn for a wide range of centrality classes. In contrast to elliptic, triangular or quadrangular flow, here we find that directed flow, v1, has the strongest potential to discriminate between different minijet production rates.
Pablos, Daniel, Singh, Mayank, Jeon, Sangyong, et al., "Minijet quenching in a concurrent <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>jet</mml:mi><mml:mo>+</mml:mo><mml:mi>hydro</mml:mi></mml:math> evolution and the nonequilibrium quark-gluon plasma," Physical Review. C 106, no. 3 (2022), https://doi.org/10.1103/physrevc.106.034901
@article{osti_1979900,
author = {Pablos, Daniel and Singh, Mayank and Jeon, Sangyong and Gale, Charles},
title = {Minijet quenching in a concurrent <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>jet</mml:mi><mml:mo>+</mml:mo><mml:mi>hydro</mml:mi></mml:math> evolution and the nonequilibrium quark-gluon plasma},
annote = {Minijets, created by perturbative hard QCD collisions at moderate energies, can represent a significant portion of the total multiplicity of a heavy-ion collision event. Since their transverse momenta are initially larger than the typical saturation scale describing the bulk of the equilibrating quark-gluon plasma (QGP), they ought to be described through the physics of parton energy loss. Indeed, their typical stopping distances are larger than the usual hydrodynamization time, so they do not in general hydrodynamize at the same pace than the bulk of the collision. Therefore, in general minijets cannot be described solely by a unique preequilibrium stage that bridges the initial, overoccupied glasma state, with the hydrodynamical evolution. In this work we make use of a new concurrent minijet+hydrodynamic framework in which the properties of the hydrodynamically evolving QGP are modified due to the injection of energy and momentum from the minijets. We study the system for different choices of the minimum transverse momentum associated with minijet production. In order to achieve a realistic description of charged particle multiplicity, the amount of entropy associated to the low- x initial state needs to be reduced. Moreover, the fact that the injected momentum from the randomly oriented minijets is not correlated with the spatial gradients of the system reduces overall flow, and the value of the QGP transport coefficients needs to be reduced accordingly in order to describe the measured flow coefficients in experiments. They are, in effect, an important new source of fluctuations, resulting in a spikier, notably modified hydrodynamical evolution when compared to the scenario in which the presence of minijets is ignored. We avow that their abundance makes it necessary to include their physics in holistic descriptions of heavy-ion collisions. We discuss the impact of the minijets on a number of observables, such as pT spectra and pT-differential flow vn for a wide range of centrality classes. In contrast to elliptic, triangular or quadrangular flow, here we find that directed flow, v1, has the strongest potential to discriminate between different minijet production rates.},
doi = {10.1103/physrevc.106.034901},
url = {https://www.osti.gov/biblio/1979900},
journal = {Physical Review. C},
issn = {ISSN 2469-9985},
number = {3},
volume = {106},
place = {United States},
publisher = {American Physical Society (APS)},
year = {2022},
month = {09}}
Proceedings of 10th International Conference on Hard and Electromagnetic Probes of High-Energy Nuclear Collisions — PoS(HardProbes2020)https://doi.org/10.22323/1.387.0160