Effective kinetic description of event-by-event pre-equilibrium dynamics in high-energy heavy-ion collisions

Aleksi Kurkela (Theoretical Physics Department, CERN, Geneva, Switzerland and Faculty of Science and Technology, University of Stavanger, 4036 Stavanger, Norway) ; Aleksas Mazeliauskas (Institut für Theoretische Physik, Universität Heidelberg, 69120 Heidelberg, Germany and Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA) ; Jean-François Paquet (Department of Physics, Duke University, Durham, North Carolina 27708, USA and Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA) ; Sören Schlichting (Fakultät für Physik, Universität Bielefeld, D-33615 Bielefeld, Germany and Department of Physics, University of Washington, Seattle, Washington 98195-1560, USA) ; Derek Teaney (Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA)

We develop a macroscopic description of the space-time evolution of the energy-momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (à la “bottom-up”), we calculate the nonequilibrium evolution of the local background energy-momentum tensor as well as the nonequilibrium linear response to transverse energy and momentum perturbations for realistic boost-invariant initial conditions for heavy-ion collisions. We demonstrate how this framework can be used on an event-by-event basis to propagate the energy-momentum tensor from far-from-equilibrium initial-state models to the time τhydro when the system is well described by relativistic viscous hydrodynamics. The subsequent hydrodynamic evolution becomes essentially independent of the hydrodynamic initialization time τhydro as long as τhydro is chosen in an appropriate range where both kinetic and hydrodynamic descriptions overlap. We find that for sNN=2.76TeV central Pb-Pb collisions, the typical timescale when viscous hydrodynamics with shear viscosity over entropy ratio η/s=0.16 becomes applicable is τhydro1fm/c after the collision.

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  "abstracts": [
    {
      "source": "APS", 
      "value": "We develop a macroscopic description of the space-time evolution of the energy-momentum tensor during the pre-equilibrium stage of a high-energy heavy-ion collision. Based on a weak coupling effective kinetic description of the microscopic equilibration process (\u00e0 la \u201cbottom-up\u201d), we calculate the nonequilibrium evolution of the local background energy-momentum tensor as well as the nonequilibrium linear response to transverse energy and momentum perturbations for realistic boost-invariant initial conditions for heavy-ion collisions. We demonstrate how this framework can be used on an event-by-event basis to propagate the energy-momentum tensor from far-from-equilibrium initial-state models to the time <math><msub><mi>\u03c4</mi><mtext>hydro</mtext></msub></math> when the system is well described by relativistic viscous hydrodynamics. The subsequent hydrodynamic evolution becomes essentially independent of the hydrodynamic initialization time <math><msub><mi>\u03c4</mi><mtext>hydro</mtext></msub></math> as long as <math><msub><mi>\u03c4</mi><mtext>hydro</mtext></msub></math> is chosen in an appropriate range where both kinetic and hydrodynamic descriptions overlap. We find that for <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>2.76</mn><mspace width=\"0.16em\"></mspace><mspace width=\"0.16em\"></mspace><mtext>TeV</mtext></mrow></math> central Pb-Pb collisions, the typical timescale when viscous hydrodynamics with shear viscosity over entropy ratio <math><mrow><mi>\u03b7</mi><mo>/</mo><mi>s</mi><mo>=</mo><mn>0.16</mn></mrow></math> becomes applicable is <math><mrow><msub><mi>\u03c4</mi><mtext>hydro</mtext></msub><mo>\u223c</mo><mn>1</mn><mspace width=\"0.16em\"></mspace><mrow><mi>fm</mi><mo>/</mo><mi>c</mi></mrow></mrow></math> after the collision."
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Published on:
27 March 2019
Publisher:
APS
Published in:
Physical Review C , Volume 99 (2019)
Issue 3
DOI:
https://doi.org/10.1103/PhysRevC.99.034910
arXiv:
1805.00961
Copyrights:
Published by the American Physical Society
Licence:
CC-BY-4.0

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