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Nuclear Theory·nucl-th

Thursday·April 26, 2018

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    Photons from thermalizing matter in heavy ion collisions

    Vladimir Khachatryan🇺🇸 · Bjoern Schenke🇺🇸 · Mickey Chiu🇺🇸 · Axel Drees🇺🇸 · Thomas K. Hemmick🇺🇸 · Norbert Novitzky🇺🇸

    We investigate the production of direct photons in heavy ion collisions within the modified bottom-up thermalization scenario, which we show to be related to the thermalizing Glasma framework. The dynamics of the parton system up to thermalization/equilibration can be described by two momentum scales, by means of which we express the photon invariant yield excluding the prompt pQCD contribution. We derive an analytic formula, which provides an estimate of photon production from thermalizing matter for a wide range of collision systems and energies. We compare the yield with that measured in the PHENIX Au+Au run04 and the combined run07+run10 data sets at root-s = 200GeV. We also make theory-data comparisons for Pb+Pb at 2760 GeV and d+Au at 200 GeV collision energies. Finally, we make predictions for the direct photon invariant yield from collisions of U+U, Cu+Au, He+Au at 200 GeV and Pb+Pb at 5020 GeV.

    nucl-thNPA(2018)·13 citations
  3. 03

    Exploring the applicability of dissipative fluid dynamics to small systems by comparison to the Boltzmann equation

    K. Gallmeister🇩🇪 · H. Niemi🇩🇪 · C. Greiner🇩🇪 · D. H. Rischke🇩🇪

    [Background] Experimental data from heavy-ion experiments at RHIC-BNL and LHC-CERN are quantitatively described using relativistic fluid dynamics. Even p+A and p+p collisions show signs of collective behavior describable in the same manner. Nevertheless, small system sizes and large gradients strain the limits of applicability of fluid-dynamical methods. [Purpose] The range of applicability of fluid dynamics for the description of the collective behavior, and in particular of the elliptic flow, of small systems needs to be explored. [Method] Results of relativistic fluid-dynamical simulations are compared with solutions of the Boltzmann equation in a longitudinally boost-invariant picture. As initial condition, several different transverse energy-density profiles for equilibrated matter are investigated. [Results] While there is overall a fair agreement of energy- and particle-density profiles, components of the shear-stress tensor are more sensitive to details of the implementation. The highest sensitivity is exhibited by quantities influenced by properties of the medium at freeze-out. [Conclusions] For some quantities, like the shear-stress tensor, agreement between fluid dynamics and transport theory extends into regions of Knudsen numbers and inverse Reynolds numbers where relativistic fluid dynamics is believed to fail.

    nucl-thhep-phPRC(2018)·22 citations

Affiliations

first authorsco-authorsvia INSPIRE