Heavy-flavor in-medium momentum evolution: Langevin versus Boltzmann approach

Santosh K. Das, Francesco Scardina, Salvatore Plumari, and Vincenzo Greco
Phys. Rev. C 90, 044901 – Published 3 October 2014

Abstract

The propagation of heavy quarks in the quark-gluon plasma was often treated within the framework of the Langevin equation (LV), i.e., assuming the momentum transfer is small or the scatterings are sufficiently forward peaked, small screening mass mD. We address a direct comparison between the Langevin dynamics and the Boltzmann collisional integral (BM) when a bulk medium is in equilibrium at fixed temperature. We show that unless the cross section is quite forward peaked (mDT) or the mass to temperature ratio is quite large (MHQ/T 810) there are significant differences in the evolution of the p spectra and consequently on the nuclear modification factor RAA(pT). However, for charm quark we find that very similar RAA(pT) between the LV and BM can be obtained, but with a modified diffusion coefficient of about 15%50% depending on the angular dependence of the cross section which regulates the momentum transfer. Studying also the momentum spread suffered by the single heavy quarks we see that at temperatures T250MeV the dynamics of the scatterings is far from being of Brownian type for charm quarks. In the case of bottom quarks we essentially find no differences in the time evolution of the momentum spectra between the LV and the BM dynamics independently of the angular dependence of the cross section, at least in the range of temperature relevant for ultrarelativistic heavy-ion collisions (HICs). Finally, we have shown the possible impact of this study on RAA(pT) and v2(pT) for a realistic simulation of relativistic HICs. For larger mD the elliptic flow can be about 50% larger for the Boltzmann dynamics with respect to the Langevin. This is helpful for a simultaneous reproduction of RAA(pT) and v2(pT).

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  • Received 13 January 2014
  • Revised 16 July 2014

DOI:https://doi.org/10.1103/PhysRevC.90.044901

©2014 American Physical Society

Authors & Affiliations

Santosh K. Das, Francesco Scardina, Salvatore Plumari, and Vincenzo Greco

  • Department of Physics and Astronomy, University of Catania, Via S. Sofia 64, 1-95125 Catania, Italy and Laboratori Nazionali del Sud, INFN-LNS, Via S. Sofia 62, I-95123 Catania, Italy

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Issue

Vol. 90, Iss. 4 — October 2014

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