Single electrons from heavy-flavor mesons in relativistic heavy-ion collisions

Abstract

We study the single electron spectra from D− and B−meson semileptonic decays in Au+Au collisions at √ sNN =200, 62.4, and 19.2 GeV by employing the parton-hadron-string dynamics (PHSD) transport approach that has been shown to reasonably describe the charm dynamics at RelativisticHeavy-Ion-Collider (RHIC) and Large-Hadron-Collider (LHC) energies on a microscopic level. In this approach the initial charm and bottom quarks are produced by using the PYTHIA event generator which is tuned to reproduce the fixed-order next-to-leading logarithm (FONLL) calculations for charm and bottom production. The produced charm and bottom quarks interact with off-shell (massive) partons in the quark-gluon plasma with scattering cross sections which are calculated in the dynamical quasi-particle model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature Tc. At energy densities close to the critical energy density (≈ 0.5 GeV/fm 3 ) the charm and bottom quarks are hadronized into D− and B−mesons through either coalescence or fragmentation. After hadronization the D− and B−mesons interact with the light hadrons by employing the scattering cross sections from an effective Lagrangian. The final D− and B−mesons then produce single electrons through semileptonic decay. We find that the PHSD approach well describes the nuclear modification factor RAA and elliptic flow v2 of single electrons in d+Au and Au+Au collisions at √ sNN = 200 GeV and the elliptic flow in Au+Au reactions at √ sNN = 62.4 GeV from the PHENIX collaboration, however, the large RAA at √ sNN = 62.4 GeV is not described at all. Furthermore, we make predictions for the RAA of D−mesons and of single electrons at the lower energy of √ sNN = 19.2 GeV. Additionally, the medium modification of the azimuthal angle φ between a heavy quark and a heavy antiquark is studied. We find that the transverse flow enhances the azimuthal angular distributions close to φ = 0 because the heavy flavors strongly interact with nuclear medium in relativistic heavy-ion collisions and almost flow with the bulk matter.

Open charm and dileptons from relativistic heavy-ion collisions

“…We recall that the PHSD approach has successfully described numerous experimental data in relativistic heavyion collisions from the Alternating Gradient Synchrotron (AGS), SPS, RHIC to LHC energies [30,33,[35][36][37]. More recently, the charm production and propagation has been explicitly implemented in the PHSD and detailed studies on the charm dynamics and hadronization/fragmention have been performed at top RHIC and LHC energies in comparison to the available data [38][39][40]. In the PHSD approach the initial charm and anticharm quarks are produced by using the PYTHIA event generator [41] which is tuned to the transverse momentum and rapidity distributions of charm and anticharm quarks from the Fixed-Order Next-to-Leading Logarithm (FONLL) calculations [42].…”

Exploring non-equilibrium quark-gluon plasma effects on charm transport coefficients

“…FIG. 2: Drag coefficient divided by the charm quark momentum (upper), q scaled by T 3 (middle), and the spatial diffusion coefficient (lower) of charm quarks as a function of temperature and/or charm quark momentum from the DQPM [22,23] in comparison with the spatial diffusion coefficients from lQCD calculations [31].…”

“…To describe the QGP we employ the dynamical quasiparticle model (DQPM) [21], where a QGP is composed of strongly interacting quasiparticles whose pole mass and spectral width are fitted to the equation-of-state obtained by lattice quantum chromodynamics (lQCD) calculation. The scattering between heavy quarks and the off-shell partons is calculated using leading order Feynman diagrams [22,23]. This is motivated by the fact that the DQPM reproduces the spatial diffusion coefficient of heavy quarks as a function of temperature, which is presently the only observable for heavy quarks from lQCD.…”

Impact of off-shell dynamics on the transport properties and the dynamical evolution of charm quarks at RHIC and LHC temperatures

“…In literature several studies have been performed in these years, to study theoretically both these observables with the aim to understand heavy quark dynamics in QGP employing the Langevin or the on-shell Boltzmann transport equation [9,12,13,22,25,29,[35][36][37][38][39][40][41][42][43][44]. However, being the QGP strongly interacting, a full quantum description of the charm quark interaction should include in principle also the off-shell dynamics, an approach that has been developed only in [45] for the study of the transport coefficients and it is included in the PHSD approach to heavy-ion collisions [27,38,46]. Recently, it has been shown that also off-shell effects can play a role in the hadronization processes [47].…”