Charm production in Pb + Pb collisions at energies available at the CERN Large Hadron Collider

Abstract

We study charm production in Pb+Pb collisions at √ sNN =2.76 TeV in the Parton-Hadron-StringDynamics transport approach and the charm dynamics in the partonic and hadronic medium. The charm quarks are produced through initial binary nucleon-nucleon collisions by using the PYTHIA event generator taking into account the (anti-)shadowing incorporated in the EPS09 package. The produced charm quarks interact with off-shell massive partons in the quark-gluon plasma and are hadronized into D mesons through coalescence or fragmentation close to the critical energy density, and then interact with hadrons in the final hadronic stage with scattering cross sections calculated in an effective Lagrangian approach with heavy-quark spin symmetry. The PHSD results show a reasonable RAA and elliptic flow of D mesons in comparison to the experimental data for Pb+Pb collisions at √ sNN = 2.76 TeV from the ALICE Collaboration. We also study the effect of temperature-dependent off-shell charm quarks in relativistic heavy-ion collisions. We find that the scattering cross sections are only moderately affected by off-shell charm degrees of freedom. However, the position of the peak of RAA for D mesons depends on the strength of the scalar partonic forces which also have an impact on the D meson elliptic flow. The comparison with experimental data on the RAA suggests that the repulsive force is weaker for off-shell charm quarks as compared to that for light quarks. Furthermore, the effects from radiative charm energy loss appear to be low compared to the collisional energy loss up to transverse momenta of ∼ 15 GeV/c.

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

“…The hadronized D−mesons then interact with light hadrons in the hadronic phase until freeze out and subsequently undergoes semileptonic decay. We have found that the PHSD approach, which has been applied for charm production in Au+Au collisions at √ s NN =200 GeV [29] and in Pb+Pb collisions at √ s NN =2.76 TeV [30], describes the R AA as well as the v 2 of D−mesons in reasonable agreement with the experimental data from the STAR collaboration [33,34] and from the ALICE collaboration [35,36] when including the initial shadowing effect in the latter case.…”

“…The dotted lines in figure 12 and 13 are, respectively, the R AA of heavy mesons and D−mesons and B−mesons at √ s NN =200 GeV. They also show that the shadowing effect is not so critical in reproducing experimental data, which is different from the LHC energies [30]. [37,38].…”

“…The Parton-Hadron-String Dynamics (PHSD) approach has been employed since it successfully describes D−meson production in relativistic heavy-ion collisions at RHIC and LHC energies [29,30]. In this work, we have extended the PHSD to B−meson production and compared single electron production from heavy-meson decays with the experimental data from the PHENIX collaboration, because there are no experimental data exclusively for B−mesons at the RHIC energies.…”

“…The EPS09 package [50] parameterizes this behavior of R A i (x, q) and fits the heights and positions of the local extrema of the ratio to the experimental data from deep inelastic l+A scattering, Drell-Yan dilepton production in p+A collisions, and inclusive pion production in d+Au and p+p collisions at RHIC. We also employ the EPS09 package [50] in our PHSD calculations [30].…”

“…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 [29,30]. In the PHSD approach the initial charm and anticharm quarks are produced by using the PYTHIA event generator [31] 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 [32].…”