Radiative energy loss reduction in an absorptive plasma

The influence of the damping of radiation on the radiative energy loss spectrum of a relativistic charge in an infinite, absorptive plasma is studied. We find increasing reduction of the spectrum with increasing damping. Our studies, which represent an Abelian approximation for the colour charge dynamics in the quark-gluon plasma, may influence the analysis of jet quenching phenomena observed in high-energy nuclear collisions. Here, we focus on a formal discussion of the limiting behaviour with increasing radiation frequency. In an absorptive (and polarizable) medium, this is determined by the behaviour of the exponential damping factor entering the spectrum and the formation time of radiation.Comment: Jan 2012. 4pp. Talk given at Quark Matter 2011, 23-28 May 2011, Annecy, Franc

Gluon radiation by heavy quarks at intermediate energies

Employing scalar QCD we study the gluon emission of heavy quarks created by the interaction with light quarks considered as dynamical scattering centers. We develop approximation formulas for the high energy limit and study when the full calculation reaches this high energy limit. For zero quark masses and in the high energy limit our model reproduces the Gunion-Bertsch results. We justify why scalar QCD represents a good approximation to the full QCD approach for the energy loss of heavy quarks. In the regime of accessible phenomenology we observe that the emission at small transverse momentum (dead cone effect) is less suppressed than originally suggested. We also investigate the influence of a finite gluon mass on the discussed results

Azimuthal correlations of heavy quarks in Pb+Pb collisions at LHC (s=2.76\sqrt{s}=2.76 TeV)

In this paper we study the azimuthal correlations of heavy quarks in Pb+Pb collisions with $\sqrt{s}=2.76$ TeV at LHC. Due to the interaction with the medium heavy quarks and antiquarks are deflected from their original direction and the initial correlation of the pair is broadened. We investigate this effect for different transverse momentum classes. Low-momentum heavy-quark pairs lose their leading order back-to-back initial correlation, while a significant residual correlation survives at large momenta. Due to the larger acquired average deflection from their original directions the azimuthal correlations of heavy-quark pairs are broadened more efficiently in a purely collisional energy loss mechanism compared to including radiative corrections. This discriminatory feature survives when next-to-leading order production processes are included.Comment: final, published versio

Radiative energy loss in the absorptive QGP: taming the long formation lengths in coherent emission

In an absorptive plasma, damping of radiation mechanisms can influence the bremsstrahlung formation in case of large radiation formation lengths. We study qualitatively the influence of this effect on the gluon bremsstrahlung spectrum off heavy quarks in the quark-gluon plasma. Independent of the heavy-quark mass, the spectrum is found to be strongly suppressed in an intermediate gluon energy region which grows with increasing gluon damping rate and increasing energy of the heavy quark. Thus, just as polarization effects in the plasma render the bremsstrahlung spectra independent of the quark mass in the soft gluon regime, damping effects tend to have a similar impact for larger gluon energies.Comment: contribution to the International Meeting "Excited QCD", Peniche, Portugal, 06 - 12 May 201

Heavy flavor production in the Parton-Hadron-String Dynamics (PHSD)

Relativistic heavy-ion collisions produce a hot and dense nuclear matter, through which one can study the phase diagram of QCD. Open and hidden heavy flavors are promising probes to search for the properties of the hot and dense nuclear matter under extreme conditions. We present how the production and interactions of open and hidden heavy flavors in heavy-ion collisions are realized in the Parton-Hadron-String Dynamics, which is a non-equilibrium microscopic transport approach for the description of the dynamics of strongly interacting hadronic and partonic matter.Comment: 6 pages, 2 figure

Heavy-flavor observables at RHIC and LHC

We investigate the charm-quark propagation in the QGP media produced in ultrarelativistic heavy-ion collisions at RHIC and the LHC. Purely collisional and radiative processes lead to a significant suppression of final $D$-meson spectra at high transverse momentum and a finite flow of heavy quarks inside the fluid dynamical evolution of the light partons. The $D$-meson nuclear modification factor and the elliptic flow are studied at two collision energies. We further propose to measure the triangular flow of $D$ mesons, which we find to be nonzero in non-central collisions.Comment: Proceedings of the 24th Quark Matter conference, 19-24 May 2014, Darmstadt, Germany. 4 p

Plasma damping effects on the radiative energy loss of relativistic particles

The energy loss of a relativistic charge undergoing multiple scatterings while traversing an infinite, polarizable and absorptive plasma is investigated. Polarization and damping mechanisms in the medium are phenomenologically modelled by a complex index of refraction. Apart from the known Ter-Mikaelian effect related to the dielectric polarization of matter, we find an additional, substantial reduction of the energy loss due to damping of radiation. The observed effect is more prominent for larger damping and/or larger energy of the charge. A conceivable analog of this phenomenon in QCD could influence the study of jet quenching phenomena in ultra-relativistic heavy-ion collisions at RHIC and LHC.Comment: Sep 2012. 4pp. 3 figures. Revised journal version - Erratu