arXiv subjects

T. Renk

Publications and source records attributed to T. Renk.

10 recordsLinked to original sources

arXiv2010

Jet quenching in the strongly-interacting quark-gluon plasma

We propose a hybrid model for medium-induced parton energy loss, in which the hard scales in the process are treated perturbatively, while the soft scales which involve strong coupling dynamics are modeled by AdS/CFT calculations. After fitting a single parameter on R_AA for central Au+Au collisions, we are able to predict different observables like R_AA and I_AA as a function of centrality and reaction plane. We obtain a consistent picture of how jet quenching is modified if the quark-gluon plasma is strongly interacting, and we provide quantitative predictions.

hep-ph↗

arXiv2008

Systematic Comparison of Jet Energy-Loss Schemes in a 3D hydrodynamic medium

We utilize a 3D hydrodynamic model to provide the medium evolution for a systematic comparison of jet energy-loss calculations in the BDMPS/ASW, HT and AMY approaches. We find that the parameters of all three calculations can be adjusted to provide a good description of inclusive data on $R_{AA}$ versus transverse momentum. However, we do observe slight differences in their predictions for the azimuthal angular dependence of $R_{AA}$ vs. $p_T$. We also note that the value of the transport coefficient $\hat{q}$ needed in the three approaches to describe the data differs significantly.

nucl-th↗

arXiv2007

Hard and soft probe - medium interactions in a 3D hydro+micro approach at RHIC

We utilize a 3D hybrid hydro+micro model for a comprehensive and consistent description of soft and hard particle production in ultra-relativistic heavy-ion collisions at RHIC. In the soft sector we focus on the dynamics of (multi-)strange baryons, where a clear strangeness dependence of their collision rates and freeze-out is observed. In the hard sector we study the radiative energy loss of hard partons in a soft medium in the multiple soft scattering approximation. While the nuclear suppression factor $R_{AA}$ does not reflect the high quality of the medium description (except in a reduced systematic uncertainty in extracting the quenching power of the medium), the hydrodynamical model also allows to study different centralities and in particular the angular variation of $R_{AA}$ with respect to the reaction plane, allowing for a controlled variation of the in-medium path-length.

nucl-th↗

arXiv2002

Probing the QCD Equation of State

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrisation of the onset of confinement in the vicinity of the phase transition. Lattice results of bulk thermodynamic quantities are well reproduced, the extension to small quark chemical potential is also successful. We then apply the model to dilepton production and charm suppression in ultrarelativistic heavy-ion collisions.

hep-ph↗

arXiv2002

Phases of QCD, Thermal Quasiparticles and Dilepton Radiation from a Fireball

We calculate dilepton production rates from a fireball adapted to the kinematical conditions realized in ultrarelativistic heavy ion collisions over a broad range of beam energies. The freeze-out state of the fireball is fixed by hadronic observables. We use this information combined with the initial geometry of the collision region to follow the space-time evolution of the fireball. Assuming entropy conservation, its bulk thermodynamic properties can then be uniquely obtained once the equation of state (EoS) is specified. The high-temperature (QGP) phase is modelled by a non-perturbative quasiparticle model that incorporates a phenomenological confinement description, adapted to lattice QCD results. For the hadronic phase, we interpolate the EoS into the region where a resonance gas approach seems applicable, keeping track of a possible overpopulation of the pion phase space. In this way, the fireball evolution is specified without reference to dilepton data, thus eliminating it as an adjustable parameter in the rate calculations. Dilepton emission in the QGP phase is then calculated within the quasiparticle model. In the hadronic phase, both temperature and finite baryon density effects on the photon spectral function are incorporated. Existing dilepton data from CERES at 158 and 40 AGeV Pb-Au collisions are well described, and a prediction for the PHENIX setup at RHIC for sqrt(s) = 200 AGeV is given.

hep-ph↗

arXiv2002

Quasiparticles in QCD thermodynamics and applications

We propose a novel quasiparticle interpretation of the equation of state of deconfined QCD at finite temperature. Using appropriate thermal masses, we introduce a phenomenological parametrization of the onset of confinement in the vicinity of the phase transition. Lattice results of the energy density, the pressure and the interaction measure of pure SU(3) gauge theory are well reproduced. A relation between the thermal energy density of the Yang-Mills vacuum and the chromomagnetic condensate _T is found. We also present the two flavour QCD equation of state for realistic quark masses and apply the model to dilepton production in ultrarelativistic heavy-ion collisions.

hep-ph↗

arXiv2002

QCD Thermodynamics and Fireball Evolution in URHICs

The fireball created in an ultrarelativistic heavy ion collision is the environment in which all processes providing clues about the possible formation of the quark-gluon plasma (QGP) happen. It is therefore crucial to understand the dynamics of this hot and dense system. We set up a model in which the fireball evolution is reconstructed between two stages, the freeze-out, which is accessible by hadronic observables, and the initial collision for which the overlap geometry can be calculated. Using the equation of state (EoS) provided by a quasiparticle model of the QGP, we are able to calculate thermodynamical properties in volume slices of constant proper time and determine the volume expansion self-consistently. The resulting evolution model can then be tested against other observables, such as dilepton yields.

hep-ph↗

arXiv2001

Hadronic and Quark-Gluon Excitations of Dense and Hot Matter

We summarize recent developments in our understanding of low-mass quark-antiquark excitations in hadronic matter under various different conditions. This includes the thermodynamics of the chiral condensate, pions as Goldstone bosons in normal nuclear matter, and excursions into extreme territory of the QCD phase diagram: lepton pair production from a fireball expanding through the transition boundary between the quark-gluon and hadron pha ses of QCD.

hep-ph↗

arXiv2001

Model for dilepton rates from a fireball

We calculate the dilepton emission rate from a fireball created in an ultra-relativistic heavy-ion collision. For the partonic phase, we complement the perturbative results by a phenomenological approach based on lattice QCD results, whereas in the hadronic phase temperature and finite baryon density effects on the spectral function are considered. The resulting rates are compared to data from CERES/NA45.

hep-ph↗

arXiv2000

Coherence Effects in Diffractive Electroproduction of rho Mesons from Nuclei

A systematic multiple scattering formalism for vector meson electroproduction from nuclei is developed, with emphasis on the formation, propagation and hadronization scales for quark-gluon fluctuations of the virtual high-energy photon. The theory is compared to HERMES measurements of rho electroproduction on 14N. The nuclear transparency as a function of the vector meson propagation length is well reproduced.

hep-ph↗