Jorge Casalderrey-Solana

Transverse momentum broadening of a fast quark in a Script N = 4 Yang-Mills plasma

We compute the momentum broadening of a heavy fundamental charge propagating through a = 4 Yang Mills plasma at large t Hooft coupling. We do this by expressing the medium modification of the probes density matrix in terms of a Wilson loop averaged over the plasma. We then use the AdS/CFT correspondence to evaluate this loop, by identifying the dual semi-classical string solution. The calculation introduces the type ``1 and type ``2 fields of the thermal field theory and associates the corresponding sources with the two boundaries of the AdS space containing a black hole. The transverse fluctuations of the endpoints of the string determine κT = (γλ)1/2T3π—the mean squared momentum transfer per unit time. (γ is the Lorentz gamma factor of the quark.) The result reproduces previous results for the diffusion coefficient of a heavy quark. We compare our results with previous AdS/CFT calculations of .

Energy dependence of jet transport parameter and parton saturation in quark-gluon plasma

We study the evolution and saturation of the gluon distribution function in the quark–gluon plasma as probed by a propagating parton and its effect on the computation of the jet quenching or transport parameter . For hard probes, evolution at small x = Q2s/6ET leads to a jet energy dependence of . Implications on the study of jet quenching at RHIC and LHC are discussed.

Prediction of a photon peak in relativistic heavy ion collisions.

We show that if a flavorless vector meson remains bound after deconfinement, and if its limiting velocity in the quark-gluon plasma is subluminal, then this meson produces a distinct peak in the spectrum of thermal photons emitted by the plasma. We also demonstrate that this effect is a universal property of all strongly coupled, large-N_{c} plasmas with a gravity dual. For the J/psi, the corresponding peak lies between 3 and 5 GeV and could be observed in heavy-ion collisions at the LHC.

Mach cones in quark gluon plasma

The experimental azimuthal dihadron distributions at RHIC show a double peak structure in the away side (? = ? ? 1.2 rad) for intermediate pt particles. A variety of models have appeared trying to describe this modification. We will review most of them, with special emphasis on the conical flow scenario in which the observed shape is a consequence of the emission of sound by a supersonic high momentum particle propagating in the quark gluon plasma.

Gauge/String Duality, Hot QCD and Heavy Ion Collisions: A heavy ion phenomenology primer

Over the last decade, both experimental and theoretical advances have brought the need for strong coupling techniques in the analysis of deconfined QCD matter and heavy ion collisions to the forefront. As a consequence, a fruitful interplay has developed between analyses of strongly-coupled non-abelian plasmas via the gauge/string duality (also referred to as the AdS/CFT correspondence) and the phenomenology of heavy ion collisions. We review some of the main insights gained from this interplay to date. To establish a common language, we start with an introduction to heavy ion phenomenology and finite-temperature QCD, and a corresponding introduction to important concepts and techniques in the gauge/string duality. These introductory sections are written for nonspecialists, with the goal of bringing readers ranging from beginning graduate students to experienced practitioners of either QCD or gauge/string duality to the point that they understand enough about both fields that they can then appreciate their interplay in all appropriate contexts. We then review the current state-of-the art in the application of the duality to the description of the dynamics of strongly coupled plasmas, with emphases that include: its thermodynamic, hydrodynamic and transport properties; the way it both modifies the dynamics of, and is perturbed by, highenergy or heavy quarks passing through it; and the physics of quarkonium mesons within it. We seek throughout to stress the lessons that can be extracted from these computations for heavy ion physics as well as to discuss future directions and open problems for the field. ar X iv :1 10 1. 06 18 v2 [ he pth ] 8 A ug 2 01 2

Results from lattice QCD at nonzero temperature

At very high temperature, where the QCD coupling constant g(T) is perturbatively small, hard thermal loop resummed perturbation theory provides a quantitatively controlled approach to QCD thermodynamics. However, in a wide temperature range around the QCD phase transition which encompasses the experimentally accessible regime, perturbative techniques become unreliable. Nonperturbative lattice-regularized calculations provide the only known, quantitatively reliable, technique for the determination of thermodynamic properties of QCD matter within this regime. We shall not review the techniques by which lattice-regularized calculations are implemented. We merely recall that the starting point of lattice-regularized calculations at nonzero temperature is the imaginary time formalism, which allows one to write the QCD partition function in Euclidean spacetime with a periodic imaginary time direction of length 1/ T [541]. Any thermodynamic quantity can be obtained via suitable differentiation of the partition function. At zero baryon chemical potential, the QCD partition function is given by the exponent of a real action, integrated over all field configurations in the Euclidean spacetime. Since the action is real, the QCD partition function can then be evaluated using standard Monte Carlo techniques, which require the discretization of the field configurations and the evaluation of the action on a finite lattice of spacetime points.