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Jorge Casalderrey-Solana

Publications and source records attributed to Jorge Casalderrey-Solana.

61 records · Page 4Linked to original sources
arXiv2008

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 jet quenching or transport parameter $\hat{q}$. For thermal partons, the saturation scale $Q^2_s$ is found to be proportional to the Debye screening mass $μ_D^2$. For hard probes, evolution at small $x=Q^2_s/6ET$ leads to jet energy dependence of $\hat{q}$. We study this dependence for both a conformal gauge theory in weak and strong coupling limit and for (pure gluon) QCD. The energy dependence can be used to extract the shear viscosity $η$ of the medium since $η$ can be related to the transport parameter for thermal partons in a transport description. We also derive upper bounds on the transport parameter for both energetic and thermal partons. The later leads to a lower bound on shear viscosity-to-entropy density ratio which is consistent with the conjectured lower bound $η/s\geq 1/4π$. We also discuss the implications on the study of jet quenching at the BNL Relativistic Heavy Ion Collider and the CERN Large Hadron Collider and the bulk properties of the dense matter.

hep-ph↗
arXiv2007

Introductory lectures on jet quenching in heavy ion collisions

Jet quenching has become an essential signal for the characterization of the medium formed in experiments of heavy-ion collisions. After a brief introduction to the field, we present the full derivation of the medium-induced gluon radiation spectrum, starting from the diagrammatical origin of the Wilson lines and the medium averages and including all intermediate steps. The application of this spectrum to actual phenomenological calculations is then presented, making comparisons with experimental data and indicating some improvements of the formalism to the future LHC program. The last part of the lectures reviews calculations based on the AdS/CFT correspondence on the medium parameters controlling the jet quenching phenomenon.

hep-ph↗
arXiv2007

Mach Cones in Quark Gluon Plasma

The experimental azimuthal dihadron distributions at RHIC show a double peak structure in the away side ($Δϕ= π\pm 1.2$ rad.) for intermediate $p_t$ particles. A variety of models have appeared trying to describe this modification. We will review most of them, with special emphasis in 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.

hep-ph↗
arXiv2007

Transverse Momentum Broadening of a Fast Quark in a $\N=4$ Yang Mills Plasma

We compute the momentum broadening of a heavy fundamental charge propagating through a $\mathcal{N}=4$ Yang Mills plasma at large t' Hooft coupling. We do this by expressing the medium modification of the probe's 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 $κ_T = \sqrt{γλ} T^3 π$ -- 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 $\hat{q}$.

hep-th↗
arXiv2006

Heavy Quark Diffusion in Strongly Coupled $\N=4$ Yang Mills

We express the heavy quark diffusion coefficient as the temporal variation of a Wilson line along the Schwinger-Keldysh contour. This generalizes the classical formula for diffusion as a force-force correlator to a non-abelian theory. We use this formula to compute the diffusion coefficient in strongly coupled $\N=4$ Yang-Mills by studying the fluctuations of a string in $AdS_5\times S_5$. The string solution spans the full Kruskal plane and gives access to contour correlations. The diffusion coefficient is $D=2/\sqrtλ πT$ and is therefore parametrically smaller than momentum diffusion, $η/(e+p)=1/4πT$. The quark mass must be much greater than $T\sqrtλ$ in order to treat the quark as a heavy quasi-particle. The result is discussed in the context of the RHIC experiments.

hep-ph↗
arXiv2004

Can Binary Bound States in a Strongly Coupled Quark-Gluon Plasma be observed via dileptons and photons?

Recently there was a significant change of views on physical properties and underlying dynamics of Quark-Gluon Plasma at $T=170-350 MeV$, produced in heavy ion collisions at RHIC. Instead of weakly coupled gas of quasiparticles, it is rather a liquid-like matter with multiple bound states. In this paper we discuss how one can test these ideas experimentally, using the ``penetrating probes'' and looking for certain peaks at some invariant masses. In dileptons the most promising are modified $ρ,ω$, with $M(T\approx T_c)\sim .5 GeV$ and also near zero binding at $M(T\approx (1.5-2)T_c)=1.5-2 GeV$. We also discuss the observability of peaks corresponding to scalar/pseudoscalar mesons in the two-photon channel.

hep-ph↗