Jet Quenching: the medium modification of the single and double fragmentation functions

The physics of the quenching of hard jets in dense matter is briefly reviewed. This is presented within the framework of the partonic medium modification of the fragmentation functions. Modifications in both deeply inelastic scattering (DIS) off large nuclei and high-energy heavy-ion collisions are presented.Comment: 4 pages, 4 figures, Proceedings of the First Meeting of the APS Topical Group on Hadronic Physics, Fermilab, Batavia, Illinois, Oct 24-26, 200

Hadron-hadron correlations at low and high pTp_T in heavy-ion collisions

The modification of two particle correlations within a jet due to its propagation through dense strongly interacting matter is explored. Different properties of the medium may be probed by varying the momentum of the detected hadrons. Very high transverse momentum ($p_T$) correlations sample the gluon density of the medium; the minimal modification on the same side as the trigger is consistent with the picture and parameters of partonic energy loss. Lower momentum hadrons, sensitive to the presence of composite structures in the medium may excite collective modes such as Cherenkov radiation, resulting in conical patterns in the detected correlations.Comment: 4 pages, 4 figures, Latex. To appear in the proceedings of the International Conference on Strong & Electroweak Matter 2006, Brookhaven National Laboratory, May 10-13, 200

Equilibrium in Heavy Ion Collisions

We discuss the question of equilibriation in heavy ion collisions and how it can be addressed in experimentComment: Proceedings 19th Winter Workshop on Nuclear Dynamics, Breckenridge, Co, 200

Suppression of the high pTp_T charged hadron RAAR_{AA} at the LHC

We present a parameter free postdiction of the high-$p_T$ charged-hadron nuclear modification factor ($R_{AA}$) in two centralities, measured by the CMS collaboration in $Pb$-$Pb$ collisions at the Large Hadron Collider (LHC). The evolution of the bulk medium is modeled using viscous fluid dynamics, with parameters adjusted to describe the soft hadron yields and elliptic flow. Assuming the dominance of radiative energy loss, we compute the medium modification of the $R_{AA}$ using a perturbative QCD based formalism, the higher twist scheme. The transverse momentum diffusion coefficient $\hat{q}$ is assumed to scale with the entropy density and normalized by fitting the $R_{AA}$ in the most central $Au$-$Au$ collisions at the Relativistic Heavy-Ion Collider (RHIC). This set up is validated in non-central $Au$-$Au$ collisions at RHIC and then extrapolated to $Pb$-$Pb$ collisions at the LHC, keeping the relation between $\hat{q}$ and entropy density unchanged. We obtain a satisfactory description of the CMS $R_{AA}$ over the $p_{T}$ range from 10-100 GeV.Comment: 4 pages, 3 figures, revtex4, new experimental data used, new calculations with systematic error bands, changed abstract and contents, conclusions unchange

Deciphering Deconfinement in Correlations of Conserved Charges

Diagonal and off-diagonal flavor and conserved charge susceptibilities reveal the prevalent degrees of freedom of heated strongly interacting matter. Results obtained from lattice simulations are compared with various model estimates in an effort to weed down various possible pictures of a quark gluon plasma. We argue that the vanishing of the off-diagonal quark flavor susceptibilities and its derivatives with respect to chemical potential, at temperatures above 1.5Tc, can only be understood in a picture of a gas or liquid composed of quasi-particles which carry the same quantum numbers as quarks and antiquarks. A potential new observable, blind to neutral and non-strange particles, is introduced and related via isospin symmetry to the ratio of susceptibilities of baryonic strangeness to strangeness generated in the excited matter created at RHIC.Comment: 5 pages, 3 figures, LATEX, To appear in the proceedings of the International Conference on Strangeness in Quark Matter, Los Angeles, CA, Mar 26-31, 200