CGC, QCD Saturation and RHIC data (Kharzeev-Levin-McLerran-Nardi point of view)

This is the talk given at the Workshop:"Focus on Multiplicitioes", Bari, Italy, 17-19 June,2004.. In this talk, we are going to discuss ion-ion and deuteron - nucleus RHIC data and show that they support, if not more, the idea of the new QCD phase: colour glass condensate with saturated parton density. .Comment: 26 pages with 33 figure

A Comment on Conical Flow Induced by Heavy-Quark Jets

The suppression of high transverse momentum particles, recently discovered at RHIC, is commonly interpreted as due to parton energy loss. In high energy nuclear collisions, QCD jets would deposit a large fraction of their energy and into the produced matter. The question of how this energy is degraded and whether we can use this phenomenon to probe the properties of the produced matter is now under active discussion. It has been proposed that if this matter, which is now being referred to as a {\em strongly coupled Quark-Gluon Plasma} (sQGP), may behave as a liquid with a very small viscosity. In this case, a very specific collective excitation should be produced, called the ``conical flow'', similar e.g. to the sonic booms generated by the shock waves produced by supersonic planes. The RHIC experiments seem indeed to be obtaining some indication that the production of particles emitted opposite to a high-$p_t$ jet may actually be peaked away from the quenched jet direction, at an angle roughly consistent with the direction expected in case a shock wave is produced (i.e. orthogonal to the Mach cone). In this note we speculate that for tagged heavy-quark jets one may observe a shrinkage of the Mach cone at moderate $p_t$. The experimental observation of such an effect would be a very good test for the validity of the whole picture currently emerging from the study of partonic matter in nuclear collisions

Centrality and sNNDependenceofthe\sqrt{s_{NN}} Dependence of the dE_{T}/d\etaand and dN_{ch}/d\eta$ in Heavy Ion Collisions at Mid-Rapidity

The PHENIX experiment at RHIC has measured transverse energy and charged particle multiplicity at mid-rapidity in Au + Au collisions at $\sqrt{s_{NN}}$ = 19.6, 130, 62.4 and 200 GeV as a function of centrality. The presented results are compared to measurements from other RHIC experiments, and experiments at lower energies. The $\sqrt{s_{NN}}$ dependence of $dE_{T}/d\eta$ and $dN_{ch}/d\eta$ per pair of participants is consistent with logarithmic scaling for the most central events. The centrality dependence of $dE_{T}/d\eta$ and $dN_{ch}/d\eta$ is similar at all measured incident energies. At RHIC energies the ratio of transverse energy per charged particle was found independent of centrality and growing slowly with $\sqrt{s_{NN}}$. A survey of comparisons between the data and available theoretical models is also presented.Comment: Proccedings of the Workshop: Focus on Multiplcity at Bari, Italy, June 17-19,2004. To be submitted to the Jornal of Physics, "Conference series". Includes: 20 Pages, 15 figures, 3 Tables, 80 Referencie

Heavy Flavor Probes of Quark Matter

A brief survey of the role of heavy flavors as a probe of the state of matter produced by high energy heavy ion collisions is presented. Specific examples include energy loss, initial state gluon saturation, thermalization and flow. The formation of quarkonium bound states from interactions in which multiple heavy quark-antiquark pairs are initially produced is examined in general. Results from statistical hadronization and kinetic models are summarized. New predictions from the kinetic model for J/Psi at RHIC are presented.Comment: Based on invited plenary talk at Strange Quark Matter 2004, Cape Town, South Africa, September 15-20, 2004, references completed, published in J. Phys. G: Nucl. Part. Phys. 31 (2005) S641-S64

Reconstructed Jets at RHIC

To precisely measure jets over a large background such as pile up in high luminosity p+p collisions at LHC, a new generation of jet reconstruction algorithms is developed. These algorithms are also applicable to reconstruct jets in the heavy ion environment where large event multiplicities are produced. Energy loss in the medium created in heavy ion collisions are already observed indirectly via inclusive hadron distributions and di-hadron correlations. Jets can be used to study this energy loss in detail with reduced biases. We review the latest results on jet-medium interactions as seen in A+A collisions at RHIC, focusing on the recent progress on jet reconstruction in heavy ion collisions.Comment: Proceedings for the 26th Winter Workshop on Nuclear Dynamic

Jet-like correlations of heavy-flavor particles - from RHIC to LHC

Measurements at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory have revealed strong modification of the jet structure in high-energy heavy-ion collisions, which can be attributed to the interaction of hard scattered partons with the hot and dense QCD matter. The study of heavy-quark (charm and bottom) production in such collisions provides key tests of parton energy-loss models and, thus, yields profound insight into the properties of the produced matter. The high-pT yield of heavy-flavor decay electrons exhibits an unexpected large suppression. Since those single electrons have contributions from charm and bottom decays an experimental method is needed to investigate them separately. Heavy-flavor particle correlations provide information about the underlying production mechanism. In this contribution, a review on recent measurements on azimuthal correlations of single electrons and open charmed mesons at RHIC and perspectives of such measurements at the CERN-Large Hadron Collider (LHC) are presented. Moreover, it has been shown that next-to-leading-order (NLO) QCD processes, such as gluon splitting, become important at LHC energies. It will be demonstrated how this contribution can be determined through the measurement of the charm content in jets.Comment: 8 pages, 6 figures, Proceedings of the 27th Winter Workshop on Nuclear Dynamics, Winter Park, Colorado, USA. To be published in Journal of Physics: Conference Series (JPCS

CGC, Hydrodynamics, and the Parton Energy Loss

Hadron spectra in Au+Au collisions at RHIC are calculated by hydrodynamics with initial conditions from the Color Glass Condensate (CGC). Minijet components with parton energy loss in medium are also taken into account by using parton density obtained from hydrodynamical simulations. We found that CGC provides a good initial condition for hydrodynamics in Au+Au collisions at RHIC.Comment: Quark Matter 2004 contribution, 4 pages, 2 figure

Evolution of shower parton distributions in a jet from quark recombination model

The evolution of shower parton distributions in a jet is investigated in the framework of quark recombination model. The distributions are parameterized and the $Q^2$ dependence of the parameters is given by polynomials of $\ln Q^2$ for a wide range of $Q^2$.Comment: 5 pages in RevTeX, 3 figures in ep

Particle production azimuthal asymmetries in a clustering of color sources model

The collective interactions of many partons in the first stage of the collisions is the usual accepted explanation of the sizable elliptical flow. The clustering of color sources provides a framework of partonic interactions. In this scheme, we show a reasonable agreement with RHIC data for pT<1.5 GeV/c in both the dependence of v2 transverse momentum and in the shape of the nuclear modified factor on the azimuthal angle for different centralities. We show the predictions at LHC energies for Pb-Pb. In the case of proton-proton collisions a sizable v2 is obtained at this energy.Comment: To appear in Journal of Physics

Evidence from Identified Particles for Active Quark and Gluon Degrees of Freedom

Measurements of intermediate pT (1.5 < pT < 5.0 GeV/c) identified particle distributions in heavy ion collisions at SPS and RHIC energies display striking dependencies on the number of constituent quarks in the corresponding hadron. One finds that elliptic flow at intermediate pT follows a constituent quark scaling law as predicted by models of hadron formation through coalescence. In addition, baryon production is also found to increase with event multiplicity much faster than meson production. The rate of increase is similar for all baryons, and seemingly independent of mass. This indicates that the number of constituent quarks determines the multiplicity dependence of identified hadron production at intermediate pT. We review these measurements and interpret the experimental findings.Comment: 8 pages, 5 figures, proceedings for SQM2006 conference in Los Angele