J/\psi Suppression in Pb+Pb Collisions: A New Look at Hadrons vs. Plasma

A reexamination of hadronic comover scattering indicates that this mechanism cannot explain the observed $\psi$ suppression in Pb+Pb interactions. The possibility of quark-gluon plasma formation is therefore considered.Comment: Calculations redone, figures updated, conclusions unchanged, to be published in Phys. Lett. B. 13 pages, LaTeX, uses epsf style, 4 figure

Some Field Theoretic Issues Regarding the Chiral Magnetic Effect

In this paper, we shall address some field theoretic issues regarding the chiral magnetic effect. The general structure of the magnetic current consistent with the electromagnetic gauge invariance is obtained and the impact of the infrared divergence is examined. Some subtleties on the relation between the chiral magnetic effect and the axial anomaly are clarified through a careful examination of the infrared limit of the relevant thermal diagrams.Comment: 19 pages, 4 figures in Latex. Typos fixed, version accepted to be published in JHE

Absorption and J/psi Suppression in Heavy Ion Collisions

We discuss the J/psi suppression in the framework of multiple collision models. From the analysis of the Pb-Pb NA50 data we conclude that the strength of the absorption has increased, but we find no clear evidence for the formation of the quark-gluon plasma.Comment: 8 pages, 4 figure

Percolation of color sources and critical temperature

We argue that clustering of color sources, leading to the percolation transition, may be the way to achieve deconfinement in heavy ion collisions. The critical density for percolation is related to the effective critical temperature of the thermal bath asociated to the presence of strong color fields inside the percolating cluster. We find that the temperature is rapidity, centrality and energy dependent. We emphasize the similarities of percolation of strings with color glass condensate.Comment: LaTeX, 9 page

Chiral Heat Wave and mixing of Magnetic, Vortical and Heat waves in chiral media

We show that a hot rotating fluid of relativistic chiral fermions possesses a new gapless collective mode associated with coherent propagation of energy density and chiral density waves along the axis of rotation. This mode, which we call the Chiral Heat Wave, emerges due to a mixed gauge-gravitational anomaly. At finite density the Chiral Heat Wave couples to the Chiral Vortical Wave while in the presence of an external magnetic field it mixes with the Chiral Magnetic Wave. The coupling of the Chiral Magnetic and Chiral Vortical Waves is also demonstrated. We find that the coupled waves - which are coherent fluctuations of the vector, axial and energy currents - have generally different velocities compared to the velocities of the individual waves.Comment: 33 pages, 6 figures; v2: minor changes, published versio

Quantum black holes and thermalization in relativistic heavy ion collisions

A new thermalization scenario for heavy ion collisions is discussed. It is based on the Hawking--Unruh effect: an observer moving with an acceleration $a$ experiences the influence of a thermal bath with an effective temperature $T = a / 2\pi$, similar to the one present in the vicinity of a black hole horizon. In the case of heavy ion collisions, the acceleration is caused by a pulse of chromo--electric field $E \sim Q_s^2/g$ ($Q_s$ is the saturation scale, and $g$ is the strong coupling), the typical acceleration is $a \sim Q_s$, and the heat bath temperature is $T \simeq Q_s / 2\pi \sim 200$ MeV. In nuclear collisions at sufficiently high energies the effect can induce a rapid thermalization over the time period of $\tau \sim \pi/Q_s$ accompanied by phase transitions. A specific example of chiral symmetry restoration induced by the chromo--electric field is considered; it is mathematically analogous to the phase transition occurring in the vicinity of a black hole.Comment: 10 pages, 2 figures, based on invited talks given at the "Quark Matter 2005" Conference, Budapest, Hungary, 4-9 August 2005, and Workshop on "Quark-Gluon Plasma Thermalization", Vienna, Austria, 10-12 August 200

Observations on dA scattering at forward rapidities

We point out that the suppression in the ratio R_dAu recently observed by the BRAHMS collaboration in forward scattering is stronger than usually appreciated. This is related to the fact that at forward rapidities BRAHMS measures negatively charged hadrons and that R_dAu is defined from the ratio of dA and pp scattering cross sections. We also investigate the influence of standard shadowing on R_dAu, and the typical values of partonic momentum fractions relevant in forward scattering. We find that x_Au > 0.02 dominate in the cross section.Comment: 19 pages, LaTeX, 10 figures as eps files, minor addition, version to appear in Phys.Lett.

Has saturation physics been observed in deuteron-gold collisions at RHIC?

In the framework of the recently proposed saturation picture, we examine in a systematic way whether the nuclear modification factor measured for d-Au collisions at RHIC may be simply explained. The Cronin peak which is obtained at mid-rapidity around $k_{\bot}\simeq 3$ GeV may be reproduced at the proper height only by boosting the saturation momentum by an additional nuclear component as already shown in the literature. In this respect, mid-rapidity RHIC data cannot necessarily be seen as a probe of the saturation picture. The large rapidity ($\eta\simeq 3$) region allows us to test the shape of the unintegrated gluon distribution in the nucleus, investigating various parameterizations inspired by large rapidity solutions (of the BFKL and) of the Balitsky-Kovchegov (BK) equation. A satisfactory description of $R_{CP}$ at RHIC is obtained in the BK picture.Comment: 13 pages, 5 figure

Color Glass Condensate at the LHC: hadron multiplicities in pppp, pApA and AAAA collisions

We make quantitative predictions for the rapidity and centrality dependencies of hadron multiplicities in $AA$, $pA$ and $pp$ collisions at the LHC energies basing on the ideas of parton saturation in the Color Glass Condensate.Comment: 26 pages, 8 figure

Generalized scaling of the transverse mass spectrum at the Relativistic Heavy-Ion Collider

We argue that the transverse mass spectra of identified hadrons as measured in gold-gold collisions at BNL's Relativistic Heavy-Ion Collider (RHIC) follows a generalized scaling law. Such a scaling behavior is motivated by the idea of a Color Glass Condensate, or more generally, saturation of the gluon density. In particular, we describe the shapes of transverse mass spectra as a function of centrality. This scaling of the transverse mass spectrum is shown to be consistent with previously observed scaling of multiplicity with centrality.Comment: 15 pages, 6 figures, refs. updated, version to appear in Nucl. Phys.