Heavy-ion collisions at the Large Hadron Collider: a review of the results from Run 1

We present an overview of the results obtained in pPb and PbPb collisions at the Large Hadron Collider during Run 1. We first discuss the results for global characteristics: cross sections, hadron multiplicities, azimuthal asymmetries, correlations at low transverse momentum, hadrochemistry, and femtoscopy. We then review hard and electromagnetic probes: particles with high transverse momentum, jets, heavy quarks, quarkonium, electroweak bosons and high transverse momentum photons, low transverse momentum photons and dileptons, and ultraperipheral collisions. We mainly focus on the experimental results, and present very briefly the main current theoretical explanations.Comment: 33 pages, 29 figure

On correlations and discreteness in non-linear QCD evolution

We consider modifications of the standard non-linear QCD evolution in an attempt to account for some of the missing ingredients discussed recently, such as correlations, discreteness in gluon emission and Pomeron loops. The evolution is numerically performed using the Balitsky-Kovchegov equation on individual configurations defined by a given initial value of the saturation scale, for reduced rapidities $y=(\alpha_s N_c/\pi) Y<10$. We consider the effects of averaging over configurations as a way to implement correlations, using three types of Gaussian averaging around a mean saturation scale. Further, we heuristically mimic discreteness in gluon emission by considering a modified evolution in which the tails of the gluon distributions are cut-off. The approach to scaling and the behavior of the saturation scale with rapidity in these modified evolutions are studied and compared with the standard mean-field results. For the large but finite values of rapidity explored, no strong quantitative difference in scaling for transverse momenta around the saturation scale is observed. At larger transverse momenta, the influence of the modifications in the evolution seems most noticeable in the first steps of the evolution. No influence on the rapidity behavior of the saturation scale due to the averaging procedure is found. In the cut-off evolution the rapidity evolution of the saturation scale is slowed down and strongly depends on the value of the cut-off. Our results stress the need to go beyond simple modifications of evolution by developing proper theoretical tools that implement such recently discussed ingredients.Comment: 20 pages, LaTeX, 18 eps figures included using epsfig; changes in v3: new kind of averaging added, 5 new plots, discussions and conclusions extended, final versio

High-enegy effective action from scattering of QCD shock waves

At high energies, the relevant degrees of freedom are Wilson lines - infinite gauge links ordered along straight lines collinear to the velocities of colliding particles. The effective action for these Wilson lines is determined by the scattering of QCD shock waves. I develop the symmetric expansion of the effective action in powers of strength of one of the shock waves and calculate the leading term of the series. The corresponding first-order effective action, symmetric with respect to projectile and target, includes both up and down fan diagrams and pomeron loops.Comment: 15 pages, 10 eps figure

J/psi suppression at SPS and RHIC in the comovers approach

The NA50 collaboration data on the $J/\psi$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/\psi$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.Comment: 4 pages, contribution to QM200

Ultrahigh energy neutrinos and non-linear QCD dynamics

The ultrahigh energy neutrino-nucleon cross sections are computed taking into account different phenomenological implementations of the non-linear QCD dynamic s. Based on the color dipole framework, the results for the saturation model supplemented by DGLAP evolution as well as for the BFKL formalism in the geometric scaling regime are presented. They are contrasted with recent calculations using NLO DGLAP and unified BFKL-DGLAP formalisms.Comment: 5 pages, 2 figures. Version to be published in Physical Review

First correction to JIMWLK evolution from the classical equations of motion

We calculate some ${\cal O}(\alpha_s^2)$ corrections to the JIMWLK kernel in the framework of the light-cone wave function approach to the high energy limit of QCD. The contributions that we consider originate from higher order corrections in the strong coupling and in the density of the projectile to the solution of the classical Yang-Mills equations of motion that determine the Weizs\"acker-Williams fields of the projectile. We study the structure of these corrections in the dipole limit, showing that they are subleading in the limit of large number of colours $N$, and that they cannot be fully recast in the form of dipole degrees of freedom.Comment: 4 pages, LaTeX, 2 eps figures included using graphicx, uses enclosed iopart.cls; contribution to the proceedings of Quark Matter 2006 (Shanghai, November 14th-20th 2006

Treading on the cut: Semi inclusive observables at high energy

We develop the formalizm for calculating semi inclusive observables at high energy in the JIMWLK/KLWMIJ approach. We consider several examples including diffractive processes, elastic and inclusive over the target degrees of freedom, scattering with fixed total transverse momentum transfer and inclusive gluon production. We discuss evolution of these observables with respect to various rapidity variables involved in their definitions (total rapidity, rapidity gap, width of diffractive interval etc.). We also discuss the dipole model limit of these observables and derive closed simple (as opposed to functional) differential equations in this approximation. We point out that there are some interesting differences between the full JIMWLK/KLWMIJ evolution and the dipole model evolution of diffractive cross section. In particular we show that in the dipole approximation the target does not diffract beyond the valence rapidity interval, consistently with the intuition suggested by the Pomeron fan diagramms. On the other hand such diffractive processes do exist in the full JIMWLK/KLWMIJ approach, albeit suppressed by the factor 1/N_c^2.Comment: 37 pages, 3 figures. A few remarks added. To appear in PR