Color strings, pomeron shadowing and Color Glass Condensate

I review the problem of parton saturation and its implications through three in principal different approaches, but somewhat related: saturation in a geometrical approach, QCD saturation through the Color Glass Condensate and shadowing in a Pomeron approach.Comment: 8 pages, 3 figures, Fifth International Conference on Perspectives in Hadronic Physics 22-26 May 2006 Trieste, Ital

Aspects of the unitarized soft multipomeron approach in DIS and diffraction

We studyin detail the main features of the unitarized Regge model (CFKS), recentlyprop osed to describe the small-Q2 domain. It takes into account a two-component description with two types of unitarized contributions: one is the multiple pomeron exchange contribution, interacting with the large dipole size configurations, and the other one consists of a unitarized dipole cross section, describing the interaction with the small size dipoles. We analyze the ratio between soft and hard pieces as a function of the virtuality, and also compare the resulting dipole cross section to that from the saturation model. Diffraction dissociation is also considered, showing the scaling violations in diffractive DIS and estimating the corresponding logarithmic slope

Quarkonium as a tool: cold nuclear matter effects

We discuss the quarkonium production as a tool for the study of the Quark Gluon Plasma. In particular, we concentrate on the Cold Nuclear Matter effetcs. We show that quarkonium production is also useful for the study of Quantum Chromodynamics first principles and the nuclear Parton Distribution Functions.Comment: Contribution to the proceedings of QUARKONIUM 2010: Three Days Of Quarkonium Production in pp and pA Collisions, 29-31 July 2010, Palaiseau, France. 4 pages, 4 figure

On the jet spectrum in nucleus-nucleus interactions

We derive the inclusive transverse spectrum of minijets in nuclear collisions at very high energies by assuming that the nuclear S-matrix factorizes into a product of elastic S-matrices for elementary partonic collisions. Interference effects and, in particular, the contribution of loop diagrams are fully taken into account in the derivation of the spectrum, which is shown to coincide with the result earlier obtained by superposing the elementary interactions incoherently. A quantitative analysis confirms that the deformation induced by multiple collsions is a large effect at RHIC and LHC energies, for transverse momenta ~ 20 GeV.Comment: text in LaTex, 4 figures in P

Centrality, rapidity, and transverse-momentum dependence of gluon shadowing and antishadowing on J/ψJ/\psi production in ddAu collisions at s\sqrt{s}=200 GeV

We have carried out a wide study of shadowing and antishadowing effects on \jpsi\ production in \dAu\ collisions at $\sqrt{s_{NN}}=200$ GeV. We have studied the effects of three different gluon nPDF sets, using the exact kinematics for a $2\to 2$ process, namely $g+g\to J/\psi+g$ as expected from LO pQCD. We have computed the rapidity dependence of \RCP\ and $R_{d\rm Au}$ for the different centrality classes of the PHENIX data. For mid rapidities, we have also computed the transverse-momentum dependence of the nuclear modification factor, which cannot be predicted with the usual $2\to 1$ simplified kinematics. All these observables have been compared to the PHENIX data in \dAu\ collisions.Comment: 10 pages, 11 figures, talk given by N. Matagne at the conference "thirty years of hadronic physics", Spa, Belgium, April 6-8, 2011, to appear in Few Body System

Universal behavior of baryons and mesons' transverse momentum distributions in the framework of percolation of strings

In the framework of percolation of strings, we present predictions for the $R_{AA}$ and $R_{CP}$ for mesons and baryons and for $\bar{p}/\pi^{0}$ ratios at LHC energies.Comment: Presented at "Heavy Ion Collisions at the LHC: last call for predictions", Geneva Switzerland, May 14th-June 8t

Cold nuclear matter effects on J/psi production: intrinsic and extrinsic transverse momentum effects

Cold nuclear matter effects on J/psi production in proton-nucleus and nucleus-nucleus collisions are evaluated taking into account the specific J/psi production kinematics at the partonic level, the shadowing of the initial parton distributions and the absorption in the nuclear matter. We consider two different parton processes for the c-cbar pair production: one with collinear gluons and a recoiling gluon in the final state and the other with initial gluons carrying intrinsic transverse momentum. Our results are compared to RHIC observables. The smaller values of the nuclear modification factor R_AA in the forward rapidity region (with respect to the mid rapidity region) are partially explained, therefore potentially reducing the need for recombination effects.Comment: 7 pages, 11 figures, LaTeX, uses elsarticle.cls (included).v2: version (with minor text revisions and Fig 2 and 4a modified) to appear in Phys.Lett.

Baryon and Antibaryon Production in Hadronic and Nuclear Interactions

We introduce a new formulation of the diquark breaking mechanism which describes with no free parameters the huge nuclear stopping observed in central nucleus-nucleus collisions. Supplemented, in the dual parton model, with strings originating from diquark--antidiquark pairs from the nucleon sea, it gives a substantial increase of hyperon and antihyperon yields from $pPb$ to central $PbPb$ collisions. Compared to data, this increase is slightly underestimated for $\Lambda$'s and $\Xi$'s but is five times too small for $\Omega$'s. Introducing final state interactions, a reasonable description of all baryon and antibaryon yields is achieved.Comment: 17 pages, 4 postscript figure

Heavy-ion Physics at a Fixed-Target Experiment Using the LHC Proton and Lead Beams (AFTER@LHC): Feasibility Studies for Quarkonium and Drell-Yan Production

We outline the case for heavy-ion-physics studies using the multi-TeV lead LHC beams in the fixed-target mode. After a brief contextual reminder, we detail the possible contributions of AFTER@LHC to heavy-ion physics with a specific emphasis on quarkonia. We then present performance simulations for a selection of observables. These show that $\varUpsilon (nS)$ , $J/\psi$ and $\psi (2S)$ production in heavy-ion collisions can be studied in new energy and rapidity domains with the LHCb and ALICE detectors. We also discuss the relevance to analyse the Drell–Yan pair production in asymmetric nucleus–nucleus collisions to study the factorisation of the nuclear modification of partonic densities and of further quarkonium states to restore their status of golden probes of the quark–gluon plasma formation.Peer Reviewe

Schwinger Model and String Percolation in Hadron-Hadron and Heavy Ion Collisions

In the framework of the Schwinger Model for percolating strings we establish a general relation between multiplicity and transverse momentum square distributions in hadron-hadron and heavy ion collisions. Some of our results agree with the Colour Glass Condensate model.Comment: 7 pages, 1 figur