J/ψ\psi suppression at s=\sqrt{{\bf s}} = 200 GeV in the comovers interaction model

The yield of $J/\psi$ per binary nucleon-nucleon collision in $AuAu$ and $CuCu$ collisions at $\sqrt{s} = 200$ GeV is computed in the framework of the dual parton model, supplemented with final state interaction (comovers interaction). For the latter we use the same value of the cross-section, $\sigma_{co} = 0.65$ mb, which describes the anomalous $J/\psi$ suppression observed at CERN-SPS energies. Several possibilities for the value of the absorptive cross-section are considered. Shadowing is introduced in both the comovers and the $J/\psi$ yields. A comparison with the results at CERN-SPS, including a prediction for $InIn$ collisions, is also presented.Comment: 15 pages, 3 figure

Large transverse momentum suppression at RHIC: Shadowing and absorption

We propose a model of suppression of $\pi^0$'s based on two different effects: at low $p_T$ we take into account the shadowing corrections, which are non-linear and essential for the description of the inclusive spectra, while at large $p_T$ the suppression is produced through the interaction of the large $p_T$ pion with the dense medium created in the collision. The main features of the data on $AuAu$ and $dAu$ collisions at RHIC energies are reproduced both at mid and at forward rapidities.Comment: 6 pages, 2 figures. Contribution to the 8th Workshop on Non-Perturbative Quantum Chromodynamics, June 7-11, 2004, l'Institut Astrophysique de Paris, Franc

Baryon stopping and hyperon enhancement in the improved dual parton model

We present an improved version of the dual parton model which contains a new realization of the diquark breaking mechanism of baryon stopping. We reproduce in this way the net baryon yield in nuclear collisions. The model, which also considers strings originating from diquark-antidiquark pairs in the nucleon sea, reproduces the observed yields of p and Lambda and their antiparticles and underestimates cascades by less than 50 %. However, Omega's are underestimated by a factor five. Agreement with data is restored by final state interaction, with an averaged cross-section as small as 0.14 mb. Hyperon yields increase significantly faster than antihyperons, in agreement with experiment.Comment: 40 pages, 18 postscript figure

Elliptic Flow and Fixed p_T Suppression in a Final State Interaction Model

It has been shown that a final state interaction model, used to describe J/psi suppression, can also describe the fixed p_T suppression of the pi^0 (and charged pions) yield at all values of p_T, with a final state interaction cross-section sigma close to one milibarn. We propose an extension of the model to the pion motion in the transverse plane - which introduces a dependence of the suppression on the azimuthal angle theta_R. Using the same value of sigma, we obtain values of the elliptic flow v_2 close to the experimental ones, for all values of p_T, including the soft p_T region.Comment: 21 pages, 6 figure

Anomalous suppression of π0\pi^0 production at large transverse momentum in Au + Au and d + Au collisions at sNN=\sqrt{{\bf s}_{\bf NN}} = 200 GeV

We propose a model of suppression of large $p_T$-pions in heavy ion collisions based on the interaction of the large $p_T$ pion with the dense medium created in the collision. The model is practically the same as the one previously introduced to describe $J/\psi$ suppression. Both the $p_T$ and the centrality dependence of the data are reproduced. In deuteron-gold collisions, the effect of the final state interaction with the dense medium turns out to be negligibly small. Here the main features of the data are also reproduced both at mid and at forward rapidities.Comment: 20 pages, latex, 3 postscript figures. Last version, to be published in EJP