Quarkonium Production and Proposal of the New Experiments on Fixed Target at the LHC

The brief review of the experimental data on quarkonium productions measured at the CERN SPS, at the Brookhaven Collider RHIC, and at the LHC is presented. The dissociation of quarkonium resonances produced in heavy ion collisions was suggested as a possible signal of the Quark-Gluon Plasma formation. At the CERN SPS, the anomalous suppression of theJ/ψproduction was observed in central Pb-Pb collisions by the NA50 collaboration. However, the effects ofJ/ψsuppression on cold nuclear matter, feed-down production from higher charmonium states, and regeneration processes should be taken into account. If proton and ion beams at the LHC will be used with fixed targets, the energy interval between the SPS energy and the nominal RHIC energy (200 GeV) could be investigated. The high statistics data on quarkonium productions at these energies will give the possibility of clarifying the mechanism of charmonium productions to investigate the importance of the recombination process, since the probability of recombination decreases with decreasing the energy of collisions.

J/ψ AZIMUTHAL DISTRIBUTION RELATIVE TO THE REACTION PLANE IN Pb-Pb COLLISIONS AT 158 GeV/NUCLEON

J/ψ azimuthal distribution relative to the reaction plane has been studied Pb - Pb collisions at 158 A GeV /c. Different [Formula: see text] absorption mechanisms are expected to induce J/ψ azimuthal anisotropy at this energy. The present analysis has been performed on the data sample of 100 000 J/ψ's collected in year 2000 by the NA50 Collaboration. The reaction plane is estimated from the azimuthal distribution of the neutral transverse energy measured by the electromagnetic calorimeter. The numbers of J/ψ's in different bins of azimuthal angle relative to the reaction plane as well as the Fourier coefficients [Formula: see text] and [Formula: see text] (uncorrected for event plane resolution) are presented in this paper.