J/\Psi production, $\chi$ polarization and Color Fluctuations

Abstract

The hard contributions to the heavy quarkonium-nucleon cross sections are calculated based on the QCD factorization theorem and the nonrelativistic quarkonium model. We evaluate the nonperturbative part of these cross sections which dominates at $\sqrt{s_{NN}}\approx 20$ GeV at the Cern Super Proton Synchrotron (SPS) and becomes a correction at $\sqrt{s_{NN}}\approx 6$ TeV at the CERN Large Hadron Collider (LHC). $\J$ production at the CERN SPS is well described by hard QCD, when the larger absorption cross sections of the $\chi$ states predicted by QCD are taken into account. We predict an $A$-dependent polarization of the $\chi$ states. The expansion of small wave packets is discussed.