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Abstract:
Nuclear shadowing and colour glass condensate need sufficiently small x to provide an overlap of parton clouds in the longitudinal direction. Another condition vital for these effects is overlap of partons in impact parameters, which is not easy to fulfil for gluons, even in heavy nuclei. This is because of smallness of gluonic spots related to the weakness of diffractive gluon radiation appearing in data. The predicted weak gluon shadowing and colour glass condensate effect are now appearing in data for J/Ψ production and Cronin effect in d–Au collisions at RHIC. Smallness of gluonic spots leads to a rather small value of α'P, the slope of the Pomeron trajectory, indeed appearing in elastic photoproduction of J/Ψ. At the same time, unitarity saturation in elastic pp collisions leads to a substantial increase of α'P in good agreement with data.
