A geometrical estimation of saturation of partonic densities

Abstract

We propose a new criterium for saturation of the density of partons both in nucleons and nuclei. It is applicable to any multiple scattering model which would be used to compute the number of strings exchanged in $ep$ and $eA$ collisions. The criterium is based on percolation of strings, and the onset of percolation is estimated from expectations coming from the study of heavy ion collisions at high energies. We interpret this onset as an indication of saturation of the density of partons in the wave function of the hadron. In order to produce quantitative results, a particular model fitted to describe present HERA data and generalized to the nuclear case is used. Nevertheless, with the number of scatterings controlled by the relation between inclusive and diffractive processes, conclusions are weakly model-dependent as long as different models are tuned to describe the experimental data. This constitutes a new approach, based on the eikonal description of soft hadronic collisions, and different from others which employ either perturbative QCD ideas or semiclassical methods. It offers an alternative picture for saturation in the small $Q^2$ region.

LaTeX, 15 pages, 2 eps figures included using epsfig; final version, abstract and discussions enlarged, references added and updated, results unchanged; more references added

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Cited by in corpus (5)

• Nuclear shadowing
• Nuclear parton distribution functions and their uncertainties
• Nuclear Structure Functions at Small x from Inelastic Shadowing and Diffraction
• Hard probes in heavy ion collisions at the LHC: PDFs, shadowing and $pA$ collisions
• Gluon distributions in nuclei at small x: guidance from different models