Proton-nucleus scattering and cross section fluctuations at RHIC and LHC

We consider high-energy proton-heavy nucleus scattering within the framework of the Glauber-Gribov approximation and taking into account cross section fluctuations. Fixing parameters of the model for cross section fluctuations by the available data, we make predictions for the total, elastic and coherent diffractive dissociation proton-nucleus cross sections for the RHIC and LHC energy range. We predict a strong change of the A-dependence of diffraction dissociation from A^{0.42} at RHIC energies to A^{0.27} at LHC energies. Based on the obtained results, we discuss the approach of the interactions to the black body (unitarity) limit. We estimate the electromagnetic contribution to coherent pA diffraction and find that it dominates the coherent diffractive cross section on heavy nuclear targets in the RHIC and LHC kinematics.