Abstract: We study quantum fluctuations of the nucleon's parton densities by combining QCD factorization for hard processes with the notion of cross section fluctuations in soft diffraction. The fluctuations of the small-x gluon density are related to the ratio of inelastic and elastic vector meson production in ep scattering. A simple dynamical model explains the HERA data and predicts the x and Q(2) dependence of the ratio. In pp/(p) over barp scattering, fluctuations enhance multiple hard processes ( but cannot explain the Tevatron CDF data), and reduce gap survival in central exclusive diffraction.
