Evidence for color fluctuations in the nucleon in high-energy scattering

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 e-p scattering. A simple dynamical model explains the HERA data and predicts the x- and Q^2-dependence of the ratio. In p-p/pbar-p scattering, fluctuations enhance multiple hard processes (but cannot explain the Tevatron CDF data), and reduce gap survival in central exclusive diffraction.