Diffractive dijet production with a leading proton in ep collisions at HERA

The cross section of the diffractive process e⁺p → e⁺Xp is measured at a centre-of mass energies of 319 GeV, where the system X contains at least two jets and the leading final state proton p is detected in the H1 Very Forward Proton Spectrometer. The measurement is performed in photoproduction defined by photon virtualities Q² < 2 GeV² and in deep-inelastic scattering with 4 GeV² < Q² < 80 GeV². The results are compared to next-to-leading order QCD calculations based on diffractive parton distribution functions as extracted from measurements of inclusive cross sections in diffractive deep-inelastic scattering. A collinear QCD factorization theorem is tested against the measured cross sections and their ratios.