Observation of events with a large rapidity gap in deep inelastic scattering at HERA

Abstract In deep inelastic, neutral currentscattering of electrons and protons at s =296 GeV , we observe in the ZEUS detector events with a large rapidity gap in the hadronic final state. They occur in the region of small Bjorken x and are observed up to Q 2 of 100 GeV 2 . They account for about 5% of the events with Q 2 ⩾10 GeV 2 . Their general propertiesare inconsistent with the dominant mechanism of deep inelastic scattering, where color is transferred between the scattered quark and the proton remnant, and suggest that the underlying production mechanism is the diffractive dissociation of the virtual photon.