Inclusive diffraction in DIS – H1 Results

Results are presented of three analyses on the diffractive deep-inelastic scattering cross section measured by the H1 experiment at HERA. In the first analysis [1], the process ep →eXY is studied where Y is a proton or low mass proton excitation carrying a fraction 1- xIP> 0.95 of the incident proton longitudinal momentum and the squared four-momentum transfer at the proton vertex satisfies |t | < 1 GeV2. Events are selected based on the presence of a large rapidity gap between the two hadronic final state systems X and Y. The cross section is measured for photon virtualities in the range 3.5 ≤ Q2 ≤ 1600 GeV2, triple differentially in xIP, Q2 and β=x/xIP, where x is the Bjorken scaling variable. At low xIP, the data are consistent with a factorisable xIP dependence. In the second analysis [2], the process ep →eXp is measured by selecting events with a leading final state proton detected in the H1 Forward Proton Spectrometer. The cross section is measured also as a function of t; the β and Q2 dependences factorise from the t dependence within uncertainties. The ratio of the cross sections measured by these two analyses, and thus the MY dependence of the diffractive cross section, is seen to be independent of xIP, β and Q2 dependences within uncertainties. Diffractive parton distribution functions and their uncertainties are determined from a next-to-leading order DGLAP QCD analysis of the Q