NLO QCD Fit to H 1 Diffractive DIS Data ∗

Measurements of the cross section σ(xIP , β,Q 2) for diffractive deep inelastic scattering (DIS) processes of the type ep → eXp by H1 at HERA have reached high precision [1]. Here, Q2 is the photon virtuality, xIP is the longitudinal momentum fraction of the diffractive exchange with respect to the proton and β = x/xIP is the exchange’s longitudinal momentum fraction of the quark which couples to the virtual photon. The recent H1 data are presented in terms of a reduced cross section σ r , integrated over t, the 4-momentum transfer squared at the proton vertex,