FIRST MEASUREMENT OF THE DEEP-INELASTIC STRUCTURE OF PROTON DIFFRACTION

A measurement is presented, using data taken with the H1 detector at HERA, of the contribution of diffractive interactions to deep-inelastic electron-proton (ep) scattering in the kinematic range 8.5 < Q(2) < 50 GeV2, 2.4 x 10(-4) < Bjorken-x < 0.0133, and 3.7 x 10(-4) < xp < 0.043. The diffractive contribution to the proton structure function F-2(x, e2) is evaluated as a function of the appropriate deep-inelastic scattering variables xp, Q(2), and beta (= x/xp) using a class of deep-inelastic ep scattering events with no hadronic energy flow in an interval of pseudo-rapidity adjacent to the proton beam direction. The dependence of this contribution on xp is measured to be xp(-n) with n = 1.19 +/- 0.06(stat.) +/- 0.07(syst.) independent of beta and Q(2), which is consistent with both a diffractive interpretation and a factorisable ep diffractive cross section. A first measurement of the deep-inelastic structure of the pomeron in the form of the Q(2) and beta dependences of a factorised structure function is presented. For all measured beta, this structure function is observed to be consistent with scale invariance.