First measurement of the deep inelastic structure of proton diffraction

Abstract 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 2 , 2.4 × 10 −4 x −4 χ p F 2 ( x , Q 2 ) is evaluated as a function of the appropriate deep-inelastic scattering variables χ p , Q 2 , β (= χ χ p ) 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 χ p is measured to be χ p − n with n = 1.19 ± 0.06 (stat.) ± 0.07 (syst.) independent of β 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 β dependences of a factorised structure function is presented. For all measured β, this structure function is observed to be consistent with scale invariance.