Hard diffraction and the nature of the Pomeron Original Research Article

We ask the question whether the quark and gluon distributions in the Pomeron obtained from QCD fits to hard diffraction processes at HERA can be dynamically generated from a state made of valence-like gluons and sea quarks as input. By a method combining backward Q2-evolution for data exploration and forward Q2-evolution for a best fit determination, we find that the diffractive structure functions published by the H1 Collaboration at HERA can be described by a simple valence-like input at an initial scale of order μ2∼2.3–2.7 GeV2. The parton number sum rules at the initial scale μ2 for the H1 fit gives 2.1±0.1±0.1 and 0.13±0.01±0.02 for gluon and sea quarks, respectively, corresponding to an initial Pomeron state made of (almost) only two gluons. It has flat gluon density leading to a plausible interpretation in terms of a gluonium state.