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 {\\it valence-like} gluons and sea
quarks as input. By a method combining {\\it backward} $Q^2$-evolution for data
exploration and {\\it forward} $Q^2$-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 {\\it
valence-like} input at an initial scale of order $\\mu^2 \\sim 2.3-2.7\\ GeV^2$.
The parton number sum rules at the initial scale $\\mu^2$ for the H1 fit gives
$2.1\\pm .1\\pm .1$ and
$.13\\pm .01 \\pm .02$ 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.
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