Triple-pomeron dynamics: valence vs. glue

Three pomerons are known to couple via the gluon loop and interactions of this kind, which are responsible for high-mass diffraction, are described in terms of the gluonic structure function of the QCD pomeron. We show that the triple-pomeron coupling via the light quark loop associated with the 'valence' in the pomeron is of the same strength as the purely gluonic coupling. The large Q2 behavior of this new contribution is described by the DLLA evolution from the non-perturbative ff-bar valence state of the pomeron. Numerical estimates of the high-mass diffraction structure functions based on the consistent account of both couplings are in good agreement with experimental data