Direct calculation of the triple-pomeron coupling for diffractive DIS and real photoproduction

Abstract

We present a unified direct calculation of the triple-pomeron coupling A_{3\Pom}(Q^{2}) for diffractive real photoproduction ($Q^{2}=0$) and deep inelastic scattering at large $Q^{2}$ in the framework of the dipole approach to the generalized BFKL pomeron. The small phenomenological value of A_{3\Pom}(0)\approx 0.16\,GeV$^{2}$, which was a mystery, is related to the small correlation radius $R_{c}\approx 0.3$\,fm for the perturbative gluons. We confirm the early expectations of weak $Q^{2}$ dependence of the dimensionfull coupling A_{3\Pom}(Q^{2}) and predict that it rises by the factor $\sim 1.6$ from real photoproduction to deep inelastic scattering.Comment: 14 pages, 1 figure (request from [email protected]), Juelich preprint KFA-IKP(Th)-1994-3