Selection rules at the quark-antiquark vertex of the QCD pomeron

We derive the full analytic expression for the QCD eikonal coupling of a quark-antiquark state to the exchanged gluon-gluon state in the BFKL formalism. The formula is valid for all conformal spin configurations of the qq and gg states. In particular, a new selection rule on conformal spins characterizes the non-dominant BFKL components with intercept below the pomeron in the conformal-invariant framework. (orig.)