The QCD triple Pomeron coupling from string amplitudes

Using the recent solution of the triple Pomeron coupling in the QCD dipole picture as a closed string amplitude with six legs, its analytical form in terms of hypergeometric functions and numerical value are derived. 1. The triple Pomeron coupling has since a long time catalyzed a series of phenomenological and theoretical problems. In practice, it is associated to high-mass diffractive scattering at high-energy which has been observed experimentally and studied in various hadron-hadron reactions. More recently, the observation of high-mass diffraction at the virtual photon vertex of lepton-proton interactions at HERA [1] has led to a new domain of investigation where the non-negligeable virtuality Q of the photon implies a (at least partial) connection with perturbative QCD. On the theoretical point of view, the coupling between three Pomerons in an S-Matrix framework has its counterpart in the six-gluon amplitude in QCD which, in the framework of the BFKL dynamics [2] has been derived in Refs. [3] and obtained in Ref. [4] as a 1→ 2 dipole vertex in the related (1/Nc limit of the) QCD dipole framework [5]. Recently we reported [6] a derivation of the high-mass diffractive dissociation which shows explicitly the implication of the QCD ∗Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Cracow, Poland †CEA, Service de Physique Theorique, CE-Saclay, F-91191 Gif-sur-Yvette Cedex, France