/ 93 11 15 9 v 1 2 6 N ov 1 99 3 Effective action for high energy scattering in QCD

We study the behavior of scattering amplitudes in the perturbative Regge region, s ≫ κ 2 ⊥ ≫ µ 2 had , (1) with a large energy squared s and transverse momenta of exchanged particles κ ⊥ much smaller but large enough compared to the hadron mass scale µ had to allow for perturbative expansion. This asymptotics determines the behaviour of structure functions at small x or of two-jet events with a large rapidity gap. In this region the dominant contributions come from multi-particle states with the momenta k i of produced particles obeying the conditions of multi-Regge kinematics. p A and p B are the momenta of incoming particles.