Rare fluctuations and the high-energy limit of the S-matrix in QCD

We argue that one cannot correctly calculate the elastic scattering S-matrix for high-energy dipole-dipole scattering, in the region where S is small, without taking fluctuations into account. The relevant fluctuations are rare and unimportant for general properties of inelastic collisions. We find that the Kovchegov equation, while giving the functional form of the S-matrix correctly, gives the exponential factor twice as large as the result which emerges when fluctuations are taken into account. (C) 2003 Elsevier B.V. All rights reserved.