High energy amplitude in the dipole approach with Pomeron loops: asymptotic solution

Abstract

In this paper an analytical solution for the high energy scattering amplitude is suggested. This solution has several unexpected features:(i) the asymptotic amplitude is a function of dipole sizes and, therefore, this amplitude shows the gray disc structure at high energy, instead of black disc behaviour which was expected; (ii) the amplitude approaches the asymptotic limit in the same way as the solution to the Balitsky-Kovchegov equation does ($\propto \exp(- C Y^2) $), but the coefficient $C$ in eight times smaller than for the Balitsky-Kovchegov equation; (iii) the process of merging of two dipoles into one, only influences the high energy asymptotic behaviour by changing the initial condition from $Z(Y; [u_i = 1]) = 1 $ to $Z(Y; [u_i = 1 - \gamma_{0,i}]) =1$. The value of $\gamma_0$ is determined by the process of merging of two dipoles into one. With this new initial condition the Balitsky-JIMWLK approach describes the high energy asymptotic behaviour of the scattering amplitude without any modifications recently suggested.