BFKL approach and 2->5 MHV amplitude

TL;DR

This paper analyzes the 2->5 MHV scattering amplitude in multi-Regge kinematics, providing a closed-form expression for the remainder function at any loop order within the leading logarithmic approximation, and confirming consistency with known two-loop results.

Contribution

It introduces a recursive approach to express the 2->5 amplitude's remainder function in terms of 2->4 functions and generalizes to more external particles, advancing the understanding of scattering amplitudes in multi-Regge kinematics.

Findings

Two-loop LLA remainder function expressed as sum of two 2->4 functions.

Closed integral form for the all-loop remainder function.

Results agree with the two-loop symbol derived by Caron-Huot.

Abstract

We study MHV amplitude for the 2 -> 5 scattering in the multi-Regge kinematics. The Mandelstam cut correction to the BDS amplitude is calculated in the leading logarithmic approximation (LLA) and the corresponding remainder function is given to any loop order in a closed integral form. We show that the LLA remainder function at two loops for 2 -> 5 amplitude can be written as a sum of two 2 -> 4 remainder functions due to recursive properties of the leading order impact factors. We also make some generalizations for the MHV amplitudes with more external particles. The results of the present study are in agreement with all leg two loop symbol derived by Caron-Huot as shown in a parallel paper of one of the authors with collaborators.