Two-parton scattering in the high-energy limit: climbing two- and three-Reggeon ladders

TL;DR

This paper reviews recent advances in calculating high-energy scattering amplitudes, focusing on two-parton interactions, using shockwave formalism and high-order loop computations to understand their analytic and infrared properties.

Contribution

It presents new calculations of the imaginary and real parts of 2-to-2 parton scattering amplitudes at high energies, including all-order and multi-loop results in full colour.

Findings

Imaginary part computed at next-to-leading logarithmic accuracy, up to 13 loops.

Real part computed at next-to-next-to-leading logarithmic accuracy, up to four loops.

Provides insights into the analytic structure and infrared singularities of scattering amplitudes.

Abstract

We review recent progress on the calculation of scattering amplitudes in the high-energy limit. We start by illustrating the shockwave formalism, which allows one to calculate amplitudes as iterated solutions of rapidity evolution equations. We then focus on our recent results regarding $2\to 2$ parton scattering. We present the calculation of the imaginary part of the amplitude, at next-to-leading logarithmic accuracy in the high-energy logarithms, formally to all orders, and in practice to 13 loops. We then discuss the computation of the real part of the amplitude at next-to-next-to-leading logarithmic accuracy and through four loops. Both computations are carried in full colour, and provide new insight into the analytic structure of scattering amplitudes and their infrared singularity structure.