Regge Limit of Gauge Theory Amplitudes beyond Leading Power Approximation

TL;DR

This paper investigates the behavior of gauge theory amplitudes in the Regge limit beyond leading power, revealing that double-logarithmic effects can dominate at small angles and connecting subleading effects to unitarity issues in QED and QCD.

Contribution

It provides the first all-order resummation of double-logarithmic corrections for power-suppressed terms in gauge theories and uncovers their potential dominance at high energies.

Findings

Double-logarithmic corrections overcome power suppression at small angles.

Power-suppressed terms become comparable to BFKL pomeron contributions.

Discovered a relation between Regge and Sudakov asymptotics.

Abstract

We study the high-energy small-angle {\it Regge} limit of the fermion-antifermion scattering in gauge theories and consider the part of the amplitude suppressed by a power of the scattering angle. For abelian gauge group all-order resummation of the double-logarithmic radiative corrections to the leading power-suppressed term is performed. We find that when the logarithm of the scattering angle is comparable to the inverse gauge coupling constant the asymptotic double-logarithmic enhancement overcomes the power suppression, a formally subleading term becomes dominant, and the small-angle expansion breaks down. For the nonabelian gauge group we show that in the color-singlet channel for sufficiently small scattering angles the power-suppressed contribution becomes comparable to the one of BFKL pomeron. Possible role of the subleading-power effects for the solution of the unitarity problem of perturbative Regge analysis in QED and QCD is discussed. An intriguing relation between the asymptotic behavior of the power-suppressed amplitudes in Regge and Sudakov limits is discovered.