Combining Fixed-Order Helicity Amplitudes With Resummation Using SCET

TL;DR

The paper addresses the challenge of marrying fixed-order helicity amplitude calculations with all-orders resummation for exclusive jet cross sections. It introduces a helicity-based SCET operator basis in which hard Wilson coefficients are given by the IR-finite parts of color-ordered QCD amplitudes, providing a direct bridge between NLO building blocks and SCET resummation. By decomposing Wilson coefficients in a color basis and using helicity fields, the approach yields a practical matching rule C_k = A_fin^k for arbitrary multileg processes, demonstrated through examples like ggqqH. The framework enables seamless integration of NLO results with NNLL resummation, delivering more precise predictions for exclusive jet observables while highlighting the need to account for color-space RG evolution. This advance facilitates improved theoretical control over jet-based measurements and new-physics searches at colliders.

Abstract

We discuss how to construct a simple and easy-to-use helicity operator basis in Soft-Collinear Effective Theory (SCET), for which the hard Wilson coefficients from matching QCD onto SCET are directly given in terms of the color-ordered QCD helicity amplitudes. This provides an interface to seamlessly combine fixed-order helicity amplitudes, which are the basic building blocks of state-of-the-art next-to-leading order calculations for multileg processes, with a resummation of higher-order logarithmic corrections using SCET.