Power Corrections and Nonlocal Operators

TL;DR

Power corrections to infrared-safe observables in QCD are analyzed, focusing on $Q^{-2-m}$ suppressed contributions arising from infrared regions of perturbation theory. The authors propose a substitution framework that identifies IR-sensitive momentum regions and replaces their effect with a universal matrix element, linking to infrared renormalons and the OPE where applicable. They apply the method to event shapes near the two-jet limit, demonstrating that leading $1/Q$ corrections originate from a universal nonperturbative energy flow encoded in a nonlocal operator defined by Wilson lines. This provides a unified perturbative-nonperturbative description of power corrections across observables and yields a concrete operator interpretation via the energy-flow function ${\cal E}(\hat{y})$. The results suggest a path toward universal predictions for $1/Q$ effects in infrared-safe quantities.

Abstract

We discuss power corrections to infrared safe cross sections and event shapes, and identify a nonperturbative function that governs 1/Q corrections to these quantities.