Power corrections to the heavy electron form factor

Abstract

We study the first power correction to the heavy electron form factor in QED and show that it factorizes as a derivative operator. We discuss the result in QED with no light fermions, where the first power correction can be written explicitly in terms of one-loop integrals and the anomalous magnetic moment. In the presence of light fermions, the heavy electron form factor admits a representation as a sum over matrix elements, each of which receives corrections from higher orders in perturbation theory. From this analysis, we are able to extract the next-to-leading power soft photon theorem in the limit of heavy fermion-initiated dijet events. This is a first step towards studying the heavy quark form factor in the non-abelian theory.

Journal version, typos fixed, discussion added on the parameters of power expansion