A new approach to semi-inclusive deep-inelastic scattering with QED and QCD factorization

TL;DR

This paper introduces a novel factorized approach for semi-inclusive deep-inelastic scattering that simultaneously accounts for QED and QCD radiation, improving the extraction of transverse momentum dependent parton distributions.

Contribution

It develops a systematically improvable method treating QED and QCD radiation equally, with applications to spin asymmetries in scattering processes.

Findings

QED contributions can be approximated by collinear factorization.

Radiation effects complicate the definition of the photon-nucleon frame.

The method successfully applied to Sivers and Collins asymmetries.

Abstract

We present the details of a new factorized approach to semi-inclusive deep-inelastic scattering which treats QED and QCD radiation on equal footing, and provides a systematically improvable approximation to the extraction of transverse momentum dependent parton distributions. We demonstrate how the QED contributions can be well approximated by collinear factorization, and illustrate the application of the factorized approach to QED radiation in inclusive scattering. For semi-inclusive processes, we show how radiation effects prevent a well-defined "photon-nucleon" frame, forcing one to use a two-step process to account for the radiation. We illustrate the utility of the new method by explicit application to the spin-dependent Sivers and Collins asymmetries.