Basics of factorization in a scalar Yukawa field theory

TL;DR

This paper explores the principles of factorization in a scalar Yukawa field theory, providing insights into TMD factorization, power corrections, and the generalized parton model, serving as a simplified testing ground for QCD concepts.

Contribution

It systematically reviews factorization procedures in Yukawa theory for DIS and SIDIS, including TMD factorization, coordinate space formulation, and GPM comparison, highlighting issues relevant to QCD.

Findings

Separation of small and large transverse momentum regions in SIDIS.

Impact of subleading power corrections on factorization.

Comparison between GPM and fully factorized approaches.

Abstract

The factorization theorems of quantum chromodynamics (QCD) apply equally well to most simple quantum field theories that require renormalization but where direct calculations are much more straightforward. Working with these simpler theories is convenient for stress-testing the limits of the factorization program and for examining general properties of the parton density functions (pdfs) or other correlation functions that might be necessary for a factorized description of a process. With this view in mind, we review the steps of factorization in a real scalar Yukawa field theory for both deep inelastic scattering (DIS) and semi-inclusive deep inelastic scattering (SIDIS) cross sections. In the case of SIDIS, we illustrate how to separate the small transverse momentum region, where transverse momentum dependent (TMD) pdfs are needed, from a purely collinear large transverse momentum region, and we examine the influence of subleading power corrections. We also review the steps for formulating TMD factorization in transverse coordinate space, and we study the effect of transforming to the well-known $b_*$-scheme. Within the Yukawa theory, we investigate the consequences of switching to a generalized parton model (GPM) approach, and compare with a fully factorized approach. Our results highlight the need to address similar or analogous issues in QCD.