The muon g-2: Dyson-Schwinger status on hadronic light-by-light scattering

TL;DR

This paper reviews the Dyson-Schwinger approach to calculating the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment, emphasizing model-independent properties and kinematic regions.

Contribution

It introduces a covariant decomposition of the light-by-light amplitude respecting gauge invariance and Bose symmetry, and analyzes the relevance of different diagrams at the quark level.

Findings

Covariant decomposition of the amplitude respecting symmetries

Identification of key kinematic regions in the integral

Relation of diagram contributions to model approaches

Abstract

We give a status report on the hadronic light-by-light scattering contribution to the muon's anomalous magnetic moment from the Dyson-Schwinger approach. We discuss novel, model-independent properties of the light-by-light amplitude: we give its covariant decomposition in view of electromagnetic gauge invariance and Bose symmetry, and we identify the relevant kinematic regions that are probed under the integral. The decomposition of the amplitude at the quark level and the importance of its various diagrams are discussed and related to model approaches.