Hadronic light-by-light scattering in the muon g-2: A Dyson-Schwinger equation approach

We determine the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon using the framework of Dyson-Schwinger and Bethe-Salpeter equations of QCD. Our result for the pseudoscalar (π0,η,η') meson-exchange diagram is commensurate with previous calculations. In our calculation of the quark-loop contribution we improve upon previous approaches by explicitly implementing constraints due to gauge invariance. The impact of transverse contributions, presumably dominated by vector-meson poles, are only estimated at this stage. As a consequence, our value aμLBL;quarkloop=(136±59)x10-11 is significantly larger. Taken at face value, this then leads to a revised estimate of the total aμ=116 591 891.0(105.0)x10-11.