A fresh look at hadronic light-by-light scattering in the muon g - 2 with the Dyson-Schwinger approach

Using the Dyson-Schwinger and Bethe-Salpeter equations, we calculate the hadronic light-by-light scattering contribution to the anomalous magnetic moment of the muon $\ensuremath a_\mu$ , using a phenomenological model for the gluon and quark-gluon interaction. We find $\ensuremath a_\mu=(84 \pm 13)\times 10^{-11}$ for meson exchange, and $\ensuremath a_\mu = (107 \pm 2 \pm 46)\times 10^{-11}$ for the quark loop. The former is commensurate with past calculations; the latter much larger due to dressing effects. This leads to a revised estimate of $\ensuremath a_\mu=116 591 865.0(96.6)\times 10^{-11}$ , reducing the difference between theory and experiment to ≃ 1.9$ \sigma$