Prof. Dr. Anton Rebhan (TU Wien): The anomalous magnetic moment of the muon and holographic QCD
Currently there is a discrepancy between the Standard Model prediction for the anomalous magnetic moment of the muon and the experimental value above 4 standard deviations according to the Muon g-2 Theory Initiative White Paper. With further experimental improvements expected in the near future, it is imperative to further sharpen the theoretical prediction which is limited by uncertainties of QCD contributions. I describe the recent progress made in using holographic QCD to study hadronic contributions to the anomalous magnetic moment of the muon, in particular the hadronic light-by-light scattering contribution, where the short-distance constraints associated with the axial anomaly are notoriously difficult to satisfy in hadronic models. This requires the summation of an infinite tower of axial vector mesons, which is naturally present in holographic QCD models. Numerically the results of simple hard-wall holographic QCD models point to larger contributions from axial vector mesons than assumed previously, while the predicted contributions from pseudo-Goldstone bosons agree nicely with data-driven approaches.