Speaker
Description
We evaluate axial vector transition form factors in holographic QCD models that have been shown to reproduce well recent experimental and theoretical results for the pion transition form factor. Comparing with L3 data on f1→γγ∗ we find remarkable agreement regarding the shape of single-virtual form factors, while deviating, in the double-virtual case, from a simple dipole model used previously to estimate the axial vector contribution to the anomalous magnetic moment of the muon through hadronic light-by-light scattering. We demonstrate that the holographic models can satisfy the Melnikov-Vainshtein short-distance constraint, if and only if the infinite tower of axial vector states is included. Numerically, we obtain a contribution to g-2 that is smaller than the original estimate by Melnikov and Vainshtein, but larger than other phenomenological approaches.
