Speaker
Description
The uncertainty of the Standard Model prediction of the anomalous magnetic moment of the muon $(g-2)_\mu$ is dominated by hadronic contributions. As part of these hadronic inputs, the pseudoscalar-pole contribution in hadronic-light-by-light scattering plays a vital role. The currently sought precision of the Standard Model prediction of $(g-2)_\mu$ requires a careful evaluation not only of the pion-pole contribution but also of the $\eta$ and $\eta'$.
We report on the first dispersive, data-driven determination of the $\eta$ and $
\eta'$ transition form factors in the space-like regime, which can be unambiguously related to their pole contributions. The analysis takes into account all of the lowest-lying singularities and encapsulates factorization-breaking effects by means of a left-hand-cut contribution due to the impact of the $a_2(1320)$ tensor meson.
