Orateur
Description
The latest Standard Model prediction of the muon anomalous magnetic moment is now consistent with the experimental value, but it has an uncertainty that is more than four times larger than the experimental error. To fully exploit the experimental result as a constraint on or indicator for BSM physics, the Standard Model prediction needs to be further improved. The theoretical uncertainty is entirely due to hadronic contributions, namely from hadronic vacuum polarization (HVP) and from hadronic light-by-light (HLbL) scattering. In the case of HVP, the earlier Standard Model prediction from 2020, which was dominated by the data-driven dispersive approach, had to be abandoned due to growing discrepancies in the experimental input, whereas lattice QCD has now reached almost the previously assumed accuracy while shifting the result significantly. On the other hand, the smaller but less precisely known HLbL contribution has been improved with only a small tension between lattice QCD and the dispersive approach. In the latter, the previous uncertainty from poorly determined axial-vector meson contributions and related short-distance contributions could be significantly reduced, in remarkably quantitative agreement with holographic QCD calculations. The largest HLbL uncertainty is now due to tensor-meson contributions, where dispersive and holographic results however strongly disagree. The latter would remove the tension with current HLbL lattice results, while the former enhance it. Upcoming results from experiments such as BESIII hold the promise to resolve this issue and could further sharpen the precision of the HLbL contribution.
| Working Group | WG0. Inter WG or Interdisciplinary |
|---|---|
| Type of oral contribution | Both |