Holographic QCD and the muon anomalous magnetic moment

TL;DR

This paper reviews how holographic QCD models help calculate hadronic contributions to the muon's anomalous magnetic moment, especially the challenging axial anomaly constraints, showing improved estimates for axial vector mesons.

Contribution

It demonstrates that holographic QCD naturally incorporates an infinite tower of axial vector mesons, satisfying short-distance constraints and refining the estimation of hadronic light-by-light scattering contributions.

Findings

Holographic QCD models predict larger axial vector meson contributions than previous estimates.

Pseudo-Goldstone boson contributions align well with data-driven results.

The approach effectively satisfies axial anomaly constraints in calculations.

Abstract

We review 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, and indeed takes care of the longitudinal short-distance constraint due to Melnikov and Vainshtein. 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.