Status of the hadronic light-by-light contribution to the muon $g-2$ and holographic QCD predictions

TL;DR

This paper reviews recent advances in calculating the hadronic light-by-light contribution to the muon g-2, comparing holographic QCD predictions with other models and data, highlighting new tensor-meson contributions.

Contribution

It introduces holographic QCD predictions for tensor-meson contributions to HLbL, emphasizing their impact on the muon g-2 and the agreement with experimental data.

Findings

Holographic QCD predicts significant tensor-meson contributions to HLbL.

Matching short-distance constraints yields form factors consistent with data.

Tensor-meson contributions could explain the current muon g-2 discrepancy.

Abstract

We review the recent progress made with regard to the hadronic light-by-light (HLbL) contribution to the Standard Model prediction of the muon anomalous magnetic moment and how well this compares with predictions from holographic QCD models, which had predicted larger contributions from axial vector mesons and short-distance constraints than the White Paper of 2020. A new holographic prediction concerns tensor-meson contributions, which in holographic QCD play a significant role in short-distance constraints beyond the Melnikov-Vainshtein constraint. When matching also the symmetric longitudinal short-distance constraint, the resulting prediction for the tensor-meson transition form factors agree well with available singly virtual data, but lead to different results than the traditional quark-model ansatz and a sizable positive contribution that could explain the remaining current tension between lattice and data-driven results for the HLbL contribution.