Hadronic Light-by-light contribution to muon (g-2)

Abstract

Recent lattice QCD results for hadron light-by-light scattering (HLbL) and its contribution to muon anomalous magnetic moments (𝑔 − 2) will be reviewed. Combining the first results from Fermilab's Muon 𝑔 − 2 measurement and the previous BNL Muon 𝑔 − 2 experiment, there are currently 4.2 standard deviations between the experimental result and the theoretical prediction. The precision of Fermilab's experimental result will continue to improve in the coming years as more data is being analyzed. The uncertainty of theory prediction needs to be reduced to a similar level. Theoretically, HLbL and hadron vacuum polarization (HVP) contributions are the two major sources of uncertainty. In the past, the HLbL was only estimated by models. Recent developments in lattice calculations and data-driven approaches allow a reliable and systematically improvable determination of the HLbL contribution muon 𝑔 − 2.