Speaker
Description
The tension between theory and experiment for the anomalous magnetic moment of the muon ($a_\mu$) is one of the long-standing puzzles of modern particle physics. After the update by the Fermilab E989 experiment in April 2021, the discrepancy between both sides lies at the 4.2-sigma level, as of the consensus made in the 2020 muon g-2 theory White Paper. The theory error is entirely dominated by the hadronic contributions, which can be calculated using lattice QCD. The order $\alpha_{\textrm{QED}}^3$ hadronic light-by-light (hlbl) contribution $a_\mu^{\textrm{hlbl}}$ admits a large relative uncertainty and represents a non-negligible source of uncertainty for the total error budget. In this talk, the Mainz approach and result for $a_\mu^{\textrm{hlbl}}$ computed with $N_f=2+1$ lattice ensembles [arXiv:2104.02632] will be presented. We obtain a value of $a_\mu^{\textrm{hlbl}}=106.8(14.7)\times 10^{-11}$ after a chiral, continuum and infinite-volume extrapolation. This result contains all five Wick-contraction topologies needed for a complete lattice determination of $a_\mu^{\textrm{hlbl}}$.
