Abstract

The Muon g-2 experiment (E989) at Fermilab has recently unveiled a new determination of the anomalous magnetic moment of the muon. This has confirmed the tantalising discrepancy (4 sigma) that existed earlier between experiment and Standard Model expectations; a larger data sample will further improve the experimental uncertainties. At the same time the race is on to improve the theoretical uncertainties from the Standard Model. The largest SM uncertainty comes from the hadronic vacuum polarisation (HVP) contribution, currently determined from data-driven approaches. Lattice QCD has a key role to play here in providing an ‘ab initio’ value for the HVP . Uncertainties from lattice QCD were large initially, but are now close to reaching small enough values to have some impact. I will give a general background to the theoretical inputs to the SM determination of a_mu and then discuss recent lattice QCD results in this area and where things are heading.