Muon g - 2 theory: The hadronic part

Abstract

I present a status report of the hadronic vacuum polarization effects for the muon g-2, to be considered as an update of [1]. The update concerns recent new inclusive R measurements from KEDR in the energy range 1.84 to 3.72 GeV. For the leading order contributions I find ahad(1)μ = (688.07±4.14)[688.77±3.38]×10-10 based on e+e- data [incl. τ data], ahad(2)μ = (-9.93±0.07)×10-10 (NLO) and ahad(3)μ = (1.22±0.01)×10-10 (NNLO). Collecting recent progress in the hadronic light-by-light scattering I adopt π0, η, η′ [95 ± 12] + axial-vector [8 ± 3] + scalar [-6 ± 1] + π, K loops [-20±5] + quark loops [22 ± 4] + tensor [1 ± 0] + NLO [3 ± 2] which yields a(6)μ (lbl, had) = (103 ± 29) × 10-11. With these updates I find aexpμ - atheμ = (31.3 ± 7.7) × 10-10 a 4.1 σ deviation. Recent lattice QCD results and future prospects to improve hadronic contributions are discussed.