Hadronic Leading Order Contribution to the Muon g-2

Abstract

Abstract. We calculate the Standard Model (SM) prediction for the muon anomalous magnetic moment. By using the latest experimental data for e + e − → hadrons as input to dispersive integrals, we obtain the values of the leading order (LO) and the next-to-leading-order (NLO) hadronic vacuum polarisation contributions as a had, LO VP µ = (693.27 ± 2.46) × 10 −10 and a had, NLO VP µ = (−9.82 ± 0.04) × 10 −10 , respectively. When combined with other contributions to the SM prediction, we obtain a µ (SM) = (11659182.05 ± 3.56) × 10 −10 , which is deviated from the experimental value by ∆a µ ≡ a µ (exp) − a µ (SM) = (27.05 ± 7.26) × 10 −10 . This means that there is a 3.7 σ discrepancy between the experimental value and the SM prediction. We also discuss another closely related quantity, the running QED coupling at the Z-pole, α(M 2 Z ). By using the same e + e − → hadrons data as input, our result for the 5-flavour quark contribution to the running QED coupling at the Z pole is ∆α (5) had (M 2 Z ) = (276.11 ± 1.11) × 10 −4 , from which we obtain α −1 (M 2 Z ) = 128.946 ± 0.015.