Hadronic Leading Order Contribution to the Muon g-2

¹ KEK Theory Center, Tsukuba, Ibaraki, 305-0801 Japan
² Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto, 606-8502, Japan

^* e-mail: dnomura@post.kek.jp

Published online: 23 May 2018

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) × 1010-¹⁰, respectively. When combined with other contributions to the SM prediction, we obtain aμ(SM) = (11659182:05 ± 3.56) × 10-¹⁰; which is deviated from the experimental value by Δaμ(exp) _ aμ(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(M² _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 Δ⁽⁵⁾_had(M² _Z) = (276.11 ± 1.11) × 10-⁴, from which we obtain Δ(M² _Z) = 128.946 ± 0.015.