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 ahad, LO VPμ = (693:27 ± 2:46) × 10-10 and ahad, 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.
Highlights
The anomalous magnetic moment of the muon, aμ, known as the muon g − 2, is an extremely important quantity in particle physics since it can be used to probe/constrain new physics beyond the Standard Model (SM)
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 ∆aμ ≡ aμ(exp) − aμ(SM) = (27.05 ± 7.26) × 10−10
Where the leading order (LO), NLO and NNLO hadronic vacuum polarisation (VP) contributions in the first line can be calculated by using dispersive integrals, whilst to compute the lightby-light (LbL) contributions in the second line we have to rely on hadronic models to some extent
Summary
The anomalous magnetic moment of the muon, aμ, known as the muon g − 2, is an extremely important quantity in particle physics since it can be used to probe/constrain new physics beyond the Standard Model (SM). Aμ(exp) = (11659209.1 ± 6.3) × 10−10. This value should be compared to the SM prediction for aμ. [1], the most recent value of the SM prediction is aμ(SM) = (11659182.05 ± 3.56) × 10−10 . (1) and (2) is ∆aμ ≡ aμ(exp) − aμ(SM) = (27.05 ± 7.26) × 10−10 , (3). This deviation may be due to a contribution from physics beyond the SM, which makes aμ extremely important. There are two experiments which aim to improve the experimental uncertainty by a factor of 4 [4, 5], which further enhances the importance of this quantity
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