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 [see formula in PDF] based on e+e- data [incl. τ data], [see formula in PDF] (NLO) and [see formula in PDF] (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 [see formula in PDF]. With these updates I find [see formula in PDF] a 4.1 σ deviation. Recent lattice QCD results and future prospects to improve hadronic contributions are discussed.
Highlights
This review of the hadronic vacuum polarization (HVP) contributions to the muon g − 2 is to be considered as a complement to the theory reviews by Marc Knecht and Massimiliano Procura which focus on the hadronic light-by-light (HLbL) part and the reviews on hadronic cross sections by Graziano Venanzoni, Simon Eidelman and Achim Denig in these Proceedings
It means that the new muon g − 2 experiments are expected to establish a possible new physics contribution at the level ∆aμ = aeμxp − atμhe = 6.7 σ provided theory remains as it is today and the central value does not move significantly
Virtual effect form low energy hadronic excitations are the standard problem in electroweak precision physics
Summary
The hadronic contribution to the vacuum polarization can be evaluated, with γ the help of dispersion relations, from the energy scan of the ratio Rγ(s) ≡. In the low energy region, which is important for the dispersive evaluation of the hadronic contribution to the muon g − 2, data have improved dramatically in the past decade for the dominant e+e− → π+π− channel (CMD-2 [12], SND/Novosibirsk [13], KLOE/Frascati [14–16], BaBar/SLAC [17], BES-III/Beijing [18]) and the statistical errors are a minor problem now. A new inclusive determination of Rγ(s) in the range 1.84 to 3.72 GeV has been obtained with the KEDR detector at Novosibirsk [29] (see figure 5). Recent new experimental input for HVP has been obtained by CMD-3 and SND at VEPP-2000 via energy scan and by BESIII at PEPC in the ISR setup
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