Reevaluation of the hadronic contributions to the muon g−2 and to $\alpha (M^{2}_{Z})$

Abstract

We reevaluate the hadronic contributions to the muon magnetic anomaly, and to the running of the electromagnetic coupling constant at the Z-boson mass. We include new π + π − cross-section data from KLOE, all available multi-hadron data from BABAR, a reestimation of missing low-energy contributions using results on cross sections and process dynamics from BABAR, a reevaluation of all experimental contributions using the software package HVPTools together with a reanalysis of inter-experiment and inter-channel correlations, and a reevaluation of the continuum contributions from perturbative QCD at four loops. These improvements lead to a decrease in the hadronic contributions with respect to earlier evaluations. For the muon g − 2 we find lowest-order hadronic contributions of (692.3 ± 4.2) • 10 −10 and (701.5 ± 4.7) • 10 −10 for the e + e −based and τ-based analyses, respectively, and full Standard Model predictions that differ by 3.6σ and 2.4σ from the experimental value. For the e + e −-based five-quark hadronic contribution to α(M 2 Z) we find Δα (5) had (M 2 Z) = (274.9 ± 1.0) • 10 −4. The reduced electromagnetic coupling strength at M Z leads to an increase by 12 GeV in the central value of the Higgs boson mass obtained by the standard Gfitter fit to electroweak precision data.

Predictions for the neutrino parameters in the minimal gauged $$\hbox {U}(1)_{L_\mu -L_\tau }$$ U ( 1 ) L μ - L τ model

“…An attractive feature of this a e-mail: asai@hep-th.phys.s.u-tokyo.ac.jp class of models is that the muon g − 2 anomaly [5][6][7][8] may be explained by the loop contribution of the U(1) L μ −L τ gauge boson if its mass lies around the weak scale or lower [9][10][11][12], though this possibility is severely restricted by the searches of the neutrino trident production process [13][14][15][16]. These models may also explain anomalies in flavor physics [15,17] and offer promising candidates for dark matter in the Universe [18][19][20][21][22].…”

“…1 2 , and m 2 , which means δ = 0.353π or 1.647π , and justifies the expected accuracy of the approximated formula (21). 7 From Eqs. (13) and (19), we obtain m 1 as a function of δ.…”

Pseudoscalar meson transition form factors in nonperturbative QCD approach

“…The discrepancy between the present SM prediction of the muon AMM and its experimental determination [1] is (28.7 ± 8.0) · 10 −10 (3.6σ) [2]. The theoretical error is dominated by hadronic corrections.…”

“…At the moment, there are some problems with the matching of the experimental data with the predictions of the SM. The most famous one is the discrepancy by three standard deviations between experiment [1] and SM theory [2,3] for the muon anomalous magnetic moment (AMM). Another example is similarly large deviation between the recent precise experimental result on the rare π 0 decay into e − e + pair [4] and the SM prediction [5].…”

Muon g-2 and LHC phenomenology in the L μ − L τ gauge symmetric model

“…Following this line, in [6] 31.6 ± 7.9 (4.0σ) [7] 11659208.9 ± 6. 3 33.5 ± 8.2 (4.1σ) [8] 28.3 ± 8.7 (3.3σ) [9] 29.0 ± 9.0 (3.2σ) [10] 28.7 ± 8.0 (3.6σ) [11] Table 1. Measured muon g-2 (a Exp µ ) and the estimated differences (δa µ ) from the recent SM predictions in several references.…”