Scalar mesons and the muon anomaly

We evaluate systematically some new contributions of the QCD scalar mesons, including radiative decay-productions, not considered with a better attention until now in the evaluation of the hadronic contributions to the muon anomaly. The sum of the scalar contributions to be added to the existing Standard Model predictions aμSM are estimated in units 10−10 to be aSμ=1.0(0.6) [TH based] and 13(11) [PDG based], where the errors are dominated by the ones from the experimental widths of these scalar mesons. PDG based results suggest that the value of aμSM and its errors might have been underestimated in previous works. The inclusion of these new effects leads to a perfect agreement (⩽1.1σ) of the measured value aexpμ and aμSM from τ-decay and implies a (1.5∼3.3)σ discrepancy between aexpμ and aμSM from e+e−→ hadrons data. More refined unbiased estimates of aμSM require improved measurements of the scalar meson masses and widths. The impact of our results to aμSM is summarized in the conclusions.