Scalar mesons and the muon anomaly

Abstract

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 a_mu^{SM} are estimated in units 10^{-10} to be a^{S}_mu= 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 a_mu^{SM} and its errors might have been underestimated in previous works. The inclusion of these new effects leads to a perfect agreement (< 1.1\sigma) of the measured value a^{exp}_mu and a_mu^{SM} from tau-decay and implies a (1.5 ~ 3.3) sigma discrepancy between a^{exp}_mu and a_mu^{SM} from e^+e^- into hadrons data. More refined unbiased estimates of a_mu^{SM} require improved measurements of the scalar meson masses and widths. The impact of our results to a_mu^{SM} is summarized in the conclusions.