Scalar meson contributions to aμ from hadronic light-by-light scattering

Abstract

Using an effective σ/f0(500) resonance, which describes the ππ→ππ and γγ→ππ scattering data, we evaluate its contribution and the ones of the other scalar mesons to the hadronic light-by-light (HLbL) scattering component of the anomalous magnetic moment aμ of the muon. We obtain the conservative range of values: ∑Saμlbl|S≃−(4.51±4.12)×10−11, which is dominated by the σ/f0(500) contribution (50%∼98%), and where the large error is due to the uncertainties on the parametrisation of the form factors. Considering our new result, we update the sum of the different theoretical contributions to aμ within the standard model, which we then compare to experiment. This comparison gives (aμexp−aμSM)=+(312.1±64.6)×10−11, where the theoretical errors from HLbL are dominated by the scalar meson contributions. Keywords: Anomalous magnetic moment, Muon, Scalar mesons, Radiative width, Non perturbative effects