Scalar resonances in the hadronic light-by-light contribution to the muon (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>g</mml:mi><mml:mo>−</mml:mo><mml:mn>2</mml:mn></mml:mrow></mml:math>)
Luigi Cappiello, Oscar Catà, Giancarlo D’Ambrosio
Abstract
We evaluate the contribution of scalar mesons to the hadronic light-by-light piece of the muon anomalous magnetic moment, using a warped five-dimensional model and holographic methods. We assess the contribution of the lightest, sub-GeV scalars $\ensuremath{\sigma}(500)$, ${a}_{0}(980)$, and ${f}_{0}(980)$ together with their associated towers of excited states, which the model generates automatically. Our results point at a clearly negative contribution, overwhelmingly dominated by the $\ensuremath{\sigma}(500)$ meson, that we estimate at ${a}_{\ensuremath{\mu}}^{\mathrm{HLbL},\mathrm{S}}=\ensuremath{-}9(2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}11}$. This number is in very good agreement with the most recent determinations from dispersive analyses.