An empirical model of the long-distance contributions to ${\bar{B}}^0\to {\bar{K}}^{\ast 0}{\mu }^{+}{\mu }^{-}$ transitions

Abstract

A method for analysing the hadronic resonance contributions in ${\bar{B}}^0\to {\bar{K}}^{\ast 0}{\mu }^{+}{\mu }^{-}$ decays is presented. This method uses an empirical model that relies on measurements of the branching fractions and polarisation amplitudes of final states involving $J^{PC}=1^{--}$ resonances, relative to the short-distance component, across the full dimuon mass spectrum of ${\bar{B}}^0\to {\bar{K}}^{\ast 0}{\mu }^{+}{\mu }^{-}$ transitions. The model is in good agreement with existing calculations of hadronic non-local effects. The effect of this contribution to the angular observables is presented and it is demonstrated how the narrow resonances in the $q^2$ spectrum provide a dramatic enhancement to $CP$-violating effects in the short-distance amplitude. Finally, a study of the hadronic resonance effects on lepton universality ratios, $R_{K^{(\ast )}}$, in the presence of new physics is presented.

Comments: 24 pages, 6 figures in main text, 2 figures in appendix, version accepted by journal