Angular analysis of charged and neutral B → Kµ⁺µ^- decays

The angular distributions of the rare decays B → K ⁺µ ⁺µ ^- and B ⁰ → K ⁰ _aSμ ⁺μ ^- are studied with data corresponding to 3 fb ^-1 of integrated luminosity, collected in proton-proton collisions at 7 and 8TeV centre-of-mass energies with the LHCb detector. The angular distribution is described by two parameters, FH and the forward-backward asymmetry of the dimuon system A ^FB, which are determined in bins of the dimuon mass squared. The parameter F _H is a measure of the contribution from (pseudo)scalar and tensor amplitudes to the decay width. The measurements of A _FB and F _H reported here are the most precise to date and are compatible with predictions from the Standard Model.