Measurements of the S-wave fraction in B⁰ → K⁺π⁻μ⁺μ⁻ decays and the B⁰ → K^∗(892)⁰μ⁺μ⁻ differential branching fraction

摘要

A measurement of the differential branching fraction of the decay → (892) is presented together with a determination of the S-wave fraction of the system in the decay → π. The analysis is based on -collision data corresponding to an integrated luminosity of 3 fb collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, . Precise theoretical predictions for the differential branching fraction of → (892) decays are available for the region 11 60 GeV. In this region, for the π invariant mass range 796 996 MeV, the S-wave fraction of the π system in → π decays is found to be FS=0.101±0.017(stat)±0.009(syst), and the differential branching fraction of → (892) decays is determined to be dB/dq2=(0.392+0.020−0.019(stat)±0.010(syst)±0.027(norm))×10−7c4/GeV2.The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.