Improved measurement of the branching fraction of Ds+ →μ+νμ

Abstract

Using e+e- collision data with an integrated luminosity of 7.33 fb-1 collected at center-of-mass energies between 4.128 and 4.226 GeV with the BESIII detector operating at the BEPCII collider, the branching fraction of the leptonic decay Ds+→μ+νμ is measured to be (0.5294±0.0108stat±0.0085syst)%. Based on this, the product of the Ds+ decay constant fDs+ and the magnitude of the c→s quark mixing matrix element |Vcs| is determined to be fDs+|Vcs|=241.8±2.5stat±2.2syst MeV. Using the value of |Vcs| given by the global standard model fit, fDs+ is found to be 248.4±2.5stat±2.2syst MeV. Alternatively, using the value of fDs+ from a recent lattice quantum chromodynamics calculation, |Vcs| is determined to be 0.968±0.010stat±0.009syst.