Improved measurement of the semileptonic decay Ds+ →k0e+νe

Abstract

Analyzing e+e- collision data corresponding to 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, we measure the branching fraction of the semileptonic decay Ds+→K0e+νe to be (2.98±0.23stat±0.12syst)×10-3. Based on fit to the partial decay rates in various q2 intervals, the product value of Ds+→K0 hadronic form factor and Cabibbo-Kobayashi-Maskawa element is measured to be f+K0(0)|Vcd|=0.143±0.011stat±0.003syst. With |Vcd|=0.22486±0.00067 as an input, the hadronic form factor is evaluated to be f+K0(0)=0.636±0.049stat±0.013syst. The branching fraction and form factor measurements are factors of 1.6 and 1.7 more precise than the previous world averages, respectively.