First Measurement of the Form Factors in Ds+ →k0e+νe and Ds+ →k∗0e+νe Decays

Abstract

We report on new measurements of Cabibbo-suppressed semileptonic Ds+ decays using 3.19 fb-1 of e+e-annihilation data sample collected at a center-of-mass energy of 4.178 GeV with the BESIII detector at the BEPCII collider. Our results include branching fractions B(Ds+→K0e+νe)=[3.25±0.38(stat)±0.16(syst)]×10-3 and B(Ds+→K∗0e+νe)=[2.37±0.26(stat)±0.20(syst)]×10-3, which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For Ds+→K0e+νe, we obtain f+(0)=0.720±0.084(stat)±0.013(syst), and for Ds+→K∗0e+νe, we find form-factor ratios rV=V(0)/A1(0)=1.67±0.34(stat)±0.16(syst) and r2=A2(0)/A1(0)=0.77±0.28(stat)±0.07(syst).