First measurement of the form factors in d-s(+) -> k(0)e(+)nu(e) and d-s(+) -> k*(0)e(+)nu(e) decays

Abstract

We report on new measurements of Cabibbo-suppressed semileptonic D-s(broken vertical bar) decays using 3.19 fb(-1) of e(broken vertical bar)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(D-s(+) -> K(0)e(+)nu(e)) = [3.25 +/- 0.38(stat) +/- 0.16(syst)] x 10(-3) and B(D-s(+) -> K*(0)e(+)nu(e)) = [2.37 +/- 0.26(stat) +/- 0.20(syst)] x 10(-3), which are much improved relative to previous measurements, and the first measurements of the hadronic form-factor parameters for these decays. For D-s(+) -> K(0)e(+)nu(e), we obtain f(+)(0) = 0.720 +/- 0.084(stat) +/- 0.013(syst), and for D-s(+) -> K*(0)e(+)nu(e), we find form-factor ratios r(V) = V(0)/A(1)(0) = 1.67 +/- 0.34(stat) +/- 0.16(syst) and r(2) = A(2)(0)/A(1)(0) = 0.77 +/- 0.28(stat) +/- 0.07(syst).