We examine e+e-→Ds-Ds*+ and Ds*-Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+. We use the Ds+→ℓ+ν channel, where the ℓ+ designates either a μ+ or a τ+, when the τ+→π+ν̄. Analyzing both modes independently, we determine B(Ds+→μ+ν)=(0.594±0.066±0. 031)%, and B(Ds+→τ+ν)=(8.0±1.3±0.4)%. We also analyze them simultaneously to find an effective value of Beff(Ds+→μ+ν)=(0. 638±0.059±0.033)% and extract fDs+=274±13±7MeV. Combining with our previous determination of B(D+→μ+ν), we also find the ratio fDs+/fD+=1.23±0.11±0.04. We compare to current theoretical estimates. Finally, we find B(Ds+→e+ν)<1.3×10-4 at 90% confidence level. © 2007 The American Physical Society.
Pedlar, T. K., Cronin-Hennessy, D., Gao, K. Y., Hietala, J., Kubota, Y., Klein, T., … Besson, D. (2007). Measurement of B(Ds+→l+ν) and the decay constant fDS+. Physical Review D - Particles, Fields, Gravitation and Cosmology, 76(7). https://doi.org/10.1103/PhysRevD.76.072002