Measurement of B(Ds+→l+ν) and the decay constant fDs+ from 600  pb-1 of e+e- annihilation data near 4170 MeV

We examine e(+)e(-) -> D-s(-) D-s*(+) and D-s*(-) D-s(+) interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant f(Ds+) with good precision. Previously our measurements were substantially higher than the most precise lattice based QCD calculation of (241 +/- 3) MeV. Here we use the D-s(+) -> l(+) v channel, where the l(+) designates either a mu(+) or a tau(+) when the tau(+) -> pi(+) (v) over bar Analyzing both modes independently, we determine B(D-s(+) -> mu(+)v) = (0.565 +/- 0.045 +/- 0.017)%, and B(D-s(+) -> tau(+) v) = (6.42 +/- 0.81 +/- 0.18)%. We also analyze them simultaneously to find an effective value of B-eff(D-s(+) -> mu(+)v) = (0.591 +/- 0.037 +/- 0.018)% and f(Ds+) = (263.3 +/- 8.2 +/- 3.9) MeV. Combining with the CLEO-c value determined independently using D-s(+) -> tau(+) v, tau(+) -> e(+) v (v) over bar decays, we extract f(Ds+) = (259.5 +/- 6.6 +/- 3.1) MeV. Combining with our previous determination of B(D+ -> mu(+)v), we extract the ratio f(Ds+) / f(D+) = 1.26 +/- 0.06 +/- 0.02. No evidence is found for a CP asymmetry between Gamma(D-s(+) -> mu(+)v) and Gamma(D-s(-) -> mu(+)v); specifically the fractional difference in rates is measured to be (4.8 +/- 6.1)%. Finally, we find B(D-s(+) -> e(+)v) < 1.2 x 10(-4) at 90% confidence level.