Measuring β(D+→μ+ν) and the pseudoscalar decay constant fD+ -: art. no. 112004

In 60 pb(-1) of data taken on the psi(3770) resonance with the CLEO-c detector, we find eight D+-->mu(+)nu decay candidates that are mostly signal, containing only one estimated background. Using this statistically compelling sample, we measure a value of B(D+-->mu(+)nu)=(3.5+/-1.4+/-0.6)x10(-4), and determine f(D)(+)=(202+/-41+/-17) MeV.