Measuring B(D^+ -> μ^+ν) and the Pseudoscalar Decay Constant f_{D^+}

Abstract

In 60 pb$^{-1}$ of data taken on the $ψ(3770)$ resonance with the CLEO-c detector, we find 8 $D^+\toμ^+ν$ event candidates that are mostly signal, containing only 1 estimated background. Using this statistically compelling sample, we measure the value of ${\cal{B}}(D^+\toμ^+ν)=(3.5\pm 1.4 \pm 0.6)\times 10^{-4}$, and determine $f_{D^+}=(198\pm 41\pm 17)$ MeV.