Measuring B(D^+ -> \mu^+\nu) and the Pseudoscalar Decay Constant f_{D^+}

TL;DR

This paper reports a measurement of the branching fraction and decay constant of the D+ meson using data from the CLEO-c detector, providing important tests of theoretical models of heavy meson decays.

Contribution

First measurement of B(D+ to mu+ nu) and f_D+ using CLEO-c data at the psi(3770) resonance.

Findings

Branching fraction B(D+ to mu+ nu) = (3.5 ± 1.4 ± 0.6) × 10^{-4}

Decay constant f_D+ = (198 ± 41 ± 17) MeV

Sample contained 8 signal candidates with minimal background.

Abstract

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