Direct measurement of the absolute branching fraction for $D^+ \to {\bar K}^0\mu^+\nu_\mu$ and determination of $ \Gamma (D^0 \to K^-\mu^+\nu_\mu)/\Gamma (D^+ \to {\bar K}^0\mu^+\nu_\mu)$

TL;DR

This paper measures the absolute branching fraction of the decay $D^+ o {ar K}^0\mu^+ u_\mu$ and compares the partial widths of related decays, providing key data for understanding charm meson semileptonic decays.

Contribution

It provides the first direct measurement of the absolute branching fraction for $D^+ o {ar K}^0\mu^+ u_\mu$ and determines the ratio of decay widths between $D^0$ and $D^+$ semileptonic decays.

Findings

BF($D^+ o {ar K}^0\mu^+ u_\mu$) = (10.3 ± 2.3 ± 0.8)%

Width ratio $rac{\Gamma(D^0 o K^-\mu^+ u_\mu)}{\Gamma(D^+ o {ar K}^0\mu^+ u_\mu)}$ = 0.87 ± 0.24 ± 0.15

Provides experimental data for charm semileptonic decay rates.

Abstract

The absolute branching fraction for the decay $D^+ \to {\bar K}^0\mu^+\nu_\mu$ is determined using $5321 \pm 149 \pm160$ singly tagged $D^-$ sample from the data collected around 3.773 GeV with the BESII detector at the BEPC collider. In the system recoiling against the singly tagged $D^-$ mesons, $28.7 \pm 6.4$ events for $D^+ \to {\bar K}^0\mu^+\nu_\mu$ are observed. These yield the absolute branching fraction to be $BF(D^+ \to {\bar K}^0\mu^+\nu_\mu) = (10.3\pm2.3\pm0.8)%$. The ratio of the two partial widths for the decays $D^0 \to K^-\mu^+\nu_\mu$ and $D^+ \to {\bar K}^0\mu^+\nu_\mu$ is determined to be $\Gamma (D^0 \to K^-\mu^+\nu_\mu)/\Gamma (D^+ \to {\bar K}^0\mu^+\nu_\mu) = 0.87 \pm 0.24 \pm 0.15$.