Direct Measurement of the Branching Fraction for the Decay of $D^+ \to \bar K^0 e^+\nu_e$ and Determination of $\Gamma (D^0 \to K^-e^+\nu_e)/ \Gamma (D^+ \to \bar K^0 e^+\nu_e)$

TL;DR

This paper measures the branching fraction of the decay D+ to K0bar e+ nu_e and compares it to the D0 decay, providing precise experimental data relevant for understanding charm meson semileptonic decays.

Contribution

It provides the first absolute measurement of the branching fraction for D+ to K0bar e+ nu_e and determines the ratio of decay widths between D0 and D+ semileptonic decays.

Findings

BF(D+ to K0bar e+ nu_e) = (8.95 ± 1.59 ± 0.67)%

Width ratio Γ(D0 to K- e+ nu_e) / Γ(D+ to K0bar e+ nu_e) = 1.08 ± 0.22 ± 0.07

Experimental data for charm semileptonic decay branching fractions

Abstract

The absolute branching fraction for the decay $D^+ \to \bar K^0 e^+\nu_e$ is determined using $5321\pm 149 \pm 160$ singly tagged $D^-$ sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC collider. In the system recoiling against the singly tagged $D^-$ meson, $34.4\pm 6.1$ events for $D^+ \to \bar K^0 e ^+\nu_e$ is observed. Those yield the absolute branching fraction to be $BF(D^+ \to \bar K^0 e^+\nu_e)=(8.95 \pm 1.59\pm 0.67)%$. The ratio of the two partial widths for the decays of $D^0 \to K^-e^+\nu_e$ and $D^+ \to \bar K^0 e ^+\nu_e$ is determined to be $ \Gamma (D^0 \to K^-e^+\nu_e)/ \Gamma (D^+ \to \bar K^0 e^+\nu_e) = 1.08\pm 0.22 \pm 0.07$.