Precision Measurements of the Semileptonic Charm Decays $D^0 \to \pi^- \ell^+ \nu$ and $D^0 \to K^- \ell^+ \nu$

TL;DR

This paper presents precise measurements of semileptonic charm decays D^0 to pi and K with electron and muon channels, providing form factor parameters and ratios crucial for understanding weak interactions and CKM matrix elements.

Contribution

The study offers the first detailed form factor analysis and decay rate ratios for D^0 semileptonic decays using CLEO III data, enhancing understanding of charm semileptonic processes.

Findings

Measured decay rate ratio R_0 = 0.082 ± 0.006 ± 0.005

Determined form factor parameters for both decay modes

Calculated ratio of form factor and CKM matrix elements as 0.038^{+0.006+0.005}_{-0.007-0.003}

Abstract

We investigate the decays $D^0\to\pi^-\ell^+\nu$ and $D^0\to K^-\ell^+ \nu$, where $\ell$ is $e$ or $\mu$, using approximately 7 ${\rm fb}^{-1}$ of data collected with the CLEO III detector. We find $R_0\equiv {\cal B}(D^0\to \pi^-e^+\nu)/{\cal B}(D^0\to K^-e^+\nu)= 0.082 \pm 0.006 \pm 0.005$. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and $R_0$ gives $|f^{\pi}_{+}(0)|^2 |V_{cd}|^2/|f^K_{+}(0)|^2 |V_{cs}|^2 = 0.038^{+0.006+0.005}_{-0.007-0.003}$.