Preliminary Results For Exclusive $b\to u\ell\nu$ Decays From CLEO

TL;DR

This paper presents preliminary measurements of exclusive $b o u \, ext{l} \, u$ decays from CLEO, including the first measurement of the $bpi$ branching fraction and limits on $brho$, aiding in understanding form factors.

Contribution

First measurement of the exclusive $b o u \, ext{l} \, u$ branching fraction $bpi$ and limits on $brho$, providing data to discriminate between theoretical form factor models.

Findings

Measured $bpi$ branching fraction as $(1.19 imes 10^{-4})$ with uncertainties.

Set a 90 ext{% C.L. upper limit on $brho$ similar to previous results.

Found the ratio $rac{brho}{bpi} < 3.4$, constraining form factor models.

Abstract

A preliminary analysis of exclusive $\btou$ decays to the final states $\pi^\pm\ell\nu$, $\pi^0\ell\nu$, $\rho^\pm\ell\nu$, $\rho^0\ell\nu$\ and $\omega\ell\nu$ based on $2.2\e{6}$ $\bbar$ decays collected at CLEO is presented. We have measured the first exclusive $\btou$ branching fraction $\bbpi=[1.19\pm0.41\pm0.21\pm0.19]\e{-4}$ ($[1.70\pm0.51\pm0.31\pm0.27]\e{-4}$), with the ISGW (WSB) model used for efficiency determination. A 90\% C.L. upper limit on $\bbrho$ similar to the previous CLEO limit is obtained. The ratio $\gamrho/\gampi<3.4$ at the 90\% confidence level for both the ISGW and WSB models. This ratio provides some discrimination between form factor models.