Semileptonic Branching Fraction of Charged and Neutral B Mesons

TL;DR

This paper measures the semileptonic branching fractions of charged and neutral B mesons using ${}$(4S) events, providing the first such measurement for charged B mesons and comparing their lifetimes.

Contribution

It presents the first measurement of the semileptonic branching fraction for charged B mesons and compares it to neutral B mesons, assuming equal semileptonic widths.

Findings

Charged B mesons have a semileptonic branching fraction of about 10.1%.

Neutral B mesons have a semileptonic branching fraction of about 10.9%.

The ratio of branching fractions suggests similar lifetimes for charged and neutral B mesons.

Abstract

An examination of leptons in ${\Upsilon (4S)}$ events tagged by reconstructed $B$ decays yields semileptonic branching fractions of $b_-=(10.1 \pm 1.8\pm 1.4)\%$ for charged and $b_0=(10.9 \pm 0.7\pm 1.1)\%$ for neutral $B$ mesons. This is the first measurement for charged $B$. Assuming equality of the charged and neutral semileptonic widths, the ratio $b_-/b_0=0.93 \pm 0.18 \pm 0.12$ is equivalent to the ratio of lifetimes. A postscript version is available through World-Wide-Web in http://w4.lns.cornell.edu/public/CLNS/1994