Decay of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>b</mml:mi></mml:math>-Flavored Hadrons to Single-Muon and Dimuon Final States

An enhancement in the inclusive cross section for single muons produced in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at the $\ensuremath{\Upsilon}(4S)$ is observed, confirming the interpretation that a new bare flavor ($B$ mesons) is produced at the $\ensuremath{\Upsilon}(4S)$. A branching ratio for $B\ensuremath{\rightarrow}X\ensuremath{\mu}\ensuremath{\nu}$ of (9.4\ifmmode\pm\else\textpm\fi{}3.6)% is obtained. The two-muon decay, $B\ensuremath{\rightarrow}X{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ is not observed, providing a 90%-confidence-level upper limit for the branching ratio for that decay of 1.7%. Combining this with our previously reported limit of 5% for $B\ensuremath{\rightarrow}X{e}^{+}{e}^{\ensuremath{-}}$, we obtain 1.3% as an upper limit for $B\ensuremath{\rightarrow}X{l}^{+}{l}^{\ensuremath{-}}$.