Decay ofb-Flavored Hadrons to Single-Muon and Dimuon Final States

An enhancement in the inclusive cross section for single muons produced in e⁺e^- annihilation at the Υ(4S) is observed, confirming the interpretation that a new bare flavor (B mesons) is produced at the Υ(4S). A branching ratio for B→Xμν of (9.4±{}3.6)% is obtained. The two-muon decay, B→Xμ⁺μ^- 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→Xe⁺e^-, we obtain 1.3% as an upper limit for B→Xl⁺l^-.