Direct measurement of the branching fraction for D+→K¯0μ+νμ and determination of Γ(D0→K−μ+νμ)/Γ(D+→K¯0μ+νμ)

The absolute branching fraction for the decay D+→K¯0μ+νμ is determined using 5321±149±1605321±149±160 singly tagged D−D− sample from the data collected around s=3.773 GeV with the BESII detector at the BEPC collider. In the system recoiling against the singly tagged D−D− mesons, 28.7±6.428.7±6.4 events for D+→K¯0μ+νμ are observed. These yield the absolute branching fraction to be BF(D+→K¯0μ+νμ)=(10.3±2.3±0.8)%. The ratio of the two partial widths for the decays D0→K−μ+νμD0→K−μ+νμ and D+→K¯0μ+νμ is determined to be Γ(D0→K−μ+νμ)/Γ(D+→K¯0μ+νμ)=0.87±0.24±0.15.