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

Abstract The absolute branching fraction for the decay D + → K ¯ 0 μ + ν μ is determined using 5321 ± 149 ± 160 singly tagged 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 − mesons, 28.7 ± 6.4 events for D + → K ¯ 0 μ + ν μ are observed. These yield the absolute branching fraction to be BF ( D + → K ¯ 0 μ + ν μ ) = ( 10.3 ± 2.3 ± 0.8 ) % . The ratio of the two partial widths for the decays D 0 → K − μ + ν μ and D + → K ¯ 0 μ + ν μ is determined to be Γ ( D 0 → K − μ + ν μ ) / Γ ( D + → K ¯ 0 μ + ν μ ) = 0.87 ± 0.24 ± 0.15 .