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

The absolute branching fraction for the decay D+→K¯0e+νe is determined using 5321±149±160 singly tagged D− event sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC collider. In the system recoiling against the singly tagged D− mesons, 34.4±6.1 events for D+→K¯0e+νe are observed. Those yield the absolute branching fraction to be BF(D+→K¯0e+νe)=(8.95±1.59±0.67)%. The ratio of the two partial widths for the decays of D0→K−e+νe and D+→K¯0e+νe is determined to be Γ(D0→K−e+νe)/Γ(D+→K¯0e+νe)=1.08±0.22±0.07.