Measurement of the semileptonic branching fractions of the D0 meson

Abstract Using the ARGUS detector at the e+ e− storage ring DORISII, we have measured the semileptonic branching ratios of the D 0 meson to be Br ( D 0 → e+ ν eX ) = (6.9 ± 0.3 ± 0.5) % and Br ( D 0 → μ + ν μ X ) = (6.0 ± 0.7 ± 1.2) %, and the semileptonic branching ratio of the charmed hadron mixture from e+ e− annihilation around 10 GeV to be Br ( c → e+ ν eX ) = (9.6 ± 0.4 ± 1.1) %.