A measurement of semileptonic B decaysto narrow orbitally-excited charm mesons

The decay chain b --> (B) over bar --> D-**0 l(-) (nu) over bar X , D-**0 --> D(*+)pi(-), D*+ --> D(0)pi(+), D-0 --> (Kpi or K3pi) is identified in a sample of 3.9 million hadronic Z decays collected with the OPAL detector at LEP. The branching ratio BR (b --> (B) over bar) x BR ((B) over bar --> D-1(0) l(-) (nu) over bar X) x BR (D-1(0) --> D(*+)pi(-)) is measured to be (2.64 +/- 0.79 (stat) +/- 0.39 (syst)) x 10(-3) for the J(P)=1(+) (D-1(0)) state. For decays into the J(P)=2(+) (D-2(*0)) state, an upper limit of 1.4 x 10(-3) is placed on the branching ratio at the 95% confidence level.