Leptonic decays of the $D_{s}$ meson and production of orbitally excited D and $D_{s}$ mesons

The purely leptonic decays D/sub s/ to mu nu and D/sub s/ to tau nu are studied in a sample of four million hadronic Z decays collected in 1991-1995 with the ALEPH detector at LEP. A linear discriminant analysis is used to measure the branching fraction B(D/sub s/ to mu nu )=(0.64+or-0.08[stat]+or-0.21[syst]+or-0.15[ phi pi ])% (preliminary), where the last uncertainty is from the branching fraction B(D/sub s/ to phi pi ). Within the standard model, this result corresponds to f/sub Ds/=(284+or-18[stat]+or-49[syst]+or-34[ phi pi ]) MeV. Preliminary results are also reported from an investigation of orbitally excited (L=1) charm mesons in Z to cc and bb events. Significant production of such mesons is observed, and the production rates are measured. (10 refs).