Production of D_s^** mesons in hadronic Z decays

The production rates of the orbitally excited D_s^** mesons, D_s1^± and D_s2^*±, are measured with the 4.1 million hadronic Z decays recorded by the ALEPH detector during 1991-1995. The D_s^** mesons are reconstructed in the decay modes D_s1⁺ → D^*+K⁰, D_s1⁺ → D^*0K⁺ and D_s2^*+ → D⁰K⁺. The production rate of the D_s1^± is measured to be f(Z → D_s1^±) = (0.52 ± 0.09 ± 0.06)%, under the assumption that the two considered decay modes of the D_s1^± saturate the branching ratio. The production rate of the D_s2^*± is determined to be f(Z → D_s2^*±) = (0.83 ± 0.29_-0.13^+0.07)%, assuming that the branching fraction of the decay D_s2^*+ → D⁰K⁺ is 45%. The production rates in Z → cc̄ and Z → bb̄ decays are measured separately.