| Using 13.4fb-1 of e +e- collision data taken with the CLEO-II detector at center-of-mass energies near 10.6 GeV, we present two analyses to study the spectroscopy and decays of charmed strange mesons.; In the first analysis, we have obtained the first confirming evidence for the existence of the D*sJ (2317)+. We have also observed and established the existence of a second narrow resonance, denoted as the DsJ(2463) +. The two narrow resonances are observed in the D+s pi0 and D*+s pi0 final state, respectively. Accounting for the cross-feed backgrounds due to the addition or omission of photons, we have measured the mean mass differences ⟨DeltaM( Dspi0)⟩ = 350.0 +/- 1.2 [stat.] +/- 1.0 [syst.] MeV/c2 for the D*sJ (2317)+ state, and ⟨DeltaM( D*s pi0)⟩ = 351.2 +/- 1.7 [stat.] +/- 1.0 [syst.] MeV/c2 for the new DsJ(2463) + state. We have also searched, but find no evidence, for decays of the two states via the channels D*+s gamma, D+s gamma, and D+s pi+pi-. The observations of the two states at 2.32 and 2.46 GeV/c2, in the D+s pi0 and D*+s pi0 decay channels respectively, are consistent with their interpretations as cs¯ mesons with orbital angular momentum L = 1, and spin-parity JP = 0+ and 1+.; In the second analysis, we report an improved measurement of the partial width for the decay D+s → mu+numu. Using a neutrino reconstruction method based on missing energy and momentum, we identify a sample of D+s → mu+numu candidates. Specifically we measure the branching fraction to be B (Ds → mu+nu mu)/ B (Ds → &phis;pi+) = 0.167 +/- 0.031 [stat.] +/- 0.011 [syst.], from which we extract the pseudoscalar decay constant fDs = (270 +/- 25 +/- 9 +/- 34) MeV where the last error in fDs is due to the uncertainty on the previously measured value for B ( D+s → &phis;pi+). |
