Observation of B_s Production at the Upsilon(5S) Resonance

Using the CLEO detector at the Cornell Electron Storage Ring, we have observed the Bs meson in e+e- annihilation at the Upsilon(5S) resonance. We find 14 candidates consistent with Bs decays into final states with a J/psi or a Ds(*)-. The probability that we have observed a background fluctuation is less than 8x10e-10. We have established that at the energy of the Upsilon(5S) resonance Bs meson production proceeds predominantly through the creation of Bs*Bs* pairs. We find sigma(e+e- -> Bs*Bs*) = [0.11 (+0.04-0.03)(stat.)+/-0.02(syst.)] nb, and set the following limits: sigma(e+e- -> BsBs) / sigma(e+e- -> Bs*Bs*) < 0.16 and sigma(e+e- -> BsBs*) / sigma(e+e- -> Bs*Bs*) < 0.16 at the 90% confidence level. The mass of the Bs* meson is measured to be M(Bs*) = [5.414 +/- 0.001(stat.) +/- 0.003(syst.)] GeV.
8 pages postscript,also available through http://www.lns.cornell.edu/public/CLNS/2005/, Submitted to PRL