First Flavor-Tagged Determination of Bounds on Mixing-Induced CP Violation in Bs -> J/psi phi Decays

This Letter describes the first determination of bounds on the CP-violation parameter 2*beta_s using Bs decays in which the flavor of the bottom meson at production is identified. The result is based on approximately 2,000 Bs -> J/psi phi decays reconstructed in a 1.35 fb-1 data sample collected with the CDF II detector using p-bar p collisions produced at the Fermilab Tevatron. We report confidence regions in the two-dimensional space of 2*beta_s and the decay-width difference Delta-Gamma. Assuming the standard model predictions of 2*beta_s and Delta-Gamma, the probability of a deviation as large as the level of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations. Dedicated to the memory of our dear friend and colleague, Michael P. Schmidt.