First Flavor-Tagged Determination of Bounds on Mixing-Induced $CP$ Violation in ${B}_{s}^{0}\ensuremath{\rightarrow}J/\ensuremath{\psi}\ensuremath{\phi}$ Decays

First Flavor-Tagged Determination of Bounds on Mixing-Induced $C P$ Violation in $B_{s}^{0} \to J / ψ ϕ$ Decays

T. Aaltonen et al. (CDF Collaboration)

Phys. Rev. Lett. 100, 161802 – Published 22 April 2008

Abstract

This Letter describes the first determination of bounds on the $C P$ -violation parameter $2 β_{s}$ using $B_{s}^{0}$ decays in which the flavor of the bottom meson at production is identified. The result is based on approximately 2000 $B_{s}^{0} \to J / ψ ϕ$ 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 $2 β_{s}$ and the decay-width difference $Δ Γ$ . Assuming the standard model predictions of $2 β_{s}$ and $Δ Γ$ , the probability of a deviation as large as the level of the observed data is 15%, corresponding to 1.5 Gaussian standard deviations.