First Evidence for $B_s^0 \to ϕϕ$ Decay and Measurements of Branching Ratio and $A_{CP}$ for $B^+ \to ϕK^+$

Abstract

We present the first evidence of charmless decays of the $B_s^0$ meson, the decay \phiphi, and a measurement of the Branching Ratio $\BR(\phiphi)$ using $180 {\rm pb}^{-1}$ of data collected by the \cdfii experiment at the Fermilab Tevatron collider. In addition, the BR and direct CP asymmetry for the \phik\ decay are measured. We obtain: $\BR (\phiphi) = (14 \ase{6}{5}(stat.) \pm 6(syst.)) \times 10^{-6}$, $\BR (\phik) = (7.6 \pm 1.3(stat.) \pm 0.6(syst.)) \times 10^{-6}$, and $\ACP(\phik) = -0.07 \pm 0.17 (stat.) \ase{0.03}{0.02} (syst.)$. Both decays are governed in the Standard Model by second order (penguin) $b \myto s\bar{s}s$ amplitudes.