First measurement of the CP-violating phase in bs0→φφ decays

A first flavor-tagged measurement of the time-dependent CP-violating asymmetry in Bs0→φφ decays is presented. In this decay channel, the CP-violating weak phase arises due to CP violation in the interference between Bs0-B̄s0 mixing and the b→ss̄s gluonic penguin decay amplitude. Using a sample of pp collision data corresponding to an integrated luminosity of 1.0 fb ^-1 and collected at a center-of-mass energy of 7 TeV with the LHCb detector, 880 Bs0→φφ signal decays are obtained. The CP-violating phase is measured to be in the interval [-2.46,-0.76] rad at a 68% confidence level. The p value of the standard model prediction is 16%.