Measurement of CP violation in $B_s^0\to \varphi \varphi$ decays

A measurement of the decay time dependent CP-violating asymmetry in $B_s^0 \to \phi\phi$decaysispresented,alongwithmeasurementsofthe$T$-odd triple-product asymmetries. In this decay channel, the CP-violating weak phase arises from the interference between $B_s^0$-${\bar{B}}_s^0$ mixing and the loop-induced decay amplitude. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $3.0f{b}^{-1}$ collected with the LHCb detector, a signal yield of approximately 4000 $B_s^0\to \varphi \varphi$ decays is obtained. The CP-violating phase is measured to be ${\phi_s =-0.17\pm0.15$(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})$\pm0.03$(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$}$ rad. The triple-product asymmetries are measured to be $A_U=-0.003\pm 0.017(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.006(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$ and $A_V=-0.017\pm 0.017(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t})\pm 0.006(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t})$. Results are consistent with the hypothesis of CP conservation.