Abstract
A measurement of the time-dependent CP-violating asymmetry in {B}_s^0to phi phi decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of 5.0 fb−1 collected by the LHCb experiment at centre-of-mass energies sqrt{s} = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 {B}_s^0to phi phi decays is obtained. The CP-violating phase {phi}_s^{soverline{s}s} is measured to be −0.073 ± 0.115(stat) ± 0.027(syst) rad, under the assumption it is independent of the helicity of the ϕϕ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be |λ| = 0.99 ± 0.05(stat) ± 0.01(syst). In addition, T-odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in overline{b}to overline{s}soverline{s}s transitions. Finally, a limit on the branching fraction of the B0 → ϕϕ decay is determined to be mathcal{B}left({B}^0to phi phi right)<2.7times {10}^{-8} at 90 % confidence level.
Highlights
In the Standard Model (SM) the Bs0 → φφ decay, where the φ(1020) is implied throughout this paper, is forbidden at tree level and proceeds predominantly via a gluonic b → sss loop process
Interference caused by the resulting weak phase difference between the 0 s oscillation and decay amplitudes leads to a CP asymmetry in the decay-time distributions of Bs0 and B0s mesons
This paper reports a time-dependent analysis of Bs0 → φφ decays, where the φ meson is reconstructed in the K+K− final state, that measures the CP -violating phase, φssss, and the parameter |λ|, that is related to the direct CP violation
Summary
In the Standard Model (SM) the Bs0 → φφ decay, where the φ(1020) is implied throughout this paper, is forbidden at tree level and proceeds predominantly via a gluonic b → sss loop (penguin) process. The LHCb collaboration has measured the weak phase in several decay processes: Bs0 → J/ψ K+K−, Bs0 → J/ψ π+π−, Bs0 → J/ψ K+K− for the K+K− invariant mass region above 1.05 GeV/c, Bs0 → ψ(2S)φ and Bs0 → Ds+Ds−, corresponding to the combined result of −0.041 ± 0.025 rad [8]. These measurements are consistent with the SM prediction and place stringent constraints on CP violation in Bs0-. Results presented here supersede the previous measurements based on data collected in 2011 and 2012 [10]
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