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Article

Measurement of CP violation in the Bs0→ϕϕ decay and search for the B 0 → ϕϕ decay

Journal of High Energy Physics. 2019. No. 12. P. 155.
A. Boldyrev, D. Derkach, M. Hushchyn, N. Kazeev, A. Maevskiy, F. Ratnikov, A. Ustyuzhanin, K. Arzymatov, V. Belavin, M. Borisyak.

A measurement of the time-dependent CP-violating asymmetry in B0 s → φφ 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 √ s = 7 TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 B0 s → φφ decays is obtained. The CP-violating phase φ sss¯ 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 ¯b → ss¯ ss¯ transitions. Finally, a limit on the branching fraction of the B0 → φφ decay is determined to be B(B0 → φφ) < 2.7 × 10−8 at 90 % confidence level.