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## First measurement of the CP-violating phase ϕdds in B s 0 → (K+π−)(K−π+) decays

Journal of High Energy Physics. 2018. Vol. 2018. P. 1-31.
Ratnikov F., Баранов А. С., Borisyak M. A., Derkach D., Гущин М. И., Kazeev N., Ustyuzhanin A.

A flavour-tagged decay-time-dependent amplitude analysis of B s 0  → (K+π−)(Kπ+) decays is presented in the K±π∓ mass range from 750 to 1600MeV/c2. The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb−1. Several quasi-two-body decay modes are considered, corresponding to K±π∓ combinations with spin 0, 1 and 2, which are dominated by the K 0 *(800)0 and K 0 * (1430)0, the K*(892)0 and the K 2 * (1430)0 resonances, respectively. The longitudinal polarisation fraction for the B0s→K∗(892)∘K∗(892)0Bs0→K∗(892)∘K¯∗(892)0 decay is measured as fL = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase, ϕdd⎯⎯⎯⎯sϕsdd¯, in b→dd⎯⎯⎯sb→dd¯s transitions is performed, yielding a value of ϕdd⎯⎯⎯⎯s=−0.10±0.13(stat)±0.14ϕsdd¯=−0.10±0.13(stat)±0.14 (syst) rad.