First measurement of the CP-violating phase ϕsdd¯ in Bs 0 → (K + π −)(K − π +) decays

Abstract

A flavour-tagged decay-time-dependent amplitude analysis of B0 s → (K+π −)(K−π +) decays is presented in the K±π ∓ mass range from 750 to 1600 MeV/c 2 . 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 B0 s → K∗ (892)0K ∗ (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, φ dd¯ s , in b → d ¯ds transitions is performed, yielding a value of φ dd¯ s = −0.10 ± 0.13 (stat) ± 0.14 (syst) rad.