First measurement of the CP -violating phase φdd ̄ in s Bs0→(K+π−)(K−π+) decays

Abstract

A flavour-tagged decay-time-dependent amplitude analysis of Bs0 →(K+π−)(K−π+) 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 8TeV, corresponding to an integrated luminosity of 3.0fb−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 K0∗ (800)0 and K0∗ (1430)0 , the K ∗ (892)0 and the K2∗(1430)0 resonances, respectively. The longitudinal polarisation fraction for the Bs0 → K ∗ (892)0 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 dd mixing-induced CP-violating phase, φs , in b → dds transitions is performed, yielding a value of φdd ̄ = −0.10 ± 0.13 (stat) ± 0.14 (syst) rad