Measurement of the ckm angle γ using b± → dk± with d → ks π+π−, ks k+k− decays

Abstract

A binned Dalitz plot analysis of B± → DK± decays, with D → KS π+π− and D → KS K+K−, is performed to measure the CP -violating observables x± and y±, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle γ. The analysis exploits a sample of proton-proton collision data corresponding to 3.0 fb−1 collected by the LHCb experiment. Measurements from CLEO-c of the variation of the strong-interaction phase of the D decay over the Dalitz plot are used as inputs. The values of the parameters are found to be x+ = (−7.7 ± 2.4 ± 1.0 ± 0.4) × 10−2, x− = (2.5 ± 2.5 ± 1.0 ± 0.5) × 10−2, y+ = (−2.2 ± 2.5 ± 0.4 ± 1.0) × 10−2, and y− = (7.5 ± 2.9 ± 0.5 ± 1.4) × 10−2. The first, second, and third uncertainties are the statistical, the experimental systematic, and that associated with the precision of the strong-phase parameters. These are the most precise measurements of these observables and correspond to γ = (62 −14)◦, with a second solution at γ → γ + 180◦, and rB = 0.080−0.021, where rB is the ratio between the suppressed and favoured B decay amplitudes.