A binned Dalitz plot analysis of B± DK± decays, with D K S 0 + and D K S 0 K+K, is used to perform a measurement of the CP-violating observables x± and y±, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle . The analysis is performed without assuming any D decay model, through the use of information on the strong-phase variation over the Dalitz plot from the CLEO collaboration. Using a sample of proton-proton collision data collected with the LHCb experiment in 2015 and 2016, and corresponding to an integrated luminosity of 2.0 fb1, the values of the CP violation parameters are found to be x = (9.0 ± 1.7 ± 0.7 ± 0.4) × 102, y = (2.1 ± 2.2 ± 0.5 ± 1.1) × 102, x+ = (7.7 ± 1.9 ± 0.7 ± 0.4) × 102, and y+ = (1.0 ± 1.9 ± 0.4 ± 0.9) × 102. The first uncertainty is statistical, the second is systematic, and the third is due to the uncertainty (on the strong-phase measurements. These values are used to obtain = (87 12 + 11 ), rB = 0.086 0.014 + 0.013 , and B = (101±11)°, where rB is the ratio between the suppressed and favoured B-decay amplitudes and B is the corresponding strong-interaction phase difference. This measurement is combined with the result obtained using 2011 and 2012 data collected with the LHCb experiment, to give = (80 9 + 10 ), rB = 0.080 ± 0.011, and B = (110 ± 10)°. Open image in new window
