Measurement of the CKM angle γ using B ± → DK ± with D → K S 0 π + π − , K S 0 K + K − decays

bstract A binned Dalitz plot analysis of B ± → DK ± decays, with D → K S 0 π + π − 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 γ . 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 fb −1 , the values of the CP violation parameters are found to be x − = (9.0 ± 1.7 ± 0.7 ± 0.4) × 10 −2 , y − = (2.1 ± 2.2 ± 0.5 ± 1.1) × 10 −2 , x + = (−7.7 ± 1.9 ± 0.7 ± 0.4) × 10 −2 , and y + = (−1.0 ± 1.9 ± 0.4 ± 0.9) × 10 −2 . 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 γ = (87 − 12 + 11 ) ∘ , r B = 0.086 − 0.014 + 0.013 , and δ B = (101±11)°, where r B is the ratio between the suppressed and favoured B -decay amplitudes and δ 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 γ = (80 − 9 + 10 ) ∘ , r B = 0.080 ± 0.011, and δ B = (110 ± 10)°.