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

Abstract

Abstract: A binned Dalitz plot analysis of B± → DK± decays, with D → K0 S π +π − and D → K0 SK+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 +11 −12 ◦ , rB = 0.086+0.013 −0.014, and δB = (101±11)◦ , where rB is the ratio between the suppressed and favoured B-decay amplitudes and δB 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 +10 −9 ◦ , rB = 0.080 ± 0.011, and δB = (110 ± 10)◦