# Measurement of the CKM angle γ using $B^\pm \to DK^\pm$ with $D \to K {_S}{^0} \pi^+\pi^-, K {_S}{^0} K^+K^-$ decays

LHCb Collaboration; Bernet, R; Müller, K; Serra, N; Steinkamp, O; Straumann, U; Vollhardt, A; et al (2018). Measurement of the CKM angle γ using $B^\pm \to DK^\pm$ with $D \to K {_S}{^0} \pi^+\pi^-, K {_S}{^0} K^+K^-$ decays. Journal of High Energy Physics, 08:176.

## Abstract

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 )∘, rB = 0.086 − 0.014 + 0.013 , 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 − 9 + 10 )∘, rB = 0.080 ± 0.011, and δB = (110 ± 10)°.

## Abstract

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 )∘, rB = 0.086 − 0.014 + 0.013 , 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 − 9 + 10 )∘, rB = 0.080 ± 0.011, and δB = (110 ± 10)°.

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Item Type: Journal Article, refereed, original work 07 Faculty of Science > Physics Institute 530 Physics Physical Sciences > Nuclear and High Energy Physics English 2018 06 Mar 2019 16:15 26 Jan 2022 19:31 Springer 1029-8479 Erratum: https://doi.org/ 10.1007/JHEP10(2018)107 Gold Publisher DOI. An embargo period may apply. https://doi.org/10.1007/JHEP08(2018)176