Measurement of cos 2β in B^0 → D(*)h^0 with D → K^0_Sπ^+π^− decays by a combined time-dependent Dalitz plot analysis of BABAR and Belle data

Abstract

We report measurements of sin 2β and cos 2β using a time-dependent Dalitz plot analysis of B^0 → D(*)h^0 with D → K^0_Sπ^+π^− decays, where the light unflavored and neutral hadron h^0 is a π^0, η, or ω meson. The analysis uses a combination of the final data sets of the BABAR and Belle experiments containing 471×10^6 and 772×10^6  BB pairs collected at the Υ(4S) resonance at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. We measure sin 2β = 0.80±0.14(stat)±0.06(syst)±0.03(model) and cos 2β = 0.91±0.22(stat)±0.09(syst)±0.07(model). The result for the direct measurement of the angle is β = (22.5±4.4(stat)±1.2(syst)±0.6(model))°. The last quoted uncertainties are due to the composition of the D^0 → K^0_Sπ^+π^− decay amplitude model, which is newly established by a Dalitz plot amplitude analysis of a high-statistics e^+e^− → cc data sample as part of this analysis. We find the first evidence for cos 2β > 0 at the level of 3.7 standard deviations. The measurement excludes the trigonometric multifold solution π/2−β = (68.1±0.7)° at the level of 7.3 standard deviations and therefore resolves an ambiguity in the determination of the apex of the CKM Unitarity Triangle. The hypothesis of β = 0° is ruled out at the level of 5.1 standard deviations, and thus CP violation is observed in B^0 → D(*)h^0 decays. The measurement assumes no direct CP violation in B^0 → D(*)h^0 decays.

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© 2018 Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Received 17 April 2018; published 26 December 2018. We thank the PEP-II and KEKB groups for the excellent operation of the accelerators. The BaBar experiment acknowledges the expertise and dedication of the computing organizations for their support. The collaborating institutions wish to thank SLAC for its support and the kind hospitality extended to them. The Belle experiment wishes to acknowledge the KEK cryogenics group for the efficient operation of the solenoid; and the KEK computer group, the National Institute of Informatics, and the PNNL/EMSL computing group for valuable computing and SINET5 network support. This work was supported by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan, the Japan Society for the Promotion of Science (JSPS), and the Tau-Lepton Physics Research Center of Nagoya University; the Australian Research Council; Austrian Science Fund under Grant No. P 26794-N20; the Canadian Natural Sciences and Engineering Research Council; the National Natural Science Foundation of China under Contracts No. 10575109, No. 10775142, No. 10875115, No. 11175187, No. 11475187, No. 11521505 and No. 11575017; the Chinese Academy of Science Center for Excellence in Particle Physics; the Ministry of Education, Youth and Sports of the Czech Republic under Contract No. LTT17020; the French Commissariat à l'Energie Atomique and Institut National de Physique Nucléaire et de Physique des Particules; the German Bundesministerium für Bildung und Forschung, the Carl Zeiss Foundation, the Deutsche Forschungsgemeinschaft, the Excellence Cluster Universe, and the VolkswagenStiftung; the Department of Science and Technology of India; the Istituto Nazionale di Fisica Nucleare of Italy; National Research Foundation (NRF) of Korea Grants No. 2014R1A2A2A01005286, No. 2015R1A2A2A01003280, No. 2015H1A2A1033649, No. 2016R1D1A1B01010135, No. 2016K1A3A7A09005603, and No. 2016R1D1A1B02012900; Radiation Science Research Institute, Foreign Large-Size Research Facility Application Supporting project and the Global Science Experimental Data Hub Center of the Korea Institute of Science and Technology Information; the Foundation for Fundamental Research on Matter of the Netherlands; the Research Council of Norway; the Polish Ministry of Science and Higher Education and the National Science Center; the Ministry of Education and Science of the Russian Federation and the Russian Foundation for Basic Research; the Slovenian Research Agency; Ikerbasque, Basque Foundation for Science and MINECO (Juan de la Cierva), Spain; the Swiss National Science Foundation; the Ministry of Education and the Ministry of Science and Technology of Taiwan; the Science and Technology Facilities Council of the United Kingdom; the Binational Science Foundation (U.S.-Israel); and the U.S. Department of Energy and the National Science Foundation. Individuals have received support from the Marie Curie EIF (European Union) and the A. P. Sloan Foundation (USA).

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