We measure the branching fraction and CP violation asymmetry in the decay B0 → π0π0, using a data sample of 752 × 106 BB¯ pairs collected at the ϒð4SÞ resonance with the Belle detector at the KEKB eþe− collider. The obtained branching fraction and direct CP asymmetry are BðB → π0π0Þ ¼ ½1.31 0.19ðstatÞ 0.19ðsystÞ × 10−6 and ACP ¼ þ0.14 0.36ðstatÞ 0.10ðsystÞ, respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belle’s earlier measurements of B0 → πþπ− and B → ππ0 to exclude the CP-violating parameter ϕ2 from the range 15.5° < ϕ2 < 75.0° at 95% confidence level.
Bibliographical noteFunding Information:
computing group for valuable computing and SINET5 network support. We acknowledge support from 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 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 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; the WCU program of the Ministry of Education, National Research Foundation (NRF) of Korea Grants No. 2011-0029457, No. 2012-0008143, No. 2014R1A2A2A01005286, No. 2014R1A2A2A01002734, No. 2015R1A2A2A01003280, No. 2015H1A2A1033649, No. 2016R1D1A1B01010135, No. 2016K1A3A7A09005603, No. 2016K1A3A7A09005604, No. 2016R1D1A1B02012900, No. 2016K1A3A7A09005606, No. NRF-2013K1A3A7A06056592; the Brain Korea 21-Plus program, 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 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; and the U.S. Department of Energy and the National Science Foundation.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy (miscellaneous)