Search for lepton-flavor-violating tau decays into three leptons with 719 million produced tau(+)tau(-) pairs

We present a search for lepton-flavor-violating tau decays into three leptons (electrons or muons) using 782 fb(-1) of data collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. No evidence for these decays is observed and we set 90% confidence level upper limits on the branching fractions between 1.5 x 10(-8) and 2.7 x 10(-8). (C) 2010 Elsevier B.V. All rights reserved.We are grateful to M.J. Herrero for useful discussions. We thank the KEKB group for the excellent operation of the accelerator, the KEK cryogenics group for the efficient operation of the solenoid, and the KEK computer group and the National Institute of Informatics for valuable computing and SINET3 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 and the Australian Department of Industry, Innovation, Science and Research; the National Natural Science Foundation of China under contract Nos. 10575109, 10775142, 10875115 and 10825524; the Department of Science and Technology of India; the BK21 and WCU program of the Ministry of Education, Science and Technology, the CHEP SRC program and Basic Research program (grant No. R01-2008-000-10477-0) of the Korea Science and Engineering Foundation, Korea Research Foundation (KRF-2008-313-000177), and the Korea Institute of Science and Technology Information; the Polish Ministry of Science and Higher Education; the Ministry of Education and Science of the Russian Federation and the Russian Federal Agency for Atomic Energy; the Slovenian Research Agency; the Swiss National Science Foundation; the National Science Council and the Ministry of Education of Taiwan; and the U.S. Department of Energy. This work is supported by a Grant-in-Aid from MEXT for Science Research in a Priority Area ("New Development of Flavor Physics"), and from JSPS for Creative Scientific Research ("Evolution of Tau-Lepton Physics")