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We report the result for a search for the leptonic decay of B+ -> mu(+)nu mu using the full Belle dataset of 711 fb(-1) of integrated luminosity at the gamma(4S) resonance. In the Standard Model leptonic B-meson decays are helicity and Cabibbo-Kobayashi-Maskawa suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second B meson produced in the collision. The directional information from this second B meson is used to boost the observed mu into the signal B-meson rest frame, in which the mu has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the mu momentum spectrum in this frame we find B(B+ -> mu(+)nu mu)=(5.3 +/- 2.0 +/- 0.9) x 10(-7) with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of B(B+ -> mu(+)nu mu) < 8.6 x 10(-7) at 90% confidence level. The experimental spectrum is then used to search for a massive sterile neutrino, B+ -> mu N+, but no evidence is observed for a sterile neutrino with a mass in a range of 01.5 GeV. The determined B+ -> mu(+)nu mu branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.
Jian Wang, Matthias Finger, Qian Wang, Yiming Li, Matthias Wolf, Varun Sharma, Yi Zhang, Konstantin Androsov, Jan Steggemann, Leonardo Cristella, Xin Chen, Davide Di Croce, Rakesh Chawla, Matteo Galli, Anna Mascellani, João Miguel das Neves Duarte, Tagir Aushev, Lei Zhang, Tian Cheng, Yixing Chen, Werner Lustermann, Andromachi Tsirou, Alexis Kalogeropoulos, Andrea Rizzi, Ioannis Papadopoulos, Paolo Ronchese, Hua Zhang, Siyuan Wang, Tao Huang, David Vannerom, Michele Bianco, Sebastiana Gianì, Sun Hee Kim, Kun Shi, Wei Shi, Abhisek Datta, Jian Zhao, Federica Legger, Gabriele Grosso, Ji Hyun Kim, Donghyun Kim, Zheng Wang, Sanjeev Kumar, Wei Li, Yong Yang, Geng Chen, Ajay Kumar, Ashish Sharma, Georgios Anagnostou, Joao Varela, Csaba Hajdu, Muhammad Ahmad, Ekaterina Kuznetsova, Ioannis Evangelou, Muhammad Shoaib, Milos Dordevic, Meng Xiao, Sourav Sen, Xiao Wang, Kai Yi, Jing Li, Rajat Gupta, Zhen Liu, Muhammad Waqas, Hui Wang, Seungkyu Ha, Long Wang, Pratyush Das, Miao Hu, Anton Petrov, Xin Sun, Xin Gao, Chen Chen, Valérie Scheurer, Giovanni Mocellin, Muhammad Ansar Iqbal, Lukas Layer
Riccardo Rattazzi, Angelo Esposito, Alfredo Glioti