Search for B⁺→μ⁺⁢ν_μ and B⁺→μ⁺⁢N with inclusive tagging

Prim, M.  T.; Bernlochner, F.  U.; Goldenzweig, P.; Heck, M.; Adachi, I.; Adamczyk, K.; Aihara, H.; Al Said, S.; Asner, D.  M.; Atmacan, H.; Aulchenko, V.; Aushev, T.; Ayad, R.; Babu, V.; Bakich, A.  M.; Bansal, V.; Behera, P.; Beleño, C.; Bhardwaj, V.; Bhuyan, B.; Bilka, T.; Biswal, J.; Bobrov, A.; Bozek, A.; Bračko, M.; Braun, N.; Browder, T.  E.; Campajola, M.; Cao, L.; Červenkov, D.; Chang, P.; Chekelian, V.; Chen, A.; Cheon, B.  G.; Chilikin, K.; Cho, H.  E.; Cho, K.; Choi, Y.; Choudhury, S.; Cinabro, D.; Cunliffe, S.; Doležal, Z.; Eidelman, S.; Epifanov, D.; Fast, J.  E.; Ferber, T.; Fulsom, B.  G.; Garg, R.; Gaur, V.; Garmash, A.; Giri, A.; Grzymkowska, O.; Guan, Y.; Haba, J.; Hara, T.; Hayasaka, K.; Hayashii, H.; Hou, W. -S.; Iijima, T.; Inami, K.; Inguglia, G.; Ishikawa, A.; Iwasaki, M.; Iwasaki, Y.; Jia, S.; Jin, Y.; Joffe, D.; Joo, K.  K.; Kaliyar, A.  B.; Karyan, G.; Kawasaki, T.; Kichimi, H.; Kiesling, C.; Kim, C.  H.; Kim, D.  Y.; Kim, K.  T.; Kim, S.  H.; Kinoshita, K.; Kodyš, P.; Korpar, S.; Kotchetkov, D.; Križan, P.; Kroeger, R.; Krokovny, P.; Kuhr, T.; Kulasiri, R.; Kumar, R.; Kumita, T.; Kuzmin, A.; Kwon, Y. -J.; Lalwani, K.; Lange, J.  S.; Lee, I.  S.; Lee, J.  K.; Lee, J.  Y.; Lee, S.  C.; Lewis, P.; C.  H., Li; Li Gioi, L.; Libby, J.; Lieret, K.; Liventsev, D.; P. -C., Lu; Luo, T.; Macnaughton, J.; Masuda, M.; Matsuda, T.; Matvienko, D.; Merola, M.; Metzner, F.; Miyabayashi, K.; Mizuk, R.; Mohanty, G.  B.; Mussa, R.; Nakao, M.; De Nardo, G.; Nath, K.  J.; Natkaniec, Z.; Nayak, M.; Niiyama, M.; Nisar, N.  K.; Nishida, S.; Nishimura, K.; Ogawa, S.; Ono, H.; Onuki, Y.; Pakhlov, P.; Pakhlova, G.; Pal, B.; Pardi, S.; Park, H.; Park, S. -H.; Patra, S.; Paul, S.; Pedlar, T.  K.; Pestotnik, R.; Piilonen, L.  E.; Popov, V.; Prencipe, E.; Ritter, M.; Rostomyan, A.; Rozanska, M.; Russo, G.; Sahoo, D.; Sakai, Y.; Santelj, L.; Savinov, V.; Schneider, O.; Schnell, G.; Schueler, J.; Schwanda, C.; Seino, Y.; Senyo, K.; Sevior, M.  E.; Shebalin, V.; Shiu, J. -G.; Shwartz, B.; Simon, F.; Sokolov, A.; Solovieva, E.; Starič, M.; Strube, J.  F.; Sumihama, M.; Sumiyoshi, T.; Sutcliffe, W.; Takizawa, M.; Tamponi, U.; Tao, Y.; Tenchini, F.; Trabelsi, K.; Uchida, M.; Uglov, T.; Unno, Y.; Uno, S.; Ushiroda, Y.; Usov, Y.; Vahsen, S.  E.; Van Tonder, R.; Varner, G.; Varvell, K.  E.; Vinokurova, A.; Wang, B.; Wang, C.  H.; Wang, M. -Z.; Wang, P.; Watanuki, S.; Won, E.; Yang, S.  B.; Ye, H.; Yin, J.  H.; Yusa, Y.; Zhang, Z.  P.; Zhilich, V.; Zhukova, V.; Zhulanov, V.

doi:10.1103/physrevd.101.032007

We report the result for a search for the leptonic decay of B+→μ+⁢ν_μ using the full Belle dataset of 711 fb−1 of integrated luminosity at the ⁡Y(4⁢S) 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 μ into the signal B-meson rest frame, in which the μ has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the μ momentum spectrum in this frame we find B(B+→μ+⁢ν_μ)=(5.3±2.0±0.9)×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+→μ+⁢ν_μ)<8.6×10^−7 at 90% confidence level. The experimental spectrum is then used to search for a massive sterile neutrino, B+→μ+⁢N, but no evidence is observed for a sterile neutrino with a mass in a range of 0–1.5 GeV. The determined B+→μ+⁢ν_μ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.