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新山 雅之 所属 京都産業大学 理学部 物理科学科 職種 教授 |
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| 発行・発表の年月 | 2019/11 |
| 形態種別 | その他 |
| 査読 | 査読あり |
| 標題 | Search for $B^+ \to μ^+\, ν_μ$ and $B^+ \to μ^+\, N$ with inclusive tagging |
| 執筆形態 | その他 |
| 著者・共著者 | M. T. Prim,F. U. Bernlochner,P. Goldenzweig,M. Heck,I. Adachi,K. Adamczyk,H. Aihara,S. Al Said,D. M. Asner,H. Atmacan,V. Aulchenko,T. Aushev,R. Ayad,V. Babu,A. M. Bakich,V. Bansal,P. Behera,C. Beleño,V. Bhardwaj,B. Bhuyan,T. Bilka,J. Biswal,A. Bobrov,A. Bozek,M. Bračko,N. Braun,T. E. Browder,M. Campajola,L. Cao,D. Červenkov,P. Chang,V. Chekelian,A. Chen,B. G. Cheon,K. Chilikin,H. E. Cho,K. Cho,Y. Choi,S. Choudhury,D. Cinabro,S. Cunliffe,Z. Doležal,S. Eidelman,D. Epifanov,J. E. Fast,T. Ferber,B. |
| 概要 | We report the result for a search for the leptonic decay of $B^+ \to \mu^+ \,
\nu_{\mu}$ using the full Belle data set of 711 fb${}^{-1}$ of integrated luminosity at the $\Upsilon(4S)$ resonance. In the Standard Model leptonic $B$-meson decays are helicity and CKM 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 $\mathcal{B}(B^+ \to \mu^+ \, \nu_\mu) = \left( 5.3 \pm 2.0 \pm 0.9 \right) \times 10^{-7}$ with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of $\mathcal{B}(B^+ \to \mu^+ \, \nu_{\mu}) < 8.6 \times 10^{-7}$ at 90% CL. The experimental spectrum is then used to search for a massive sterile neutrino, $B^+ \to \mu^+ \, N$, but no evidence is observed for a sterile neutrino with a mass in a range of 0 - 1.5 GeV. The determined $B^+ \to \mu^+ \, \nu_{\mu}$ branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models. |
| DOI | 10.1103/PhysRevD.101.032007 |