Abstract
We report the result for a search for the leptonic decay of using the full Belle dataset of of integrated luminosity at the resonance. In the Standard Model leptonic -meson decays are helicity and Cabibbo-Kobayashi-Maskawa suppressed. To maximize sensitivity an inclusive tagging approach is used to reconstruct the second meson produced in the collision. The directional information from this second meson is used to boost the observed into the signal -meson rest frame, in which the has a monochromatic momentum spectrum. Though its momentum is smeared by the experimental resolution, this technique improves the analysis sensitivity considerably. Analyzing the momentum spectrum in this frame we find with a one-sided significance of 2.8 standard deviations over the background-only hypothesis. This translates to a frequentist upper limit of at 90% confidence level. The experimental spectrum is then used to search for a massive sterile neutrino, , but no evidence is observed for a sterile neutrino with a mass in a range of 0–1.5 GeV. The determined branching fraction limit is further used to constrain the mass and coupling space of the type II and type III two-Higgs-doublet models.
7 More- Received 10 November 2019
- Accepted 2 January 2020
DOI:https://doi.org/10.1103/PhysRevD.101.032007
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society