Abstract
We present the first measurements of branching fractions of rare tau-lepton decays, ( or ), using a data sample corresponding to collected at a center-of-mass energy of 10.58 GeV with the Belle detector at the KEKB asymmetric-energy collider. The decay is observed for the first time with significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region is measured to be , where the first uncertainty is statistical, the second is systematic, and the third is due to model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from to , respectively. An upper limit is set on the branching fraction of the decay, , at the 90% confidence level.
- Received 27 August 2019
DOI:https://doi.org/10.1103/PhysRevD.100.071101
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