Abstract
We report the first measurement of the lepton polarization in the decay as well as a new measurement of the ratio of the branching fractions , where denotes an electron or a muon, and the is reconstructed in the modes and . We use the full data sample of pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, and , are consistent with the theoretical predictions of the standard model.
- Received 1 December 2016
DOI:https://doi.org/10.1103/PhysRevLett.118.211801
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