Abstract
We report a measurement of the branching ratios for two decay modes of the lepton: and . The separation of these channels is accomplished in the DELCO detector by use of a gas Čerenkov counter to identify fast kaons. The invariant-mass distribution of the system has been used to set an upper bound on the neutrino mass of 157 MeV at 95% confidence limit.
- Received 13 November 1984
DOI:https://doi.org/10.1103/PhysRevLett.54.624
©1985 American Physical Society