Constraints on massive neutrinos in pi -->e nu decay.

Abstract

A search has been carried out for the production of neutrinos in the mass range 60 to 130 MeV coupling to the electron in the decay ${\ensuremath{\pi}}^{+}\ensuremath{\rightarrow}{e}^{+}\ensuremath{\nu}$. The dominant background from the $\ensuremath{\pi}\ensuremath{-}\ensuremath{\mu}\ensuremath{-}e$ decay chain has been suppressed by use of a new technique leading to more than an order of magnitude greater sensitivity than achieved previously.