Constraints on Massive Neutrinos inπ→eνDecay

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 ${\pi }^{+}\to e^{+}\nu$. The dominant background from the $\pi -\mu -e$ decay chain has been suppressed by use of a new technique leading to more than an order of magnitude greater sensitivity than achieved previously.