Abstract: During the runs of the PS 179 experiment at LEAR of CERN, we
photographed an event of antiproton-Ne absorption, with a complete pi+ -> mu+
->e+ chain. From the vertex of the reaction a very slow energy pi+ was
emitted. The pi+ decays into a mu+ and subsequently the mu+ decays into a
positron. At the first decay vertex a muon neutrino was emitted and at the
second decay vertex an electron neutrino and a muon antineutrino. Measuring the
pion and muon tracks and applying the momentum and energy conservation and
using a classical statistical interval estimator, we obtained an
experimental upper limit for the muon neutrino mass: m_nu < 2.2 MeV at a 90%
confidence level. A statistical analysis has been performed of the factors
contributing to the square value of the neutrino mass limit.