a Search for Electron-Associated Neutrino Appearance from Stopped Positive Pion and Positive Muon Decay at LAMPF

We report on a recent search for | nu_{e} appearance from stopped pi^+ to mu^+nu_mu and mu^+ to e^+nu_{e} |nu_mu decay made by the LAMPF experiment E645. The appearance of |nu_{e} may occur from |nu_mu to |nu_ {e}, nu_{e} to |nu _{eL}, or nu_ mu to | nu_{eL} oscillations. Appearance may also occur from rare mu^+ to e^+|nu _{e}nu_mu decay, which is allowed by a multiplicative lepton charge conservation law. The neutrino energies range from E_ nu = 0 to 52.8MeV. The neutrino detector, which is located 26.1 meters from the neutrino source, consists of a segmented liquid scintillator and proportional drift tube central detector surrounded by both active and passive shielding. The central detector detects |nu_{e} through the |nu_{e}p to ne^+ Charge Current (CC) reaction, which is signaled by the direct detection of the final state positron and neutron. The hydrogen-rich liquid scintillators act as free proton targets for the |nu_{e} p CC reaction. The neutrons are detected through radiative neutron capture on gadolinium. We find no evidence for |nu_{e} appearance in the first year of running. New limits on the |nu_mu, nu_{e}, nu_mu to |nu_{e} oscillation parameters and the rare mu^+ to e^+| nu_{e}nu_mu decay branching ratio are presented.