A Search for νₑ Appearance from Stopped π⁺ and µ⁺ Decay at LAMPF

Citation

Fujikawa, Brian Kurt (1990) A Search for νₑ Appearance from Stopped π⁺ and µ⁺ Decay at LAMPF. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9e8k-2p03. https://resolver.caltech.edu/CaltechETD:etd-06062007-121228

Abstract

We report on a recent search for ν̅ₑ appearance from stopped π⁺ → µ⁺ν_µ and µ⁺ → e⁺νₑν̅_µ decay made by the LAMPF experiment E645. The appearance of ν̅ₑ may occur from ν̅_µ → ν̅ₑ, νₑ → ν̅ₑ_L, or ν_µ → ν̅ₑ_L oscillations. Appearance may also occur from rare µ⁺ → e⁺ν̅ₑν_µ decay, which is allowed by a multiplicative lepton charge conservation law. The neutrino energies range from E_ν 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 ν̅ₑ through the ν̅ₑp → 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 ν̅ₑp CC reaction. The neutrons are detected through radiative neutron capture on gadolinium. We find no evidence for ν̅ₑ appearance in the first year of running. New limits on the ν̅_µ, ν̅ₑ, ν_µ → ν̅ₑ oscillation parameters and the rare µ⁺ → e⁺ν̅ₑν_µ decay branching ratio are presented.

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