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

Author: Fujikawa, Brian Kurt

Year: 1990

Degree: Dissertation (Ph.D.)

Advisor: McKeown, Robert D.

Committee Members: McKeown, Robert D.; Vogel, Petr; Filippone, Bradley W.; Hitlin, David G.

Option: Physics

DOI: 10.7907/9e8k-2p03

Abstract

We report on a recent search for ν̅ₑ appearance from stopped π⁺ → µ⁺νµ and µ⁺ → e⁺νₑν̅µ decay made by the LAMPF experiment E645. The appearance of ν̅ₑ may occur from ν̅µ → ν̅ₑ, νₑ → ν̅ₑL, or νµ → ν̅ₑL oscillations. Appearance may also occur from rare µ⁺ → e⁺ν̅ₑνµ decay, which is allowed by a multiplicative lepton charge conservation law. The neutrino energies range from Eν 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 ν̅µ, ν̅ₑ, νµ → ν̅ₑ oscillation parameters and the rare µ⁺ → e⁺ν̅ₑνµ decay branching ratio are presented.

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