Candidate Events in a Search for Muon Antineutrino to Electron Antineutrino Oscillations

Abstract

A search for $\nuebar$'s in excess of the number expected from conventional sources has been made using the Liquid Scintillator Neutrino Detector, located 30 m from a proton beam dump at LAMPF. A $\nuebar$ signal was detected via the reaction $\nuebar\,p \rightarrow e^{+}\,n$ with $e^{+}$ energy between 36 and $60\mev$, followed by a $\gamma$ from $np\to d\gamma$ ($2.2\mev$). Using strict cuts to identify $\gamma$'s correlated with positrons results in a signal of 9 events, with an expected background of $2.1\pm 0.3$. A likelihood fit to the entire $e^{+}$ sample yields a total excess of $16.4_{-8.9}^{+9.7}\pm 3.3$ events, where the second uncertainty is systematic. If this excess is attributed to neutrino oscillations of the type $\numubar\rightarrow\nuebar$, it corresponds to an oscillation probability of ($0.34_{-0.18}^{+0.20}\pm 0.07$)\%.

3 PS figures; corrected TeX file (April 21, 1995)