Search for muon-neutrino to electron-neutrino transitions in MINOS

TL;DR

This paper reports a search for muon-neutrino to electron-neutrino oscillations using the MINOS experiment, observing a slight excess of events consistent with previous limits on the mixing angle, but not statistically significant.

Contribution

First search for $ u_ o u_e$ transitions in MINOS with detailed background analysis and comparison to oscillation models.

Findings

Observed 35 events with a background of 27 5 (stat.)  2 (syst.)

Event excess is 1.5 sigma, compatible with existing oscillation limits

Results constrain the mixing angle (2 heta_{13}) near the CHOOZ limit.

Abstract

This letter reports on a search for $\nu_\mu \to \nu_e$ transitions by the MINOS experiment based on a \unit[$3.14\times10^{20}$]{protons-on-target} exposure in the Fermilab NuMI beam. We observe 35 events in the Far Detector with a background of $27\pm 5 {\rm (stat.)} \pm 2 {\rm (syst.)$ events predicted by the measurements in the Near Detector. If interpreted in terms of $\nu_\mu \to \nu_e$ oscillations, this 1.5 $\sigma$ excess of events is consistent with $\sin^{2}(2\theta_{13})$ comparable to the CHOOZ limit when $|\delmsq{}|$=\unit[2.43$\times 10^{-3}$] {${\rm eV^{2}}$} and \sinsq{23}=1.0 are assumed.