A search for muon neutrino to electron neutrino oscillations in the MINOS Experiment

We perform a search for vμ → ve oscillations, a process which would manifest a nonzero value of the θ13 mixing angle, in the MINOS long-baseline neutrino oscillation experiment. The analysis consists of searching for an excess of ve charged-current candidate events over the predicted backgrounds, made mostly of neutral-current events with high electromagnetic content. A novel technique to select electron neutrino events is developed, which achieves an improved separation between the signal and the backgrounds, and which consequently yields a better reach in θ13. The backgrounds are predicted in the Far Detector from Near Detector measurements. An excess is observed in the Far Detector data over the predicted backgrounds, which is consistent with the background-only hypothesis at 1.2 standard deviations.