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

This Letter reports on a search for e transitions by the MINOS experiment based on a 3.141020 protons-on-target exposure in the Fermilab NuMI beam. We observe 35 events in the Far Detector with a background of 275(stat)2(syst) events predicted by the measurements in the Near Detector. If interpreted in terms of e oscillations, this 1.5s excess of events is consistent with sin2(213) comparable to the CHOOZ limit when |m2|=2.4310-3eV2 and sin2(223)=1.0 are assume