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

This letter reports on a search for {nu}{sub {mu}} {yields} {nu}{sub e} transitions by the MINOS experiment based on a 3.14 x 10{sup 20} protons-on-target exposure in the Fermilab NuMI beam. We observe 35 events in the Far Detector with a background of 27 {+-} 5(stat.) {+-} 2(syst.) events predicted by the measurements in the Near Detector. If interpreted in terms of {nu}{sub {mu}} {yields} {nu}{sub e} oscillations, this 1.5 {sigma} excess of events is consistent with sin{sup 2}(2{theta}{sub 13}) comparable to the CHOOZ limit when |{Delta}m{sup 2}| = 2.43 x 10{sup -3} eV{sup 2} and sin{sup 2} (2{theta}{sub 23}) = 1.0 are assumed.