Improved Search for Muon-Neutrino to Electron-Neutrino Oscillations in MINOS

We report the results of a search for nu(e) appearance in a nu(mu) beam in the MINOS long-baseline neutrino experiment. With an improved analysis and an increased exposure of 8.2 x 10(20) protons on the NuMI target at Fermilab, we find that 2sin(2)(theta(23))sin(2)(2 theta(13)) < 0.12(0.20) at 90% confidence level for delta = 0 and the normal ( inverted) neutrino mass hierarchy, with a best-fit of 2sin(2)(theta(23))sin(2)(2 theta(13)) = 0.041(-0.031)(+0.047)(0.079(-0.053)(+0.071)). The theta(13) 0 hypothesis is disfavored by the MINOS data at the 89% confidence level.