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

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