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

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