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 $8.2\ifmmode\times\else\texttimes\fi{}{10}^{20}$ 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.

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