Improved search for muon-neutrino to electron-neutrino oscillations in MINOS

Abstract

We report the results of a search for $\hat{I}{½}_e$ appearance in a $\hat{I}{½}_{\hat{I}}¼$ beam in the MINOS long-baseline neutrino experiment. With an improved analysis and an increased exposure of $8.2\times 10^{20}$ protons on the NuMI target at Fermilab, we find that $2{\sin }^2(\hat{I}{¸}_{23}){\sin }^2(2\hat{I}{¸}_{13})<0.12(0.20)$ at 90% confidence level for $\hat{I}´=0$ and the normal (inverted) neutrino mass hierarchy, with a best fit of $2{\sin }^2(\hat{I}{¸}_{23}){\sin }^2(2\hat{I}{¸}_{13})=0.041_{-0.031}^{+0.047}(0.079_{-0.053}^{+0.071})$. The $\hat{I}{¸}_{13}=0$ hypothesis is disfavored by the MINOS data at the 89% confidence level.

5 pages, 3 figures