Improved Measurement of Muon Antineutrino Disappearance in MINOS

Abstract

We report an improved measurement of ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ disappearance over a distance of 735 km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$-enhanced configuration. From a total exposure of $2.95\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target, of which 42% have not been previously analyzed, we make the most precise measurement of $\ensuremath{\Delta}{\overline{m}}^{2}=[{2.62}_{\ensuremath{-}0.28}^{+0.31}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.09(\mathrm{syst})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}\text{ }\text{ }{\mathrm{eV}}^{2}$ and constrain the ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ mixing angle ${sin}^{2}(2\overline{\ensuremath{\theta}})>0.75$ (90% C.L.). These values are in agreement with $\ensuremath{\Delta}{m}^{2}$ and ${sin}^{2}(2\ensuremath{\theta})$ measured for ${\ensuremath{\nu}}_{\ensuremath{\mu}}$, removing the tension reported in [P. Adamson et al. (MINOS), Phys. Rev. Lett. 107, 021801 (2011).].