Improved Measurement of Muon Antineutrino Disappearance in MINOS

We report an improved measurement of ν_μ disappearance over a distance of 735 km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a ν_μ-enhanced configuration. From a total exposure of 2.95×10²⁰ protons on target, of which 42% have not been previously analyzed, we make the most precise measurement of ${Δ}{m̄}²=[{2.62}_{{-}0.28}+0.31(stat)±{}0.09(syst)]×{}{10}^{{-}3} {eV}²$ and constrain the ${{{ν}}}_{{μ}}$ mixing angle ${sin}²(2{{θ}})>0.75$ (90% C.L.). These values are in agreement with ${Δ}{m}²$ and ${sin}²(2{θ})$ measured for ${{ν}}_{{μ}}$, removing the tension reported in [P. Adamson et al. (MINOS), Phys. Rev. Lett. 107, 021801 (2011).].