Improved measurement of muon antineutrino disappearance in MINOS

We report an improved measurement of ν̅ μ disappearance over a distance of 735 km using the MINOS detectors and the Fermilab Main Injector neutrino beam in a ν̅ 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 Δm̅ 2=[2.62-0.28+0.31(stat)±0.09(syst)]×10-3 eV2 and constrain the ν̅ μ mixing angle sin⁡2(2θ̅ )>0.75 (90% C.L.). These values are in agreement with Δm2 and sin⁡2(2θ) measured for νμ, removing the tension reported in [ P. Adamson et al. Phys. Rev. Lett. 107 021801 (2011)]