Improved measurement of muon antineutrino disappearance in MINOS

Abstract

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