Measuring Antineutrino Oscillations in MINOS

MINOS has previously reported the results of $\bar{\nu}_{\mu}$ disappearance from a direct observation of muon antineutrinos. The antineutrinos studied for this purpose are taken from two types of beam configurations: (a) Forward Horn Current (FHC), optimized for ${\nu}_{\mu}$ selection where the $\bar{\nu}_{\mu}$ content is 7\% of the neutrino beam, and (b) Reverse Horn Current (RHC), optimized for $\bar{\nu}_{\mu}$ selection where the $\bar{\nu}_{\mu}$ content is 40\% of the beam. The previous analyses were based on 3.2e20 protons on the NuMI target in FHC configuration and 1.7e20 protons on target in RHC configuration. These analyses make a precise measurement of the oscillation parameters $\Delta\bar{m}^{2}_{23}$ and $sin^{2}2\bar\theta_{23}$ and also constrain the fraction of ${\nu}_{\mu}$ that oscillate to $\bar{\nu}_{\mu}$. In the present analysis we have an FHC $\bar{\nu}_{\mu}$ data sample with 7.1e20 protons on target which will be used to improve the previous measurements. This talk summarizes the agreement between data and simulation in the Near Detector at Fermilab.