Search for the Disappearance of Muon Antineutrinos in the NuMI Neutrino Beam

We report constraints on antineutrino oscillation parameters that were obtained by using the two MINOS detectors to measure the 7% muon antineutrino component of the NuMI neutrino beam. In the Far Detector, we select 130 events in the charged-current muon antineutrino sample, compared to a prediction of 136.4 +/- 11.7(stat)(-8.9)(+10.2)(syst) events under the assumption vertical bar Delta(m) over bar (2)vertical bar = 2.32 x 10(-3) eV(2), sin(2)(2 (theta) over bar = 1.0. Assuming no oscillations occur at the Near Detector baseline, a fit to the two-flavor oscillation approximation constrains vertical bar Delta m(2)vertical bar < 3.37 x 10(-3) eV(2) at the 90% confidence level with sin(2)(2<(theta)over bar>) = 1.0.