We report results of an electron-beam-dump search for neutral particles with masses in the range 1 to 15 MeV and lifetimes r between 10 ~1 4 and 10 -10 s. No evidence was found for such an object. We rule out the existence of any 1.8-MeV pseudoscalar boson with r > 8.2 x 10 ~1 5 s and an absorption cross section in matter less than 1 mb per nucleon, and exclude r> 1 x 10 ~1 4 s were its cross section to equal 50 mb per nucleon. In conjunction with measurements of the electron's anomalous magnetic moment, this experiment shows that the narrow positron peaks observed in heavy-ion collisions at the Gessellschaft fur Schwerionenforschung are not due to an elementary pseudoscalar.

The Main Injector Neutrino Oscillation Search (MINOS) experiment uses an acceleratorproduced neutrino beam to perform precision measurements of the neutrino oscillation parameters in the "atmospheric neutrino" sector associated with muon neutrino disappearance. This long-baseline experiment measures neutrino interactions in Fermilab's NuMI neutrino beam with a near detector at Fermilab and again 735 km downstream with a far detector in the Soudan Underground Laboratory in northern Minnesota. The two detectors are magnetized steel-scintillator tracking calorimeters. They are designed to be as similar as possible in order to ensure that differences in detector response have minimal impact on the comparisons of event rates, energy spectra and topologies that are essential to MINOS measurements of oscillation parameters. The design, construction, calibration and performance of the far and near detectors are described in this paper.

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