We report final results of a series of measurements of continuum dimuon production in proton-nucleus collisions at Femilab. New results with 6 times more statistics are included. A full description of the apparatus and methods used in the analysis of this series of measurements is given. The sea quark distribution of the nucleon is determined within the context of Drell-Yan and quantum-chromodynamic descriptions of dilepton production in hadron collisions.

The properties of the dimuon enhancement seen in 400-GeV proton-nucleus collisions have been clarified by a threefold increase in data. We find two peaks whose widths are consistent with our resolution: M x = 9.4 GeV with B dcr/dy \ y =o= 1.8 x 10" 37 cm 2 /nucleon and M 2 = 10.0 GeV with B da/dy | y=0 =0 o 7xl0" 37 cm 2 /micleon. Evidence for the possible existence of a third peak near 10.4 GeV is discussed as are the comparisons with the properties of a qq system, where q is a new heavy quark.

The MEGA experiment, which searched for the muon-and electron-number violating decay ϩ →e ϩ ␥, is described. The spectrometer system, the calibrations, the data taking procedures, the data analysis, and the sensitivity of the experiment are discussed. The most stringent upper limit on the branching ratio, B( ϩ →e ϩ ␥)Ͻ1.2ϫ10 Ϫ11 with 90% confidence, is derived from a likelihood analysis.

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