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Brief Reports are short papers which report on completed research which, while meeting the usual Physical Review standards of scientific quality, does not warrant a regular article. (Addenda to papers previously published in the Physical Review by the same authors are included in Brief Reports.) A Brief Report may be no longer than 3f printed pages and must be accompanied by an abstract. The same publication schedule as for regular articles is followed, and page proofs are sent to authors.A discussion is given of the mechanisms by which a light scalar or pseudoscalar boson, such as a familon, may be emitted in the radiative decay of a muon. The results of a new experimental search for the decay p f +e + y f , where f is such a boson, are presented. The resulting bounds on the coupling strength are comparable to, but of wider validity than, those from p + -e + f .

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.

Ne atoms from an atomic beam are captured in a holding cell, where the decay positrons and recoil ions are observed. The new value for the asymmetry parameter for this correlation is D = 0.004± 0.0008, which is consistent with timereversal symmetry.

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