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This paper reports on a search for {}₄ from ^+e^+{}₄_, allowed by multiplicative but not additive muon conservation, and for ₄ from ^+e^+₄{}_, allowed by both. Neutrinos from the Clinton P. Anderson Meson Physics Facility have been used, together with a six-ton Cherenkov counter filled with H₂O (D₂O) to look for ₄pe^+ (₄de^-). The branching ratio ({^+e^+₄_) } ({^+) }=-0. 0010. 040 is in excellent agreement with the additive law. The cross section 〈 (₄de^-) 〉= (0. 520. 18) 10^-40 cm^2 agrees with theory.
Willis et al. (Mon,) studied this question.