Observation of the Decay K+ --> pi+ mu+ mu-

E787 Collaboration, S. Adler, M. S. Atiya +37

We have observed the rare decay K+ --> pi+ mu+ mu- and measured the branching ratio Gamma(K+ --> pi+ mu+ mu-)/Gamma(K+ --> all) = (5.0 +/- 0.4 (stat.) +/- 0.7 (sys.) +/- 0.6 (theor…