LEPTON-FLAVOR VIOLATION IN LIGHT HADRON DECAYS

The lepton-flavor-violating decays of light pseudoscalar mesons and li ght baryons are investigated within extensions of the SU(2) x U(1) mod el. These models contain heavy Dirac or Majorana neutrinos and allow l arge lepton-heavy-neutrino mixings. The free-parameter space of these models is carefully studied. Special care is devoted to the comparison of results of different models. A large ''nondecoupling'' window is f ound, and the decoupling of extremely heavy neutrinos is explicitly sh own in all models except one, for which the free-parameter space is bo unded. Among the decays studied, the experimentally most interesting d ecays are K-L-->e mu and pi(o)-->e mu. The pi(o)-->e mu, decay is foun d to be equally interesting for the study of lepton-flavor violation a s K-L-->e mu, decay. The constraint on the model parameters, coming fr om the nonobservation of the mu-->e gamma decay, leads to the maximal decay rates B(K-L-->e mu) similar to 5 x 10(-16) and B(pi(o)-->e mu)le ss than or similar to(2n(R)-2) x 10(-15), where n(R) is number of heav y neutrinos, much smaller than the present experimental upper limits. [S0556-2821(98)01607-5].