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Lepton-flavor violation in light hadron decays

The lepton-flavour violating decays of light pseudoscalar mesons and light baryons are investigated within extensions of the SU(2)xU(1) model. These models contain heavy Dirac or Majorana neutrinos and allow large 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. The large "nondecoupling" window is found, and the decoupling of extremely heavy neutrinos is explicitly shown in all models except one, for which the free-parameter space is bounded. Among the decays studied, the experimentally most interesting decays are K_L --> e mu and pi^0 --> e mu. The pi^0 --> e mu decay is found to be equally interesting for the study of lepton flavor-violation as K_L --> e mu decay. The constraint on the model parameters, coming from the nonobservation of the mu --> e gamma decay, leads to the maximal decay rates B(K_L --> e mu) ~ 5 imes 10^{; ; -16}; ; and B(pi^0 --> e mu)< (2n_R-2)x10^{; ; -15}; ; , where n_R is number of heavy neutrinos, much smaller than the present experimental upper limits.

psudoscalar mesons ; lepton flavor violation ; heavy neutrino ; decoupling

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