Three-body supersymmetric top decays

We discuss three-body supersymmetric top decays, in schemes both with and without R-parity conservation, assuming that sfermion masses are larger than m(t). We find that MSSM top decays into chargino/neutralino pairs have a strong kinematic suppression in the region of the supersymmetric parameter space consistent with the LEP limits, with a decay width less than or equal to 10(-5) GeV. MSSM top decays into neutralino pairs have less kinematical suppression, but require a flavour-changing vertex, and are likely to have a smaller rate. On the other hand, R-violating decays to single charginos, neutralinos and conventional fermions can be larger for values of the R-violating couplings still permitted by other upper limits. The cascade decays of the charginos and neutralinos may lead to spectacular signals with explicit lepton-number violation, such as like-sign lepton events. (C) 2000 Elsevier Science B.V. All rights reserved.