Abstract

We study possible contributions of heavy sterile neutrinos ?h to the decays ?-?e±(?±)???-. From the experimental upper bounds on their rates we derive new constraints on the ?h-?? mixing in the mass region 140.5 MeV?m?h?1637 MeV. We discuss cosmological and astrophysical status of ?h in this mass region and compare our constraints with those recently derived by the NOMAD Collaboration. © 2001 Elsevier Science B.V.