Improved constraints on sterile neutrinos in the MeV to GeV mass range

Abstract

Improved upper bounds are presented on the coupling |Ue4|2 of an electron to a sterile neutrino ν4 from analyses of data on nuclear and particle decays, including superallowed nuclear beta decays, the ratios Re/μ(π)=BR(π+→e+νe)/BR(π+→μ+νμ), Re/μ(K), Re/τ(Ds), and Be2+ decay, covering the mass range from MeV to GeV.