Constraints on singlet right-handed neutrinos coming from the $Z^0$-width

Abstract

We study the constraints on masses and mixing angles imposed by the measured $Z^0$ invisible width, in a model in which a singlet right-handed neutrino mixes with all the Standard Model neutrinos.

Comments: Revtex, 7 pages, two figures available from the authors, preprint IFT-P.040/92 IFUSP/P-1023/92