Title: First measeurements in search for keV-sterile neutrino in tritium beta-decay by Troitsk nu-mass experiment,
Abstract: We present the first measurements of tritium beta-decay spectrum in the
electron energy range 16-18.6 keV. The goal is to find distortions which may
correspond to the presence of a heavy sterile neutrinos. A possible
contribution of this kind would manifest itself as a kink in the spectrum with
a similar shape but with end point shifted by the value of a heavy neutrino
mass. We set a new upper limits to the neutrino mixing matrix element U^2_{e4}
which improve existing limits by a factor from 2 to 5 in the mass range 0.1-2
keV.