Direct search for mass of neutrino and anomaly in the tritium beta-spectrum

Results of the "Troitsk nu-mass" experiment on the search for the neutrino rest mass in the tritium beta-decay are presented. Study of time dependence of anomalous, bump-like structure at the end of beta spectrum reported ear lier gives indication of periodic shift of the position of the bump with re spect to the end-point energy with a period of 0.5 year. A new upper limit for electron antineutrino rest mass m(nu) < 2.5 eV/c(2) 95% C.L. is derived after accounting for the bump. (C) 1999 Published by Elsevier Science B.V. All rights reserved.