An electron antineutrino mass has been measured in tritium β-decay in the Troitsk ν-mass experiment. The setup consists of a windowless gaseous tritium source and an electrostatic electron spectrometer. The whole data set acquired from 1994 to 2004 was reanalyzed. A thorough selection of data with the reliable experimental conditions has been performed. We checked every known systematic effect and obtained the following experimental estimate for neutrino mass squared m 2 ν = −0.67 ± 2.53 eV 2 . This gives an experimental upper sensitivity limit of mν < 2.2 eV , 95% C . L. and upper limit estimates mν < 2.12 eV , 95% C .L. for Bayesian statistics and mν < 2.05 eV , 95% C .L. for the Feldman and Cousins approach.

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We performed a search for any sign of an additional neutrino mass state in β-electron spectrum based on data reanalysis of direct electron antineutrino mass measurements in Tritium beta-decay in the Troitsk nu-mass experiment. The existing data set allows us to search for such a state in the mass range up to 100 eV . The lowest value at a 95% C.L. upper limit for the contribution of a heavy eigenstate into electron neutrino is around or less than 1% for masses above 20 eV .Throughout the last couple decades it has become clear that the Standard Model (SM) of elementary particles cannot explain some of the observed phenomena in particle physics, astrophysics and cosmology. These are baryon asymmetry, dark matter, neutrino oscillations and others. Neutrino oscillations from short baseline experiments favor the existence of an additional neutrino mass state to the three active neutrinos in the SM. Astrophysical observations and cosmology also point to the fact that the effective number of neutrinos is greater than 3 [1]. This can be interpreted as a possible existence of at least one sterile neutrino. Sterile neutrino is a natural consequence of the non-zero neutrino mass and appears in many theories beyond the SM. From this point of view, addition of a. Would a sterile neutrino be found it will be the first particle beyond the Standard Model. While there is a number of the results which disfavor or even are in contradiction with the hypothesis of sterile neutrino, many experiments are undergoing or are planning to search for them. For details we refer to the "Light sterile neutrinos: a white paper" [2].It becomes important to check all possible experimental data to prove, disprove or set an upper limit for the sterile neutrino hypothesis. Results of the reanalysis of our data on the direct electron antineutrino mass measurements in Tritium β-decay in the Troitsk nu-mass experiment [4] are presented in this paper. The group led by V. M. Lobashev was obtaining these data in the period of 1997-2004. We used the same file set and analysis framework as for the electron antineutrino mass. We performed a search for any sign of an additional neutrino mass state in the β-electron spectrum. Such a state with a finite mass would exhibit itself as a kink in the spectrum. Recently a similar analysis was published based on the Mainz data [3].The Troitsk experiment has two major parts: an integrating electrostatic spectrometer with adiabatic magnetic collimation and a windowless gaseous tritium source as a volume for β-decays. The spectrometer resolution was about 4 eV. We measured an integrated electron spectrum at the region of the last 200-300 eV from the spectrum endpoint (18575 eV) by varying the electrostatic potential V on the spectrometer electrode. All details on experimental setup, data taking, analysis, corrections and estimation of systematic error are published in Ref. [4]. For electron antineutrino mass squared we published the value m 2 ν = −0.67 ± 2.53 eV 2 . In accordance with Ref.[4], the spectrum of electrons ...

Measurements of the energy loss of fast electrons at an energy of 18 keV have been performed on molecules of hydrogen isotopes, gaseous T2 and frozen D2. Whereas in the case of gaseous T2 the values of total inelastic cross-section (σtot, gaseous = (3.40 ± 0.07) × 10 −18 cm 2 for E = 18.6 keV), average energy loss (εgaseous = (29.9 ± 1.0) eV) and peak position of the energy loss spectra (ε1, gaseous = 12.6 eV) agree well with the expectations, the corresponding values for quench condensed D2 differ significantly from the ones for gaseous T2. We observe a significant lower total inelastic cross-section (σ tot, solid = (2.98 ± 0.16) × 10 −18 cm 2 , for E = 18.6 keV) larger average energy loss (ε solid = (34.4 ± 3.0) eV) and higher peak position (ε 1, solid = (14.1 +0.7 −0.6 ) eV). These differences may be interpreted in terms of changes of the final state spectrum. A CI calculation for a D2 cluster shows indeed a clear shift of the excited states in agreement with the observation. PACS.34.80.Gs Molecular excitation and ionization by electron impact -78.90.+t Other topics in optical properties, condensed matter spectroscopy and other interactions of particles and radiation with condensed matter