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  • 1
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The International Germanium Experiment (IGEX) has now analyzed 117 mol yr of data from its isotopically enriched (86% 76Ge) germanium detectors. Applying pulse shape discrimination (PSD) to the more recent data, the lower bound on the half-life for neutrinoless double-beta decay of 76Ge is deduced: T 1/2(0ν)〉1.57×1025 yr (90% C.L.). This corresponds to an upper bound on the Majorana neutrino mass parameter, 〈m ν〉, between 0.33 eV and 1.35 eV depending on the choice of theoretical nuclear matrix elements used in the analysis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To search for cold dark matter (CDM) particles, the data from two (Ge-76 and Ge-natural) detectors, fabricated in the first phase of the IGEX collaboration, were accumulated and analyzed for a period from May 1995 to May 1999. The use of effective passive and active shielding together with pulse shape discrimination allowed us to perform long-term measurements with an energy threshold of 2 keV at a level of the residual background 0.1 counts/(kg keV d). New restrictions on masses of weakly interacting massive particles and the cross section of their elastic scattering on nuclei have been obtained from the data corresponding to 810 d of live time. The derived exclusion plots compete with the best bounds obtained so far. Annual modulations of the CDM signal have been also investigated. It is shown that the planned operation of all IGEX detectors (at Canfranc and Baksan) with the recently achieved low-energy thresholds gives a chance to achieve the DAMA annual modulation sensitivity region in a nearest future.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Physics of atomic nuclei 63 (2000), S. 1341-1355 
    ISSN: 1063-7788
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The current situation in experiments studying double-beta decay is surveyed. The amount of experimental information about the two-neutrino mode of the process has grown considerably over the last decade. The two-neutrino double-beta decay of ten nuclei (48Ca, 76Ge, 82Se, 96Zr, 100Mo, 116Cd, 128Te, 130Te, 150Nd, and 238U) was observed in direct and geochemical experiments. However, the main fundamental question—that of neutrinoless double-beta decay, which has not yet been recorded, although the sensitivity of present-day facilities featuring germanium detectors is higher than 1025 yr—remains open. The constraint on the effective Majorana mass on the basis of these results is 〈m v〉〈(0.4–1.1) eV. Further advancements in searches for neutrinoless double-beta decays must rely on developing fundamentally new experimental facilities, since the potential of those that already exist has been exhausted to a considerable extent.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Atomic energy 7 (1961), S. 898-911 
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Notes: Abstract The design and building of reactors requires a knowledge of the interaction cross sections of neutrons with different materials over a broad energy range. Interactions between neutrons and nuclei (radiative capture, fission, scattering) are viewed in the light of current concepts as processes involving the formation of a compound nucleus and displaying a clearly pronounced resonance response: the interaction increases sharply at certain neutron energies. The position and quantitative value of the resonance levels still defy theoretical prediction, and direct measurements of the cross sections concerned are consequently the sole sources of the required information. This article comprises a survey of papers appearing between the first and second Geneva conferences (1955 and 1958) on the peaceful uses of atomic energy, dealing with the study of the properties of resonances of fissionable nuclei. Various methods of describing the interactions between neutrons and fissionable nuclei are considered in the light of the available data. The experimental data have yet to be interpreted fully and unambiguously, though nonetheless some characteristic aspects of the fission process are already apparent. A brief description is given of several refinements in technique employed in the measurement of resonance level parameters, and the results thereby obtained are discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Atomic energy 16 (1964), S. 251-257 
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Atomic energy 23 (1967), S. 669-682 
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Notes: Conclusion The development of techniques for measuring cross-sections has permitted a considerable extension of the range of energies over which these measurements can be carried out with a resolution that is sufficiently high for analysis; simultaneously, the range of nuclei studied has been extended. However, certain difficulties have appeared in processing the experimental data which complicate the interpretation of the results obtained. It is possible to compute more or less reliably the established form of statistical distributions of the level parameters only for Pu239. For fissile nuclei such as U233, U235 and Pu241, the nature of the distributions indicates the existence of significant distortions, associated with the methods of data processing used. Analysis of cross-section models of fissile nuclei shows that the origin of these distortions is associated with both the neglect of interference effects and difficulties of principles, raising doubt on the feasibility of carrying out unambiguous cross-section analysis. In order to verify this conclusion, it is necessary to carry out careful interference analysis of cross-sections over wider energy ranges. At present, the possibilities of processing cross-sections are limited by insufficiently high measurement accuracy of cross-sections between resonances and the absence of information about spin mechanisms of the levels. In order to increase the reliability of the analysis it will be necessary to undertake measurements of the energy dependence of η and the radiative capture cross-sections of the nuclei studied.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-8205
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Physics
    Notes: Abstract Values of ν and total neutron cross sections of the nuclides U236 and Pu239 were measured on a neutron spectrometer, using a pulsed cyclotron beam [1]. Energy relations of the cross sections for fission and radiative capture in the neutron energy region from thermal energies up to 20 eV for U235 and from 5 to 100 eV for Pu239 were obtained, The parameters of an appreciable number of resonances were determined.
    Type of Medium: Electronic Resource
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