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  • Bezrukov, L.  (4)
  • 2020-2024  (4)
  • 2021  (4)
  • 1
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2021
    In:  The European Physical Journal C Vol. 81, No. 8 ( 2021-08)
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 81, No. 8 ( 2021-08)
    Abstract: We present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e. comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range $${5 \times 10^{-3}}\,\mathrm{eV}^2 \lesssim \varDelta m^2_{41} \lesssim {3 \times 10^{-1}}\,\mathrm{eV}^2 $$ 5 × 10 - 3 eV 2 ≲ Δ m 41 2 ≲ 3 × 10 - 1 eV 2 for mixing angles down to $$\sin ^2 2\theta _{14} \gtrsim {0.02} $$ sin 2 2 θ 14 ≳ 0.02 . No significant disappearance additionally to the conventional disappearance related to $$\theta _{13} $$ θ 13 is observed and correspondingly exclusion bounds on the sterile mixing parameter $$\theta _{14} $$ θ 14 as a function of $$ \varDelta m^2_{41} $$ Δ m 41 2 are obtained.
    Type of Medium: Online Resource
    ISSN: 1434-6044 , 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1397769-6
    detail.hit.zdb_id: 1459069-4
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  • 2
    In: Journal of High Energy Physics, Springer Science and Business Media LLC, Vol. 2021, No. 1 ( 2021-01)
    Abstract: A θ 13 oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a so far unique simultaneous determination of θ 13 and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis considers the $$ {\overline{\nu}}_e $$ ν ¯ e interactions up to a visible energy of 8.5 MeV, using the events at higher energies to build a cosmogenic background model considering fast-neutrons interactions and 9 Li decays. The background-model-independent determination of the mixing angle yields sin 2 (2 θ 13 ) = 0 . 094 ± 0 . 017, being the best-fit total background rates fully consistent with the cosmogenic background model. A second oscillation analysis is also performed constraining the total background rates to the cosmogenic background estimates. While the central value is not significantly modified due to the consistency between the reactor-off data and the background estimates, the addition of the background model reduces the uncertainty on θ 13 to 0.015. Along with the oscillation results, the normalization of the anti-neutrino rate is measured with a precision of 0.86%, reducing the 1.43% uncertainty associated to the expectation.
    Type of Medium: Online Resource
    ISSN: 1029-8479
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2027350-2
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  • 3
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2021
    In:  The European Physical Journal C Vol. 81, No. 8 ( 2021-08)
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 81, No. 8 ( 2021-08)
    Abstract: The GERmanium Detector Array ( Gerda ) collaboration searched for neutrinoless double- $$\beta $$ β decay in $$^{76}$$ 76 Ge with an array of about 40 high-purity isotopically-enriched germanium detectors. The experimental signature of the decay is a monoenergetic signal at $$Q_{\beta \beta }$$ Q β β $$=2039.061(7)$$ = 2039.061 ( 7 )  keV in the measured summed energy spectrum of the two emitted electrons. Both the energy reconstruction and resolution of the germanium detectors are crucial to separate a potential signal from various backgrounds, such as neutrino-accompanied double- $$\beta $$ β decays allowed by the Standard Model. The energy resolution and stability were determined and monitored as a function of time using data from regular $$^{228}$$ 228 Th calibrations. In this work, we describe the calibration process and associated data analysis of the full Gerda dataset, tailored to preserve the excellent resolution of the individual germanium detectors when combining data over several years.
    Type of Medium: Online Resource
    ISSN: 1434-6044 , 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1397769-6
    detail.hit.zdb_id: 1459069-4
    Location Call Number Limitation Availability
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  • 4
    In: The European Physical Journal C, Springer Science and Business Media LLC, Vol. 81, No. 6 ( 2021-06)
    Abstract: Neutrinoless double- $$\beta $$ β decay of $$^{76}$$ 76 Ge is searched for with germanium detectors where source and detector of the decay are identical. For the success of future experiments it is important to increase the mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in $$^{76}$$ 76 Ge. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the Gerda setup. The measured resolutions at the Q -value for double- $$\beta $$ β decay of $$^{76}$$ 76 Ge ( $$Q_{\beta \beta }$$ Q β β  = 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array ( Gerda ) experiment and an accumulated exposure of 8.5 kg $$\cdot $$ · year, the background index after analysis cuts is measured to be $$4.9^{+7.3}_{-3.4}\times 10^{-4} \ \text {counts}/(\text {keV} \cdot \text {kg} \cdot \text {year})$$ 4 . 9 - 3.4 + 7.3 × 10 - 4 counts / ( keV · kg · year ) around $$Q_{\beta \beta }$$ Q β β . This work confirms the feasibility of IC detectors for the next-generation experiment Legend .
    Type of Medium: Online Resource
    ISSN: 1434-6044 , 1434-6052
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 1397769-6
    detail.hit.zdb_id: 1459069-4
    Location Call Number Limitation Availability
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