3,338 research outputs found

    Solar neutrino measurements using the full data period of Super-Kamiokande-IV

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    International audienceAn analysis of solar neutrino data from the fourth phase of Super-Kamiokande~(SK-IV) from October 2008 to May 2018 is performed and the results are presented. The observation time of the data set of SK-IV corresponds to 29702970~days and the total live time for all four phases is 58055805~days. For more precise solar neutrino measurements, several improvements are applied in this analysis: lowering the data acquisition threshold in May 2015, further reduction of the spallation background using neutron clustering events, precise energy reconstruction considering the time variation of the PMT gain. The observed number of solar neutrino events in 3.493.49--19.4919.49~MeV electron kinetic energy region during SK-IV is 65,443388+390(stat.)±925(syst.)65,443^{+390}_{-388}\,(\mathrm{stat.})\pm 925\,(\mathrm{syst.}) events. Corresponding 8B\mathrm{^{8}B} solar neutrino flux is (2.314±0.014(stat.)±0.040(syst.))×106 cm2s1(2.314 \pm 0.014\, \rm{(stat.)} \pm 0.040 \, \rm{(syst.)}) \times 10^{6}~\mathrm{cm^{-2}\,s^{-1}}, assuming a pure electron-neutrino flavor component without neutrino oscillations. The flux combined with all SK phases up to SK-IV is (2.336±0.011(stat.)±0.043(syst.))×106 cm2s1(2.336 \pm 0.011\, \rm{(stat.)} \pm 0.043 \, \rm{(syst.)}) \times 10^{6}~\mathrm{cm^{-2}\,s^{-1}}. Based on the neutrino oscillation analysis from all solar experiments, including the SK 58055805~days data set, the best-fit neutrino oscillation parameters are sin2θ12,solar=0.306±0.013\rm{sin^{2} \theta_{12,\,solar}} = 0.306 \pm 0.013 and Δm21,solar2=(6.100.81+0.95)×105 eV2\Delta m^{2}_{21,\,\mathrm{solar}} = (6.10^{+ 0.95}_{-0.81}) \times 10^{-5}~\rm{eV}^{2}, with a deviation of about 1.5σ\sigma from the Δm212\Delta m^{2}_{21} parameter obtained by KamLAND. The best-fit neutrino oscillation parameters obtained from all solar experiments and KamLAND are sin2θ12,global=0.307±0.012\sin^{2} \theta_{12,\,\mathrm{global}} = 0.307 \pm 0.012 and Δm21,global2=(7.500.18+0.19)×105 eV2\Delta m^{2}_{21,\,\mathrm{global}} = (7.50^{+ 0.19}_{-0.18}) \times 10^{-5}~\rm{eV}^{2}

    Solar neutrino measurements using the full data period of Super-Kamiokande-IV

    No full text
    International audienceAn analysis of solar neutrino data from the fourth phase of Super-Kamiokande~(SK-IV) from October 2008 to May 2018 is performed and the results are presented. The observation time of the data set of SK-IV corresponds to 29702970~days and the total live time for all four phases is 58055805~days. For more precise solar neutrino measurements, several improvements are applied in this analysis: lowering the data acquisition threshold in May 2015, further reduction of the spallation background using neutron clustering events, precise energy reconstruction considering the time variation of the PMT gain. The observed number of solar neutrino events in 3.493.49--19.4919.49~MeV electron kinetic energy region during SK-IV is 65,443388+390(stat.)±925(syst.)65,443^{+390}_{-388}\,(\mathrm{stat.})\pm 925\,(\mathrm{syst.}) events. Corresponding 8B\mathrm{^{8}B} solar neutrino flux is (2.314±0.014(stat.)±0.040(syst.))×106 cm2s1(2.314 \pm 0.014\, \rm{(stat.)} \pm 0.040 \, \rm{(syst.)}) \times 10^{6}~\mathrm{cm^{-2}\,s^{-1}}, assuming a pure electron-neutrino flavor component without neutrino oscillations. The flux combined with all SK phases up to SK-IV is (2.336±0.011(stat.)±0.043(syst.))×106 cm2s1(2.336 \pm 0.011\, \rm{(stat.)} \pm 0.043 \, \rm{(syst.)}) \times 10^{6}~\mathrm{cm^{-2}\,s^{-1}}. Based on the neutrino oscillation analysis from all solar experiments, including the SK 58055805~days data set, the best-fit neutrino oscillation parameters are sin2θ12,solar=0.306±0.013\rm{sin^{2} \theta_{12,\,solar}} = 0.306 \pm 0.013 and Δm21,solar2=(6.100.81+0.95)×105 eV2\Delta m^{2}_{21,\,\mathrm{solar}} = (6.10^{+ 0.95}_{-0.81}) \times 10^{-5}~\rm{eV}^{2}, with a deviation of about 1.5σ\sigma from the Δm212\Delta m^{2}_{21} parameter obtained by KamLAND. The best-fit neutrino oscillation parameters obtained from all solar experiments and KamLAND are sin2θ12,global=0.307±0.012\sin^{2} \theta_{12,\,\mathrm{global}} = 0.307 \pm 0.012 and Δm21,global2=(7.500.18+0.19)×105 eV2\Delta m^{2}_{21,\,\mathrm{global}} = (7.50^{+ 0.19}_{-0.18}) \times 10^{-5}~\rm{eV}^{2}

    Updated T2K measurements of muon neutrino and antineutrino disappearance using 3.6 ×\times 1021^{21} protons on target

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    International audienceMuon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but CPT violation and non-standard interactions can violate this symmetry. In this work we report the measurements of sin2θ23\sin^{2} \theta_{23} and Δm322\Delta m_{32}^2 independently for neutrinos and antineutrinos. The aforementioned symmetry violation would manifest as an inconsistency in the neutrino and antineutrino oscillation parameters. The analysis discussed here uses a total of 1.97×\times1021^{21} and 1.63×\times1021^{21} protons on target taken with a neutrino and antineutrino beam respectively, and benefits from improved flux and cross-section models, new near detector samples and more than double the data reducing the overall uncertainty of the result. No significant deviation is observed, consistent with the standard neutrino oscillation picture

    Measurements of neutrino oscillation parameters from the T2K experiment using 3.6 x 1021 protons on target

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    Updated T2K measurements of muon neutrino and antineutrino disappearance using 3.6 ×\times 1021^{21} protons on target

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    International audienceMuon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but CPT violation and non-standard interactions can violate this symmetry. In this work we report the measurements of sin2θ23\sin^{2} \theta_{23} and Δm322\Delta m_{32}^2 independently for neutrinos and antineutrinos. The aforementioned symmetry violation would manifest as an inconsistency in the neutrino and antineutrino oscillation parameters. The analysis discussed here uses a total of 1.97×\times1021^{21} and 1.63×\times1021^{21} protons on target taken with a neutrino and antineutrino beam respectively, and benefits from improved flux and cross-section models, new near detector samples and more than double the data reducing the overall uncertainty of the result. No significant deviation is observed, consistent with the standard neutrino oscillation picture

    Measurement of the cosmogenic neutron yield in Super-Kamiokande with gadolinium loaded water

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    International audienceCosmic-ray muons that enter the Super-Kamiokande detector cause hadronic showers due to spallation in water, producing neutrons and radioactive isotopes. Those are a major background source for studies of MeV-scale neutrinos and searches for rare events. Since 2020, gadolinium was introduced in the ultra-pure water in the Super-Kamiokande detector to improve the detection efficiency of neutrons. In this study, the cosmogenic neutron yield was measured using data acquired during the period after the gadolinium loading. The yield was found to be (2.76±0.02(stat.)±0.19(syst.))×104μ1g1cm2(2.76 \pm 0.02\,\mathrm{(stat.) \pm 0.19\,\mathrm{(syst.)}}) \times 10^{-4}\,\mu^{-1} \mathrm{g^{-1} cm^{2}} at 259 GeV of average muon energy at the Super-Kamiokande detector

    Updated T2K measurements of muon neutrino and antineutrino disappearance using 3.6 x 1021 protons on target

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    Search for Cosmic-Ray Boosted Sub-GeV Dark Matter Using Recoil Protons at Super-Kamiokande.

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    We report a search for cosmic-ray boosted dark matter with protons using the 0.37  megaton×years data collected at Super-Kamiokande experiment during the 1996-2018 period (SKI-IV phase). We searched for an excess of proton recoils above the atmospheric neutrino background from the vicinity of the Galactic Center. No such excess is observed, and limits are calculated for two reference models of dark matter with either a constant interaction cross section or through a scalar mediator. This is the first experimental search for boosted dark matter with hadrons using directional information. The results present the most stringent limits on cosmic-ray boosted dark matter and exclude the dark matter-nucleon elastic scattering cross section between 10^{-33}cm^{2} and 10^{-27}cm^{2} for dark matter mass from 1  MeV/c^{2} to 300  MeV/c^{2}

    Measurement of the helicity asymmetry E\mathbb{E} for the γppπ0\vec{\gamma}\vec{p} \to p \pi^0 reaction in the resonance region

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    International audienceThe double-spin-polarization observable E\mathbb{E} for γppπ0\vec{\gamma}\vec{p}\to p\pi^0 has been measured with the CEBAF Large Acceptance Spectrometer (CLAS) at photon beam energies EγE_\gamma from 0.367 to 2.173 GeV2.173~\mathrm{GeV} (corresponding to center-of-mass energies from 1.240 to 2.200 GeV2.200~\mathrm{GeV}) for pion center-of-mass angles, cosθπ0c.m.\cos\theta_{\pi^0}^{c.m.}, between -0.86 and 0.82. These new CLAS measurements cover a broader energy range and have smaller uncertainties compared to previous CBELSA data and provide an important independent check on systematics. These measurements are compared to predictions as well as new global fits from The George Washington University, Mainz, and Bonn-Gatchina groups. Their inclusion in multipole analyses will refine our understanding of the single-pion production contribution to the Gerasimov-Drell-Hearn sum rule and improve the determination of resonance properties

    Updated T2K measurements of muon neutrino and antineutrino disappearance using 3.6 ×\times 1021^{21} protons on target

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    Muon neutrino and antineutrino disappearance probabilities are identical in the standard three-flavor neutrino oscillation framework, but CPT violation and non-standard interactions can violate this symmetry. In this work we report the measurements of sin2θ23\sin^{2} \theta_{23} and Δm322\Delta m_{32}^2 independently for neutrinos and antineutrinos. The aforementioned symmetry violation would manifest as an inconsistency in the neutrino and antineutrino oscillation parameters. The analysis discussed here uses a total of 1.97×\times1021^{21} and 1.63×\times1021^{21} protons on target taken with a neutrino and antineutrino beam respectively, and benefits from improved flux and cross-section models, new near detector samples and more than double the data reducing the overall uncertainty of the result. No significant deviation is observed, consistent with the standard neutrino oscillation picture
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