39 research outputs found

    Testing Non-Standard Interactions Between Solar Neutrinos and Quarks with Super-Kamiokande

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    Non-Standard Interactions (NSI) between neutrinos and matter affect the neutrino flavor oscillations. Due to the high matter density in the core of the Sun, solar neutrinos are suited to probe these interactions. Using the 277277 kton-yr exposure of Super-Kamiokande to 8^{8}B solar neutrinos, we search for the presence of NSI. Our data favors the presence of NSI with down quarks at 1.8σ\sigma, and with up quarks at 1.6σ\sigma, with the best fit NSI parameters being (ϵ11d,ϵ12d\epsilon_{11}^{d},\epsilon_{12}^{d}) = (-3.3, -3.1) for dd-quarks and (ϵ11u,ϵ12u\epsilon_{11}^{u},\epsilon_{12}^{u}) = (-2.5, -3.1) for uu-quarks. After combining with data from the Sudbury Neutrino Observatory and Borexino, the significance increases by 0.1σ\sigma

    Neutron tagging following atmospheric neutrino events in a water Cherenkov detector

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    International audienceWe present the development of neutron-tagging techniques in Super-Kamiokande IV using a neural network analysis. The detection efficiency of neutron capture on hydrogen is estimated to be 26%, with a mis-tag rate of 0.016 per neutrino event. The uncertainty of the tagging efficiency is estimated to be 9.0%. Measurement of the tagging efficiency with data from an Americium-Beryllium calibration agrees with this value within 10%. The tagging procedure was performed on 3,244.4 days of SK-IV atmospheric neutrino data, identifying 18,091 neutrons in 26,473 neutrino events. The fitted neutron capture lifetime was measured as 218±9 μs

    Neutron Tagging following Atmospheric Neutrino Events in a Water Cherenkov Detector

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    International audienceWe present the development of neutron-tagging techniques in Super-Kamiokande IV using a neural network analysis. The detection efficiency of neutron capture on hydrogen is estimated to be 26%, with a mis-tag rate of 0.016 per neutrino event. The uncertainty of the tagging efficiency is estimated to be 9.0%. Measurement of the tagging efficiency with data from an Americium-Beryllium calibration agrees with this value within 10%. The tagging procedure was performed on 3,244.4 days of SK-IV atmospheric neutrino data, identifying 18,091 neutrons in 26,473 neutrino events. The fitted neutron capture lifetime was measured as 218 \pm 9 \mu s

    Search for Boosted Dark Matter Interacting with Electrons in Super-Kamiokande

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    A search for boosted dark matter using 161.9 kt yr of Super-Kamiokande IV data is presented. We search for an excess of elastically scattered electrons above the atmospheric neutrino background, with a visible energy between 100 MeV and 1 TeV, pointing back to the Galactic center or the Sun. No such excess is observed. Limits on boosted dark matter event rates in multiple angular cones around the Galactic center and Sun are calculated. Limits are also calculated for a baseline model of boosted dark matter produced from cold dark matter annihilation or decay. This is the first experimental search for boosted dark matter from the Galactic center or the Sun interacting in a terrestrial detector

    Search for Neutrinos in Super-Kamiokande Associated with the GW170817 Neutron-star Merger

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    We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the first detected gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to ~100 PeV, in a time window ±500 s around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is 16.00.6+0.7{16.0}_{-0.6}^{+0.7} (21.30.8+1.1{21.3}_{-0.8}^{+1.1}) cm−2 for muon neutrinos (muon antineutrinos), with an error range of ±5° around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of −2. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is 6.6 × 107 cm−2 for anti-electron neutrinos under the assumption of a Fermi–Dirac spectrum with average energy of 20 MeV

    Search for nucleon decay into charged antilepton plus meson in 0.316 megaton . years exposure of the Super-Kamiokande water Cherenkov detector

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    We have searched for proton decays into a charged antilepton (e+, μ+) plus a meson (η, ρ0, ω) and for neutron decays into a charged antilepton (e+, μ+) plus a meson (π−, ρ−) using Super-Kamiokande I-IV data, corresponding to 0.316  megaton⋅years of exposure. This measurement updates the previous published result by using 2.26 times more data and improved analysis methods. No significant evidence for nucleon decay is observed and lower limits on the partial lifetime of the nucleon are obtained. The limits range from 3×1031 to 1×1034  years at 90% confidence level, depending on the decay mode

    Real-time supernova neutrino burst monitor at Super-Kamiokande

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    We present a real-time supernova neutrino burst monitor at Super-Kamiokande (SK). Detecting supernova explosions by neutrinos in real time is crucial for giving a clear picture of the explosion mechanism. Since the neutrinos are expected to come earlier than light, a fast broadcasting of the detection may give astronomers a chance to make electromagnetic radiation observations of the explosions right at the onset. The role of the monitor includes a fast announcement of the neutrino burst detection to the world and a determination of the supernova direction. We present the online neutrino burst detection system and studies of the direction determination accuracy based on simulations at SK.Comment: 15 pages, 8 figures, accepted for publication in Astroparticle Physic

    Search for Neutral Q-balls in Super-Kamiokande II

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    A search for Q-balls induced groups of successive contained events has been carried out in Super-Kamiokande II with 541.7 days of live time. Neutral Q-balls would emit pions when colliding with nuclei, generating a signal of successive contained pion events along a track. No candidate for successive contained event groups has been found in Super-Kamiokande II, so upper limits on the possible flux of such Q-balls have been obtained.Comment: 5 pages, 5 figures, Submitted to Phys. Lett.

    A Proposal for a Detector 2 km Away From the T2K Neutrino Source

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    We propose building a detector site 2km from the neutrino production point of the the T2K experiment. At this distance, almost the same neutrino flux is measured as that seen at Super-K 295 km away. We propose to measure this flux with both a 1 kton water Cherenkov detector which has been optimized to match Super-K resolution, and a 100 ton fiducial volume liquid argon time projection chamber which will provide fine grain imaging and low particle detection thresholds for a precise study of neutrino interactions at the relevant energies. High energy muons which exit the water Cherenkov detector will be measured by an iron muon ranger. In this document, we show that combination of a detector made with the same target as Super-K, with almost the same detector response, and an extremely fine-grained tracking chamber sited in the off-axis beam, will allow us to predict the events seen at Super-K with very little correction other than that of geometric acceptance
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