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Search for Boosted Dark Matter Interacting with Electrons in Super-Kamiokande
Kachulis, C.,Abe, K.,Bronner, C.,Hayato, Y.,Ikeda, M.,Iyogi, K.,Kameda, J.,Kato, Y.,Kishimoto, Y.,Marti, Ll.,Miura, M.,Moriyama, S.,Nakahata, M.,Nakano, Y.,Nakayama, S.,Okajima, Y.,Orii, A.,Pronost, G American Physical Society 2018 Physical Review Letters Vol.120 No.22
<P>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.</P>
Abe, K.,Bronner, C.,Pronost, G.,Hayato, Y.,Ikeda, M.,Iyogi, K.,Kameda, J.,Kato, Y.,Kishimoto, Y.,Marti, Ll.,Miura, M.,Moriyama, S.,Nakahata, M.,Nakano, Y.,Nakayama, S.,Okajima, Y.,Orii, A.,Sekiya, H. American Physical Society 2017 Physical Review D Vol.96 No.1
<P>We have searched for proton decays into a charged antilepton (e(+), mu(+)) plus a meson (eta, rho(0), omega) and for neutron decays into a charged antilepton (e(+), mu(+)) plus a meson (pi(-), rho(-)) 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 x 10(31) to 1 x 10(34) years at 90% confidence level, depending on the decay mode.</P>
Solar neutrino measurements in Super-Kamiokande-IV
Abe, K.,Haga, Y.,Hayato, Y.,Ikeda, M.,Iyogi, K.,Kameda, J.,Kishimoto, Y.,Marti, Ll.,Miura, M.,Moriyama, S.,Nakahata, M.,Nakajima, T.,Nakayama, S.,Orii, A.,Sekiya, H.,Shiozawa, M.,Sonoda, Y.,Takeda, A. American Physical Society 2016 Physical Review D Vol.94 No.5
<P>Upgraded electronics, improved water system dynamics, better calibration and analysis techniques allowed Super-Kamiokande-IV to clearly observe very low-energy B-8 solar neutrino interactions, with recoil electron kinetic energies as low as similar to 3.5 MeV. Super-Kamiokande-IV data-taking began in September of 2008; this paper includes data until February 2014, a total livetime of 1664 days. The measured solar neutrino flux is (2.308 +/- 0.020)(stat)(-0.040)(+0.039) (syst)) x 10(6)/(cm(2) sec) assuming no oscillations. The observed recoil electron energy spectrum is consistent with no distortions due to neutrino oscillations. An extended maximum likelihood fit to the amplitude of the expected solar zenith angle variation of the neutrino-electron elastic scattering rate in SK-IV results in a day/night asymmetry of (-3.6 +/- 1.6(stat) +/- 0.6(syst)%. The SK-IV solar neutrino data determine the solar mixing angle as sin(2)theta(12) = 0.327(-0.031)(+0.026), all SK solar data (SK-I, SK-II, SK III and SK-IV) measures this angle to be sin(2)theta(12) = 0.334(-0.023)(+0.027), the determined mass-squared splitting is Delta m(21)(2) = 4.8(-0.8)(+1.5) x 10(-5) eV(2).</P>
Abe, K.,Bronner, C.,Pronost, G.,Hayato, Y.,Ikeda, M.,Iyogi, K.,Kameda, J.,Kato, Y.,Kishimoto, Y.,Marti, Ll.,Miura, M.,Moriyama, S.,Nakahata, M.,Nakano, Y.,Nakayama, S.,Okajima, Y.,Orii, A.,Sekiya, H. American Astronomical Society 2017 The Astrophysical journal Vol.850 No.2
<P>We present the results of a search in the Super-Kamiokande (SK) detector for excesses of neutrinos with energies above a few GeV that are in the direction of the track events reported in IceCube. Data from all SK phases (SK-I through SK-IV) were used, spanning a period from 1996 April to 2016 April and corresponding to an exposure of 225 kiloton-years. We considered the 14 IceCube track events from a data set with 1347 livetime days taken from 2010 to 2014. We use Poisson counting to determine if there is an excess of neutrinos detected in SK in a 10 degrees search cone (5 degrees for the highest energy data set) around the reconstructed direction of the IceCube event. No significant excess was found in any of the search directions we examined. We also looked for coincidences with a recently reported IceCube multiplet event. No events were detected within a +/- 500 s time window around the first detected event, and no significant excess was seen from that direction over the lifetime of SK.</P>