We present the result of an indirect search for high energy neutrinos from Weakly Interacting Massive Particle (WIMP) annihilation in the Sun using upward-going muon (upmu) events at ...Super-Kamiokande. Data sets from SKI-SKIII (3109.6 days) were used for the analysis. We looked for an excess of neutrino signal from the Sun as compared with the expected atmospheric neutrino background in three upmu categories: stopping, non-showering, and showering. No significant excess was observed. The 90% C.L. upper limits of upmu flux induced by WIMPs of 100 GeV c-2 were 6.4 X 10--15 cm--2 s--1 and 4.0 X 10--15 cm--2 s--1 for the soft and hard annihilation channels, respectively. These limits correspond to upper limits of 4.5 X 10--39 cm--2 and 2.7 X 10--40 cm--2 for spin-dependent WIMP-nucleon scattering cross sections in the soft and hard annihilation channels, respectively.
A search for the dinucleon decay pp → K+ K+ has been performed using 91.6 kton·yr data from Super-Kamiokande-I. This decay provides a sensitive probe of the R-parity-violating parameter λ112''. A ...boosted decision tree analysis found no signal candidates in the data. The expected background was 0.28±0.19 atmospheric neutrino induced events and the estimated signal detection efficiency was 12.6%±3.2%. A lower limit of 1.7×10(32) years has been placed on the partial lifetime of the decay O16 → C14K+ K+ at 90% C.L. A corresponding upper limit of 7.8×10(-9) has been placed on the parameter λ112''.
It has been hypothesized that large fluxes of neutrinos may be created in astrophysical 'cosmic accelerators.' The primary background for a search for astrophysical neutrinos comes from atmospheric ...neutrinos, which do not exhibit the pointlike directional clustering that characterizes a distant astrophysical signal. We perform a search for neutrino point sources using the upward-going muon data from three phases of operation (SK-I, SK-II, and SK-III) spanning 2623 days of live time taken from 1996 April 1 to 2007 August 11. The search looks for signals from suspected galactic and extragalactic sources, transient sources, and uncataloged sources. While we find interesting signatures from two objects-RX J1713.7-3946 (97.5% CL) and GRB 991004D (95.3% CL)-these signatures lack compelling statistical significance given trial factors. We set limits on the flux and fluence of neutrino point sources above energies of 1.6 GeV.
A first study of neutron tagging is conducted in Super-Kamiokande, a 50,000 ton water Cherenkov detector. The tagging efficiencies of thermal neutrons are evaluated in a 0.2%
GdCl
3
-water solution ...and pure water. They are determined to be, respectively, 66.7% for events above 3
MeV and 20% with corresponding background probabilities of
2
×
10
-
4
and
3
×
10
-
2
. This newly developed technique may enable water Cherenkov detectors to identify
ν
¯
e
’s from astrophysical sources as well as those produced by commercial reactors via the delayed coincidence scheme.
To develop a technology of forming grooves for low cost cell production, a multi-blade wheel grinding method was investigated. The process time of groove formation on the surface of 10 × 10 cm
2 ...polycrystalline silicon substrate was reduced to 30 s by a newly developed high-speed groove formation machine. Simultaneous formation of junction and anti-reflection coating by atmospheric pressure chemical vapor deposition (APCVD) technique was also investigated. For electrodes formation process, single firing method for both side electrodes made possible to simplify the firing process and to speed up from a conventional speed of 400 mm/min to 5000 mm/min.
We have searched for proton decays via p-->e;{+}pi;{0} and p-->micro;{+}pi;{0} using data from a 91.7 kt.yr exposure of Super-Kamiokande-I and a 49.2 kt.yr exposure of Super-Kamiokande-II. No ...candidate events were observed with expected backgrounds induced by atmospheric neutrinos of 0.3 events for each decay mode. From these results, we set lower limits on the partial lifetime of 8.2 x 10;{33} and 6.6 x 10;{33} years at 90% confidence level for p-->e;{+}pi;{0} and p-->micro;{+}pi;{0} modes, respectively.
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