Abstract
At Kamioka Observatory many activities for low energy rare event search are ongoing. Super-Kamiokande(SK), the largest water Cherenkov neutrino detector, currently continues data taking as the fourth phase of the experiment (SK-IV). In SK-IV, we have upgraded the water purification system and tuned water flow in the SK tank. Consequently the background level was lowered significantly. This allowed SK-IV to derive solar neutrino results down to 3.5 MeV energy region. With these data, neutrino oscillation parameters are updated from global fit; Δm212 = 7.44+0.2−0.19 × 10−5eV2, sin2 θ12 = 0.304 ± 0.013, sin2 θ13 = 0.0301+0.017−0.015. NEWAGE, the directional sensitive dark matter search experiment, is currently operated as "NEWAGE-0.3a" which is a 0.20 × 0.25 × 0.31 m3 micro-TPC filled with CF4 gas at 152 Torr. Recently we have developed "NEWAGE-0.3b". It was succeeded to lower the operation pressure down to 76 Torr and the threshold down to 50 keV (F recoils). XMASS experiment is looking for scintillation signals from dark matter interaction in 1 ton of liquid xenon. It was designed utilizing its self-shielding capability with fiducial volume confinement. However, we could lower the analysis threshold down to 0.3 keVee using whole volume of the detector. In February 2012, low threshold and very large exposure data (5591 kg·days) were collected. With these data, we have excluded some part of the parameter spaces claimed by DAMA/LIBRA and CoGeNT experiments.
Highlights
SK detects solar neutrinos through neutrino-electron elastic scattering, where the energy, direction, and time of the recoil electron are measured
In the low energy region below ∼20 MeV, solar neutrino interactions are detected by neutrino-electron scattering
Atmospheric neutrino interactions covering 5 orders of magnitude are detectable by neutral- and charged-current neutrino-nucleon interactions
Summary
SK detects solar neutrinos through neutrino-electron elastic scattering, where the energy, direction, and time of the recoil electron are measured. The water flow in the detector was precisely investigated and optimized to reduce the background contamination in the fiducial volume as much as possible.
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