ABSTRACT In the late stages of nuclear burning for massive stars (M > 8 M ), the production of neutrino-antineutrino pairs through various processes becomes the dominant stellar cooling mechanism. As ...the star evolves, the energy of these neutrinos increases and in the days preceding the supernova a significant fraction of emitted electron anti-neutrinos exceeds the energy threshold for inverse beta decay on free hydrogen. This is the golden channel for liquid scintillator detectors because the coincidence signature allows for significant reductions in background signals. We find that the kiloton-scale liquid scintillator detector KamLAND can detect these pre-supernova neutrinos from a star with a mass of 25 M at a distance less than 690 pc with 3 significance before the supernova. This limit is dependent on the neutrino mass ordering and background levels. KamLAND takes data continuously and can provide a supernova alert to the community.
XMASS, a low-background, large liquid-xenon detector, was used to search for solar axions that would be produced by bremsstrahlung and Compton effects in the Sun. With an exposure of 5.6 ton days of ...liquid xenon, the model-independent limit on the coupling for mass ≪1 keV is |gaee|<5.4×10−11 (90% C.L.), which is a factor of two stronger than the existing experimental limit. The bounds on the axion masses for the DFSZ and KSVZ axion models are 1.9 and 250 eV, respectively. In the mass range of 10–40 keV, this study produced the most stringent limit, which is better than that previously derived from astrophysical arguments regarding the Sun to date.
A search for light dark matter using low-threshold data from the single phase liquid xenon scintillation detector XMASS, has been conducted. Using the entire 835 kg inner volume as target, the ...analysis threshold can be lowered to 0.3 keVee (electron-equivalent) to search for light dark matter. With low-threshold data corresponding to a 5591.4 kg day exposure of the detector and without discriminating between nuclear-recoil and electronic events, XMASS excludes part of the parameter space favored by other experiments.
In a dedicated test setup at the Kamioka Observatory we studied pulse shape discrimination (PSD) in liquid xenon (LXe) for dark matter searches in the absence of an externally applied electric field. ...PSD in LXe was based on the observation that scintillation light from electron events was emitted over a longer period of time than that of nuclear recoil events, and our method used a simple ratio of early to total scintillation light emission in a single scintillation event. Requiring an efficiency of 50% for nuclear recoil retention we reduced the electron background by a factor of 7.7±1.1(stat)±0.61.2(sys)×10−2 at energies between 4.8 and 7.2keVee and 7.7±2.8(stat)±2.82.5(sys)×10−3 at energies between 9.6 and 12keVee for a scintillation light yield of 20.9photoelectrons/keVee. Further study was done by masking some of that light to reduce this yield to 4.6photoelectrons/keVee. Under these conditions the same method results in an electron event reduction by a factor of 2.4±0.2(stat)±0.20.3(sys)×10−1 for the lower of the energy regions above. We also observe that in contrast to nuclear recoils the fluctuations in our early to total ratio for electron events are larger than expected from statistical fluctuations.
Radon removal from gaseous xenon with activated charcoal Abe, K.; Hieda, K.; Hiraide, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
2012, 2012-01-00, 20120101, Volume:
661, Issue:
1
Journal Article
Peer reviewed
Many low background experiments using xenon need to remove radioactive radon to improve their sensitivities. However, no method of continually removing radon from xenon has been described in the ...literature. We studied a method to remove radon from xenon gas through an activated charcoal trap. From our measurements we infer a linear relationship between the mean propagation velocity
v
Rn
of radon and
v
Xe
of xenon in the trap with
v
Rn
/
v
Xe
=
(
0.96
±
0.10
)
×
10
−
3
at −85
°C. As the mechanism for radon removal in this charcoal trap is its decay, knowledge of this parameter allows us to design an efficient radon removal system for the XMASS experiment. The verification of this system found that it reduces radon by a factor of 0.07, which is in line with its expected average retention time of 14.8 days for radon.
A high performance distillation system to remove krypton from xenon was constructed, and a purity level of Kr/Xe
=
∼3
×
10
−12 was achieved. This development is crucial in facilitating ...high-sensitivity low-background experiments such as the search for dark matter in the universe.
► A prototype single phase liquid xenon detector was developed and operated. ► We have tested performance of this prototype detector. ► We have measured the physical properties of liquid xenon. ► We ...have established vertex and energy reconstruction methods. ► We have demonstrated liquid xenon’s self-shielding power against γ-rays.
Liquid xenon is a suitable material for a dark matter search. For future large scale experiments, single phase detectors are attractive due to their simple configuration and scalability. However, in order to reduce backgrounds, they need to fully rely on liquid xenon’s self-shielding property. A prototype detector was developed at Kamioka Observatory to establish vertex and energy reconstruction methods and to demonstrate the self-shielding power against γ-rays from outside of the detector. 662keV γ-rays from 137Cs are attenuated by a factor of about 50 over a distance of 20cm.
XMASS detector Abe, K.; Hieda, K.; Hiraide, K. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2013, Volume:
716
Journal Article
Peer reviewed
Open access
The XMASS project aims to detect dark matter, pp and 7Be solar neutrinos, and neutrinoless double beta decay using ultra pure liquid xenon. The first phase of the XMASS experiment searches for dark ...matter. In this paper, we describe the XMASS detector in detail, including its configuration, data acquisition equipment and calibration system.
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