More than 30 years have passed since the successful detection of supernova (SN) neutrinos from SN 1987A. In the last few decades, remarkable progress has been made in neutrino detection techniques, ...through which it may be possible to detect neutrinos from a new source, presupernova (pre-SN) neutrinos. They are emitted from a massive star prior to core bounce. Because neutrinos escape from the core freely, they carry information about the stellar physics directly. Pre-SN neutrinos may play an important role in verifying our understanding of stellar evolution for massive stars. Observation of pre-SN neutrinos, moreover, may serve as an alarm regarding an SN explosion a few days in advance if the progenitor is located in our vicinity, enabling us to observe the next galactic SN. In this review, we summarize the current status of pre-SN neutrino studies from both the theoretical and observational points of view.
Supernova Neutrino Burst Search at KamLAND Eizuka, M; Ishidoshiro, K; Obara, S
Journal of physics. Conference series,
12/2021, Letnik:
2156, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
We report a result of supernova neutrino burst search at KamLAND in a neutrino energy range of 1.8–111 MeV via the inverse-beta decay (IBD). The search was performed using data from 2002 ...March 9th to 2020 July 17th, and the corresponding livetime is 5001.21 days. We searched for two or more sequential IBD events within 10 s as a supernova neutrino burst candidate. The dominant background is the accidental cluster of 2 or more IBD events caused by neutrinos from other sources, though, which are estimated to be almost negligible. We evaluated detectable ranges for some emitted supernova neutrino burst models. The conservative detectable ranges are 38kpc for core-collapse supernova (ccSN) and 42kpc for failed ccSN. We found no significant supernova neutrino burst events and set a 90% upper limit on the supernova neutrino detection rate in KamLAND as 0.178 burst/yr.
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.
Concept of KamLAND2 DAQ system Ieki, S.; Asami, S.; Axani, S. ...
Journal of physics. Conference series,
11/2022, Letnik:
2374, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The KamLAND-Zen experiment is searching for neutrinoless double-beta decay of
136
Xe. We are preparing for the upgrade of the KamLAND detector, KamLAND2. It is designed to improve the discrimination ...power of two-neutrino double-beta decay and cosmic-ray muon spallation backgrounds. Data acquisition of all neutrino events from nearby supernova is also an important issue of the KamLAND2 experiment and the data rate is a key factor to design a new DAQ system. High speed sampling will be realized with RFSoC on the front-end electronics. Data is read out from FEE to DAQ computers via 10 GbE, and FairMQ is one of the candidates for KamLAND2 DAQ software. In the KamLAND DAQ, the whole trigger system is implemented in hardware, while the KamLAND2 DAQ adopts hardware trigger for photon detection and software trigger to extract physics events. A simulation study of the software trigger is proceeding in order to detect low energy events using timing and charge information.
Abstract
We report a search for electron antineutrinos at KamLAND with an 8.3−30.8 MeV energy range via the inverse beta decay. In 6.72 kton-yr of KamLAND data, we found 18 neutrino candidates and no ...significant excess over estimated backgrounds. From data interpretation, with the assumption of some supernova relic neutrino spectrum predictions, we give upper flux limits of 60−110 cm
−2
s
−1
(90% CL) in the analysis range and present a model-independent flux. These upper limits are the most stringent for 8−13 MeV region. We also improve on the upper probability limit of
8
B solar neutrinos converting into antineutrinos via the Resonant Spin Flavor Precession with the neutrino magnetic moment. Besides, we could set limits on the annihilation cross-section for light dark matter pairs to neutrino pairs.
Abstract
We present the results of a search for MeV-scale electron antineutrino events in KamLAND coincident with the 60 gravitational wave events/candidates reported by the LIGO/Virgo collaboration ...during their second and third observing runs. We find no significant coincident signals within a ±500 s timing window from each gravitational wave and present 90% C.L. upper limits on the electron antineutrino fluence between 10
8
and 10
13
cm
−2
for neutrino energies in the energy range of 1.8–111 MeV.
KamLAND-Zen searches for neutrinoless double-beta decay with an ultra-pure liquid-scintillator (LS) filled with a custom-made clean nylon balloon. The primary backgrounds are radioactive impurities ...such as uranium and thorium series. To reduce them, we studied a self-vetoing balloon-shaped vessel for a future upgrade program, “KamLAND2-Zen”. We selected Polyethylene-Naphthalate (PEN) film which emit fluorescent light and performed the feasibility studies. Owing to its scintillation properties,
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Bi background could be identified in the KamLAND2-Zen. Moreover, thanks to the different waveforms between the LS and the PEN, we can apply the pulse-shape-discrimination for
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Bi-Po pileup background. We evaluated its background rejection efficiency as more than 90%. Resulting from these studies, it is possible to remove restrictions on fiducial volume in KamLAND2-Zen.
Abstract
Environmental radioactivity is a dominant background for rare decay search experiments, and it is difficult to completely remove such an impurity from detector vessels. We propose a ...scintillation balloon as the active vessel of a liquid scintillator in order to identify this undesirable radioactivity. According to our feasibility studies, the scintillation balloon enables the bismuth–polonium sequential decay to be tagged with a 99.7% efficiency, assuming a KamLAND-type (KamLAND = Kamioka Liquid scintillator AntiNeutrino Detector) liquid scintillator detector. This tagging of sequential decay using alpha rays from the polonium improves the sensitivity to neutrinoless double-beta decay while rejecting beta ray background from the bismuth.
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter (χ0) accompanied by a negatively charged excited state (χ−) with a small mass difference ...(e.g. < 20 MeV) can form a bound-state with a nucleus such as xenon. This bound-state formation is rare and the released energy is O(1−10) MeV depending on the nucleus, making large liquid scintillator detectors suitable for detection. We searched for bound-state formation events with xenon in two experimental phases of the KamLAND-Zen experiment, a xenon-doped liquid scintillator detector. No statistically significant events were observed. For a benchmark parameter set of WIMP mass mχ0=1 TeV and mass difference Δm=17 MeV, we set the most stringent upper limits on the recombination cross section times velocity 〈σv〉 and the decay-width of χ− to 9.2×10−30cm3/s and 8.7×10−14 GeV, respectively at 90% confidence level.
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