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.
We present an improved search for neutrinoless double-beta (0νββ) decay of ^{136}Xe in the KamLAND-Zen experiment. Owing to purification of the xenon-loaded liquid scintillator, we achieved a ...significant reduction of the ^{110m}Ag contaminant identified in previous searches. Combining the results from the first and second phase, we obtain a lower limit for the 0νββ decay half-life of T_{1/2}^{0ν}>1.07×10^{26} yr at 90% C.L., an almost sixfold improvement over previous limits. Using commonly adopted nuclear matrix element calculations, the corresponding upper limits on the effective Majorana neutrino mass are in the range 61-165 meV. For the most optimistic nuclear matrix elements, this limit reaches the bottom of the quasidegenerate neutrino mass region.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
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, Volume:
2374, Issue:
1
Journal Article
Peer reviewed
Open access
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,
214
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
212
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
We present the results of a search for core-collapse supernova neutrinos, using long-term KamLAND data from 2002 March 9 to 2020 April 25. We focus on the electron antineutrinos emitted from ...supernovae in the energy range of 1.8–111 MeV. Supernovae will make a neutrino event cluster with the duration of ∼10 s in the KamLAND data. We find no neutrino clusters and give the upper limit on the supernova rate to be 0.15 yr
−1
with a 90% confidence level. The detectable range, which corresponds to a >95% detection probability, is 40–59 kpc and 65–81 kpc for core-collapse supernovae and failed core-collapse supernovae, respectively. This paper proposes to convert the supernova rate obtained by the neutrino observation to the Galactic star formation rate. Assuming a modified Salpeter-type initial mass function, the upper limit on the Galactic star formation rate is <(17.5–22.7)
M
⊙
yr
−1
with a 90% confidence level.
Abstract
We present the results of a time-coincident event search for low-energy electron antineutrinos in the KamLAND detector with gamma-ray bursts (GRBs) from the Gamma-ray Coordinates Network and ...Fermi Gamma-ray Burst Monitor. Using a variable coincidence time window of ±500 s plus the duration of each GRB, no statistically significant excess above the background is observed. We place the world’s most stringent 90% confidence level upper limit on the electron antineutrino fluence below 17.5 MeV. Assuming a Fermi–Dirac neutrino energy spectrum from the GRB source, we use the available redshift data to constrain the electron antineutrino luminosity and effective temperature.
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