S. Abe

The KamLAND-Zen experiment has provided stringent constraints on the neutrinoless double-beta (0νββ) decay half-life in ^{136}Xe using a xenon-loaded liquid scintillator. We report an improved search using an upgraded detector with almost double the amount of xenon and an ultralow radioactivity container, corresponding to an exposure of 970 kg yr of ^{136}Xe. These new data provide valuable insight into backgrounds, especially from cosmic muon spallation of xenon, and have required the use of no

Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in $\ensuremath{\nu}$ detectors, double-$\ensuremath{\beta}$-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the $\mathit{pep}$ and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of $^{11}\mathrm{C}$. Data from the Kamioka liquid-sci

We report a measurement of the neutrino-electron elastic scattering rate from ${}^{8}$B solar neutrinos based on a 123 kton-day exposure of KamLAND. The background-subtracted electron recoil rate, above a 5.5-MeV analysis threshold is 1.49 $\ifmmode\pm\else\textpm\fi{}$ 0.14(stat) $\ifmmode\pm\else\textpm\fi{}$ 0.17(syst) events per kton-day. Interpreted as due to a pure electron flavor flux with a ${}^{8}$B neutrino spectrum, this corresponds to a spectrum integrated flux of 2.77 $\ifmmode\pm\e

Abstract The decay of the primordial isotopes 238 U, 235 U, 232 Th, and 40 K has contributed to the terrestrial heat budget throughout the Earth's history. Hence, the individual abundance of those isotopes are key parameters in reconstructing contemporary Earth models. The geoneutrinos produced by the radioactive decays of uranium and thorium have been observed with the Kamioka Liquid‐Scintillator Antineutrino Detector (KamLAND). Those measurements have been improved with more than 18‐year obser

We report a measurement of the strange axial coupling constant ${g}_{A}^{s}$ using atmospheric neutrino data at KamLAND. This constant is a component of the axial form factor of the neutral-current quasielastic (NCQE) interaction. The value of ${g}_{A}^{s}$ significantly changes the ratio of proton and neutron NCQE cross sections. KamLAND is suitable for measuring NCQE interactions as it can detect nucleon recoils with low-energy thresholds and measure neutron multiplicity with high efficiency.

Cosmic-ray muons produce various radioisotopes when passing through material. These spallation products can be backgrounds for rare event searches such as in solar neutrino, double-$\ensuremath{\beta}$ decay, and dark matter search experiments. The KamLAND-Zen experiment searches for neutrinoless double-$\ensuremath{\beta}$ decay in 745 kg of xenon dissolved in liquid scintillator. The experiment includes dead-time-free electronics with a high efficiency for detecting muon-induced neutrons. The

Nuclear deexcitation associated with neutrino interactions and nucleon decays has a significant impact on a recent key observable for neutrino detectors: neutron multiplicity. Although several deexcitation simulation studies have been conducted, most are closed-source or have limitations in application. Therefore, we need an open-source deexcitation simulator to be used as a standard deexcitation module in existing neutrino Monte Carlo event generators. To predict the neutron multiplicity compre

Abstract We report the result of a search for neutrinos in coincidence with solar flares from the GOES flare database. The search was performed on a 10.8 kton-year exposure of KamLAND collected from 2002 to 2019. This large exposure allows us to explore previously unconstrained parameter space for solar flare neutrinos. We found no statistical excess of neutrinos and established 90% confidence level upper limits of 8.4 × 10 7 cm −2 (3.0 × 10 9 cm −2 ) on the electron antineutrino (electron neutr

Abstract Neutrino interactions in low energy regions below 30 MeV, where the experimental searches for supernova relic neutrino are conducted, have a large uncertainty due to complicated nuclear effects such as the Pauli blocking effect and de-excitation of a residual nucleus. Understanding the effect of nuclear de-excitation is especially critical since neutrons measured by liquid scintillator detectors can be emitted via de-excitation. We build a systematic method to predict nuclear de-excitat

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 correspon

Understanding nuclear effects is essential for improving the sensitivity of neutrino oscillation measurements. Validating nuclear models solely through neutrino scattering data is challenging due to limited statistics and the broad energy spectrum of neutrinos. In contrast, electron scattering experiments provide abundant high-precision data with various monochromatic energies and angles. Since both neutrinos and electrons interact via electroweak interactions, the same nuclear models can be app

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

Inter-channel mis-synchronisation can be a limiting factor to the time resolution of high performance timing detectors with multiple readout channels and independent electronics units. In these systems, time calibration methods employed must be able to efficiently correct for minimal mis-synchronisation between channels and achieve the best detector performance. We present an iterative time calibration method based on Markov Chains, suitable for detector systems with multiple readout channels. S

International audience

Received 9 December 2008DOI:https://doi.org/10.1103/PhysRevLett.101.259901©2008 American Physical Society