20 research outputs found
First measurement of the strange axial coupling constant using neutral-current quasi-elastic interactions of atmospheric neutrinos at KamLAND
We report a measurement of the strange axial coupling constant using
atmospheric neutrino data at KamLAND. This constant is a component of the axial
form factor of the neutral current quasi-elastic (NCQE) interaction. The value
of 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. KamLAND data, including the information on neutron
multiplicity associated with the NCQE interactions, makes it possible to
measure with a suppressed dependence on the axial mass , which has
not yet been determined. For a comprehensive prediction of the neutron emission
associated with neutrino interactions, we establish a simulation of particle
emission via nuclear de-excitation of C, a process not considered in
existing neutrino Monte Carlo event generators. Energy spectrum fitting for
each neutron multiplicity gives , which is the
most stringent limit obtained using NCQE interactions without
constraints
Measurement of cosmic-ray muon spallation products in a xenon-loaded liquid scintillator with KamLAND
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-beta decay, and dark matter search experiments. The
KamLAND-Zen experiment searches for neutrinoless double-beta decay in 745kg of
xenon dissolved in liquid scintillator. The experiment includes dead-time-free
electronics with a high efficiency for detecting muon-induced neutrons. The
production yields of different radioisotopes are measured with a combination of
delayed coincidence techniques, newly developed muon reconstruction and xenon
spallation identification methods. The observed xenon spallation products are
consistent with results from the FLUKA and Geant4 simulation codes
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Search for charged excited states of dark matter with KamLAND-Zen
Particle dark matter could belong to a multiplet that includes an electrically charged state. WIMP dark matter (Ï0) accompanied by a negatively charged excited state (Ïâ) 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(1â10) 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 mÏ0=1 TeV and mass difference Îm=17 MeV, we set the most stringent upper limits on the recombination cross section times velocity ăÏvă and the decay-width of Ïâ to 9.2Ă10â30 cm3/s and 8.7Ă10â14 GeV, respectively at 90% confidence level
KamLAND's search for correlated low-energy electron antineutrinos with astrophysical neutrinos from IceCube
We report the results of a search for MeV-scale astrophysical neutrinos in
KamLAND presented as an excess in the number of coincident neutrino
interactions associated with the publicly available high-energy neutrino
datasets from the IceCube Neutrino Observatory. We find no statistically
significant excess in the number of observed low-energy electron antineutrinos
in KamLAND, given a coincidence time window of 500s, 1,000s,
3,600s, and 10,000s around each of the IceCube neutrinos. We use this
observation to present limits from 1.8 MeV to 100 MeV on the electron
antineutrino fluence, assuming a mono-energetic flux. We then compare the
results to several astrophysical measurements performed by IceCube and place a
limit at the 90% confidence level on the electron antineutrino isotropic
thermal luminosity from the TXS 0506+056 blazar.Comment: 12 pages, 5 figure
A Search for Correlated Low-energy Electron Antineutrinos in KamLAND with Gamma-Ray Bursts
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 worldâs most stringent 90% confidence level upper limit on the electron antineutrino fluence below 17.5 MeV. Assuming a FermiâDirac 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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A Search for Correlated Low-energy Electron Antineutrinos in KamLAND with Gamma-Ray Bursts
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