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Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND  [PDF]
The KamLAND Collaboration
Physics , 2009, DOI: 10.1103/PhysRevC.81.025807
Abstract: Radioactive isotopes produced through cosmic muon spallation are a background for rare-event detection in $\nu$ detectors, double-$\beta$-decay experiments, and dark-matter searches. Understanding the nature of cosmogenic backgrounds is particularly important for future experiments aiming to determine the pep and CNO solar neutrino fluxes, for which the background is dominated by the spallation production of $^{11}$C. Data from the Kamioka liquid-scintillator antineutrino detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillators, and for checking estimates from current simulations based upon MUSIC, FLUKA, and GEANT4. Using the time correlation between detected muons and neutron captures, the neutron production yield in the KamLAND liquid scintillator is measured to be $(2.8 \pm 0.3) \times 10^{-4} \mu^{-1} g^{-1} cm^{2}$. For other isotopes, the production yield is determined from the observed time correlation related to known isotope lifetimes. We find some yields are inconsistent with extrapolations based on an accelerator muon beam experiment.
Quasiparticle spectrum inside the vortex core: crossover from dirty to clean limit  [PDF]
A. Fujita
Physics , 1999,
Abstract: The quasiparticle spectrum inside the vortex core in the mixed state of a strongly type-II superconductors are studied. The s-wave symmetry for the gap parameter is assumed. The crossover behavior from dirty to clean limit is shown by numerical calculation based on the random matrix theory.
The KamLAND Full-Volume Calibration System  [PDF]
The KamLAND Collaboration
Physics , 2009, DOI: 10.1088/1748-0221/4/04/P04017
Abstract: We have successfully built and operated a source deployment system for the KamLAND detector. This system was used to position radioactive sources throughout the delicate 1-kton liquid scintillator volume, while meeting stringent material cleanliness, material compatibility, and safety requirements. The calibration data obtained with this device were used to fully characterize detector position and energy reconstruction biases. As a result, the uncertainty in the size of the detector fiducial volume was reduced by a factor of two. Prior to calibration with this system, the fiducial volume was the largest source of systematic uncertainty in measuring the number of anti-neutrinos detected by KamLAND. This paper describes the design, operation and performance of this unique calibration system.
Kamland Results  [PDF]
K. Inoue
Physics , 2003,
Abstract: The LMA solution of the solar neutrino problem has been explored with the 1,000 ton liquid scinatillator detector, KamLAND. It utilizes nuclear power reactors distributing effectively 180km from the experimental site. Comparing observed neutrino rate with the calculation of reactor operation histories, an evidence for reactor neutrino disapearance has been obtained from 162 ton-year exposure data. This deficit is only compatible with the LMA solution and the other solutions in the two neutrino oscillation hypotheisis are excluded at 99.95% confidence level.
Recent Results from KamLAND  [PDF]
Koichi Ichimura,for the KamLAND Collaboration
Statistics , 2008,
Abstract: The main goal of the KamLAND reactor electron anti-neutrino experiment is a search for electron anti-neutrino oscillation using inverse-beta decay reaction in 1,000 ton of ultra-pure liquid scintillator. The data-set is 1490.8 days from Mar. 2002 to May 2007. The best-fit oscillation parameters are Delta m^{2}_{21} = 7.58^{+0.14}_{-0.13} (stat.) +/- 0.15 (syst.) x 10$^{-5} eV^{2} and tan^{2}theta_{12} = 0.56^{+0.10}_{-0.07} (stat.) ^{+0.10}_{-0.06} (syst.). The statistical significance for reactor electron anti-neutrino disappearance is 8.8 sigma, and an undistorted electron anti-neutrino energy spectrum is disfavored at > 5 sigma.
Recent Results from KamLAND  [PDF]
Jason Detwiler
Physics , 2003,
Abstract: The Kamioka Liquid-scintillator Anti-Neutrino Detector (KamLAND) has detected for the first time the disappearance of electron antineutrinos from a terrestrial source at the 99.95% C.L. Interpreted in terms of neutrino oscillations, the best fit to the KamLAND data gives a mixing angle 1.0 and a mass-squared difference 6.9 x 10^-5 eV^2, in excellent agreement with the Large Mixing Angle solution to the solar neutrino problem. Assuming CPT invariance, this result excludes other solutions to the solar neutrino problem at > 99.95% C.L.
Antineutrino Science in KamLAND  [PDF]
Atsuto Suzuki
Physics , 2014, DOI: 10.1140/epjc/s10052-014-3094-x
Abstract: The primary goal of KamLAND is a search for the oscillation of $\bar{\nu}_{\rm e}$$'$s emitted from distant power reactors. The long baseline, typically 180 km, enables KamLAND to address the oscillation solution of the solar neutrino problem with $\bar{\nu}_{\rm e}$ under laboratory conditions. KamLAND found fewer reactor $\bar{\nu}_{\rm e}$ events than expected from standard assumptions about $\bar{\nu}_{\rm e}$$'$s propagation at more than 9 {\sigma} confidence level (C.L.). The observed energy spectrum disagrees with the expected spectral shape at more than 5 {\sigma} C.L., and prefers the distortion from neutrino oscillation effects. A three-flavor oscillation analysis of the data from KamLAND and KamLAND + solar neutrino experiments with CPT invariance, yields ${\Delta}{\rm m}^{2}_{21} = [{7.54}^{+0.19}_{0.18},\ {7.53}^{+0.19}_{0.18}]$ $\times {10}^{-5} {\rm eV}^{2}$, $\tan^{2} {\theta}_{12} = [{0.481}^{+0.092}_{-0.080},\ {0.437}^{+0.029}_{-0.026}]$, and ${\sin}^{2} {\theta}_{13} = [{0.010}^{+0.033}_{-0.034},{0.023}^{+0.015}_{-0.015}]$. All solutions to the solar neutrino problem except for the large mixing angle (LMA) region are excluded. KamLAND also demonstrated almost two cycles of the periodic feature expected from neutrino oscillation effects. KamLAND performed the first experimental study of antineutrinos from the Earth$'$s interior so-called geoneutrinos (geo $\bar{\nu}_{\rm e}$$'$s), and succeeded in detecting geo $\bar{\nu}_{\rm e}$$`$s produced by the decays of $^{238}$U and $^{232}$Th within the Earth. Assuming a chondritic Th/U mass ratio, we obtain ${116}^{+28}_{-27}$ $\bar{\nu}_{\rm e}$ events from $^{238}$U and $^{232}$Th, corresponding a geo $\bar{\nu}_{\rm e}$ flux of ${3.4}^{+0.8}_{-0.8} \times {10}^{6} {\rm cm}^{-2}{\rm s}^{-1}$ at the KamLAND location. We evaluate various bulk silicate Earth composition models using the observed geoneutrino rate.
Mantle geoneutrinos in KamLAND and Borexino  [PDF]
G. Fiorentini,G. L. Fogli,E. Lisi,F. Mantovani,A. M. Rotunno
Physics , 2012, DOI: 10.1103/PhysRevD.86.033004
Abstract: The KamLAND and Borexino experiments have observed, each at ~4 sigma level, signals of electron antineutrinos produced in the decay chains of thorium and uranium in the Earth's crust and mantle (Th and U geoneutrinos). Various pieces of geochemical and geophysical information allow an estimation of the crustal geoneutrino flux components with relatively small uncertainties. The mantle component may then be inferred by subtracting the estimated crustal flux from the measured total flux. To this purpose, we analyze in detail the experimental Th and U geoneutrino event rates in KamLAND and Borexino, including neutrino oscillation effects. We estimate the crustal flux at the two detector sites, using state-of-the-art information about the Th and U distribution on global and local scales. We find that crust-subtracted signals show hints of a residual mantle component, emerging at ~2.4 sigma level by combining the KamLAND and Borexino data. The inferred mantle flux slightly favors scenarios with relatively high Th and U abundances, within +-1 sigma uncertainties comparable to the spread of predictions from recent mantle models.
Neutrino Physics after KamLAND  [PDF]
Alexei Yu. Smirnov
Physics , 2003,
Abstract: The neutrino anomalies were driving force of the developments in neutrino physics during the last 30 - 35 years. I will consider status of the anomalies after the first KamLAND result. The main questions are "What is left?" and "What is the next?" In the new phase, the phenomenological objectives of neutrino physics consist of accomplishing the program of reconstruction of the neutrino mass and flavor spectrum and searches for physics beyond the ``standard'' picture. The latter includes searches for new (sterile) neutrino states, new neutrino interactions, effects of violation of the fundamental symmetries in the neutrino sector.
How much Uranium is in the Earth? Predictions for geo-neutrinos at KamLAND  [PDF]
Gianni Fiorentini,Marcello Lissia,Fabio Mantovani,Riccardo Vannucci
Physics , 2005, DOI: 10.1103/PhysRevD.72.033017
Abstract: Geo-neutrino detection can determine the amount of long-lived radioactive elements within our planet, thus providing a direct test of the Bulk Silicate Earth (BSE) model and fixing the radiogenic contribution to the terrestrial heat. We present a prediction for the geo-neutrino signal at KamLAND as a function of the Uranium mass in the Earth. The prediction is based on global mass balance, supplemented by a detailed geochemical and geophysical study of the region near the detector. The prediction is weakly dependent on mantle modeling. If BSE is correct, Uranium geo-neutrinos will produce between 25 and 35 events per year and 10^32 protons at Kamioka.
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