49 research outputs found
A compact ultra-clean system for deploying radioactive sources inside the KamLAND detector
We describe a compact, ultra-clean device used to deploy radioactive sources
along the vertical axis of the KamLAND liquid-scintillator neutrino detector
for purposes of calibration. The device worked by paying out and reeling in
precise lengths of a hanging, small-gauge wire rope (cable); an assortment of
interchangeable radioactive sources could be attached to a weight at the end of
the cable. All components exposed to the radiopure liquid scintillator were
made of chemically compatible UHV-cleaned materials, primarily stainless steel,
in order to avoid contaminating or degrading the scintillator. To prevent radon
intrusion, the apparatus was enclosed in a hermetically sealed housing inside a
glove box, and both volumes were regularly flushed with purified nitrogen gas.
An infrared camera attached to the side of the housing permitted real-time
visual monitoring of the cable's motion, and the system was controlled via a
graphical user interface.Comment: Revised author affiliations, corrected typos, made minor improvements
to text, and revised reference
7Be Solar Neutrino Measurement with KamLAND
We report a measurement of the neutrino-electron elastic scattering rate of
862 keV 7Be solar neutrinos based on a 165.4 kton-day exposure of KamLAND. The
observed rate is 582 +/- 90 (kton-day)^-1, which corresponds to a 862 keV 7Be
solar neutrino flux of (3.26 +/- 0.50) x 10^9 cm^-2s^-1, assuming a pure
electron flavor flux. Comparing this flux with the standard solar model
prediction and further assuming three flavor mixing, a nu_e survival
probability of 0.66 +/- 0.14 is determined from the KamLAND data. Utilizing a
global three flavor oscillation analysis, we obtain a total 7Be solar neutrino
flux of (5.82 +/- 0.98) x 10^9 cm^-2s^-1, which is consistent with the standard
solar model predictions.Comment: 8 pages, 6 figures, submitted to Phys. Rev.
Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND
Radioactive isotopes produced through cosmic muon spallation are a background
for rare-event detection in detectors, double--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 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 . 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.Comment: 16 pages, 20 figure
Measurement of the 8B Solar Neutrino Flux with the KamLAND Liquid Scintillator Detector
We report a measurement of the neutrino-electron elastic scattering rate from
8B 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+/-0.14(stat)+/-0.17(syst) events per kton-day. Interpreted as due to a
pure electron flavor flux with a 8B neutrino spectrum, this corresponds to a
spectrum integrated flux of 2.77+/-0.26(stat)+/-0.32(syst) x 10^6 cm^-2s^-1.
The analysis threshold is driven by 208Tl present in the liquid scintillator,
and the main source of systematic uncertainty is due to background from
cosmogenic 11Be. The measured rate is consistent with existing measurements and
with Standard Solar Model predictions which include matter enhanced neutrino
oscillation.Comment: 6 pages, 3 figure
Search for extraterrestrial antineutrino sources with the KamLAND detector
We present the results of a search for extraterrestrial electron
antineutrinos ('s) in the energy range using the KamLAND detector. In an exposure of
4.53 kton-year, we identify 25 candidate events. All of the candidate events
can be attributed to background, most importantly neutral current atmospheric
neutrino interactions, setting an upper limit on the probability of B
solar 's converting into 's at
(90% C.L.), if we assume an undistorted shape. This limit
corresponds to a solar flux of or an event
rate of above the energy threshold
. The present data also allows us to set more
stringent limits on the diffuse supernova neutrino flux and on the annihilation
rates for light dark matter particles.Comment: 22 pages, 6 figure
Nucleon-Nucleon Interaction: A Typical/Concise Review
Nearly a recent century of work is divided to Nucleon-Nucleon (NN)
interaction issue. We review some overall perspectives of NN interaction with a
brief discussion about deuteron, general structure and symmetries of NN
Lagrangian as well as equations of motion and solutions. Meanwhile, the main NN
interaction models, as frameworks to build NN potentials, are reviewed
concisely. We try to include and study almost all well-known potentials in a
similar way, discuss more on various commonly used plain forms for two-nucleon
interaction with an emphasis on the phenomenological and meson-exchange
potentials as well as the constituent-quark potentials and new ones based on
chiral effective field theory and working in coordinate-space mostly. The
potentials are constructed in a way that fit NN scattering data, phase shifts,
and are also compared in this way usually. An extra goal of this study is to
start comparing various potentials forms in a unified manner. So, we also
comment on the advantages and disadvantages of the models and potentials partly
with reference to some relevant works and probable future studies.Comment: 85 pages, 5 figures, than the previous v3 edition, minor changes, and
typos fixe
Precision Measurement of Neutrino Oscillation Parameters with KamLAND
The KamLAND experiment has determined a precise value for the neutrino
oscillation parameter and stringent constraints on
. The exposure to nuclear reactor anti-neutrinos is increased
almost fourfold over previous results to 2.44 proton-yr due to
longer livetime and an enlarged fiducial volume. An undistorted reactor
energy spectrum is now rejected at >5. Extending the
analysis down to the inverse beta decay energy threshold, and incorporating
geo-neutrinos, gives a best-fit at =
eV and
=. Local
-minima at higher and lower are disfavored
at >4. Combining with solar neutrino data, we obtain = eV and =.Comment: Version as published in PRL. Revised Fig. 2 (allowed contours) due to
an error in the figure generating code (numbers or conclusions did not
change). The full dChi2-map for this analysis is available at
http://www.awa.tohoku.ac.jp/KamLAND/chi2map_3rdresult/chi2map.html . Fig. 3
(low E spectrum) was dropped due to space limitation
The KamLAND Full-Volume Calibration System
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.Comment: 30 pages, 22 figures, to be submitted to JINS
Constraints on from A Three-Flavor Oscillation Analysis of Reactor Antineutrinos at KamLAND
We present new constraints on the neutrino oscillation parameters , , and from a
three-flavor analysis of solar and KamLAND data. The KamLAND data set includes
data acquired following a radiopurity upgrade and amounts to a total exposure
of 3.49 \textyen times 10^{32} target-proton-year. Under the assumption of
{\textyen it CPT} invariance, a two-flavor analysis (/textyen mbox{\textyen
theta_{13} = 0}) of the KamLAND and solar data yields the best-fit values
\textyen tan^{2} \textyen theta_{12} = 0.444^{+0.036}_{-0.030} and \textyen
Delta m^{2}_{21} = 7.50^{+0.19}_{-0.20} \textyen times 10^{-5} ~ {\textyen rm
eV}^{2}; a three-flavor analysis with \textyen theta_{13} as a free
parameter yields the best-fit values \textyen tan^{2} \textyen theta_{12} =
0.452^{+0.035}_{-0.033}, \textyen Delta m^{2}_{21} = 7.50^{+0.19}_{-0.20}
\textyen times 10^{-5} ~ {\textyen rm eV}^{2}, and \textyen sin^{2} \textyen
theta_{13} = 0.020^{+0.016}_{-0.016}. This \textyen theta_{13} interval is
consistent with other recent work combining the CHOOZ, atmospheric and
long-baseline accelerator experiments. We also present a new global \textyen
theta_{13} analysis, incorporating the CHOOZ, atmospheric and accelerator
data, which indicates \textyen sin^{2} \textyen theta_{13} =
0.009^{+0.013}_{-0.007}. A nonzero value is suggested, but only at the
79\textyen% C.L.Comment: 10 pages, 7 figures. Version as published in PRD. The dChi2-map and
prompt energy spectrum for this analysis are available at
http://www.awa.tohoku.ac.jp/KamLAND/4th_result_data_release/4th_result_data_release.htm
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Study of the Production of Radioactive Isotopes through Cosmic Muon Spallation in KamLAND
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 {sup 11}C. Data from the Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND) provides valuable information for better understanding these backgrounds, especially in liquid scintillator, 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 {+-} 0.3) x 10{sup -4} n/({mu} {center_dot} (g/cm{sup 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