240 research outputs found
Neutrino physics with multi-ton scale liquid xenon detectors
We study the sensitivity of large-scale xenon detectors to low-energy solar
neutrinos, to coherent neutrino-nucleus scattering and to neutrinoless double
beta decay. As a concrete example, we consider the xenon part of the proposed
DARWIN (Dark Matter WIMP Search with Noble Liquids) experiment. We perform
detailed Monte Carlo simulations of the expected backgrounds, considering
realistic energy resolutions and thresholds in the detector. In a low-energy
window of 2-30 keV, where the sensitivity to solar pp and Be-neutrinos is
highest, an integrated pp-neutrino rate of 5900 events can be reached in a
fiducial mass of 14 tons of natural xenon, after 5 years of data. The
pp-neutrino flux could thus be measured with a statistical uncertainty around
1%, reaching the precision of solar model predictions. These low-energy solar
neutrinos will be the limiting background to the dark matter search channel for
WIMP-nucleon cross sections below 210 cm and WIMP
masses around 50 GeVc, for an assumed 99.5% rejection of
electronic recoils due to elastic neutrino-electron scatters. Nuclear recoils
from coherent scattering of solar neutrinos will limit the sensitivity to WIMP
masses below 6 GeVc to cross sections above
410cm. DARWIN could reach a competitive half-life
sensitivity of 5.610 y to the neutrinoless double beta decay of
Xe after 5 years of data, using 6 tons of natural xenon in the central
detector region.Comment: 17 pages, 4 figure
Fluorescence decay-time constants in organic liquid scintillators
The fluorescence decay-time constants have been measured for several
scintillator mixtures based on phenyl-o-xylylethane (PXE) and linear
alkylbenzene (LAB) solvents. The resulting values are of relevance for the
physics performance of the proposed large-volume liquid scintillator detector
LENA (Low Energy Neutrino Astronomy). In particular, the impact of the measured
values to the search for proton decay via p -> K+ antineutrino is evaluated in
this work.Comment: 7 pages, 5 figure
Spectroscopy of electron-induced fluorescence in organic liquid scintillators
Emission spectra of several organic liquid-scintillator mixtures which are
relevant for the proposed LENA detector have been measured by exciting the
medium with electrons of ~10keV. The results are compared with spectra
resulting from ultraviolet light excitation. Good agreement between spectra
measured by both methods has been found.Comment: 6 pages, 7 figure
Spatially uniform calibration of a liquid xenon detector at low energies using 83m-Kr
A difficult task with many particle detectors focusing on interactions below
~100 keV is to perform a calibration in the appropriate energy range that
adequately probes all regions of the detector. Because detector response can
vary greatly in various locations within the device, a spatially uniform
calibration is important. We present a new method for calibration of liquid
xenon (LXe) detectors, using the short-lived 83m-Kr. This source has
transitions at 9.4 and 32.1 keV, and as a noble gas like Xe, it disperses
uniformly in all regions of the detector. Even for low source activities, the
existence of the two transitions provides a method of identifying the decays
that is free of background. We find that at decreasing energies, the LXe light
yield increases, while the amount of electric field quenching is diminished.
Additionally, we show that if any long-lived radioactive backgrounds are
introduced by this method, they will present less than 67E-6 events/kg/day in
the next generation of LXe dark matter direct detection searchesComment: 9 pages, 9 figures. Accepted to Review of Scientific Instrument
Spectroscopy of electron-induced fluorescence in organic liquidscintillators
Emission spectra of several organic liquid-scintillator mixtures which are relevant for the proposed LENA detector have been measured by exciting the medium with electrons of ∼10keV. The results are compared with spectra resulting from ultraviolet light excitation. Good agreement between spectra measured by both methods has been foun
Qualification Tests of the R11410-21 Photomultiplier Tubes for the XENON1T Detector
The Hamamatsu R11410-21 photomultiplier tube is the photodetector of choice
for the XENON1T dual-phase time projection chamber. The device has been
optimized for a very low intrinsic radioactivity, a high quantum efficiency and
a high sensitivity to single photon detection. A total of 248 tubes are
currently operated in XENON1T, selected out of 321 tested units. In this
article the procedures implemented to evaluate the large number of tubes prior
to their installation in XENON1T are described. The parameter distributions for
all tested tubes are shown, with an emphasis on those selected for XENON1T, of
which the impact on the detector performance is discussed. All photomultipliers
have been tested in a nitrogen atmosphere at cryogenic temperatures, with a
subset of the tubes being tested in gaseous and liquid xenon, simulating their
operating conditions in the dark matter detector. The performance and
evaluation of the tubes in the different environments is reported and the
criteria for rejection of PMTs are outlined and quantified.Comment: 24 pages, 16 figure
Gator: a low-background counting facility at the Gran Sasso Underground Laboratory
A low-background germanium spectrometer has been installed and is being
operated in an ultra-low background shield (the Gator facility) at the Gran
Sasso underground laboratory in Italy (LNGS). With an integrated rate of ~0.16
events/min in the energy range between 100-2700 keV, the background is
comparable to those of the world's most sensitive germanium detectors. After a
detailed description of the facility, its background sources as well as the
calibration and efficiency measurements are introduced. Two independent
analysis methods are described and compared using examples from selected sample
measurements. The Gator facility is used to screen materials for XENON, GERDA,
and in the context of next-generation astroparticle physics facilities such as
DARWIN.Comment: 14 pages, 6 figures, published versio
Radon daughter removal from PTFE surfaces and its application in liquid xenon detectors
Long-lived radon daughters are a critical background source in experiments
searching for low-energy rare events. Originating from radon in ambient air,
radioactive polonium, bismuth and lead isotopes plate-out on materials that are
later employed in the experiment. In this paper, we examine cleaning procedures
for their capability to remove radon daughters from PTFE surfaces, a material
often used in liquid xenon TPCs. We found a large difference between the
removal efficiency obtained for the decay chains of Rn and Rn,
respectively. This indicates that the plate-out mechanism has an effect on the
cleaning success. While the long-lived Rn daughters could be reduced by
a factor of ~2, the removal of Rn daughters was up to 10 times more
efficient depending on the treatment. Furthermore, the impact of a nitric acid
based PTFE cleaning on the liquid xenon purity is investigated in a small-scale
liquid xenon TPC
Low energy neutrino astronomy with the large liquid scintillation detector LENA
The detection of low energy neutrinos in a large scintillation detector may
provide further important information on astrophysical processes as supernova
physics, solar physics and elementary particle physics as well as geophysics.
In this contribution, a new project for Low Energy Neutrino Astronomy (LENA)
consisting of a 50kt scintillation detector is presented.Comment: Proccedings of the International School of Nuclear Physics, Neutrinos
in Cosmology, in Astro, Particle and Nuclear Physics, Erice (SICILY) 16 - 24
Sept. 200
Optical Scattering Lengths in Large Liquid-Scintillator Neutrino Detectors
For liquid-scintillator neutrino detectors of kiloton scale, the transparency
of the organic solvent is of central importance. The present paper reports on
laboratory measurements of the optical scattering lengths of the organic
solvents PXE, LAB, and Dodecane which are under discussion for next-generation
experiments like SNO+, Hanohano, or LENA. Results comprise the wavelength range
from 415 to 440nm. The contributions from Rayleigh and Mie scattering as well
as from absorption/re-emission processes are discussed. Based on the present
results, LAB seems to be the preferred solvent for a large-volume detector.Comment: 9 pages, 3 figures, accepted for publication by Rev. Scient. Instr
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