286 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
Investigating the slow component of the infrared scintillation time response in gaseous xenon
Xenon is the target material of choice in several rare event searches. The
use of infrared (IR) scintillation light, in addition to the commonly used
vacuum ultraviolet (VUV) light, could increase the sensitivity of these
experiments. Understanding the IR scintillation response of xenon is essential
in assessing the potential for improvement. This study focuses on
characterizing the time response and light yield (LY) of IR scintillation in
gaseous xenon for alpha particles at atmospheric pressure and room temperature.
We have previously observed that the time response can be described by two
components: one with a fast time constant of O(ns) and one with a slow time
constant of O(s). This work presents new measurements that
improve our understanding of the slow component. The experimental setup was
modified to allow for a measurement of the IR scintillation time response with
a ten times longer time window of about 3 s, effectively
mitigating the dominant systematic uncertainty of the LY measurement. We find
that the slow component at about 1 bar pressure can be described by a single
exponential function with a decay time of about 850 ns. The LY is found to be
(6347 22 (stat) 400 (syst)) ph / MeV, consistent with our previous
measurement. In addition, a measurement with zero electric field along the
alpha particle tracks was conducted to rule out the possibility that the slow
component is dominated by light emission from drifting electrons or the
recombination of electrons and ions.Comment: 9 pages, 4 figure
Background Measurements in the Gran Sasso Underground Laboratory
The gamma background flux below 3000 keV in the Laboratori Nazionali del Gran
Sasso (LNGS), Italy, has been measured using a 3" diameter NaI(Tl) detector at
different underground positions: In hall A, hall B, the interferometer tunnel,
and inside the Large Volume Detector (LVD). The integrated flux is 0.3--0.4
scm at the first three locations, and is lower by two orders of
magnitude inside LVD. With the help of Monte Carlo simulations for every
location, the contribution of the individual primordial isotopes to the
background has been determined. Using an 11" diameter NaI(Tl) detector, the
background neutron flux in the LNGS interferometer tunnel has been estimated.
Within the uncertainties, the result agrees with those from other neutron
measurements in the main halls.Comment: 6 pages, 6 figures, accepted versio
Self-Calibration of Neutrino Detectors using characteristic Backgrounds
We introduce the possibility to use characteristic natural neutrino
backgrounds, such as Geoneutrinos (\bar{\nu}_e) or solar neutrinos (\nu_e),
with known spectral shape for the energy calibration of future neutrino
detectors, e.g. Large Liquid Scintillator Detectors. This "CalEffect" could be
used without the need to apply any modifications to the experiment in all
situations where one has a suitable background with sufficient statistics.
After deriving the effect analytically using \chi^2 statistics, we show that it
is only tiny for reactor neutrino experiments, but can be applicable in other
situations. As an example, we present its impact on the identification of the
wiggles in the power spectrum of supernova neutrinos caused by Earth matter
effects. The Self-Calibration Effect could be used for cross checking other
calibration methods and to resolve systematical effects in the primary neutrino
interaction processes, in particular in the low energy cross sections.Comment: 6 pages, 4 figure
Probing the Earth's interior with a large-volume liquid scintillator detector
A future large-volume liquid scintillator detector would provide a
high-statistics measurement of terrestrial antineutrinos originating from
-decays of the uranium and thorium chains. In addition, the forward
displacement of the neutron in the detection reaction
provides directional information. We investigate the requirements on such
detectors to distinguish between certain geophysical models on the basis of the
angular dependence of the geoneutrino flux. Our analysis is based on a
Monte-Carlo simulation with different levels of light yield, considering both
unloaded and gadolinium-loaded scintillators. We find that a 50 kt detector
such as the proposed LENA (Low Energy Neutrino Astronomy) will detect
deviations from isotropy of the geoneutrino flux significantly. However, with
an unloaded scintillator the time needed for a useful discrimination between
different geophysical models is too large if one uses the directional
information alone. A Gd-loaded scintillator improves the situation
considerably, although a 50 kt detector would still need several decades to
distinguish between a geophysical reference model and one with a large neutrino
source in the Earth's core. However, a high-statistics measurement of the total
geoneutrino flux and its spectrum still provides an extremely useful glance at
the Earth's interior.Comment: 21 pages, 9 figures. Minor changes, version accepted for publication
in Astroparticle Physic
Spectroscopy of Solar Neutrinos
In the last years, liquid-scintillator detectors have opened a new window for
the observation of low-energetic astrophysical neutrino sources. In 2007, the
solar neutrino experiment Borexino began its data-taking in the Gran Sasso
underground laboratory. High energy resolution and excellent radioactive
background conditions in the detector allow the first-time spectroscopic
measurement of solar neutrinos in the sub-MeV energy regime. The experimental
results of the Beryllium-7 neutrino flux measurements as well as the prospects
for the detection of solar Boron-8, pep and CNO neutrinos are presented in the
context of the currently discussed ambiguities in solar metallicity. In
addition, the potential of the future SNO+ and LENA experiments for
high-precision solar neutrino spectroscopy will be outlined.Comment: 6 pages, 5 figures, highlight talk at the annual fall meeting of the
German Astronomische Gesellschaft in Potsdam (Sep 2009
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
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