367 research outputs found
Double-beta decay of Te to the first 0 excited state of Xe with CUORICINO
The CUORICINO experiment was an array of 62 TeO single-crystal
bolometers with a total Te mass of kg. The experiment finished
in 2008 after more than 3 years of active operating time. Searches for both
and double-beta decay to the first excited state in
Xe were performed by studying different coincidence scenarios. The
analysis was based on data representing a total exposure of
N(Te)t=y. No evidence for a signal was
found. The resulting lower limits on the half lives are y (90% C.L.), and
y (90%
C.L.).Comment: 6 pages, 4 figure
Search for nucleon decays with EXO-200
A search for instability of nucleons bound in Xe nuclei is reported
with 223 kgyr exposure of Xe in the EXO-200 experiment. Lifetime
limits of 3.3 and 1.9 yrs are established for
nucleon decay to Sb and Te, respectively. These are the most
stringent to date, exceeding the prior decay limits by a factor of 9 and 7,
respectively
Measurement of the Spectral Shape of the beta-decay of 137Xe to the Ground State of 137Cs in EXO-200 and Comparison with Theory
We report on a comparison between the theoretically predicted and
experimentally measured spectra of the first-forbidden non-unique -decay
transition ^{137}\textrm{Xe}(7/2^-)\to\,^{137}\textrm{Cs}(7/2^+). The
experimental data were acquired by the EXO-200 experiment during a deployment
of an AmBe neutron source. The ultra-low background environment of EXO-200,
together with dedicated source deployment and analysis procedures, allowed for
collection of a pure sample of the decays, with an estimated
signal-to-background ratio of more than 99-to-1 in the energy range from 1075
to 4175 keV. In addition to providing a rare and accurate measurement of the
first-forbidden non-unique -decay shape, this work constitutes a novel
test of the calculated electron spectral shapes in the context of the reactor
antineutrino anomaly and spectral bump.Comment: Version as accepted by PR
Deep Neural Networks for Energy and Position Reconstruction in EXO-200
We apply deep neural networks (DNN) to data from the EXO-200 experiment. In
the studied cases, the DNN is able to reconstruct the relevant parameters -
total energy and position - directly from raw digitized waveforms, with minimal
exceptions. For the first time, the developed algorithms are evaluated on real
detector calibration data. The accuracy of reconstruction either reaches or
exceeds what was achieved by the conventional approaches developed by EXO-200
over the course of the experiment. Most existing DNN approaches to event
reconstruction and classification in particle physics are trained on Monte
Carlo simulated events. Such algorithms are inherently limited by the accuracy
of the simulation. We describe a unique approach that, in an experiment such as
EXO-200, allows to successfully perform certain reconstruction and analysis
tasks by training the network on waveforms from experimental data, either
reducing or eliminating the reliance on the Monte Carlo.Comment: Accepted version. 33 pages, 28 figure
Search for Neutrinoless Double-Beta Decay in Xe with EXO-200
We report on a search for neutrinoless double-beta decay of Xe with
EXO-200. No signal is observed for an exposure of 32.5 kg-yr, with a background
of ~1.5 x 10^{-3} /(kg yr keV) in the region of interest. This
sets a lower limit on the half-life of the neutrinoless double-beta decay
(Xe) > 1.6 x 10 yr (90% CL),
corresponding to effective Majorana masses of less than 140-380 meV, depending
on the matrix element calculation
Investigation of radioactivity-induced backgrounds in EXO-200
The search for neutrinoless double-beta decay (0{\nu}{\beta}{\beta}) requires
extremely low background and a good understanding of their sources and their
influence on the rate in the region of parameter space relevant to the
0{\nu}{\beta}{\beta} signal. We report on studies of various {\beta}- and
{\gamma}-backgrounds in the liquid- xenon-based EXO-200 0{\nu}{\beta}{\beta}
experiment. With this work we try to better understand the location and
strength of specific background sources and compare the conclusions to
radioassay results taken before and during detector construction. Finally, we
discuss the implications of these studies for EXO-200 as well as for the
next-generation, tonne-scale nEXO detector.Comment: 9 pages, 7 figures, 3 table
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