23 research outputs found
FUV and X-ray absorption in the Warm-Hot Intergalactic Medium
The Warm-Hot Intergalactic Medium (WHIM) arises from shock-heated gas
collapsing in large-scale filaments and probably harbours a substantial
fraction of the baryons in the local Universe. Absorption-line measurements in
the ultraviolet (UV) and in the X-ray band currently represent the best method
to study the WHIM at low redshifts. We here describe the physical properties of
the WHIM and the concepts behind WHIM absorption line measurements of H I and
high ions such as O VI, O VII, and O VIII in the far-ultraviolet and X-ray
band. We review results of recent WHIM absorption line studies carried out with
UV and X-ray satellites such as FUSE, HST, Chandra, and XMM-Newton and discuss
their implications for our knowledge of the WHIM.Comment: 26 pages, 9 figures, accepted for publication in Space Science
Reviews, special issue "Clusters of galaxies: beyond the thermal view",
Editor J.S. Kaastra, Chapter 3; work done by an international team at the
International Space Science Institute (ISSI), Bern, organised by J.S.
Kaastra, A.M. Bykov, S. Schindler & J.A.M. Bleeke
Search for Neutrinoless Double- β Decay with the Complete EXO-200 Dataset
A search for neutrinoless double-β decay (0νββ) in Xe136 is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of Xe136 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0×1025 yr with a total Xe136 exposure of 234.1 kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×1025 yr at the 90% confidence level
Search for Neutrinoless Double-Beta Decay with the Upgraded EXO-200 Detector
Results from a search for neutrinoless double-beta decay (0νββ) of Xe136 are presented using the first year of data taken with the upgraded EXO-200 detector. Relative to previous searches by EXO-200, the energy resolution of the
A Novel Diversity-Controlled Genetic Algorithm for Rapid Optimization of Bandpass FRM FIR Digital Filters Over CSD Multiplier Coefficient Space
Search for nucleon decays with EXO-200
A search for instability of nucleons bound in Xe136 nuclei is reported with 223 kg·yr exposure of Xe136 in the EXO-200 experiment. Lifetime limits of 3.3×1023 and 1.9×1023 yr are established for nucleon decay to Sb133 and Te133, respectively. These are the most stringent to date, exceeding the prior decay limits by a factor of 9 and 7, respectively
Trace radioactive impurities in final construction materials for EXO-200
We report results from a systematic measurement campaign conducted to identify low radioactivity materials for the construction of the EXO-200 double beta decay experiment. Partial results from this campaign have already been reported in a 2008 paper by the EXO collaboration. Here we release the remaining data, collected since 2007, to the public. The data reported were obtained using a variety of analytic techniques. The measurement sensitivities are among the best in the field. Construction of the EXO-200 detector has been concluded, and Phase-I data was taken from 2011 to 2014. The detector's extremely low background implicitly verifies the measurements and the analysis assumptions made during construction and reported in this paper. (C) 2017 Elsevier B.V. All rights reserved1221sciescopu
Measurement of the drift velocity and transverse diffusion of electrons in liquid xenon with the EXO-200 detector
The EXO-200 Collaboration is searching for neutrinoless double β decay using a liquid xenon (LXe) time projection chamber. This measurement relies on modeling the transport of charge deposits produced by interactions in the LXe to allow discrimination between signal and background events. Here we present measurements of the transverse diffusion constant and drift velocity of electrons at drift fields between 20 V/cm and 615 V/cm using EXO-200 data. At the operating field of 380 V/cm EXO-200 measures a drift velocity of 1.705-0.010+0.014mm/μs and a transverse diffusion coefficient of 55±4cm2/s
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
Characterization of an Ionization Readout Tile for nEXO
A new design for the anode of a time projection chamber, consisting of a charge-detecting "tile, is investigated for use in large scale liquid xenon detectors. The tile is produced by depositing 60 orthogonal metal charge-collecting strips, 3 mm wide, on a 10 cm × 10 cm fused-silica wafer. These charge tiles may be employed by large detectors, such as the proposed tonne-
Imaging individual barium atoms in solid xenon for barium tagging in nEXO
Double-β-decay involves the simultaneous conversion of two neutrons into two protons, and the emission of two electrons and two neutrinos; the neutrinoless process, although not yet observed, is thought to involve the emission of the two electrons but no neutrinos. The search for neutrinoless-double-β-decay probes fundamental properties of neutrinos, including whether or not the neutrino and antineutrino are distinct particles. Double-β-decay detectors are large and expensive, so it is essential to achieve the highest possible sensitivity with each study, and removing spurious contributions (‘background’) from detected signals is crucial. In the nEXO neutrinoless-double-β-decay experiment, the identification, or ‘tagging’, of the
136
Ba daughter atom resulting from the double-β decay of
136
Xe provides a technique for discriminating background. The tagging scheme studied here uses a cryogenic probe to trap the barium atom in a solid xenon matrix, where the barium atom is tagged through fluorescence imaging. Here we demonstrate the imaging and counting of individual barium atoms in solid xenon by scanning a focused laser across a solid xenon matrix deposited on a sapphire window. When the laser irradiates an individual atom, the fluorescence persists for about 30 seconds before dropping abruptly to the background level—a clear confirmation of one-atom imaging. Following evaporation of a barium deposit, the residual barium fluorescence is 0.16 per cent or less. Our technique achieves the imaging of single atoms in a solid noble element, establishing the basic principle of barium tagging for nEXO