Many experiments that aim at the direct detection of Dark Matter are able to distinguish a dominant background from the expected feeble signals, based on some measured discrimination parameter. We ...develop a statistical model for such experiments using the Profile Likelihood ratio as a test statistic in a frequentist approach. We take data from calibrations as control measurements for signal and background, and the method allows the inclusion of data from Monte Carlo simulations. Systematic detector uncertainties, such as uncertainties in the energy scale, as well as astrophysical uncertainties, are included in the model. The statistical model can be used to either set an exclusion limit or to make a discovery claim, and the results are derived with a proper treatment of statistical and systematic uncertainties. We apply the model to the first data release of the XENON100 experiment, which allows to extract additional information from the data, and place stronger limits on the spin-independent elastic WIMP-nucleon scattering cross-section. In particular, we derive a single limit, including all relevant systematic uncertainties, with a minimum of 2.4x10^-44 cm^2 for WIMPs with a mass of 50 GeV/c^2.
Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For Xe-124 this process has not yet been observed and its detection ...would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K shell of 124Xe using 7636 kg d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90% credibility limit on the half-life T-1/2 > 6.5 x 10(20) yr. We have also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and found a sensitivity of T-1/2 > 6.1 x 10(22) yr after an exposure of 2 t yr.
We present results on the search for two-neutrino double-electron capture (2 ν ECEC) of 124 Xe and neutrinoless double- β decay (0 νββ ) of 136 Xe in XENON1T. We consider captures from the K shell up ...to the N shell in the 2 ν ECEC signal model and measure a total half-life of T 2 ν ECEC 1/2 =(1.1±0.2 stat ±0.1 sys )×10 22 yr with a 0.87 kg yr isotope exposure. The statistical significance of the signal is 7.0 σ . We use XENON1T data with 36.16 kg yr of 136 Xe exposure to search for 0 νββ . We find no evidence of a signal and set a lower limit on the half-life of T 0 νββ 1/2 >1.2×10 24 yr at 90%CL. This is the best result from a dark matter detector without an enriched target to date. We also report projections on the sensitivity of XENONnT to 0 νββ . Assuming a 275 kg yr 136 Xe exposure, the expected sensitivity is T 0 νββ 1/2 >2.1×10 25 yr at 90%CL, corresponding to an effective Majorana mass range of ⟨ mββ ⟩<(0.19–0.59)eV/c 2 .
XEMIS: A liquid xenon detector for medical imaging Gallego Manzano, L.; Bassetto, S.; Beaupere, N. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2015, Volume:
787
Journal Article
Peer reviewed
A new medical imaging technique based on the precise 3D location of a radioactive source by the simultaneous detection of 3 gamma rays has been proposed by Subatech laboratory. To take advantage of ...this novel technique a detection device based on a liquid xenon Compton telescope and a specific (beta(+), gamma) emitter radionuclide, Sc-44, are required. A first prototype of a liquid xenon time projection chamber called XEMIS1 has been successfully developed showing very promising results for the energy and spatial resolutions for the ionization signal in liquid xenon, thanks to an advanced cryogenics system, which has contributed to a high liquid xenon purity with a very good stability and an ultra-low noise front-end electronics (below 100 electrons) operating at liquid xenon temperature. The very positive results obtained with XEMIS1 have led to the development of a second prototype for small animal imaging. XEMIS2, which is now under development. To study the feasibility of the 3 gamma imaging technique and optimize the characteristics of the device, a complete Monte Carlo simulation has been also carried out. A preliminary study shows very positive results for the sensitivity, energy and spatial resolutions of XEMIS2. (C) 2014 Elsevier B.V. All rights reserved.
The selection of low-radioactive construction materials is of utmost importance for the success of low-energy rare event search experiments. Besides radioactive contaminants in the bulk, the ...emanation of radioactive radon atoms from material surfaces attains increasing relevance in the effort to further reduce the background of such experiments. In this work, we present the
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Rn emanation measurements performed for the XENON1T dark matter experiment. Together with the bulk impurity screening campaign, the results enabled us to select the radio-purest construction materials, targeting a
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Rn activity concentration of
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\begin{document}$$10\,\mathrm{\,}\upmu \mathrm{Bq}/\mathrm{kg}$$\end{document}
10
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in
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\begin{document}$$3.2\,\mathrm{t}$$\end{document}
3.2
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of xenon. The knowledge of the distribution of the
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Rn sources allowed us to selectively eliminate problematic components in the course of the experiment. The predictions from the emanation measurements were compared to data of the
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Rn activity concentration in XENON1T. The final
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Rn activity concentration of
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\begin{document}$$(4.5\pm 0.1)\,\mathrm{\,}\upmu \mathrm{Bq}/\mathrm{kg}$$\end{document}
(
4.5
±
0.1
)
μ
Bq
/
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in the target of XENON1T is the lowest ever achieved in a xenon dark matter experiment.
Abstract The DARWIN observatory is a proposed next-generation experiment to search for particle dark matter and for the neutrinoless double beta decay of $$^{136}$$ 136 Xe. Out of its 50 t total ...natural xenon inventory, 40 t will be the active target of a time projection chamber which thus contains about 3.6 t of $$^{136}$$ 136 Xe. Here, we show that its projected half-life sensitivity is $$2.4\times {10}^{27}\,{\hbox {year}}$$ 2.4×1027year , using a fiducial volume of 5 t of natural xenon and 10 year of operation with a background rate of less than 0.2 events/(t $$\cdot $$ · year) in the energy region of interest. This sensitivity is based on a detailed Monte Carlo simulation study of the background and event topologies in the large, homogeneous target. DARWIN will be comparable in its science reach to dedicated double beta decay experiments using xenon enriched in $$^{136}$$ 136 Xe.
New amplifying structures can be built exploiting the electric properties of metallic meshes a few microns thick. They can be used for preamplification with a variety of gaseous detector or for ...one-stage amplification. Detection efficiency better than 80% and 50μm (FWHM) 2D accuracy on A4 sensitive areas, with uncollimated sources of 3H or 14C, is achieved with such preamplifiers.
With two amplifying stages, the discharge rate with α sources is reduced by a factor close to 1000 compared to single-stage amplification at equivalent gain values. These results have been obtained on a new structure that has been developed, called PIM for parallel ionization multiplier. PIM is made of a thin sandwich of two metallic meshes separated by a new insulating spacer whose geometrical characteristics are made possible by state-of-the-art developments in laser etching technologies. A drastic improvement has been found in the minimal distance between spacers necessary to keep the distance between the metallic meshes stable.
A front-end BiCMOS ASIC was specially developed for the Micromegas detectors to be used in the Small Angle Tracker of the COMPASS experiment at CERN. Each of the 16 channels of this integrated ...circuit contains a low noise preamplifier with a 100 ns peaking time filter and a discriminator driving a low-level differential digital buffer. The design of the preamplifier and the choice of the shaping have been tuned to the detector signal shape in order to allow the operation of Micromegas even for very low multiplication gain values. Noise measurements show an equivalent noise charge of less than 1500 e-rms for a detector capacitance of 40 pF. The measured performances of this ASIC associated or not with the detector are fully described in this paper.
A new amplifying structure has been developed for beta imaging detectors: the Parallel Ionization Multiplier (PIM). PIM is made of a thin sandwich of two metallic micromeshes separated by a new laser ...machined insulating spacer. This structure allows high gain (10
5) with a good efficiency and a two-dimensional spatial resolution below 50
μm without strong discharge limitation. The capabilities of the PIM are now investigated in order to be used by high-energy physics experiments. A prototype of a tracking detector for charged particles using the PIM structure will be described. Thanks to the very small avalanche extension, the use of a highly segmented anode is possible. This detector would support high rate running conditions of hadron experiment.
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