NEXT-100 is an electroluminescent high-pressure xenon gas time projection chamber that will search for the neutrinoless double beta (0νββ) decay of 136 Xe. The detector possesses two features of great value for 0νββ searches: energy resolution better than 1% FWHM at the Q value of 136 Xe and track reconstruction for the discrimination of signal and background events. This combination results in excellent sensitivity, as discussed in this paper. Material-screening measurements and a detailed Monte Carlo detector simulation predict a background rate for NEXT-100 of at most 4 × 10 −4 counts keV −1 kg −1 yr −1 . Accordingly, the detector will reach a sensitivity to the 0νββ-decay half-life of 2.8 × 10 25 years (90% CL) for an exposure of 100 kg · year, or 6.0 × 10 25 years after a run of 3 effective years.

A new method to tag the barium daughter in the double-beta decay of ^{136}Xe is reported. Using the technique of single molecule fluorescent imaging (SMFI), individual barium dication (Ba^{++}) resolution at a transparent scanning surface is demonstrated. A single-step photobleach confirms the single ion interpretation. Individual ions are localized with superresolution (∼2  nm), and detected with a statistical significance of 12.9σ over backgrounds. This lays the foundation for a new and potentially background-free neutrinoless double-beta decay technology, based on SMFI coupled to high pressure xenon gas time projection chambers.

The medical records and histopathological sections of 29 dogs diagnosed with a unique eosinophilic dermatitis resembling Wells' syndrome were reviewed in an attempt to elucidate the pathogenesis of this syndrome. The medical records were reviewed for information on dermatological lesion appearance, systemic signs in other organ systems, clinical analyte abnormalities, and drug therapy. Histological sections of dogs with moderate to severe eosinophilic dermatitis without folliculitis and furunculosis were reviewed and evaluated for the presence of collagen flame figures. Three categories of patients were found. Category 1 consisted of 17 dogs treated for vomiting and/or diarrhoea (often haematochezia or haematemesis) prior (mean: 4.6 days) to the onset of skin lesions. Fourteen category 1 dogs had erythematous lesions (macules, papules or plaques) that were most pronounced on the abdomen. Sixteen of the 17 dogs received multiple classes of drugs, and 59% were hypoalbuminemic. Category 2 consisted of five dogs that had skin lesions and gastrointestinal signs at presentation and four of these dogs were hypoalbuminemic. Category 3 included seven dogs without enteric illness. A positive drug score was found in six category 1 dogs and one each from categories 2 and 3. Eighteen cases had eosinophilic dermatitis without flame figures, seven cases had early flame figures and four had well-developed flame figures. These changes did not correlate with the categories of clinical presentation. More than 50% of the dogs developed eosinophilic dermatitis following treatment for severe gastrointestinal disease. The authors propose that this represents a unique syndrome that may have causal drug association.

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A: We investigate the potential of using deep learning techniques to reject background events in searches for neutrinoless double beta decay with high pressure xenon time projection chambers capable of detailed track reconstruction. The differences in the topological signatures of background and signal events can be learned by deep neural networks via training over many thousands of events. These networks can then be used to classify further events as signal or background, providing an additional background rejection factor at an acceptable loss of efficiency. The networks trained in this study performed better than previous methods developed based on the use of the same topological signatures by a factor of 1.2 to 1.6, and there is potential for further improvement. K: Analysis and statistical methods; Pattern recognition, cluster finding, calibration and fitting methods; Double-beta decay detectors; Time projection chambers A X P : 1609.06202

In experiments searching for neutrinoless double-beta decay, the possibility of identifying the two emitted electrons is a powerful tool in rejecting background events and therefore improving the overall sensitivity of the experiment. In this paper we present the first measurement of the efficiency of a cut based on the different event signatures of double and single electron tracks, using the data of the NEXT-White detector, the first detector of the NEXT experiment operating underground. Using a 228 Th calibration source to produce signal-like and background-like events with energies near 1.6 MeV, a signal efficiency of 71.6 ± 1.5 stat ± 0.3 sys % for a background acceptance of 20.6 ± 0.4 stat ± 0.3 sys % is found, in good agreement with Monte Carlo simulations. An extrapolation to the energy region of the neutrinoless double beta decay by means of Monte Carlo simulations is also carried out, and the results obtained show an improvement in background rejection over those obtained at lower energies.

We introduce a simulation framework for the transport of high and low energy electrons in xenon-based optical time projection chambers (OTPCs). The simulation relies on elementary cross sections (electron-atom and electron-molecule) and incorporates, in order to compute the gas scintillation, the reaction/quenching rates (atom-atom and atom-molecule) of the first 41 excited states of xenon and the relevant associated excimers, together with their radiative cascade. The results compare positively with observations made in pure xenon and its mixtures with CO2 and CF4 in a range of pressures from 0.1 to 10 bar. This work sheds some light on the elementary processes responsible for the primary and secondary xenon-scintillation mechanisms in the presence of additives, that are of interest to the OTPC technology.

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