Search

Abstract Convolutional neural networks (CNNs) are widely used state-of-the-art computer vision tools that are becoming increasingly popular in high-energy physics. In this paper, we attempt to understand the potential of CNNs for event classification in the NEXT experiment, which will search for neutrinoless double-beta decay in 136Xe. To do so, we demonstrate the usage of CNNs for the identification of electron-positron pair production events, which exhibit a topology similar to that of a neutrinoless double-beta decay event. These events were produced in the NEXT-White high-pressure xenon TPC using 2.6 MeV gamma rays from a 228Th calibration source. We train a network on Monte Carlo-simulated events and show that, by applying on-the-fly data augmentation, the network can be made robust against differences between simulation and data. The use of CNNs offers significant improvement in signal efficiency and background rejection when compared to previous non-CNN-based analyses.

Abstract High pressure xenon Time Projection Chambers (TPC) based on secondary scintillation (electroluminescence) signal amplification are being proposed for rare event detection such as directional dark matter, double electron capture and double beta decay detection. The discrimination of the rare event through the topological signature of primary ionisation trails is a major asset for this type of TPC when compared to single liquid or double-phase TPCs, limited mainly by the high electron diffusion in pure xenon. Helium admixtures with xenon can be an attractive solution to reduce the electron diffu- sion significantly, improving the discrimination efficiency of these optical TPCs. We have measured the electroluminescence (EL) yield of Xe–He mixtures, in the range of 0 to 30% He and demonstrated the small impact on the EL yield of the addition of helium to pure xenon. For a typical reduced electric field of 2.5 kV/cm/bar in the EL region, the EL yield is lowered by ∼ 2%, 3%, 6% and 10% for 10%, 15%, 20% and 30% of helium concentration, respectively. This decrease is less than what has been obtained from the most recent simulation framework in the literature. The impact of the addition of helium on EL statistical fluctuations is negligible, within the experimental uncertainties. The present results are an important benchmark for the simulation tools to be applied to future optical TPCs based on Xe-He mixtures.

Abstract Natural radioactivity represents one of the main backgrounds in the search for neutrinoless double beta decay. Within the NEXT physics program, the radioactivity- induced backgrounds are measured with the NEXT-White detector. Data from 37.9 days of low-background operations at the Laboratorio Subterráneo de Canfranc with xenon depleted in 136Xe are analyzed to derive a total background rate of (0.84±0.02) mHz above 1000 keV. The comparison of data samples with and without the use of the radon abatement system demonstrates that the contribution of airborne-Rn is negligible. A radiogenic background model is built upon the extensive radiopurity screening campaign conducted by the NEXT collaboration. A spectral fit to this model yields the specific contributions of 60Co, 40K, 214Bi and 208Tl to the total background rate, as well as their location in the detector volumes. The results are used to evaluate the impact of the radiogenic backgrounds in the double beta decay analyses, after the application of topological cuts that reduce the total rate to (0.25±0.01) mHz. Based on the best-fit background model, the NEXT-White median sensitivity to the two-neutrino double beta decay is found to be 3.5σ after 1 year of data taking. The background measurement in a Q ββ ±100 keV energy window validates the best-fit background model also for the neutrinoless double beta decay search with NEXT-100. Only one event is found, while the model expectation is (0.75±0.12) events.

Abstract 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 228Th 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.

Abstract Excellent energy resolution is one of the primary advantages of electroluminescent high-pressure xenon TPCs. These detectors are promising tools in searching for rare physics events, such as neutrinoless double-beta decay (ββ0ν), which require precise energy measurements. Using the NEXT-White detector, developed by the NEXT (Neutrino Experiment with a Xenon TPC) collaboration, we show for the first time that an energy resolution of 1% FWHM can be achieved at 2.6 MeV, establishing the present technology as the one with the best energy resolution of all xenon detectors for ββ0ν searches.

Abstract The NEXT experiment aims at searching for the hypothetical neutrinoless double-beta decay from the 136Xe isotope using a high-purity xenon TPC. Efficient discrimination of the events through pattern recognition of the topology of primary ionisation tracks is a major requirement for the experiment. However, it is limited by the diffusion of electrons. It is known that the addition of a small fraction of a molecular gas to xenon reduces electron diffusion. On the other hand, the electroluminescence (EL) yield drops and the achievable energy resolution may be compromised. We have studied the effect of adding several molecular gases to xenon (CO2, CH4 and CF4) on the EL yield and energy resolution obtained in a small prototype of driftless gas proportional scintillation counter. We have compared our results on the scintillation characteristics (EL yield and energy resolution) with a microscopic simulation, obtaining the diffusion coefficients in those conditions as well. Accordingly, electron diffusion may be reduced from about 10 mm/ m $$ \sqrt{\mathrm{m}} $$ for pure xenon down to 2.5 mm/ m $$ \sqrt{\mathrm{m}} $$ using additive concentrations of about 0.05%, 0.2% and 0.02% for CO2, CH4 and CF4, respectively. Our results show that CF4 admixtures present the highest EL yield in those conditions, but very poor energy resolution as a result of huge fluctuations observed in the EL formation. CH4 presents the best energy resolution despite the EL yield being the lowest. The results obtained with xenon admixtures are extrapolated to the operational conditions of the NEXT-100 TPC. CO2 and CH4 show potential as molecular additives in a large xenon TPC. While CO2 has some operational constraints, making it difficult to be used in a large TPC, CH4 shows the best performance and stability as molecular additive to be used in the NEXT-100 TPC, with an extrapolated energy resolution of 0.4% at 2.45 MeV for concentrations below 0.4%, which is only slightly worse than the one obtained for pure xenon. We demonstrate the possibility to have an electroluminescence TPC operating very close to the thermal diffusion limit without jeopardizing the TPC performance, if CO2 or CH4 are chosen as additives.

Abstract The measurement of the internal 222Rn activity in the NEXT-White detector during the so-called Run-II period with 136Xe-depleted xenon is discussed in detail, together with its implications for double beta decay searches in NEXT. The activity is measured through the alpha production rate induced in the fiducial volume by 222Rn and its alpha-emitting progeny. The specific activity is measured to be (38.1 ± 2.2 (stat.) ± 5.9 (syst.)) mBq/m3. Radon-induced electrons have also been characterized from the decay of the 214Bi daughter ions plating out on the cathode of the time projection chamber. From our studies, we conclude that radon-induced backgrounds are sufficiently low to enable a successful NEXT-100 physics program, as the projected rate contribution should not exceed 0.1 counts/yr in the neutrinoless double beta decay sample.

The title compounds, both C23H34O5, are the 5α and 5β configurations of two diacetate epimers. The 5β-diacetate crystallizes in an hexagonal structure, unusual for steroid molecules. The unit cell has an accessible solvent volume of 358 Å3, responsible for clathrate behaviour. The 5β-epimer also features some shorter than average bond lengths in the 3α,4β-acetoxy groups. The conformations of the molecules of both epimers are compared with those obtained through ab initio quantum chemistry calculations. Cohesion of the crystals can be attributed to van der Waals and weak molecular C—H…O interactions. [ABSTRACT FROM AUTHOR]

Examines the structures of synthetic receptors and their synthetic intermediates on a crystallographic basis. Improvement in the understanding of molecular-recognition principles; Construction of steroid-based synthetic receptor; Assessment of the cholic acid derivative.

We propose a model that realistically describes the experimental noise curves of GaAs/AlGaAs quantum-well intersubband photodetectors and that, additionally, allows the determination of some important transport parameters of these devices. The analysis was based on the quantum mechanical calculation of the capture lifetime in a quantum well and on the assumption that the capture probability can be explicitly expressed as a function of the electronic thermal velocity at zero bias and of the saturation velocity at large bias. Our experimental and theoretical results point out that the plateau observed in the noise measurements at low temperature and low electric field is due to an extra conduction path through the miniband of the superlattice formed by the ground states of all the wells. [ABSTRACT FROM AUTHOR]

El objetivo del presente estudio es comprender los significados del trabajo en el proceso de vivir de trabajadores (as) del Programa de Salud de la Familia, de una ciudad del Estado de Rio Grande do Sul. Con base en un abordaje exploratorio descriptivo, los datos cualitativos fueron obtenidos con diez trabajadoras del Programa de Salud de la Familia, a través de entrevistas y grupo focal. Los datos fueron analizados usando el programa de análisis cualitativo - QSR Nvivo e interpretados a través del referencial teórico propuesto. De acuerdo con los resultados de este estudio, el trabajo surgió a partir de una red de significados que lo caracterizan como proceso (des) potencializador del vivir humano de los (las) trabajadores (as) del Programa de Salud de la Familia.

Os modos de adubação fosfatada mais estudados na cultura do milho são relacionados com a aplicação a lanço e a localizada no sulco de semeadura. No entanto, existe a possibilidade da aplicação intermediária, em sulco duplo, que pode aumentar a fração do solo fertilizada e a eficiência da adubação. Com o objetivo de avaliar os efeitos de modos de aplicação e de doses de fertilizante fosfatado em adubação de manutenção, foi realizado este presente trabalho em Latossolo Vermelho-Escuro, na região do Triângulo Mineiro, em Uberaba (MG), com a cultura do milho, no período de outubro de 1995 a abril de 1996. Os tratamentos foram constituídos pelos modos de aplicação do adubo fosfatado (superfosfato triplo), a lanço, sulco simples e sulco duplo, e pelas doses de 0; 45,0; 67,5; 90,0; 112,5 e 135,0 kg ha-1 de P2O5. As doses de P foram estimadas, tomando por base 0; 0,50; 0,75; 1,00; 1,25; 1,50 vêzes a dose recomendada para a adubação de manutenção, 90 kg ha-1 de P2O5. Verificou-se que: o uso de doses crescentes de P aumentou a produção de grãos de milho; os modos de aplicação do adubo fosfatado em sulco simples e sulco duplo foram mais eficientes que a lanço; dentre os modos de aplicação, destacou-se a aplicação em sulco duplo; o teor foliar de P variou de 2,1 a 2,4 ; 2,1 a 2,7 e de 2,1 a 2,9 g kg-1, respectivamente, para a aplicação a lanço, em sulco simples e em sulco duplo. O incremento na produção do milho foi de 0,45 a 3,04 t ha-1 no sulco simples e de 0,21 a 4,4 t ha-1 no sulco duplo.

A acidez elevada dos solos da região sudeste e centro-oeste do Brasil predomina onde se concentra a maior área cultivada com cana-de-açúcar. Grandes depósitos de escória de siderurgia, que contêm nutrientes como cálcio e magnésio e apresentam ação corretiva de acidez, localizam-se também naquelas regiões. O presente trabalho objetivou avaliar diferentes níveis de saturação por bases, utilizando como corretivo do solo a escória de siderurgia, comparando-a com calcário calcítico, nas alterações de alguns atributos químicos do solo, bem como na resposta da cana-de-açúcar, durante os dois primeiros cortes. Para isto, foi realizado um experimento com a cana-de-açúcar, variedade SP 80-1842, nos anos agrícolas 98/99 e 99/00. Os tratamentos, dispostos em blocos casualizados em esquema fatorial com quatro repetições, constaram de duas fontes de corretivos, calcário calcítico e escória de siderurgia, e quatro níveis de correção, estimados pelo método da saturação por bases (V%): testemunha sem correção e correção para V% de 50, 75 e 100. Concluiu-se que os efeitos da aplicação do calcário e da escória de siderurgia foram semelhantes na correção da acidez do solo, na elevação da concentração de cálcio e magnésio do solo e na saturação por bases. As doses de calcário proporcionaram efeito quadrático sobre a produtividade e perfilhamento da cana-de-açúcar, enquanto as de escória resultaram em resposta linear.

In the title compound, C17H27NO4, which is an hydrosinapic acid derivative with increased lipophilicity conferred by an additional alkyl chain, the central and the hexyl linear chains contain slightly shorter bond lengths [C—N = 1.316 (2) Å; average linear chain C—C = 1.487 (6) Å] than reported average values [Csp2—N = 1.334, C—C for CH2—CH2 = 1.524 and 1.513 Å for CH2—CH3]. The 4-hydroxy-3,5-dimethoxyphenyl plane [r.m.s. deviation 0.055 (12) Å] makes an angle of 59.89 (5)° with the central plane of the molecule (composed of the N atom, the carbonyl group and the two methylene C atoms linking the carbonyl group and the ring, [r.m.s. deviation 0.0026 (10) Å], which, in turn, makes an angle of 64.24 (13)° with the essentially planar hexyl chain [r.m.s. deviation 0.035 (18) Å]. The N—H group of the amide group is involved in a bifurcated hydrogen bond towards the hydroxy and one of the methoxy O atoms of the 4-hydroxy-3,5-dimethoxyphenyl substituent of a neighbouring molecule, forming a two-dimensional network in the (100) plane. In addition, the same hydroxy group acts as a donor towards the carbonyl O atom of another neighbouring molecule, forming chains running along the b axis.

In the title compound, C20H26O2, which is the 6-methylene derivative of androstenedione and a synthetic percursor of exemestane, the steroid A ring approximates to a sofa (or envelope) conformation, with the methylene group adjacent to the link to the B ring lying out of the plane of the other atoms. The B and C rings have slightly flattened chair conformations and the D ring is an envelope, with the CH group forming the flap. In the crystal, molecules are linked by two distinct C—H...O hydrogen bonds, involving acidic H atoms close to C=C and C=O double bonds.

The title compound, C21H32O4 crystallizes in a triclinic unit cell, which is very unusual for steroids. The asymmetric unit contains two independent mol­ecules with almost identical geometry, although they are slighly twisted in opposite directions. These mol­ecules form a dimer inter­connected via hydrogen bonds. Both mol­ecules have a cis A/ B ring junction characteristic of a 5β-configuration, but differ in the orientation of their hydroxyl groups. [ABSTRACT FROM AUTHOR]

The article presents information on Pentafluorophenyl 3-phenylprop-2-enoate. The compound was synthesized to study the reactivity of cinnamic acid towards pentafluorophenol and pentafluorothiophenol. In the compound, the regular geometry of the carbon skeleton of the phenyl ring is slightly modified, and the deformation is due to hybridization and conjugation effects. An intermolecular hydrogen bond results in the formation of a dimer. In an experiment, the compound was prepared by treating 3-phenyl-2-propenoic acid with dicyclohexylcarbodiimide and pentafluorophenol in anhydrous dioxane.

The title compound, C26H38O6, has a cis junction between two of the six-membered rings ( A and B). All three of the six-membered rings have chair conformations that are slightly flattened and the five-membered ring has an unusual 13β-envelope conformation. The 7α and 12α ring substituents are both axial and the 3α and 17β groups are equatorial and pseudo-equatorial, respectively. The 3α-form­yloxy group is involved in one weak inter­molecular C—H⋯O bond, which links the mol­ecules into dimers in a head-to-head fashion. [ABSTRACT FROM AUTHOR]