We report a measurement of the half-life of the 136Xe two-neutrino double-β decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with the ...NEXT-White detector operated with 136Xe-enriched and 136Xe-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of 2.34$_{-0.46}^{+0.80}$(stat)$_{-0.17}^{+0.30}$(sys)×1021yr is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-β-decay searches.
If neutrinos are their own antiparticles the otherwise-forbidden nuclear reaction known as neutrinoless double beta decay can occur. The very long lifetime expected for these exceptional events makes ...its detection a daunting task. In order to conduct an almost background-free experiment, the NEXT collaboration is investigating novel synthetic molecular sensors that may capture the Ba dication produced in the decay of certain Xe isotopes in a high-pressure gas experiment. The use of such molecular detectors immobilized on surfaces must be explored in the ultra-dry environment of a xenon gas chamber. Here, using a combination of highly sensitive surface science techniques in ultra-high vacuum, we demonstrate the possibility of employing the so-called Fluorescent Bicolor Indicator as the molecular component of the sensor. We unravel the ion capture process for these molecular indicators immobilized on a surface and explain the origin of the emission fluorescence shift associated to the ion trapping.
Here, we report a measurement of the half-life of the 136Xe two-neutrino double-β decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with ...the NEXT-White detector operated with 136Xe-enriched and 136Xe-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of 2.34$_{-0.46}^{+0.80}$(stat)$_{-0.17}^{+0.30}$(sys)×1021yr is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-β-decay searches.
Abstract
NEXT-100 is currently being constructed at the Laboratorio
Subterráneo de Canfranc in the Spanish Pyrenees and will search
for neutrinoless double beta decay using a high-pressure gaseous
...time projection chamber (TPC) with 100 kg of xenon. Charge
amplification is carried out via electroluminescence (EL) which is
the process of accelerating electrons in a high electric field
region causing secondary scintillation of the medium proportional to
the initial charge. The NEXT-100 EL and cathode regions are made
from tensioned hexagonal meshes of 1 m diameter. This paper
describes the design, characterization, and installation of these
parts for NEXT-100. Simulations of the electric field are performed
to model the drift and amplification of ionization electrons
produced in the detector under various EL region alignments and
rotations. Measurements of the electrostatic breakdown voltage in
air characterize performance under high voltage conditions and
identify breakdown points. The electrostatic deflection of the mesh
is quantified and fit to a first-principles mechanical model.
Measurements were performed with both a standalone test EL region
and with the NEXT-100 EL region before its installation in the
detector. Finally, we describe the parts as installed in NEXT-100,
following their deployment in Summer 2023.
Abstract
We present a tunable metal ion beam that delivers
controllable ion currents in the picoamp range for testing of
dry-phase ion sensors. Ion beams are formed by sequential atomic
evaporation ...and single or multiple electron impact ionization,
followed by acceleration into a sensing region. Controllability of
the ionic charge state is achieved through tuning of electrode
potentials that influence the retention time in the ionization
region. Barium, lead, and cadmium samples have been used to test the
system, with ion currents identified and quantified using a
quadrupole mass analyzer. Realization of a clean Ba
2+
ion beam within a bench-top system represents an important technical
advance toward the development and characterization of barium
tagging systems for neutrinoless double beta decay searches in xenon
gas. This system also provides a testbed for investigation of novel
ion sensing methodologies for environmental assay applications, with
dication beams of Pb
2+
and Cd
2+
also demonstrated for this
purpose.
Abstract
Polytetrafluoroethylene (PTFE) is an excellent diffuse reflector widely used in light collection systems for particle physics experiments. In noble element systems, it is often coated with ...tetraphenyl butadiene (TPB) to allow detection of vacuum ultraviolet scintillation light. In this work this dependence is investigated for PTFE coated with TPB in air for light of wavelengths of 200 nm, 260 nm, and 450 nm. The results show that TPB-coated PTFE has a reflectance of approximately 92% for thicknesses ranging from 5 mm to 10 mm at 450 nm, with negligible variation as a function of thickness within this range. A cross-check of these results using an argon chamber supports the conclusion that the change in thickness from 5 mm to 10 mm does not affect significantly the light response at 128 nm. Our results indicate that pieces of TPB-coated PTFE thinner than the typical 10 mm can be used in particle physics detectors without compromising the light signal.
Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world's brightest neutron source. As such, it has the potential for a particle physics program with a ...unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
BackgroundInterest in patient safety (PS) is growing exponentially, fuelled by epidemiological research unveiling the extent of unsafe care. However, there is little information about the frequency ...of harm in developing and transitional countries. To address this issue, the authors performed a study known as the Iberoamerican Adverse Event Study, through a collaborative between the governments of Argentina, Colombia, Costa Rica, Mexico and Peru, the Spanish Ministry of Health, Social Policy and Equality, the Pan American Health Organization and the WHO Patient Safety.MethodsThe study used a cross-sectional design, involving 58 hospitals in the five Latin American countries, to measure the point prevalence of patients presenting an adverse event (AE) on the day of observation. All inpatients at the time of the study were included.ResultsA total of 11 379 inpatients were surveyed. Of these, 1191 had at least one AE that the reviewer judged to be related to the care received rather than to the underlying conditions. The estimated point prevalence rate was 10.5% (95% CI 9.91 to 11.04), with more than 28% of AE causing disability and another 6% associated with the death of the patient. Almost 60% of AE were considered preventable.ConclusionsThe high rate of prevalent AE found suggests that PS may represent an important public-health issue in the participating hospitals. While new studies may be needed to confirm these results, these may already be useful to inspire new PS-improvement policies in those settings.
BackgroundTens of millions of patients worldwide suffer disabling injuries or death every year due to unsafe medical care. Nonetheless, there is a scarcity of research evidence on how to tackle this ...global health priority. The shortage of trained researchers is a major limitation, particularly in developing and transitional countries.ObjectivesAs a first step to strengthen capacity in this area, the authors developed a set of internationally agreed core competencies for patient safety research worldwide.MethodsA multistage process involved developing an initial framework, reviewing the existing literature relating to competencies in patient safety research, conducting a series of consultations with potential end users and international experts in the field from over 35 countries and finally convening a global consensus conference.ResultsAn initial draft list of competencies was grouped into three themes: patient safety, research methods and knowledge translation. The competencies were considered by the WHO Patient Safety task force, by potential end users in developing and transitional countries and by international experts in the field to be relevant, comprehensive, clear, easily adaptable to local contexts and useful for training patient safety researchers internationally.ConclusionsReducing patient harm worldwide will require long-term sustained efforts to build capacity to enable practical research that addresses local problems and improves patient safety. The first edition of Competencies for Patient Safety Researchers is proposed by WHO Patient Safety as a foundation for strengthening research capacity by guiding the development of training programmes for researchers in the area of patient safety, particularly in developing and transitional countries, where such research is urgently needed.
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