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"Agostini, F."
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Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of$$^{136}$$ Xe
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 × 10 27 year , 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.
Journal Article
Observation of two-neutrino double electron capture in 124Xe with XENON1T
Two-neutrino double electron capture (2
ν
ECEC) is a second-order weak-interaction process with a predicted half-life that surpasses the age of the Universe by many orders of magnitude
1
. Until now, indications of 2
ν
ECEC decays have only been seen for two isotopes
2
–
5
,
78
Kr and
130
Ba, and instruments with very low background levels are needed to detect them directly with high statistical significance
6
,
7
. The 2
ν
ECEC half-life is an important observable for nuclear structure models
8
–
14
and its measurement represents a meaningful step in the search for neutrinoless double electron capture—the detection of which would establish the Majorana nature of the neutrino and would give access to the absolute neutrino mass
15
–
17
. Here we report the direct observation of 2
ν
ECEC in
124
Xe with the XENON1T dark-matter detector. The significance of the signal is 4.4 standard deviations and the corresponding half-life of 1.8 × 10
22
years (statistical uncertainty, 0.5 × 10
22
years; systematic uncertainty, 0.1 × 10
22
years) is the longest measured directly so far. This study demonstrates that the low background and large target mass of xenon-based dark-matter detectors make them well suited for measuring rare processes and highlights the broad physics reach of larger next-generation experiments
18
–
20
.
Two-neutrino double electron capture is observed experimentally in
124
Xe with the XENON1T detector, yielding a half-life of 1.8 × 10
22
years.
Journal Article
Low-energy calibration of XENON1T with an internal$$^{{\\textbf {37}}}$$ Ar source
A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal$^{37}$$37 Ar source was performed. This calibration source features a 35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be ($$32.3\\,\\pm \\,0.3$$32.3 ± 0.3 ) photons/keV and ($$40.6\\,\\pm \\,0.5$$40.6 ± 0.5 ) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is ($$68.0^{+6.3}_{-3.7}$$68 . 0 - 3.7 + 6.3 ) electrons/keV. The$^{37}$$37 Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at ($$2.83\\,\\pm \\,0.02$$2.83 ± 0.02 ) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that$^{37}$$37 Ar can be considered as a regular calibration source for multi-tonne xenon detectors.
Journal Article
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versions. Finally, we detail the results from screening 286 tubes with ultra-low background germanium detectors, as well as their implications for the expected electronic and nuclear recoil background of the XENON1T experiment.
Journal Article
Online Formula omittedRn removal by cryogenic distillation in the XENON100 experiment
We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant [Formula omitted]Rn background originating from radon emanation. After inserting an auxiliary [Formula omitted]Rn emanation source in the gas loop, we determined a radon reduction factor of [Formula omitted] (95% C.L.) for the distillation column by monitoring the [Formula omitted]Rn activity concentration inside the XENON100 detector.
Journal Article
Exclusion of leptophilic dark matter models using XENON100 electronic recoil data
Laboratory experiments searching for galactic dark matter particles scattering off nuclei have so far not been able to establish a discovery. We use data from the XENON100 experiment to search for dark matter interacting with electrons. With no evidence for a signal above the low background of our experiment, we exclude a variety of representative dark matter models that would induce electronic recoils. For axial-vector couplings to electrons, we exclude cross sections above 6 × 10–35 cm2 for particle masses of mx = 2 GeV/c2. Independent of the dark matter halo, we exclude leptophilic models as an explanation for the long-standing DAMA/LIBRA signal, such as couplings to electrons through axial-vector interactions at a 4.4σ. confidence level, mirror dark matter at 3.6σ, and luminous dark matter at 4.6σ.
Journal Article
Erratum to: Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of 136Xe
We correct an overestimation of the production rate of
137
Xe in the DARWIN detector operated at LNGS. This formerly dominant intrinsic background source is now at a level similar to the irreducible background from solar
8
B neutrinos, thus unproblematic at the LNGS depth. The projected half-life sensitivity for the neutrinoless double beta decay (
0
ν
β
β
) of
136
Xe improves by
22
%
compared to the previously reported number and is now
T
1
/
2
0
ν
=
3.0
×
10
27
yr
(90% C.L.) after 10 years of DARWIN operation.
Journal Article
Erratum to: Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of$$^{136}$$ Xe
We correct an overestimation of the production rate of$$^{137}$$137 Xe in the DARWIN detector operated at LNGS. This formerly dominant intrinsic background source is now at a level similar to the irreducible background from solar$$^8$$8 B neutrinos, thus unproblematic at the LNGS depth. The projected half-life sensitivity for the neutrinoless double beta decay ($$0\\nu \\beta \\beta $$0 ν β β ) of$$^{136}$$136 Xe improves by$$22\\%$$22 % compared to the previously reported number and is now$$T^{0\\nu }_{1/2}= {3.0\\times 10^{27}} \\hbox { yr}$$T 1 / 2 0 ν = 3.0 × 10 27 yr (90% C.L.) after 10 years of DARWIN operation.
Journal Article
Non-Surgical and Rehabilitative Interventions in Patients with Frozen Shoulder: Umbrella Review of Systematic Reviews
Background: Frozen shoulder (FS) is a painful condition characterized by progressive loss of shoulder function with passive and active range of motion reduction. To date, there is still no consensus regarding its rehabilitative treatment for pain management. Purpose: The aim of this umbrella review of systematic reviews was to analyze the literature, investigating the effects of non-surgical and rehabilitative interventions in patients suffering from FS. Patients and Methods: A review of the scientific literature was carried out from 2010 until April 2020 using the following search databases: PubMed, Medline, PEDro, Scopus and Cochrane Library of Systematic Reviews. A combination of terms was used for the search: frozen shoulder OR adhesive capsulitis AND systematic review OR meta-analysis AND rehabilitation NOT surgery NOT surgical intervention. We included systematic reviews that specifically dealt with adults with FS, treated with non-surgical approaches. All the systematic reviews and meta-analyses included in the study that met the inclusion criteria were assessed using the Assessment of Multiple Systematic Reviews as a quality assessment tool. Results: Out of 49 studies, only 14 systematic reviews respected the eligibility criteria and were included in this study. Their results showed an important heterogeneity of the studies and all of them agree on the lack of high-quality scientific work to prove unequivocally which rehabilitative treatment is better than the other. Due to this lack of gold standard criteria, there may be also a heterogeneity in the diagnosis of the reviews analyzed. Conclusion: Non-surgical and rehabilitative interventions are undoubtedly effective in treating FS, but there is no evidence that one approach is more effective than the other regarding the methods reported. Future high-quality RCTs are needed to standardize the treatment modalities of each physiotherapy intervention to provide strong recommendations in favor. Keywords: adhesive capsulitis, frozen shoulder, pain control, pain management, rehabilitation, non-surgical interventions
Journal Article