Abstract
The nEXO neutrinoless double beta (0νββ) decay experiment is designed to use a time projection chamber and 5000 kg of isotopically enriched liquid xenon to search for the decay in 136Xe. ...Progress in the detector design, paired with higher fidelity in its simulation and an advanced data analysis, based on the one used for the final results of EXO-200, produce a sensitivity prediction that exceeds the half-life of 1028 years. Specifically, improvements have been made in the understanding of production of scintillation photons and charge as well as of their transport and reconstruction in the detector. The more detailed knowledge of the detector construction has been paired with more assays for trace radioactivity in different materials. In particular, the use of custom electroformed copper is now incorporated in the design, leading to a substantial reduction in backgrounds from the intrinsic radioactivity of detector materials. Furthermore, a number of assumptions from previous sensitivity projections have gained further support from interim work validating the nEXO experiment concept. Together these improvements and updates suggest that the nEXO experiment will reach a half-life sensitivity of 1.35 × 1028 yr at 90% confidence level in 10 years of data taking, covering the parameter space associated with the inverted neutrino mass ordering, along with a significant portion of the parameter space for the normal ordering scenario, for almost all nuclear matrix elements. The effects of backgrounds deviating from the nominal values used for the projections are also illustrated, concluding that the nEXO design is robust against a number of imperfections of the model.
The XENON1T experiment aims for the direct detection of dark matter in a detector filled with 3.3 tons of liquid xenon. In order to achieve the desired sensitivity, the background induced by ...radioactive decays inside the detector has to be sufficiently low. One major contributor is the
β
-emitter
85
Kr which is present in the xenon. For XENON1T a concentration of natural krypton in xenon
nat
Kr
/
Xe
<
200
ppq
(parts per quadrillion,
1
ppq
=
10
-
15
mol
/
mol
) is required. In this work, the design, construction and test of a novel cryogenic distillation column using the common McCabe–Thiele approach is described. The system demonstrated a krypton reduction factor of
6.4
·
10
5
with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of
nat
Kr
/
Xe
<
26
ppq
is the lowest ever achieved, almost one order of magnitude below the requirements for XENON1T and even sufficient for future dark matter experiments using liquid xenon, such as XENONnT and DARWIN.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report on a search for weakly interacting massive particles (WIMPs) using 278.8 days of data collected with the XENON1T experiment at LNGS. XENON1T utilizes a liquid xenon time projection chamber ...with a fiducial mass of (1.30±0.01) ton, resulting in a 1.0 ton yr exposure. The energy region of interest, 1.4,10.6 keV_{ee} (4.9,40.9 keV_{nr}), exhibits an ultralow electron recoil background rate of 82_{-3}^{+5}(syst)±3(stat) events/(ton yr keV_{ee}). No significant excess over background is found, and a profile likelihood analysis parametrized in spatial and energy dimensions excludes new parameter space for the WIMP-nucleon spin-independent elastic scatter cross section for WIMP masses above 6 GeV/c^{2}, with a minimum of 4.1×10^{-47} cm^{2} at 30 GeV/c^{2} and a 90% confidence level.
The XENON100 dark matter experiment uses liquid xenon in a time projection chamber (TPC) to measure xenon nuclear recoils resulting from the scattering of dark matter weakly interacting massive ...particles (WIMPs). In this paper, we report the observation of single-electron charge signals which are not related to WIMP interactions. These signals, which show the excellent sensitivity of the detector to small charge signals, are explained as being due to the photoionization of impurities in the liquid xenon and of the metal components inside the TPC. They are used as a unique calibration source to characterize the detector. We explain how we can infer crucial parameters for the XENON100 experiment: the secondary-scintillation gain, the extraction yield from the liquid to the gas phase and the electron drift velocity.
The XENON100 experiment, installed underground at the Laboratori Nazionali del Gran Sasso, aims to directly detect dark matter in the form of weakly interacting massive particles (WIMPs) via their ...elastic scattering off xenon nuclei. This paper presents a study on the nuclear recoil background of the experiment, taking into account neutron backgrounds from (α, n) reactions and spontaneous fission due to natural radioactivity in the detector and shield materials, as well as muon-induced neutrons. Based on Monte Carlo simulations and using measured radioactive contaminations of all detector components, we predict the nuclear recoil backgrounds for the WIMP search results published by the XENON100 experiment in 2011 and 2012, 0.11 events and 0.17 events, respectively, and conclude that they do not limit the sensitivity of the experiment.
Phosphatidylinositol 3-kinase-gamma (PI3Kγ) is highly expressed in leukocytes and is an attractive drug target for immune modulation. Different experimental systems have led to conflicting ...conclusions regarding inflammatory and anti-inflammatory functions of PI3Kγ. Here, we report a human patient with bi-allelic, loss-of-function mutations in PIK3CG resulting in absence of the p110γ catalytic subunit of PI3Kγ. She has a history of childhood-onset antibody defects, cytopenias, and T lymphocytic pneumonitis and colitis, with reduced peripheral blood memory B, memory CD8+ T, and regulatory T cells and increased CXCR3+ tissue-homing CD4 T cells. PI3Kγ-deficient macrophages and monocytes produce elevated inflammatory IL-12 and IL-23 in a GSK3α/β-dependent manner upon TLR stimulation. Pik3cg-deficient mice recapitulate major features of human disease after exposure to natural microbiota through co-housing with pet-store mice. Together, our results emphasize the physiological importance of PI3Kγ in restraining inflammation and promoting appropriate adaptive immune responses in both humans and mice.
Abstract Background Chronic granulomatous disease (CGD) is characterized by recurrent life-threatening bacterial and fungal infections and aberrant inflammation. Mutations in CYBB cause X-linked CGD ...and account for 65%-70% of cases in western countries. Objective To understand the clinical manifestations associated with the X-linked CGD carrier state. Methods We undertook a comprehensive retrospective study of 162 affected females. We examined dihydrorhodamine oxidation (DHR) data for percent (%) X chromosome inactivation. We correlated lyonization (%DHR+) with clinical features. Where possible, we followed %DHR+ levels over time. Results Clinical data were available for 93 females: The %DHR+ was 46% (mean) and 47% (median)(SD=24). Using %DHR+ as the criterion for X inactivation, 78% of patients had levels of inactivation 20-80%, suggesting random inactivation that was independent of age. In contrast, carriers with CGD-type infections had median %DHR+ of 8% (n=14, range 0.06-48 %); those with only autoimmune or inflammatory manifestations (AIM) had median %DHR+ of 39% (n=31, range 7.4-74%). Those with both infections and autoimmunity had low %DHR+ (n=6, range=3-14%). A %DHR+ <10 % was strongly associated with infections (OR:99). Strong association persisted when the %DHR+ was <20% (OR=12) Autoimmunity was not associated with %DHR+. In two sets of identical twins the %DHR+ populations tracked closely over time. While the %DHR+ populations were very similar between sisters, those between mothers and daughters were unrelated. Conclusions A low %DHR+ strongly predicts infection risk in X-linked CGD carriers, while the carrier state itself is associated with autoimmunity.
A coupled finite element analysis in conjunction with experiments was used to investigate hot co-extrusion of a novel composite Mg AZ80/Al 1100 billet assembly. To validate the computational model, ...results from both radiography, and metallography were used.
It is demonstrated that the billet configuration proposed in this study results in a uniform composite rod, with no indication of cracks, tears, wavy interface surfaces or voids. The computational model is first validated by the experiments and then used to thoroughly study the thermo-mechanical fields that develop during the co-extrusion process. The interplay of the thermal and mechanical fields during the process is examined for different initial temperatures, die angle and ram velocity. It is demonstrated that using the proposed billet assembly, constant compressive radial stress develops across the magnesium core, leading to sound-proportional flow conditions.
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