Search for Two-Neutrino Double Electron Capture of 124^{124}Xe with XENON100

Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For $^{124}$Xe this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K-shell of $^{124}$Xe using 7636 kg$\cdot$d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90 % credibility limit on the half-life $T_{1/2}>6.5\times10^{20}$ yr. We also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and find a sensitivity of $T_{1/2}>6.1\times10^{22}$ yr after an exposure of 2 t$\cdot$yr.Comment: 6 pages, 4 figure

Removing krypton from xenon by cryogenic distillation to the ppq level

The XENON1T experiment aims for the direct detection of dark matter in a cryostat 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 $\beta$-emitter $^{85}$Kr which is an intrinsic contamination of the xenon. For the XENON1T experiment a concentration of natural krypton in xenon $\rm{^{nat}}$Kr/Xe < 200 ppq (parts per quadrillion, 1 ppq = 10$^{-15}$ mol/mol) is required. In this work, the design of a novel cryogenic distillation column using the common McCabe-Thiele approach is described. The system demonstrated a krypton reduction factor of 6.4$\cdot$10$^5$ with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of $\rm{^{nat}}$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

Search for Two-Neutrino Double Electron Capture of ¹²⁴Xe with XENON100

Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shell. For $^{124}$Xe this process has not yet been observed and its detection would provide a new reference for nuclear matrix element calculations. We have conducted a search for two-neutrino double electron capture from the K-shell of $^{124}$Xe using 7636 kg$\cdot$d of data from the XENON100 dark matter detector. Using a Bayesian analysis we observed no significant excess above background, leading to a lower 90 % credibility limit on the half-life $T_{1/2}>6.5\times10^{20}$ yr. We also evaluated the sensitivity of the XENON1T experiment, which is currently being commissioned, and find a sensitivity of $T_{1/2}>6.1\times10^{22}$ yr after an exposure of 2 t$\cdot$yr

Online 222^{222}Rn 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 ²²²Rn background originating from radon emanation. After inserting an auxiliary ²²²Rn emanation source in the gas loop, we determined a radon reduction factor of R>27 (95% C.L.) for the distillation column by monitoring the ²²²Rn activity concentration inside the XENON100 detector

DARWIN: towards the ultimate dark matter detector

DARk matter WImp search with liquid xenoN (DARWIN) will be an experiment forthe direct detection of dark matter using a multi-ton liquid xenon timeprojection chamber at its core. Its primary goal will be to explore theexperimentally accessible parameter space for Weakly Interacting MassiveParticles (WIMPs) in a wide mass-range, until neutrino interactions with thetarget become an irreducible background. The prompt scintillation light and thecharge signals induced by particle interactions in the xenon will be observedby VUV sensitive, ultra-low background photosensors. Besides its excellentsensitivity to WIMPs above a mass of 5 GeV/c2, such a detector with its largemass, low-energy threshold and ultra-low background level will also besensitive to other rare interactions. It will search for solar axions, galacticaxion-like particles and the neutrinoless double-beta decay of 136-Xe, as wellas measure the low-energy solar neutrino flux with <1% precision, observecoherent neutrino-nucleus interactions, and detect galactic supernovae. Wepresent the concept of the DARWIN detector and discuss its physics reach, themain sources of backgrounds and the ongoing detector design and R&D efforts

Epithelial IL-6 trans-signaling defines a new asthma phenotype with increased airway inflammation

Background: Although several studies link high levels of IL-6 and soluble IL-6 receptor (sIL-6R) to asthma severity and decreased lung function, the role of IL-6 trans-signaling (IL-6TS) in asthmatic patients is unclear. Objective: We sought to explore the association between epithelial IL-6TS pathway activation and molecular and clinical phenotypes in asthmatic patients. Methods: An IL-6TS gene signature obtained from air-liquid interface cultures of human bronchial epithelial cells stimulated with IL-6 and sIL-6R was used to stratify lung epithelial transcriptomic data (Unbiased Biomarkers in Prediction of Respiratory Disease Outcomes [U-BIOPRED] cohorts) by means of hierarchical clustering. IL-6TS-specific protein markers were used to stratify sputum biomarker data (Wessex cohort). Molecular phenotyping was based on transcriptional profiling of epithelial brushings, pathway analysis, and immunohistochemical analysis of bronchial biopsy specimens. Results: Activation of IL-6TS in air-liquid interface cultures reduced epithelial integrity and induced a specific gene signature enriched in genes associated with airway remodeling. The IL-6TS signature identified a subset of patients with IL-6TS-high asthma with increased epithelial expression of IL-6TS-inducible genes in the absence of systemic inflammation. The IL-6TS-high subset had an overrepresentation of frequent exacerbators, blood eosinophilia, and submucosal infiltration of T cells and macrophages. In bronchial brushings Toll-like receptor pathway genes were upregulated, whereas expression of cell junction genes was reduced. Sputum sIL-6R and IL-6 levels correlated with sputum markers of remodeling and innate immune activation, in particular YKL-40, matrix metalloproteinase 3, macrophage inflammatory protein 1 beta, IL-8, and IL-1 beta. Conclusions: Local lung epithelial IL-6TS activation in the absence of type 2 airway inflammation defines a novel subset of asthmatic patients and might drive airway inflammation and epithelial dysfunction in these patients.Peer reviewe

Epithelial IL-6 trans-signaling defines a new asthma phenotype with increased airway inflammation

Background: Although several studies link high levels of IL-6 and soluble IL-6 receptor (sIL-6R) with asthma severity and decreased lung function, the role of IL-6 trans-signaling (IL-6TS) in asthma is unclear. Objective: To explore the association between epithelial IL-6TS pathway activation and molecular and clinical phenotypes in asthma. Methods: An IL-6TS gene signature, obtained from air-liquid interface (ALI) cultures of human bronchial epithelial cells stimulated with IL-6 and sIL-6R, was used to stratify lung epithelium transcriptomic data (U-BIOPRED cohorts) by hierarchical clustering. IL-6TS-specific protein markers were used to stratify sputum biomarker data (Wessex cohort). Molecular phenotyping was based on transcriptional profiling of epithelial brushings, pathway analysis and immunohistochemical analysis of bronchial biopsies. Results: Activation of IL-6TS in ALI cultures reduced epithelial integrity and induced a specific gene signature enriched in genes associated with airway remodeling. The IL-6TS signature identified a subset of IL-6TS. High asthma patients with increased epithelial expression of IL-6TS inducible genes in absence of systemic inflammation. The IL-6TS High subset had an overrepresentation of frequent exacerbators, blood eosinophilia, and submucosal infiltration of T cells and macrophages. In bronchial brushings, TLR pathway genes were up-regulated while the expression of tight junction genes was reduced. Sputum sIL-6R and IL-6 levels correlated with sputum markers of remodeling and innate immune activation, in particular YKL-40, MMP3, MIP-1β, IL-8 and IL-1β. Conclusions: Local lung epithelial IL-6TS activation in absence of type 2 airway inflammation defines a novel subset of asthmatics and may drive airway inflammation and epithelial dysfunction in these patients

Removing krypton from xenon by cryogenic distillation to the ppq level

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 natKr/Xe<200ppq (parts per quadrillion, 1 ppq =10−15mol/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⋅10⁵ with thermodynamic stability at process speeds above 3 kg/h. The resulting concentration of natKr/Xe<26ppq 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