First dark matter search results of the XENON1T experiment

The XENON1T experiment is the first ton-scale dual-phase (liquidgas) xenon time projection chamber, currently in operation at the Laboratori Nazionali del Gran Sasso in Italy. The experiment aims at the dark matter direct detection exploiting a ∼ 2000 kg mass of liquid xenon as a target for interactions of weakly interacting massive particles (WIMPs) with xenon nuclei. We report the blinded search results of the first science run, using 34.2 livedays of data acquired between November 2016 and January 2017. The WIMP dark matter search is performed inside a (1042 ± 12) kg fiducial mass and in the [5,40] keVnr energy range of interest, in which the electronic recoil background was (1.93 ± 0.25) × 10−4 events/( kg×day×keVee). Such a background level is the lowest ever achieved in a dark matter detector. The data analysis is performed with the profile likelihood approach and the observations result to be consistent with the background-only hypothesis, thus leading to exclusion limits on the spinindependent WIMP-nucleon interaction cross section for WIMP masses between 6 and 104 GeV/c2. The most stringent limit is obtained for 35 GeV/c2 WIMPs at 7.7 × 10−47 cm2 with 90% confidence level (XENON Collaboration (Aprile E. et al.), Phys. Res. Lett., 119 (2017) 181301), which is the lowest cross section ever probed to date

Results of the 1 tonne × year WIMP search with XENON1T

Astronomical and cosmological observations indicate that a large amount of the energy content of the Universe is made of dark matter. The most promising dark matter candidates are the so-called WIMPs (Weakly Interacting Massive Particles). The XENON project, at the Gran Sasso National Laboratory (LNGS), consists of a double-phase time projection chamber (TPCs) using ultrapure liquid Xenon as both target and detection medium for dark matter particle interactions. The WIMPs can be indeed detected via their elastic scattering off Xenon nuclei. The XENON Collaboration is now running the XENON1T experiment, the first ton scale liquid Xenon based TPC, with an active mass inside the TPC of about 2 t. Data were collected in a live time of 279 days of dark matter search up to February 2018. The detector presents the lowest electronic recoil background ever obtained in a dark matter experiment: (82+5 −3(sys) ± 3(stat)) events/(t × yr × keVee). The results allowed to set the most stringent exclusion limits on the spin-independent WIMP-nucleon interaction cross section for WIMP masses above 6 GeV/c2, with a minimum of 4.1 × 10−47 cm2 for 30 GeV/c2 WIMP mass at 90% confidence level

Intestinal tuberculosis in a child living in a country with a low incidence of tuberculosis: a case report

Background: Relatively common in adults, intestinal tuberculosis is considered rare in children and adolescents. The protean manifestations of intestinal tuberculosis mean that the diagnosis is often delayed (sometimes even for years), thus leading to increased mortality and unnecessary surgery. The main diagnostic dilemma is to differentiate intestinal tuberculosis and Crohn’s disease because a misdiagnosis can have dramatic consequences. Case presentation: A 13-year-old Caucasian, Italian female adolescent attended the Emergency Department complaining of abdominal pain, a fever of up to 38°C, night sweats, diarrhea with blood in stool, and a weight loss of about three kilograms over the previous two months. Physical examination revealed a marked skin pallor and considerable abdominal distension with relevant discomfort in all the abdominal quadrant. Laboratory tests revealed a decreased white blood cell count with anemia and increased C-reactive protein levels. The Mantoux tuberculin skin test was negative. A chest X-ray and an abdominal ultrasonography did not reveal any significant findings. The patient underwent colonoscopy that showed diffuse mucosal congestion and significant blood loss, and laparatomy showed small bowel and colon loops with a whitish appearance. A biopsy of the ileal mucosa revealed inflammation with noncaseating granulomas possibly due to bacterial infection. Given the suspicion of an opportunistic bacterial infection in a child with chronic inflammatory bowel disease (possibly Crohn’s disease), treatment with a third-generation cephalosporin was started. However, the abdominal pain, fever and poor general condition persisted and so, after 11 days, the patient underwent total body computed tomography and magnetic resonance imaging of the brain. On the basis of the radiological findings, miliary tuberculosis was suspected and bronchoscopy was performed and resulted positive for Mycobacterium tuberculosis. Miliary tuberculosis was confirmed and an effective treatment with four drugs was started. Conclusion: This case shows that the manifestations of intestinal tuberculosis can be very difficult to diagnose and mimic those of Chron’s disease. Total body computed tomography and laparotomy with an intestinal biopsy for the detection of Mycobacterium tuberculosis are the means of avoid the risks of a misdiagnosis in children with unexplained chronic abdominal problems

Network sensitivity of systemic risk

A growing body of studies on systemic risk in financial markets has emphasized the key importance of taking into consideration the complex interconnections among financial institutions. Much effort has been put into modeling the contagion dynamics of financial shocks and into assessing the resilience of specific financial markets, either using real network data, reconstruction techniques or simple toy networks. Here, we address the more general problem of how shock propagation dynamics depend on the topological details of the underlying network. To this end, we consider different realistic network topologies, all consistent with balance sheet information obtained from real data on financial institutions. In particular, we consider networks of varying density and with different block structures. In addition, we diversify in the details of the shock propagation dynamics. We confirm that the systemic risk properties of a financial network are extremely sensitive to its network features. Our results can aid in the design of regulatory policies to improve the robustness of financial markets

Adventive hydrothermal circulation on Stromboli volcano (Aeolian Islands, Italy) revealed by geophysical and geochemical approaches: Implications for general fluid flow models on volcanoes

International audienceOn March 15th 2007 a paroxysmal explosion occurred at the Stromboli volcano. This event generated a large amount of products, mostly lithic blocks, some of which impacted the ground as far as down to 200 m a.s.l., about 1.5 km far away from the active vents. Two days after the explosion, a new vapour emission was discovered on the north-eastern flank of the volcanic edifice, at 560 m a.s.l., just above the area called "Nel Cannestrà". This new vapour emission was due to a block impact. In order to investigate the block impact area to understand the appearance of the vapour emission, we conducted on May 2008 a multidisciplinary study involving Electrical Resistivity Tomography (ERT), Ground Penetrating Radar (GPR), Self-Potential (SP), CO2 soil diffuse degassing and soil temperature surveys. This complementary data set revealed the presence of an anomalous conductive body, probably related to a shallow hydrothermal level, at about 10-15 m depth, more or less parallel to the topography. It is the first time that such a hydrothermal fluid flow, with a temperature close to the water boiling point (76 °C) has been evidenced at Stromboli at this low elevation on the flank of the edifice. The ERT results suggest a possible link between (1) the main central hydrothermal system of Stromboli, located just above the plumbing system feeding the active vents, with a maximum of subsurface soil temperature close to 90 °C and limited by the NeoStromboli summit crater boundary and (2) the investigated area of Nel Cannestrà, at ~ 500 m a.s.l., a buried eruptive fissure active 9 ka ago. In parallel, SP and CO2 soil diffuse degassing measurements suggest in this sector at slightly lower elevation from the block impact crater a magmatic and hydrothermal fluid rising system along the N41° regional fault. A complementary ERT profile, on May 2009, carried out from the NeoStromboli crater boundary down to the block impact crater displayed a flank fluid flow apparently connected to a deeper system. The concept of shallow hydrothermal level have been compared to similar ERT results recently obtained on Mount Etna and La Fossa cone of Vulcano. This information needs to be taken into account in general fluid flow models on volcanoes. In particular, peripheral thermal waters (as those bordering the north-eastern coast of Stromboli) could be contaminated by hydrothermal and magmatic fluids coming from regional faults but also from the summit

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

Recommended conventions for reporting results from direct dark matter searches

The field of dark matter detection is a highly visible and highly competitive one. In this paper, we propose recommendations for presenting dark matter direct detection results particularly suited for weak-scale dark matter searches, although we believe the spirit of the recommendations can apply more broadly to searches for other dark matter candidates, such as very light dark matter or axions. To translate experimental data into a final published result, direct detection collaborations must make a series of choices in their analysis, ranging from how to model astrophysical parameters to how to make statistical inferences based on observed data. While many collaborations follow a standard set of recommendations in some areas, for example the expected flux of dark matter particles (to a large degree based on a paper from Lewin and Smith in 1995), in other areas, particularly in statistical inference, they have taken different approaches, often from result to result by the same collaboration. We set out a number of recommendations on how to apply the now commonly used Profile Likelihood Ratio method to direct detection data. In addition, updated recommendations for the Standard Halo Model astrophysical parameters and relevant neutrino fluxes are provided. The authors of this note include members of the DAMIC, DarkSide, DARWIN, DEAP, LZ, NEWS-G, PandaX, PICO, SBC, SENSEI, SuperCDMS, and XENON collaborations, and these collaborations provided input to the recommendations laid out here. Wide-spread adoption of these recommendations will make it easier to compare and combine future dark matter results

Hepatocellular Carcinoma in HIV-infected Patients: Check Ealy, Treat Hard

Purpose. Hepatocellular carcinoma (HCC) is an increasingcause of mortality in HIV-infected patients inthe highly active antiretroviral therapy (HAART) era.The aims of this study were to describe HCC tumorcharacteristics and different therapeutic approaches, toevaluate patient survival time from HCC diagnosis, andto identify clinical prognostic predictors in patients withand without HIV infection.Patients and Methods. A multicenter observationalretrospective comparison of 104 HIV-infected patientsand 484 uninfected patients was performed in four Italiancenters. HCC was staged according to the BarcelonaClinic Liver Cancer (BCLC) criteria.Results. Tumor characteristics of patients with andwithout HIV were significantly different for age, EasternCooperative Oncology Group performance status(PS) score <1, and etiology of chronic liver disease. Despitethe similar potentially curative option rate and better BCLC stage at diagnosis, the median survivaltime was significantly shorter in HIV patients. HIVpatients were less frequently retreated at relapse.Independent predictors of survival were: BCLC stage,potentially effective HCC therapy, tumor dimension <3cm, HCC diagnosis under a screening program, HCC recurrence,and portal vein thrombosis. Restricting the analysisto HIV patients only, all positive prognostic factorswere confirmed together with HAART exposure.Conclusion. This study confirms a significantlyshorter survival time in HIV HCC patients. The lessaggressive retreatment at recurrence approach does notbalance the benefit of younger age and better BCLCstage and PS score of HIV patients. Thus, consideringthe prognosis of HIV HCC patients, effective screeningtechniques, programs, and specific managementguidelines are urgently needed