Testing sterile neutrino mixing with present and future solar neutrino data

We investigate the sensitivity of solar neutrino data to mixing of sterile neutrinos with masses $\gtrsim$ eV. For current data, we perform a Feldman-Cousins analysis to derive a robust limit on the sterile neutrino mixing. The solar neutrino limit excludes significant regions of the parameter space relevant to hints from reactor and radioactive gallium source experiments. We then study the sensitivity of upcoming solar neutrino data, most notably elastic neutrino-electron scattering in the DARWIN and DUNE experiments as well as coherent neutrino-nucleus scattering in DARWIN. These high precision measurements will increase the sensitivity to sterile neutrino mixing by about a factor of 4.5 compared to present limits. As a by-product, we introduce a simplified solar neutrino analysis using only four data points: the low- and high-energy $\nu_e$ survival and transition probabilities. We show that this simplified analysis is in excellent agreement with a full solar neutrino analysis; it is very easy to handle numerically and can be applied to any new physics model in which the energy dependence of the $\nu_e$ transition probabilities is not significantly modified.Comment: 24 pages, 8 figures, 4 tables. Accepted for publication in EPJ

Material radiopurity control in the XENONnT experiment

The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and $^{222}Rn$ emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background (∼17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected $^{222}Rn$ activity concentration in XENONnT is determined to be 4.2 $(^{+0.5}_{−0.7}) μBq/kg$, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system

Erratum to: Sensitivity of the DARWIN observatory to the neutrinoless double beta decay of 136^{136}Xe

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 ($$0\nu \beta \beta$$) of $^{136}$Xe improves by $22\%$ compared to the previously reported number and is now $T^{0\nu }_{1/2}= {3.0\times 10^{27}} \hbox { yr}$ (90% C.L.) after 10 years of DARWIN operation

XENON1T dark matter data analysis: Signal reconstruction, calibration, and event selection

The XENON1T experiment at the Laboratori Nazionali del Gran Sasso is the most sensitive direct detection experiment for dark matter in the form of weakly interacting particles (WIMPs) with masses above 6  GeV/c2 scattering off nuclei. The detector employs a dual-phase time projection chamber with 2.0 metric tons of liquid xenon in the target. A one metric ton×year exposure of science data was collected between October 2016 and February 2018. This article reports on the performance of the detector during this period and describes details of the data analysis that led to the most stringent exclusion limits on various WIMP-nucleon interaction models to date. In particular, signal reconstruction, event selection, and calibration of the detector response to nuclear and electronic recoils in XENON1T are discussed

Signal yields of keV electronic recoils and their discrimination from nuclear recoils in liquid xenon

We report on the response of liquid xenon to low energy electronic recoils below 15 keV from beta decays of tritium at drift fields of 92  V/cm, 154  V/cm and 366  V/cm using the XENON100 detector. A data-to-simulation fitting method based on Markov Chain Monte Carlo is used to extract the photon yields and recombination fluctuations from the experimental data. The photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366  V/cm are presented. The electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. The results provide new measurements in the energy region of interest for dark matter searches using liquid xeno

Projected WIMP sensitivity of the XENONnT dark matter experiment

XENONnT is a dark matter direct detection experiment, utilizing 5.9 t of instrumented liquid xenon, located at the INFN Laboratori Nazionali del Gran Sasso. In this work, we predict the experimental background and project the sensitivity of XENONnT to the detection of weakly interacting massive particles (WIMPs). The expected average differential background rate in the energy region of interest, corresponding to (1, 13) keV and (4, 50) keV for electronic and nuclear recoils, amounts to 12.3 ± 0.6 (keV t y)-1 and (2.2± 0.5)× 10−3 (keV t y)-1, respectively, in a 4 t fiducial mass. We compute unified confidence intervals using the profile construction method, in order to ensure proper coverage. With the exposure goal of 20 t y, the expected sensitivity to spin-independent WIMP-nucleon interactions reaches a cross-section of 1.4×10−48 cm2 for a 50 GeV/c2 mass WIMP at 90% confidence level, more than one order of magnitude beyond the current best limit, set by XENON1T . In addition, we show that for a 50 GeV/c2 WIMP with cross-sections above 2.6×10−48 cm2 (5.0×10−48 cm2) the median XENONnT discovery significance exceeds 3σ (5σ). The expected sensitivity to the spin-dependent WIMP coupling to neutrons (protons) reaches 2.2×10−43 cm2 (6.0×10−42 cm2)