Search

Xenon dual-phase time projections chambers (TPCs) have proven to be a successful technology in studying physical phenomena that require low-background conditions. With $40\,\textrm{t}$ of liquid xenon (LXe) in the TPC baseline design, DARWIN will have a high sensitivity for the detection of particle dark matter, neutrinoless double beta decay ($0\upnu \upbeta \upbeta $), and axion-like particles (ALPs). Although cosmic muons are a source of background that cannot be entirely eliminated, they may be greatly diminished by placing the detector deep underground. In this study, we used Monte Carlo simulations to model the cosmogenic background expected for the DARWIN observatory at four underground laboratories: Laboratori Nazionali del Gran Sasso (LNGS), Sanford Underground Research Facility (SURF), Laboratoire Souterrain de Modane (LSM) and SNOLAB. We present here the results of simulations performed to determine the production rate of ${}^{137}$Xe, the most crucial isotope in the search for $0\upnu \upbeta \upbeta $ of ${}^{136}$Xe. Additionally, we explore the contribution that other muon-induced spallation products, such as other unstable xenon isotopes and tritium, may have on the cosmogenic background.

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.

We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9 ton. During the (1.09±0.03) ton yr exposure used for this search, the intrinsic 85Kr and 222Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8±1.3) events/ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5 keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58×10$^{−47}$ cm$^2$ for a WIMP mass of 28 GeV/c$^2$ at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.

Multiple viable theoretical models predict heavy dark matter particles with a mass close to the Planck mass, a range relatively unexplored by current experimental measurements. We use 219.4 days of data collected with the XENON1T experiment to conduct a blind search for signals from multiply interacting massive particles (MIMPs). Their unique track signature allows a targeted analysis with only 0.05 expected background events from muons. Following unblinding, we observe no signal candidate events. This Letter places strong constraints on spin-independent interactions of dark matter particles with a mass between 1×10$^{12}$ and 2×10$^{17}$ GeV/c$^{2}$. In addition, we present the first exclusion limits on spin-dependent MIMP-neutron and MIMP-proton cross sections for dark matter particles with masses close to the Planck scale.

We report on the first search for nuclear recoils from dark matter in the form of weakly interacting massive particles (WIMPs) with the XENONnT experiment, which is based on a two-phase time projection chamber with a sensitive liquid xenon mass of 5.9 ton. During the (1.09±0.03) ton yr exposure used for this search, the intrinsic 85Kr and 222Rn concentrations in the liquid target are reduced to unprecedentedly low levels, giving an electronic recoil background rate of (15.8±1.3) events/ton yr keV in the region of interest. A blind analysis of nuclear recoil events with energies between 3.3 and 60.5 keV finds no significant excess. This leads to a minimum upper limit on the spin-independent WIMP-nucleon cross section of 2.58×10−47 cm2 for a WIMP mass of 28 GeV/c2 at 90% confidence level. Limits for spin-dependent interactions are also provided. Both the limit and the sensitivity for the full range of WIMP masses analyzed here improve on previous results obtained with the XENON1T experiment for the same exposure.

The XENON collaboration has published stringent limits on specific dark matter – nucleon recoil spectra from dark matter recoiling on the liquid xenon detector target. In this paper, we present an approximate likelihood for the XENON1T 1 t-year nuclear recoil search applicable to any nuclear recoil spectrum. Alongside this paper, we publish data and code to compute upper limits using the method we present. The approximate likelihood is constructed in bins of reconstructed energy, profiled along the signal expectation in each bin. This approach can be used to compute an approximate likelihood and therefore most statistical results for any nuclear recoil spectrum. Computing approximate results with this method is approximately three orders of magnitude faster than the likelihood used in the original publications of XENON1T, where limits were set for specific families of recoil spectra. Using this same method, we include toy Monte Carlo simulation-derived binwise likelihoods for the upcoming XENONnT experiment that can similarly be used to assess the sensitivity to arbitrary nuclear recoil signatures in its eventual 20 t-year exposure.

The DARWIN observatory is a proposed next-generation experiment to search for particle dark matter and for the neutrinoless double beta decay of 136Xe. 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 136Xe. Here, we show that its projected half-life sensitivity is 2.4×1027year, 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 ⋅ 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 136Xe.

Direct dark matter detection experiments based on a liquid xenon target are leading the search for darkmatter particles with masses above∼5GeV=c2, but have limited sensitivity to lighter masses because ofthe small momentum transfer in dark matter-nucleus elastic scattering. However, there is an irreduciblecontribution from inelastic processes accompanying the elastic scattering, which leads to the excitation andionization of the recoiling atom (the Migdal effect) or the emission of a bremsstrahlung photon. In thisLetter, we report on a probe of low-mass dark matter with masses down to about85MeV=c2by looking forelectronic recoils induced by the Migdal effect and bremsstrahlung using data from the XENON1Texperiment. Besides the approach of detecting both scintillation and ionization signals, we exploit anapproach that uses ionization signals only, which allows for a lower detection threshold. This analysissignificantly enhances the sensitivity of XENON1T to light dark matter previously beyond its reach

In this paper, we describe the XENON100 data analyses used to assess the target-intrinsic background sources radon ( Open image in new window ), thoron ( Open image in new window ) and krypton ( Open image in new window ). We detail the event selections of high-energy alpha particles and decay-specific delayed coincidences. We derive distributions of the individual radionuclides inside the detector and quantify their abundances during the main three science runs of the experiment over a period of ∼4years, from January 2010 to January 2014. We compare our results to external measurements of radon emanation and krypton concentrations where we find good agreement. We report an observed reduction in concentrations of radon daughters that we attribute to the plating-out of charged ions on the negatively biased cathode.