We report on a blinded analysis of low-energy electronic recoil data from the first science run of the XENONnT dark matter experiment. Novel subsystems and the increased 5.9 ton liquid xenon target ...reduced the background in the (1, 30) keV search region to (15.8±1.3) events/(ton×year×keV), the lowest ever achieved in a dark matter detector and ∼5 times lower than in XENON1T. With an exposure of 1.16 ton-years, we observe no excess above background and set stringent new limits on solar axions, an enhanced neutrino magnetic moment, and bosonic dark matter.
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 ^{85}Kr and ^{222}Rn 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.
Delayed single- and few-electron emissions plague dual-phase time projection chambers, limiting their potential to search for light-mass dark matter. This paper examines the origins of these events ...in the XENON1T experiment. Characterization of the intensity of delayed electron backgrounds shows that the resulting emissions are correlated, in time and position, with high-energy events and can effectively be vetoed. In this work we extend previous S2-only analyses down to a single electron. From this analysis, after removing the correlated backgrounds, we observe rates <30 events/(electron×kg×day) in the region of interest spanning 1 to 5 electrons. We derive 90% confidence upper limits for dark matter-electron scattering, first direct limits on the electric dipole, magnetic dipole, and anapole interactions, and bosonic dark matter models, where we exclude new parameter space for dark photons and solar dark photons.
This paper details the first application of a software tagging algorithm to reduce radon-induced backgrounds in liquid noble element time projection chambers, such as XENON1T and XENONnT. The ...convection velocity field in XENON1T was mapped out using Rn 222 and Po 218 events, and the rms convection speed was measured to be 0.30 ± 0.01 cm / s . Given this velocity field, Pb 214 background events can be tagged when they are followed by Bi 214 and Po 214 decays, or preceded by Po 218 decays. This was achieved by evolving a point cloud in the direction of a measured convection velocity field, and searching for Bi 214 and Po 214 decays or Po 218 decays within a volume defined by the point cloud. In XENON1T, this tagging system achieved a Pb 214 background reduction of 6.2 − 0.9 + 0.4 % with an exposure loss of 1.8 ± 0.2 % , despite the timescales of convection being smaller than the relevant decay times. We show that the performance can be improved in XENONnT, and that the performance of such a software-tagging approach can be expected to be further improved in a diffusion-limited scenario. Finally, a similar method might be useful to tag the cosmogenic Xe 137 background, which is relevant to the search for neutrinoless double-beta decay. Published by the American Physical Society 2024
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.
In this work, we expand on the XENON1T nuclear recoil searches to study the individual signals of dark matter interactions from operators up to dimension eight in a chiral effective field theory ...(ChEFT) and a model of inelastic dark matter (iDM). We analyze data from two science runs of the XENON1T detector totaling 1 t × yr exposure. For these analyses, we extended the region of interest from 4.9 , 40.9 keV NR to 4.9 , 54.4 keV NR to enhance our sensitivity for signals that peak at nonzero energies. We show that the data are consistent with the background-only hypothesis, with a small background overfluctuation observed peaking between 20 and 50 keV NR , resulting in a maximum local discovery significance of 1.7 σ for the Vector ⊗ Vector strange ChEFT channel for a dark matter particle of 70 GeV / c 2 and 1.8 σ for an iDM particle of 50 GeV / c 2 with a mass splitting of 100 keV / c 2 . For each model, we report 90% confidence level upper limits. We also report upper limits on three benchmark models of dark matter interaction using ChEFT where we investigate the effect of isospin-breaking interactions. We observe rate-driven cancellations in regions of the isospin-breaking couplings, leading to up to 6 orders of magnitude weaker upper limits with respect to the isospin-conserving case. Published by the American Physical Society 2024
We perform a blind search for particle signals in the XENON1T dark matter detector that occur close in time to gravitational-wave signals in the LIGO and Virgo observatories. No particle signal is ...observed in the nuclear recoil and electronic recoil channels within ±500 seconds of observations of the gravitational-wave signals GW170104, GW170729, GW170817, GW170818, and GW170823. We use this null result to constrain monoenergetic neutrinos and axion-like particles emitted in the closest coalescence GW170817, a binary neutron star merger. We set new upper limits on the fluence (time-integrated flux) of coincident neutrinos down to 17 keV at the 90% confidence level. Furthermore, we constrain the product of the coincident fluence and cross section of axion-like particles to be less than 10 −29 cm 2 /cm 2 in the 5.5–210 keV energy range at the 90% confidence level.
We developed a detector signal characterization model based on a Bayesian network trained on the waveform attributes generated by a dual-phase xenon time projection chamber. By performing inference ...on the model, we produced a quantitative metric of signal characterization and demonstrate that this metric can be used to determine whether a detector signal is sourced from a scintillation or an ionization process. We describe the method and its performance on electronic-recoil (ER) data taken during the first science run of the XENONnT dark matter experiment. We demonstrate the first use of a Bayesian network in a waveform -based analysis of detector signals. This method resulted in a 3% increase in ER event-selection efficiency with a simultaneously effective rejection of events outside of the region of interest. The findings of this analysis are consistent with the previous analysis from XENONnT, namely a background-only fit of the ER data.
Abstract
A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal
$^{37}$$
37
Ar source was performed. This calibration source features a ...35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be (
$$32.3\,\pm \,0.3$$
32.3
±
0.3
) photons/keV and (
$$40.6\,\pm \,0.5$$
40.6
±
0.5
) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is (
$$68.0^{+6.3}_{-3.7}$$
68
.
0
-
3.7
+
6.3
) electrons/keV. The
$^{37}$$
37
Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at (
$$2.83\,\pm \,0.02$$
2.83
±
0.02
) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that
$^{37}$$
37
Ar can be considered as a regular calibration source for multi-tonne xenon detectors.