Searching for Heavy Dark Matter near the Planck Mass with XENON1T

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

Detector signal characterization with a Bayesian network in XENONnT

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

First Dark Matter Search with Nuclear Recoils from the XENONnT Experiment

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

Searching for Heavy Dark Matter near the Planck Mass with XENON1T

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 work places strong constraints on spin-independent interactions of dark matter particles with a mass between 1$\times$10$^{12}\,$GeV/c$^2$ and 2$\times$10$^{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.Comment: 7 pages, 6 figure

Low-energy Calibration of XENON1T with an Internal 37^{37}Ar Source

A low-energy electronic recoil calibration of XENON1T, a dual-phase xenontime projection chamber, with an internal $^{37}$Ar source was performed. Thiscalibration source features a 35-day half-life and provides two mono-energeticlines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keVare measured to be (32.3$\pm$0.3) photons/keV and (40.6$\pm$0.5) electrons/keV,respectively, in agreement with other measurements and with NEST predictions.The electron yield at 0.27 keV is also measured and it is(68.0$^{+6.3}_{-3.7}$) electrons/keV. The $^{37}$Ar calibration confirms thatthe detector is well-understood in the energy region close to the detectionthreshold, with the 2.82 keV line reconstructed at (2.83$\pm$0.02) keV, whichfurther validates the model used to interpret the low-energy electronic recoilexcess previously reported by XENON1T. The ability to efficiently remove argonwith cryogenic distillation after the calibration proves that $^{37}$Ar can beconsidered as a regular calibration source for multi-tonne xenon detectors.<br

Effective Field Theory and Inelastic Dark Matter Results from XENON1T

In this work, we expand on the XENON1T nuclear recoil searches to study theindividual signals of dark matter interactions from operators up todimension-eight in a Chiral Effective Field Theory (ChEFT) and a model ofinelastic dark matter (iDM). We analyze data from two science runs of theXENON1T detector totaling 1\,tonne$\times$year exposure. For these analyses, weextended the region of interest from [4.9, 40.9]$\,$keV$_{\text{NR}}$ to [4.9,54.4]$\,$keV$_{\text{NR}}$ to enhance our sensitivity for signals that peak atnonzero energies. We show that the data is consistent with the background-onlyhypothesis, with a small background over-fluctuation observed peaking between20 and 50$\,$keV$_{\text{NR}}$, resulting in a maximum local discoverysignificance of 1.7\,$\sigma$ for the Vector$\otimes$Vector$_{\text{strange}}$($VV_s$) ChEFT channel for a dark matter particle of 70$\,$GeV/c$^2$, and$1.8\,\sigma$ for an iDM particle of 50$\,$GeV/c$^2$ with a mass splitting of100$\,$keV/c$^2$. For each model, we report 90\,\% confidence level (CL) upperlimits. We also report upper limits on three benchmark models of dark matterinteraction using ChEFT where we investigate the effect of isospin-breakinginteractions. We observe rate-driven cancellations in regions of theisospin-breaking couplings, leading to up to 6 orders of magnitude weaker upperlimits with respect to the isospin-conserving case.<br

Emission of single and few electrons in XENON1T and limits on light dark matter

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

The Triggerless Data Acquisition System of the XENONnT Experiment

The XENONnT detector uses the latest and largest liquid xenon-based timeprojection chamber (TPC) operated by the XENON Collaboration, aimed atdetecting Weakly Interacting Massive Particles and conducting other rare eventsearches. The XENONnT data acquisition (DAQ) system constitutes an upgraded andexpanded version of the XENON1T DAQ system. For its operation, it reliespredominantly on commercially available hardware accompanied by open-source andcustom-developed software. The three constituent subsystems of the XENONnTdetector, the TPC (main detector), muon veto, and the newly introduced neutronveto, are integrated into a single DAQ, and can be operated both independentlyand as a unified system. In total, the DAQ digitizes the signals of 698photomultiplier tubes (PMTs), of which 253 from the top PMT array of the TPCare digitized twice, at $\times10$ and $\times0.5$ gain. The DAQ for the mostpart is a triggerless system, reading out and storing every signal that exceedsthe digitization thresholds. Custom-developed software is used to process theacquired data, making it available within $\mathcal{O}\left(10\text{ s}\right)$for live data quality monitoring and online analyses. The entire system withall the three subsystems was successfully commissioned and has been operatingcontinuously, comfortably withstanding readout rates that exceed $\sim500$ MB/sduring calibration. Livetime during normal operation exceeds $99\%$ and is$\sim90\%$ during most high-rate calibrations. The combined DAQ system hascollected more than 2 PB of both calibration and science data during thecommissioning of XENONnT and the first science run.<br

Low-energy calibration of XENON1T with an internal 37^{{\textbf {37}}}Ar source

A low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal 37Ar 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±0.3) photons/keV and (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) electrons/keV. The 37Ar 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±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 37Ar can be considered as a regular calibration source for multi-tonne xenon detectors