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The cryogenic underground observatory for rare events (CUORE) is a 1-ton scale bolometric experiment whose detector consists of an array of 988 TeO 2 crystals arranged in a cylindrical compact structure of 19 towers. This will be the largest bolometric mass ever operated. The experiment will work at a temperature around or below 10 mK. CUORE cryostat consists of a cryogen-free system based on pulse tubes and a custom high power dilution refrigerator, designed to match these specifications. The cryostat has been commissioned in 2014 at the Gran Sasso National Laboratories and reached a record temperature of 6 mK on a cubic meter scale. In this paper, we present results of CUORE commissioning runs. Details on the thermal characteristics and cryogenic performances of the system will be also given.

The cryogenic underground observatory for rare events (CUORE) is a 1-ton scale bolometric experiment whose detector consists of an array of 988 TeO2 crystals arranged in a cylindrical compact structure of 19 towers. This will be the largest bolometric mass ever operated. The experiment will work at a temperature around or below 10 mK. CUORE cryostat consists of a cryogen-free system based on pulse tubes and a custom high power dilution refrigerator, designed to match these specifications. The cryostat has been commissioned in 2014 at the Gran Sasso National Laboratories and reached a record temperature of 6 mK on a cubic meter scale. In this paper, we present results of CUORE commissioning runs. Details on the thermal characteristics and cryogenic performances of the system will be also given.

Radon emanation was projected to account for \\(>50\\)% of the electron recoil background in the WIMP region of interest for the LUX-ZEPLIN (LZ) experiment. To mitigate the amount of radon inside the detector volume, materials with inherently low radioactivity content were selected for LZ construction through an extensive screening campaign. The SD Mines radon emanation system was one of four emanation facilities utilized to screen materials during construction of LZ. SD Mines also employed a portable radon collection system for equipment too large or delicate to move to a radon emanation facility. This portable system was used to assay the Inner Cryostat Vessel in-situ at various stages of detector construction, resulting in the inference that the titanium cryostat is the source of significant radon emanation. Assays of a \\(^{228}\\)Th source confirmed that its \\(^{222}\\)Rn emanation is low enough for it to be used, and that 14% of the \\(^{220}\\)Rn emanates from the source at room temperature.

The LUX-ZEPLIN (LZ) experiment aims to detect rare interactions between dark matter particles and xenon. Although the detector is designed to be the most sensitive to GeV/\\(c^2\\)--TeV/\\(c^2\\) Weakly Interacting Massive Particles (WIMPs), it is also capable of measuring low-energy ionization signals down to a single electron that may be produced by scatters of sub-GeV/\\(c^2\\) dark matter. The major challenge in exploiting this sensitivity is to understand and suppress the ionization background in the few-electron regime. We report a characterization of the delayed electron backgrounds following energy depositions in the LZ detector under different detector conditions. In addition, we quantify the probability for photons to be emitted in coincidence with electron emission from the high voltage grids. We then demonstrate that spontaneous grid electron emission can be identified and rejected with a high efficiency using a coincident photon tag, which provides a tool to improve the sensitivity of future dark matter searches.

The LUX-ZEPLIN (LZ) experiment is a direct-detection dark matter experiment, optimized to search for weakly interacting massive particles (WIMPs) through WIMP-nucleon interactions. The main challenge in dark matter detection is differentiating between WIMP signals and background events. In LZ, the ratio of ionization to scintillation signals (charge-to-light) is the primary method for rejecting electronic recoil (ER) background. Pulse shape discrimination (PSD) offers a method for additional ER backgrounds rejection in liquid xenon detectors. In this paper, the discrimination power of PSD with the LZ experiment is discussed. To precisely characterize the scintillation pulse shape, an analysis framework is developed to reconstruct the detection time of individual photons. Using LZ calibration data, the photon-timing prompt fraction discriminator is optimized and achieves ER leakage as low as \\(15\\%\\). For specific background processes such as \\(^{124}\\)Xe double electron capture, the leakage is reduced further to about \\(5\\%\\). PSD is combined with charge-to-light to form two-factor discrimination (TFD). The optimized TFD performance is compared with the performance of the charge-to-light method, with the corresponding false positive rate reduced by up to a factor of two for large scintillation pulses. Finally, PSD and TFD are applied to data from LZ's WS2024 run and their performance is summarized.

High-energy cosmic-ray muons reaching deep underground laboratories can cause events in detectors that mimic signals expected from dark matter particles, neutrinos, or rare decays. Knowledge of the muon flux and energy spectrum is important for evaluating the background rate caused by muons and their secondaries. In this paper, we report the measurement of the cosmic-ray muon flux in the Davis Campus of the Sanford Underground Research Facility with the LUX-ZEPLIN detector. Using 366.4~days of exposure, the muon rate through the detector was measured as \\(10.940.17_stat.~day^-1\\) with energy thresholds of 20~MeV in the inner xenon detector and 8 MeV in the outer liquid scintillator detector. This rate corresponds to a muon flux of \\((5.090.08_stat.0.10_sys.)10^-9~cm^-2s^-1\\) in the Davis Cavern.

We present searches for light dark matter (DM) with masses 3-9 GeV/\\(c^2\\) in the presence of coherent elastic neutrino-nucleus scattering (CE\\(\\nu\\)NS) from \\(^{8}\\)B solar neutrinos with the LUX-ZEPLIN experiment. This analysis uses a 5.7 tonne-year exposure with data collected between March 2023 and April 2025. In an energy range spanning 1-6 keV, we report no significant excess of events attributable to dark matter nuclear recoils, but we observe a significant signal from \\(^{8}\\)B CE\\(\\nu\\)NS interactions that is consistent with expectation. We set world-leading limits on spin-independent and spin-dependent-neutron DM-nucleon interactions for masses down to 5 GeV/\\(c^2\\). In the no-dark-matter scenario, we observe a signal consistent with \\(^{8}\\)B CE\\(\\nu\\)NS events, corresponding to a \\(4.5\\sigma\\) statistical significance. This is the most significant evidence of \\(^{8}\\)B CE\\(\\nu\\)NS interactions and is enabled by robust background modeling and mitigation techniques. This demonstrates LZ's ability to detect rare signals at keV-scale energies.

We report results from searches for new physics models via electron recoils using data collected by the LUX-ZEPLIN (LZ) experiment during its first two science runs, with a total exposure of 4.2 tonne-years. The observed data are consistent with a background-only hypothesis. Constraints are derived for several new physics models that predict electronic recoil signals, including electromagnetic interactions of solar neutrinos, solar axion-like particles (ALPs), mirror dark matter, and the absorption of bosonic dark matter candidates. These results represent the most stringent constraints to date for solar ALPs with keV-scale masses and mirror dark matter, and they are competitive with existing limits for other investigated models.

The LUX-ZEPLIN (LZ) experiment aims to detect rare interactions between dark matter particles and xenon. Although the detector is designed to be the most sensitive to GeV/\\(c^2\\)--TeV/\\(c^2\\) Weakly Interacting Massive Particles (WIMPs), it is also capable of measuring low-energy ionization signals down to a single electron that may be produced by scatters of sub-GeV/\\(c^2\\) dark matter. The major challenge in exploiting this sensitivity is to understand and suppress the ionization background in the few-electron regime. We report a characterization of the delayed electron backgrounds following energy depositions in the LZ detector under different detector conditions. In addition, we quantify the probability for photons to be emitted in coincidence with electron emission from the high voltage grids. We then demonstrate that spontaneous grid electron emission can be identified and rejected with a high efficiency using a coincident photon tag, which provides a tool to improve the sensitivity of future dark matter searches.

The LZ experiment is a liquid xenon time-projection chamber (TPC) searching for evidence of particle dark matter interactions. In the simplest assumption of elastic scattering, many dark matter models predict an energy spectrum which rises quasi-exponentially with decreasing energy transfer to a target atom. LZ expects to detect coherent neutrino-nucleus scattering of \\(^{8}\\)B solar neutrinos, the signal from which is very similar to a dark matter particle with mass of about 5.5 GeV/\\(c^{2}\\), which result in typical nuclear recoil energies of \\(<\\)5 keV\\(_{\\text{nr}}\\). Therefore, it is of crucial importance to calibrate the response of recoiling xenon nuclei to keV-energy recoils. This analysis details the first in situ photoneutron calibration of the LZ detector and probes its response in this energy regime.