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Abstract The multi-staged XENON program at INFN Laboratori Nazionali del Gran Sasso aims to detect dark matter with two-phase liquid xenon time projection chambers of increasing size and sensitivity. The XENONnT experiment is the latest detector in the program, planned to be an upgrade of its predecessor XENON1T. It features an active target of 5.9 tonnes of cryogenic liquid xenon (8.5 tonnes total mass in cryostat). The experiment is expected to extend the sensitivity to WIMP dark matter by more than an order of magnitude compared to XENON1T, thanks to the larger active mass and the significantly reduced background, improved by novel systems such as a radon removal plant and a neutron veto. This article describes the XENONnT experiment and its sub-systems in detail and reports on the detector performance during the first science run. 

Abstract The precision in reconstructing events detected in a dual-phase time projection chamber depends on an homogeneous and well understood electric field within the liquid target. In the XENONnT TPC the field homogeneity is achieved through a double-array field cage, consisting of two nested arrays of field shaping rings connected by an easily accessible resistor chain. Rather than being connected to the gate electrode, the topmost field shaping ring is independently biased, adding a degree of freedom to tune the electric field during operation. Two-dimensional finite element simulations were used to optimize the field cage, as well as its operation. Simulation results were compared to$${}^{83\textrm{m}}\hbox {Kr }$$ ${}^{83\text{m}}\text{Kr}$calibration data. This comparison indicates an accumulation of charge on the panels of the TPC which is constant over time, as no evolution of the reconstructed position distribution of events is observed. The simulated electric field was then used to correct the charge signal for the field dependence of the charge yield. This correction resolves the inconsistent measurement of the drift electron lifetime when using different calibrations sources and different field cage tuning voltages. 

We report on a blinded search for dark matter with single- and few-electron signals in the first science run of XENONnT relying on a novel detector response framework that is physics model dependent. We derive 90% confidence upper limits for dark matter-electron interactions. Heavy and light mediator cases are considered for the standard halo model and dark matter up-scattered in the Sun. We set stringent new limits on dark matter-electron scattering via a heavy mediator with a mass within $10–20\mathrm{MeV}/c^2$and electron absorption of axionlike particles and dark photons for $m_{\chi }$below $0.03\mathrm{keV}/c^2$. Published by the American Physical Society2025 

The XENONnT experiment, located at the INFN Laboratori Nazionali del Gran Sasso, Italy, features a 5.9 tonne liquid xenon time projection chamber surrounded by an instrumented neutron veto, all of which is housed within a muon veto water tank. Because of extensive shielding and advanced purification to mitigate natural radioactivity, an exceptionally low background level of $(15.8\pm 1.3)\mathrm{events}/(\mathrm{tonne}·\mathrm{year}·\mathrm{keV})$in the (1,30) keV region is reached in the inner part of the time projection chamber. XENONnT is, thus, sensitive to a wide range of rare phenomena related to dark matter and neutrino interactions, both within and beyond the Standard Model of particle physics, with a focus on the direct detection of dark matter in the form of weakly interacting massive particles. From May 2021 to December 2021, XENONnT accumulated data in rare-event search mode with a total exposure of one $\mathrm{tonne}·\mathrm{year}$. This paper provides a detailed description of the signal reconstruction methods, event selection procedure, and detector response calibration, as well as an overview of the detector performance in this time frame. This work establishes the foundational framework for the “blind analysis” methodology we are using when reporting XENONnT physics results. Published by the American Physical Society2025 

We search for dark matter (DM) with a mass $[3,12]\mathrm{GeV}/c^2$using an exposure of $3.51\mathrm{tonne}\hspace{0.17em}\mathrm{year}$with the XENONnT experiment. We consider spin-independent DM-nucleon interactions mediated by a heavy or light mediator, spin-dependent DM-neutron interactions, momentum-dependent DM scattering, and mirror DM. Using a lowered energy threshold compared to the previous weakly interacting massive particle search, a blind analysis of [0.5, 5.0] keV nuclear recoil events reveals no significant signal excess over the background. XENONnT excludes spin-independent DM-nucleon cross sections $>2.5\times {10}^{-45}{\mathrm{cm}}^2$at 90% confidence level for $6\mathrm{GeV}/c^2$DM. In the considered mass range, the DM sensitivity approaches the “neutrino fog,” the limitation where neutrinos produce a signal that is indistinguishable from that of light DM-xenon nucleus scattering. Published by the American Physical Society2025 

We present the first measurement of nuclear recoils from solar ${}^8\mathrm{B}$neutrinos via coherent elastic neutrino-nucleus scattering with the XENONnT dark matter experiment. The central detector of XENONnT is a low-background, two-phase time projection chamber with a 5.9 t sensitive liquid xenon target. A blind analysis with an exposure of $3.51\mathrm{t}\times \mathrm{yr}$resulted in 37 observed events above 0.5 keV, with ( ${26.4}_{-1.3}^{+1.4}$) events expected from backgrounds. The background-only hypothesis is rejected with a statistical significance of $2.73\sigma$. The measured ${}^8\mathrm{B}$solar neutrino flux of $\left({4.7}_{-2.3}^{+3.6}\right)\times {10}^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$is consistent with results from the Sudbury Neutrino Observatory. The measured neutrino flux-weighted $\mathrm{CE}\nu \mathrm{NS}$cross section on Xe of $\left({1.1}_{-0.5}^{+0.8}\right)\times {10}^{-39}{\mathrm{cm}}^2$is consistent with the Standard Model prediction. This is the first direct measurement of nuclear recoils from solar neutrinos with a dark matter detector. Published by the American Physical Society2024 

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 ${}^{222}\mathrm{Rn}$and ${}^{218}\mathrm{Po}$events, and the rms convection speed was measured to be $0.30\pm 0.01\mathrm{cm}/\mathrm{s}$. Given this velocity field, ${}^{214}\mathrm{Pb}$background events can be tagged when they are followed by ${}^{214}\mathrm{Bi}$and ${}^{214}\mathrm{Po}$decays, or preceded by ${}^{218}\mathrm{Po}$decays. This was achieved by evolving a point cloud in the direction of a measured convection velocity field, and searching for ${}^{214}\mathrm{Bi}$and ${}^{214}\mathrm{Po}$decays or ${}^{218}\mathrm{Po}$decays within a volume defined by the point cloud. In XENON1T, this tagging system achieved a ${}^{214}\mathrm{Pb}$background reduction of ${6.2}_{-0.9}^{+0.4}\%$with an exposure loss of $1.8\pm 0.2\%$, 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 ${}^{137}\mathrm{Xe}$background, which is relevant to the search for neutrinoless double-beta decay. Published by the American Physical Society2024 

The Big Science projects common of multi-institute particle-physics collaborations generates unique needs for member management, including paper authorship tracking, shift assignments, subscription to mailing lists and access to 3rd party applications such as Github and Slack. For smaller collaborations under 200 people, often no facility for centralized member management is available and these needs are usually manually handled by long-term members despite the management becoming untenable as collaborations grow. To automate many of these tasks for the expanding XENON collaboration, we developed the XENONnT User Management Website, a web application that stores and updates data related to the collaboration members through the use of Node.js and MongoDB. We found that web frameworks are so mature and approachable such that a student can develop a good system to meet the unique needs of the collaboration. The application allows for the scheduling of shifts for members to coordinate between institutes. User manipulation of 3rd party applications are implemented using REST API integration. The XENONnT User Management Website is open source and is a show case of quick implementation of utility application using the web framework, which demonstrated the utility of web-based approaches for solving specific problems to aid the logistics of running Big Science collaborations. 

Effective metadata management is a consistent challenge faced by many scientific experiments. These challenges are magnified by the evolving needs of the experiment, the intricacies of seamlessly integrating a new system with existing analytical frameworks, and the crucial mandate to maintain database integrity. In this work we present the various challenges faced by experiments that produce a large amount of metadata and describe the solution used by the XENON experiment for metadata management.