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In marine ecosystems, most physiological, ecological, or physical processes are size dependent. These include metabolic rates, the uptake of carbon and other nutrients, swimming and sinking velocities, and trophic interactions, which eventually determine the stocks of commercial species, as well as biogeochemical cycles and carbon sequestration. As such, broad-scale observations of plankton size distribution are important indicators of the general functioning and state of pelagic ecosystems under anthropogenic pressures. Here, we present the first global datasets of the Pelagic Size Structure database (PSSdb), generated from plankton imaging devices. This release includes the bulk particle normalized biovolume size spectrum (NBSS) and the bulk particle size distribution (PSD), along with their related parameters (slope, intercept, and R2) measured within the epipelagic layer (0–200 m) by three imaging sensors: the Imaging FlowCytobot (IFCB), the Underwater Vision Profiler (UVP), and benchtop scanners. Collectively, these instruments effectively image organisms and detrital material in the 7–10 000 µm size range. A total of 92 472 IFCB samples, 3068 UVP profiles, and 2411 scans passed our quality control and were standardized to produce consistent instrument-specific size spectra averaged to 1° × 1° latitude and longitude and by year and month. Our instrument-specific datasets span most major ocean basins, except for the IFCB datasets we have ingested, which were exclusively collected in northern latitudes, and cover decadal time periods (2013–2022 for IFCB, 2008–2021 for UVP, and 1996–2022 for scanners), allowing for a further assessment of the pelagic size spectrum in space and time. The datasets that constitute PSSdb's first release are available at https://doi.org/10.5281/zenodo.11050013 (Dugenne et al., 2024b). In addition, future updates to these data products can be accessed at https://doi.org/10.5281/zenodo.7998799.

Total alkalinity (AT) and dissolved inorganic carbon (CT) in the oceans are important properties with respect to understanding the ocean carbon cycle and its link to global change (ocean carbon sinks and sources, ocean acidification) and ultimately finding carbon-based solutions or mitigation procedures (marine carbon removal). We present a database of more than 44 400 AT and CT observations along with basic ancillary data (spatiotemporal location, depth, temperature and salinity) from various ocean regions obtained, mainly in the framework of French projects, since 1993. This includes both surface and water column data acquired in the open ocean, coastal zones and in the Mediterranean Sea and either from time series or dedicated one-off cruises. Most AT and CT data in this synthesis were measured from discrete samples using the same closed-cell potentiometric titration calibrated with Certified Reference Material, with an overall accuracy of ±4 µmol kg−1 for both AT and CT. The data are provided in two separate datasets – for the Global Ocean and the Mediterranean Sea (https://doi.org/10.17882/95414, Metzl et al., 2023), respectively – that offer a direct use for regional or global purposes, e.g., AT–salinity relationships, long-term CT estimates, and constraint and validation of diagnostic CT and AT reconstructed fields or ocean carbon and coupled climate–carbon models simulations as well as data derived from Biogeochemical-Argo (BGC-Argo) floats. When associated with other properties, these data can also be used to calculate pH, the fugacity of CO2 (fCO2) and other carbon system properties to derive ocean acidification rates or air–sea CO2 fluxes.

Understanding the relationship between surface marine ecosystems and the export of carbon to depth by sinking organic particles is key to representing the effect of ecosystem dynamics and diversity, and their evolution under multiple stressors, on the carbon cycle and climate in models. Recent observational technologies have greatly increased the amount of data available, both for the abundance of diverse plankton groups and for the concentration and properties of particulate organic carbon in the ocean interior. Here we use synthetic model data to test the potential of using machine learning (ML) to reproduce concentrations of particulate organic carbon within the ocean interior based on surface ecosystem and environmental data. We test two machine learning methods that differ in their approaches to data-fitting, the random forest and XGBoost methods. The synthetic data are sampled from the PlankTOM12 global biogeochemical model using the time and coordinates of existing observations. We test 27 different combinations of possible drivers to reconstruct small (POCS) and large (POCL) particulate organic carbon concentrations. We show that ML can successfully be used to reproduce modelled particulate organic carbon over most of the ocean based on ecosystem and modelled environmental drivers. XGBoost showed better results compared to random forest thanks to its gradient boosting trees' architecture. The inclusion of plankton functional types (PFTs) in driver sets improved the accuracy of the model reconstruction by 58 % on average for POCS and by 22 % for POCL. Results were less robust over the equatorial Pacific and some parts of the high latitudes. For POCS reconstruction, the most important drivers were the depth level, temperature, microzooplankton and PO4, while for POCL it was the depth level, temperature, mixed-layer depth, microzooplankton, phaeocystis, PO4 and chlorophyll a averaged over the mixed-layer depth. These results suggest that it will be possible to identify linkages between surface environmental and ecosystem structure and particulate organic carbon distribution within the ocean interior using real observations and to use this knowledge to improve both our understanding of ecosystem dynamics and of their functional representation within models.

Marine particles of different nature are found throughout the global ocean. The term “marine particles” describes detritus aggregates and fecal pellets as well as bacterioplankton, phytoplankton, zooplankton and nekton. Here, we present a global particle size distribution dataset obtained with several Underwater Vision Profiler 5 (UVP5) camera systems. Overall, within the 64 µm to about 50 mm size range covered by the UVP5, detrital particles are the most abundant component of all marine particles; thus, measurements of the particle size distribution with the UVP5 can yield important information on detrital particle dynamics. During deployment, which is possible down to 6000 m depth, the UVP5 images a volume of about 1 L at a frequency of 6 to 20 Hz. Each image is segmented in real time, and size measurements of particles are automatically stored. All UVP5 units used to generate the dataset presented here were inter-calibrated using a UVP5 high-definition unit as reference. Our consistent particle size distribution dataset contains 8805 vertical profiles collected between 19 June 2008 and 23 November 2020. All major ocean basins, as well as the Mediterranean Sea and the Baltic Sea, were sampled. A total of 19 % of all profiles had a maximum sampling depth shallower than 200 dbar, 38 % sampled at least the upper 1000 dbar depth range and 11 % went down to at least 3000 dbar depth. First analysis of the particle size distribution dataset shows that particle abundance is found to be high at high latitudes and in coastal areas where surface productivity or continental inputs are elevated. The lowest values are found in the deep ocean and in the oceanic gyres. Our dataset should be valuable for more in-depth studies that focus on the analysis of regional, temporal and global patterns of particle size distribution and flux as well as for the development and adjustment of regional and global biogeochemical models. The marine particle size distribution dataset (Kiko et al., 2021) is available at https://doi.org/10.1594/PANGAEA.924375.

This paper develops non-parametric rotation invariant CUSUMs suited to the detection of changes in the mean direction as well as changes in the concentration parameter of circular data. The properties of the CUSUMs are illustrated by theoretical calculations, Monte Carlo simulation and application to sequentially observed angular data from health science and astrophysics.

We assessed the influence of the marine diazotrophic cyanobacterium Trichodesmium on the bio-optical properties of western tropical South Pacific (WTSP) waters (18–22° S, 160° E–160° W) during the February–March 2015 OUTPACE cruise. We performed measurements of backscattering and absorption coefficients, irradiance, and radiance in the euphotic zone with a Satlantic MicroPro free-fall profiler and took Underwater Vision Profiler 5 (UPV5) pictures for counting the largest Trichodesmium spp. colonies. Pigment concentrations were determined by fluorimetry and high-performance liquid chromatography and picoplankton abundance by flow cytometry. Trichome concentration was estimated from pigment algorithms and validated by surface visual counts. The abundance of large colonies counted by the UVP5 (maximum 7093 colonies m−3) was well correlated to the trichome concentrations (maximum 2093 trichomes L−1) with an aggregation factor of 600. In the Melanesian archipelago, a maximum of 4715 trichomes L−1 was enumerated in pump samples (3.2 m) at 20° S, 167 30° E. High Trichodesmium abundance was always associated with absorption peaks of mycosporine-like amino acids (330, 360 nm) and high particulate backscattering, but not with high Chl a fluorescence or blue particulate absorption (440 nm). Along the west-to-east transect, Trichodesmium together with Prochlorococcus represented the major part of total chlorophyll concentration; the contribution of other groups were relatively small or negligible. The Trichodesmium contribution to total chlorophyll concentration was the highest in the Melanesian archipelago around New Caledonia and Vanuatu (60 %), progressively decreased to the vicinity of the islands of Fiji (30 %), and reached a minimum in the South Pacific Gyre where Prochlorococcus dominated chlorophyll concentration. The contribution of Trichodesmium to zeaxanthin was respectively 50, 40 and 20 % for these regions. During the OUTPACE cruise, the relationship between normalized water-leaving radiance (nLw) in the ultraviolet and visible and chlorophyll concentration was similar to that found during the BIOSOPE cruise in the eastern tropical Pacific. Principal component analysis (PCA) of OUTPACE data showed that nLw at 305, 325, 340, 380, 412 and 440 nm was strongly correlated to chlorophyll and zeaxanthin, while nLw at 490 and 565 nm exhibited lower correlations. These results, as well as differences in the PCA of BIOSOPE data, indicated that nLw variability in the greenish blue and yellowish green during OUTPACE was influenced by other variables associated with Trichodesmium presence, such as backscattering coefficient, phycoerythrin fluorescence and/or zeaxanthin absorption, suggesting that Trichodesmium detection should involve examination of nLw in this spectral domain.

Planktonic Foraminifera are a major contributor to the deep carbonate flux and their microfossil deposits form one of the richest databases for reconstructing paleoenvironments, particularly through changes in their taxonomic and shell composition. Using an empirically based planktonic foraminifer model that incorporates three known major physiological drivers of their biogeography – temperature, food and light – we investigate (i) the global redistribution of planktonic Foraminifera under anthropogenic climate change and (ii) the alteration of the carbonate chemistry of foraminiferal habitat with ocean acidification. The present-day and future (2090–2100) 3-D distributions of Foraminifera are simulated using temperature, plankton biomass and light from an Earth system model forced with a historical and a future (IPCC A2) high CO2 emission scenario. Foraminiferal abundance and diversity are projected to decrease in the tropics and subpolar regions and increase in the subtropics and around the poles. Temperature is the dominant control on the future change in the biogeography of Foraminifera. Yet food availability acts to either reinforce or counteract the temperature-driven changes. In the tropics and subtropics the largely temperature-driven shift to depth is enhanced by the increased concentration of phytoplankton at depth. In the higher latitudes the food-driven response partly offsets the temperature-driven reduction both in the subsurface and across large geographical regions. The large-scale rearrangements in foraminiferal abundance and the reduction in the carbonate ion concentrations in the habitat range of planktonic foraminifers – from 10–30 μmol kg−1 in their polar and subpolar habitats to 30–70 μmol kg−1 in their subtropical and tropical habitats – would be expected to lead to changes in the marine carbonate flux. High-latitude species are most vulnerable to anthropogenic change: their abundance and available habitat decrease and up to 10% of the volume of their habitat drops below the calcite saturation horizon.

The relative abundance of Globigerinoides bulloides was used to infer Holocene paleo-productivity changes on the Oman margin and at the southern tip of India. Today, the primary productivity at both sites reaches its maximum during the summer season, when monsoon winds result in local Eckman pumping, which brings more nutrients to the surface. On a millennium time-scale, however, the % G. bulloides records indicate an opposite evolution of paleo-productivity at these sites through the Holocene. The Oman Margin productivity was maximal at ~9 ka (boreal summer insolation maximum) and has decreased since then, suggesting a direct response to insolation forcing. On the contrary, the productivity at the southern tip of India was minimum at ~9 ka, and strengthened towards the present. Paleo-reconstructions of wind patterns, marine productivity and foraminifera assemblages were obtained using the IPSL-CM4 climate model coupled to the PISCES marine biogeochemical model and the FORAMCLIM ecophysiological model. These reconstructions are fully coherent with the marine core data. They confirm that the evolution of particulate export production and foraminifera assemblages at our two sites were directly linked with the strength of the upwelling. Model simulations at 9 ka and 6 ka BP show that the relative evolution between the two sites since the early Holocene can be explained by the weakening but also the southward shift of monsoon winds over the Arabian Sea during boreal summer.

We present an eco-physiological model reproducing the growth of eight foraminifer species (Neogloboquadrina pachyderma, Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerina bulloides, Globigerinoides ruber, Globigerinoides sacculifer, Globigerinella siphonifera and Orbulina universa). By using the main physiological rates of foraminifers (nutrition, respiration, symbiotic photosynthesis), this model estimates their growth as a function of temperature, light availability, and food concentration. Model parameters are directly derived or calibrated from experimental observations and only the influence of food concentration (estimated via Chlorophyll-a concentration) was calibrated against field observations. Growth rates estimated from the model show positive correlation with observed abundance from plankton net data suggesting close coupling between individual growth and population abundance. This observation was used to directly estimate potential abundance from the model-derived growth. Using satellite data, the model simulate the dominant foraminifer species with a 70.5% efficiency when compared to a data set of 576 field observations worldwide. Using outputs of a biogeochemical model of the global ocean (PISCES) instead of satellite images as forcing variables gives also good results, but with lower efficiency (58.9%). Compared to core tops observations, the model also correctly reproduces the relative worldwide abundance and the diversity of the eight species when using either satellite data either PISCES results. This model allows prediction of the season and water depth at which each species has its maximum abundance potential. This offers promising perspectives for both an improved quantification of paleoceanographic reconstructions and for a better understanding of the foraminiferal role in the marine carbon cycle.

The effect of carbonate ion concentration ([CO32−]) on calcification rates estimated from shell size and weight was investigated in the planktonic foraminifera Orbulina universa and Globigerinoides sacculifer. Experiments on G. sacculifer were conducted under two irradiance levels (35 and 335 μmol photons m−2 s−1). Calcification was ca. 30% lower under low light than under high light, irrespective of the [CO32−]. Both O. universa and G. sacculifer exhibited reduced final shell weight and calcification rate under low [CO32−]. For the [CO32−] expected at the end of the century, the calcification rates of these two species are projected to be 6 to 13% lower than the present conditions, while the final shell weights are reduced by 20 to 27% for O. universa and by 4 to 6% for G. sacculifer. These results indicate that ocean acidification would impact on calcite production by foraminifera and may decrease the calcite flux contribution from these organisms.

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 Xenon dual-phase time projections chambers (TPCs) have proven to be a successful technology in studying physical phenomena that require low-background conditions. With $$40\,\textrm{t}$$ 40 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 ( $$0\upnu \upbeta \upbeta $$ 0 ν β β ), 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 $${}^{137}$$ 137 Xe, the most crucial isotope in the search for $$0\upnu \upbeta \upbeta $$ 0 ν β β of $${}^{136}$$ 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.

Introduction The relationship between autistic traits and eating disturbances, although gaining considerably more attention in the last decades, is still unclear. Most of the studies up to date were conducted on individuals with a full diagnosis of Autism Spectrum Disorders (ASD) and/or of Eating Disorders (ED). One of the common features reported in both conditions is the alteration of sensory sensitivity, which is, in both cases, widely discussed in the literature, but mostly in the pediatric age. Objectives To investigate the association between sensory sensitivity, autistic traits, and eating disorders symptomatology in a group of young adults (18-24) who were referred, for the first time, to a mental health outpatient clinic. Methods 259 patients completed: the Eating Attitude Test (EAT-26), the Autism Quotient (AQ), the Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R), the Sensory Perception Quotient - Short Form 35 item (SPQ-SF35) and the Swedish Eating Assessment for Autism Spectrum Disorders (SWEAA), which investigates specific eating behaviour related to autism. Results 23.55% participants scored above the cut-off at the EAT-26, suggesting that they should be assessed for the presence of an eating disorder by a specialized clinician. The RAADS-R explained a great proportion of variance in the relationship between sensory sensitivity and both the SWEAA (Total Score and subscales) and the EAT-26 (Total Scores and subscales). Conclusions Our study revealed a substantial prevalence of potential eating disorders among young adults in our sample, with nearly one-fourth of participants surpassing the EAT-26 cutoff score. Additionally, we observed a noteworthy association between the presence of autistic traits and not only autistic-like eating behaviors but also a broader spectrum of eating disorder symptoms; this relationship was found in a cohort of young adult patients seeking clinical attention due to generalized distress, prior to receiving specific diagnoses of Autism Spectrum Disorder (ASD) or Eating Disorders (ED). These findings give rise to several intriguing inquiries. Could the existence of autistic traits, even when subthreshold, function as a mediator between alterations in sensory sensitivity and the emergence of maladaptive eating behaviors? Furthermore, if these traits exist at subthreshold levels, might they manifest in various psychiatric conditions, distinct from traditional categorizations, during episodes of acute distress? What potential precipitating factors should be considered in such cases? Disclosure of Interest None Declared

Introduction Motor Conversion Disorders (also called Functional Movement Disorders, FMD) are a group of neuropsychiatric conditions characterized by neurological symptoms of altered voluntary motor function that cannot be explained by typical neurological diseases or other medical conditions. In the last decade, several hypotheses have been formulated with respect to their pathophysiology, and a major line of research, trying to integrate psychological, cognitive, and neurobiological factors, focused on the subjective experience that patients feel of their own bodies. However, no study has, so far, directly investigated their Body Schema (the implicit sensorimotor representation of one’s own body) and its plasticity. Objectives To investigate the Body Schema in patients with FMD through a paradigm specifically designed to assess their perceived body metrics, through a spatial estimation of body parts length, and to compare their results with the ones obtain on a group of healthy control subjects (HC) Methods 10 patients with FMD and 11 HC underwent the Forearm Bisection Task, aimed at assessing perceived body metrics, which consists in asking the subject, blindfolded, to repeatedly point at the perceived middle point of their dominant forearm with the index finger of their contralateral hand, and a psychometric assessment for anxiety, depression, alexithymia, and tendency to dissociation. Results FMD patients bisected their forearm more proximally (with an increased shift towards their elbow equal to 7.5%) with respect to HC; average bisection point was positively associated with anxiety levels in the whole sample, and with the tendency to dissociation in the FMD group. Conclusions FMD patients seem to perceive their forearm as shorter than HC do, which might suggest an alteration of their Body Schema. The Body Schema can go through short- and long-term plastic changes in the life course, mainly related to the use of each body segment; we speculate that, despite FMD being a disorder of functional nature, characterized by variability and fluctuations in symptomatology, the lack of sense of agency over a body part might be interpreted by the nervous system as disuse and hence influence the Body Schema, as deficits of organic aetiology do. Disclosure of Interest None Declared

Introduction In recent decades, there has been extensive research on the association between Autism Spectrum Disorders (ASD) and Eating Disorders (ED), as well as the existence of sensory sensitivity alterations in both diagnostic groups. Objectives The present study aimed to examine the presence of autistic traits in a sample of adult women diagnosed with different ED, and the concurrent role of autistic traits and sensory sensitivity in both their eating disorder symptomatology and their autism-related eating behaviours. Methods Seventy-five women with different ED completed the Eating Attitude Test (EAT-26), the Autism Quotient (AQ), the Ritvo Autism Asperger Diagnostic Scale-Revised (RAADS-R), the Sensory Perception Quotient - Short Form 35 item (SPQ-SF35) and the Swedish Eating Assessment for Autism Spectrum Disorders (SWEAA), which investigates specific eating behaviour related to autism. Results 12% of the sample scored above the cut-off at both the AQ and the RAADS-R, while 68% scored above the cut-off at the RAADS-R only. We found an association between: i) hypersensitivity in the taste domain and ED severity and autistic-like eating behaviours; ii) hypersensitivity in the vision domain and autistic-like eating behaviours; iii) higher autistic traits and ED severity and autistic-like eating behaviours. Conclusions This study confirms the presence of autistic traits in patients with ED and underscores the significance of conducting additional systematical investigations on this topic across all diagnostic categories of ED. It is becoming progressively evident that identifying and measuring the levels of autistic traits in patients with ASD is crucial not only for a better understanding of the causes of these disorders, but also because it would help to tailor specific therapeutic interventions, especially considering the cognitive flexibility issues presented by these patients and the socio-emotional challenges they face. Additionally, this study has laid the foundation for further insights into the relationship between sensory sensitivity and dysfunctional eating behaviours typical of ED and ASD. Disclosure of Interest None Declared

Introduction Neurofilmology is a young and evolving research field, at the intersection between neuroscience and movie experiences, that explores how the brain processes and responds to visual storytelling. It involves examining the cognitive and emotional effects of movies on viewers, including social cognition and perspective-taking aspects. However, up to date, these studies have focused only on the neurotypical population, hence constituting a considerable gap in the literature with respect to individuals with neuroatypical functioning. Objectives Aim of this study was to investigate the experience of film viewing and its correlates in individuals with a diagnosis of Autism Spectrum Disorders (ASD). Methods 30 neurotypical individuals and 30 individuals with ASD without intellectual disabilities were asked to observe 12 short video clips of 3 seconds length, showing an agent grasping an object from a table, and filmed with three different camera techniques: Still, Steadycam, Zoom; for each clip, they were asked to respond to six question on a Visual Analogue Scale (0-100) designed to investigate participants’ potential feeling of involvement with the observed scene, their comfort with the different filming conditions, and their estimation of the ecological plausibility of the different types of camera movements. Results Participants felt more involved watching videos filmed with a Steadycam, with respect to the Zoom and Still condition. Within the neurotypical group participants felt more comfortable when the camera was in motion (both Steadycam and Zoom condition) compared to the Still condition; no differences were found between conditions in the ASD group, as if they felt equally comfortable in every condition administered, regardless the filming technique. Conclusions First, our results reinforce prior findings regarding the influence of different camera techniques on neurotypical individuals. Second, they add to the existing literature suggesting that individuals with ASD may exhibit differences in their subjective experiences related to empathizing with characters and immersing themselves as actors when the camera replicates naturalistic movements, resulting in a diminished overall fulfillment in the movie-watching process. Disclosure of Interest None Declared

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.

Abstract 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.

Abstract The selection of low-radioactive construction materials is of the utmost importance for rare-event searches and thus critical to the XENONnT experiment. Results of an extensive radioassay program are reported, in which material samples have been screened with gamma-ray spectroscopy, mass spectrometry, and $$^{222}$$ 222 Rn emanation measurements. Furthermore, the cleanliness procedures applied to remove or mitigate surface contamination of detector materials are described. Screening results, used as inputs for a XENONnT Monte Carlo simulation, predict a reduction of materials background ( $$\sim $$ ∼ 17%) with respect to its predecessor XENON1T. Through radon emanation measurements, the expected $$^{222}$$ 222 Rn activity concentration in XENONnT is determined to be 4.2 ( $$^{+0.5}_{-0.7}$$ - 0.7 + 0.5 ) $$\upmu $$ μ Bq/kg, a factor three lower with respect to XENON1T. This radon concentration will be further suppressed by means of the novel radon distillation system.