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Clustering redshift distribution calibration of weak lensing surveys using the DESI-DR1 spectroscopic dataset
No full textInternational audienceWe estimate the source redshift distribution of current weak lensing surveys by applying the clustering-based redshift calibration technique, using the galaxy redshift sample provided by the Dark Energy Spectroscopic Instrument Data Release 1 (DESI-DR1). We cross-correlate the Bright Galaxy Survey (BGS), Luminous Red Galaxies (LRGs) and Emission Line Galaxies (ELGs) from DESI, within the redshift range , with overlapping tomographic source samples from the Dark Energy Survey (DES), Kilo-Degree Survey (KiDS), and Hyper Suprime-Cam (HSC) survey. Using realistic mock catalogues, we test the stability of the clustering-redshift signal to fitting scale, reference-sample choice, and the evolution of source galaxy bias, and we explicitly model and marginalise over magnification contributions, which become non-negligible at due to the depth of the DESI ELG sample. We then compare the resulting bias-weighted redshift distributions to those calibrated using self-organising map (SOM) techniques, finding agreement within uncertainties for all surveys and tomographic bins. Our results demonstrate that clustering redshifts enabled by DESI's unprecedented spectroscopic sample provides a robust, complementary, and independent constraint capable of reducing one of the dominant systematic uncertainties in weak lensing cosmology
Encapsulating textual contents into a MOC data structure for advanced applications
No full textInternational audienceThe Multi-Order Coverage map (MOC) is a widely adopted standard promoted by the International Virtual Observatory Alliance (IVOA) to support data sharing and interoperability within the Virtual Observatory (VO) ecosystem. This hierarchical data structure efficiently encodes and visualizes irregularly shaped regions of the sky, enabling applications such as cross-matching large astronomical catalogs, visualizing multi-wavelength and multi-messenger surveys, and facilitating collaborative research through seamless interoperability in big-data-driven exploration. This study aims to explore potential enhancements to the MOC data structure by encapsulating textual descriptions and semantic embeddings into sky regions. Specifically, we introduce “Textual MOCs”, in which textual content is encapsulated, and “Semantic MOCs” that transform textual content into semantic embeddings. These enhancements are designed to enable advanced operations such as similarity searches and complex queries and to integrate with generative artificial intelligence (GenAI) tools to improve context-aware interactions and response accuracy in astronomical data analysis, and support agent-based applications. We experimented with Textual MOCs by annotating detailed descriptions directly into the MOC sky regions, enriching the maps with contextual information suitable for interactive learning tools. For Semantic MOCs, we converted the textual content into semantic embeddings, numerical representations capturing textual meanings in multidimensional spaces, and stored them in high-dimensional vector databases optimized for efficient retrieval. The implementation of Textual MOCs enhances user engagement by providing meaningful descriptions within sky regions, facilitating the development of effective game-based learning. Semantic MOCs enable sophisticated query capabilities, such as similarity-based searches and context-aware data retrieval, enhancing astronomical data analyses. Integration with multimodal generative AI systems allows for more accurate and contextually relevant interactions supporting both spatial, semantic and visual operations for advancing astronomical data analysis capabilities. Through straightforward examples, we discuss the fundamentals of this new experimental implementation
LiteBIRD Science Goals and Forecasts. -mode Anomalies
No full textInternational audienceVarious so-called anomalies have been found in both the WMAP and Planck cosmic microwave background (CMB) temperature data that exert a mild tension against the highly successful best-fit 6 parameter cosmological model, potentially providing hints of new physics to be explored. That these are real features on the sky is uncontested. However, given their modest significance, whether they are indicative of true departures from the standard cosmology or simply statistical excursions, due to a mildly unusual configuration of temperature anisotropies on the sky which we refer to as the "fluke hypothesis", cannot be addressed further without new information. No theoretical model of primordial perturbations has to date been constructed that can explain all of the temperature anomalies. Therefore, we focus in this paper on testing the fluke hypothesis, based on the partial correlation between the temperature and -mode CMB polarisation signal. In particular, we compare the properties of specific statistics in polarisation, built from unconstrained realisations of the CDM cosmological model as might be observed by the LiteBIRD satellite, with those determined from constrained simulations, where the part of the -mode anisotropy correlated with temperature is constrained by observations of the latter. Specifically, we use inpainted Planck 2018 SMICA temperature data to constrain the -mode realisations. Subsequent analysis makes use of masks defined to minimise the impact of the inpainting procedure on the -mode map statistics. We find that statistical assessments of the -mode data alone do not provide any evidence for or against the fluke hypothesis. However, tests based on cross-statistical measures determined from temperature and modes can allow this hypothesis to be rejected with a moderate level of probability
Search for heavy neutral leptons in decays to positrons
No full textInternational audienceA search for heavy neutral lepton () production in in-flight decays using data collected by the NA62 experiment at CERN in 2017-2024 is reported. Upper limits for the extended neutrino mixing matrix element are established at the level of for heavy neutral leptons with mass in the range 95-126 and lifetime exceeding 50 ns
Decay spectroscopy of heavy and superheavy nuclei
No full textInternational audienceAfter more than half a century afte the first predictions of the so-called {\it "island of stability of superheavy nuclei"}, exploring the limits of nuclear stability at highest atomic numbers is still one of the most prominent challenges in low-energy nuclear physics. These exotic nuclear species reveal their character and details of some of their properties by their induced or spontaneous disintegration. The achievements in the field superheavy nuclei (SHN) research have been reported in a number of review papers throughout the decades. This review is an attempt to summarize the progress that has been made in recent years by employing the versatile tool park of Decay Spectroscopy After Separation (DSAS) for the heaviest isotopes from =99 (einsteinium) to =118 (oganesson). In addition, references to earlier reviews and the relevant papers, together with the major decay properties of all these isotopes are given
Measurement of Polarization in the Reaction at GeV/ toward a New Scattering Experiment
No full textInternational audienceThis paper presents high-precision experimental data of the polarization of the hyperon in the reaction, measured in the angular range with a fine bin width of . The data were obtained from the J-PARC E40 experiment at the K1.8 beamline in the J-PARC Hadron Experimental Facility. The observed average polarization of in the range was , demonstrating the successful extraction of precise polarization observables. This result provides essential experimental input for partial wave analysis (PWA) of dynamical coupled-channel (DCC) models, which aim to uncover the underlying mechanisms of resonances that emerge in intermediate states of and interactions. Besides, it indicates the feasibility of a strongly polarized beam suitable for future scattering experiments (e.g., J-PARC E86)
Camera calibration of the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory
No full textInternational audienceThe Cherenkov Telescope Array Observatory (CTAO), a forthcoming very-high-energy gamma-ray facility, will use the Imaging Atmospheric Cherenkov Technique (IACT) to achieve unprecedented energy and angular resolution from 20 GeV to 300 TeV. Large-Sized Telescopes (LSTs) are crucial for the low-energy range. This paper details the calibration tools and methods developed for the first LST (LST-1) to ensure the precise conversion of photomultiplier tube signals and accurate photon timing, vital for the reconstruction of extensive air showers. This framework supports LST-1’s early science and will be applied to future LSTs
Multi-technique radiometric assessment of a desert-marine ecosystem facilitating radiological-environmental safety in hyper-arid regions
No full textInternational audienceThis paper presents a rigorous, multi-technique assessment of radiometric and physiochemical characteristics of a desert-marine ecosystem in the United Arab Emirates (UAE). Current models and empirical data on the release, dispersion, retention and migration of radionuclides in hyper-arid regions are inadequate. This is a critical gap in the radiological-environmental assessments in the Arabian Peninsula, where industries producing radioactivity, such as oil and gas, mining, and both thermal and nuclear power generations, are expanding rapidly. This study offers the most diverse baseline data to date, laying the groundwork for an evidence-based radionuclide transport modeling in hyper-arid environments. It identifies the key isotopes to track and carefully selects a representative region for a comprehensive sampling. The Al Dhafra region of Abu Dhabi was chosen due to its importance in hosting oil, gas, and nuclear industries, and because it covers 71 % of the total area of the emirate. Around 30 different samples were collected, including rock, sand, groundwater, seawater, plants, and farm products. A tailored combination of advanced radiometric methods with XRD, ICP-MS, IC, and gamma spectrometry was developed for this complex and rare sample set. Majority of the instrumentation for this project were hosted in the Subatech Laboratories (France). The study yielded radioactivity compositions in the main arid environmental matrices, consistent with the previous research, and introduced novel findings on the probable host rocks to study for nuclear waste storage, desert shrubs as bioindicators, and camel milk as a medium for transfers to humans. •Diverse and multi-method radiometric characterization of an expansive hyper-arid desert region.•Baseline radionuclide concentrations measured for rocks, sand, waters, plants, and farm produces.•Identified primary rock types, groundwater chemistry and salinity, and plants for transport mechanisms.•Vital empirical data for nuclear and radioactivity-producing industries in hyper-arid ecosystems
Conductance switching and nonequilibrium phase coexistence in superconductors with intermediate bias
No full textInternational audienceSuperconducting systems may display different types of nonequilibrium states depending on the specific constraints imposed for measurement. We probe current-voltage relations of three-dimensional superconducting films by allowing finite voltages to develop across their length. Our experiments reveal sharp features of negative differential conductance which highlight the validity of the principle of minimum entropy production at the critical current transition. We have observed dissipative states with resistances intermediate between those of superconducting and normal phases at zero applied magnetic field, indicating a phenomenon of phase coexistence under nonequilibrium conditions. The features of steady states reported here are not accessible in conventional transport experiments with current-biasing methods
Differentiable Surrogate for Detector Simulation and Design with Diffusion Models
No full textInternational audienceIn this work, we present a conditional denoising-diffusion surrogate for electromagnetic calorimeter showers that is trained to generate high-fidelity energy-deposition maps conditioned on key detector and beam parameters. The model employs efficient inference using Denoising Diffusion Implicit Model sampling and is pre-trained on GEANT4 simulations before being adapted to a new calorimeter geometry through Low-Rank Adaptation, requiring only a small post-training dataset. We evaluate physically meaningful observables, including total deposited energy, energy-weighted radius, and shower dispersion, obtaining relative root mean square error values below 2% for representative high-energy cases. This is in line with state-of-the-art calorimeter surrogates which report comparable fidelity on high-level observables. Furthermore, we compare gradients of a reconstruction-based utility function with respect to design parameters between the surrogate and finite-difference references. The diffusion surrogate reproduces the qualitative structure and directional trends of the true utility landscape, providing usable sensitivities for gradient-based optimization. These results show that diffusion-based surrogates can accelerate simulation-driven detector design while enabling differentiable, gradient-informed analysis