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Production, Quality Assurance and Quality Control of the SiPM Tiles for the DarkSide-20k Time Projection Chamber
No full textInternational audienceThe DarkSide-20k dark matter direct detection experiment will employ a 21 m^2 silicon photomultiplier (SiPM) array, instrumenting a dual-phase 50 tonnes liquid argon Time Projection Chamber (TPC). SiPMs are arranged into modular photosensors called Tiles, each integrating 24 SiPMs onto a printed circuit board (PCB) that provides signal amplification, power distribution, and a single-ended output for simplified readout. 16 Tiles are further grouped into Photo-Detector Units (PDUs). This paper details the production of the Tiles and the quality assurance and quality control (QA-QC) protocol established to ensure their performance and uniformity. The production and QA-QC of the Tiles are carried out at Nuova Officina Assergi (NOA), an ISO-6 clean room facility at LNGS. This process includes wafer-level cryogenic characterisation, precision flip-chip bonding, wire bonding, and extensive electrical and optical validation of each Tile. The overall production yield exceeds 83.5%, matching the requirements of the DarkSide-20k production plan. These results validate the robustness of the Tile design and its suitability for operation in a cryogenic environment
Measurements and interpretations of production cross-sections in collisions at 13 TeV with the ATLAS detector
No full textInternational audienceMeasurements of integrated and differential cross-sections for production in proton-proton collisions are presented. The data collected by the ATLAS detector at the Large Hadron Collider from 2015 to 2018 at a centre-of-mass energy of 13 TeV are used, corresponding to an integrated luminosity of 140 fb. The candidate events are reconstructed using leptonic decay modes of the gauge bosons into electrons or muons. The integrated cross-section per lepton flavour for the production of is measured in the detector fiducial region with a relative precision of 4%. The measured value is compared with the Standard Model prediction at a precision of up to next-to-next-to-leading-order in QCD and next-to-leading-order in electroweak. Cross-sections for and production and their ratio are presented. The production is also measured differentially as functions of various kinematic variables, including new observables sensitive to CP-violation effects. All measurements are compared with state-of-the-art Standard Model predictions from fixed-order calculations or Monte Carlo generators based on next-to-leading-order matrix elements interfaced with parton showers. An effective field theory interpretation of the measurements is performed, considering both CP-conserving and CP-violating dimension-6 operators modifying the production. In the absence of observed deviations from the Standard Model, limits on CP-conserving Wilson coefficients are extracted using the transverse mass of the system. For CP-violating coefficients a machine learning approach is used to construct an observable with enhanced sensitivity to CP-violation effects
Black hole photon ring beyond General Relativity: an integrable parametrization
No full textInternational audienceIn recent years, the shape of the photon ring in black holes images has been argued to provide a sharp test of the Kerr hypothesis for future black hole imaging missions. In this work, we confront this proposal to beyond Kerr geometries and investigate the degeneracy in the estimations of the black hole parameters using the circlipse shape proposed by Gralla and Lupsasca. To that end, we consider a model-independent parametrization of the deviations to the Kerr black hole geometry, dubbed Kerr off shell (KOS), which preserves the fundamental symmetry structure of Kerr known as the Killing tower. Besides exhibiting a Killing tensor and thus a Carter-like constant, all the representants of this family also possess a Killing-Yano tensor and are of Petrov type D. The allowed deviations to Kerr, selected by the symmetry, are encoded in two free functions which depend respectively on the radial and polar angle coordinates. Using the symmetries, we provide an analytic study of the radial and polar motion of photon trajectories generating the critical curve, to which the subrings composing the photon ring converge. This allows us to derive a ready-to-use closed formula for the parametric critical curve in term of the free functions parametrizing the deviations to Kerr. Using this result, we confront the circlipse fitting function to four examples of Kerr-like objects and we show that it admits a high degree of degeneracy. At a given inclination, the same circlipse can fit both a Kerr black hole of a given mass and spin or a modified rotating black hole with different mass and spin parameters and a new parameter . Therefore, future tests of the Kerr hypothesis could be achieved only provided one can measure independently the mass and spin of the black hole to break this degeneracy
Rotational equilibrium of C2 in diffuse interstellar clouds: II. Formation-excitation at work?
No full textInternational audienceContext. Recent spectroscopic measurements have revealed absorption from higher rotational levels in C2 than previous observations. These improvements are accompanied by the availability of updated radiative and collisional data.Aims. We revisit the density and radiation field intensity diagnostics provided by the observations of many rotational levels of interstellar C2 and extensive molecular information.Methods. We built an excitation model of C2 without spatial structure, including levels up to J = 34 where updated radiative and collisional excitation data are introduced as well as excitation by chemical formation.Results. We confirm the importance of the recent collisional excitation rate coefficients of C2 by molecular H2. We show that the new higher level observations cannot be explained by the standard balance between collisional excitation and radiative transitions. We propose that chemical excitation at formation provides a plausible mechanism to explain the observed high excitation ofC2. In addition, it allows us to lift the degeneracy of the density over radiation field strength parameter in the excitation model.Conclusions. A 0D model remains limited and it is highly desirable to use a full Photon Dominated Region (PDR) model, which includes all excitation processes introduced here and full chemical and thermal balance
The polarimetric response of the Nançay Radio Telescope and its impact on precision pulsar timing
No full textInternational audienceContext. Precision pulsar timing and studies of pulsar radio emission properties require accurate polarimetric calibration of the radio observations since incorrect calibration can distort profiles and introduce noise in time of arrival (TOA) data. In a previous article we presented a new method for calibrating pulsar observations conducted with the Nançay decimetric Radio Telescope (NRT), which significantly improved NRT polarimetric measurements and pulsar timing quality for data taken after this method was developed, in November 2019.Aims. Results from the above-mentioned study hinted at a dependence of the polarimetric response of the NRT on the observed direction. We therefore investigated this potential dependence, since unaccounted variations in the instrumental response could degrade polarimetric measurements. Additionally, our aim was to develop a method for properly calibrating NRT pulsar observations conducted before November 2019.Methods. We conducted three series of observations of bright pulsars over wide declination ranges, in a special observation mode in which the feed horn rotates by ~180° degrees across the observation; this enabled us to determine the full polarimetric response of the NRT while modeling potential variations in calibration parameters with hour angle and declination. In addition, we developed a method that uses the measurement equation template matching (METM) technique to improve the calibration of pre-November 2019 data.Results. From the analysis of the series of observations of bright pulsars with horn rotation, we found that the polarimetric response of the NRT does not appear to vary with hour angle or declination. On the other hand, the new METM-based calibration method appears to significantly improve the calibration of pre-November 2019 data. By analyzing NRT data on a selection of millisecond pulsars, we found that the new polarimetric profiles are more homogeneous, they generally have higher signal-to-noise ratios, and found that the TOA data for these MSPs are more accurate and contain lower levels of noise, especially when combining the new calibration method with the matrix template matching (MTM) method for extracting TOAs from pulsar observations
Towards a unified scheme of blazar evolution
No full textInternational audienceMachine learning (ML) and deep learning (DL) techniques are increasingly used across astrophysics, enabled by the growing availability of data and improved acquisition methods. These approaches now support tasks from redshift estimation to source classification. In this work, we aim to (i) classify blazars from the Fermi 4LAC-DR3 catalogue, in particular to identify the likely origin of blazars of uncertain type (BCUs), and (ii) investigate the full blazar sample to study their structure and redshift-luminosity evolution. We focus especially on the transition region between Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BL Lacs), which may yield insights into accretion disk evolution. We examine Changing-Look Blazars (CLBs) as potential intermediates in this transition. We implement a classification pipeline using both a strong benchmark model (XGBoost) and a foundation model pre-trained on millions of tabular datasets (TabPFN). By extracting and reducing the high-dimensional latent space of the best model, we provide a 2D representation of the blazar population. This reveals a continuum between FSRQs and BL Lacs, including CLBs as transitional sources. These results support a scenario of gradual evolution from radiatively efficient (FSRQ-like) to inefficient (BL Lac-like) accretion. Ultimately, we show that a single probability score, combined with the latent space, offers a new framework for interpreting blazar diversity beyond discrete classes
The Gaia RVS Benchmark Stars. III . Confirmed and New High Radial Velocity Stars From Gaia DR3
No full textInternational audienceABSTRACT High‐velocity stars are interesting targets to unveil the formation of the Milky Way. In fact they can be recently accreted from an infalling dwarf galaxies or they can be the result of a turbulent merging of galaxies. Gaia is providing the community a way to select stars for their kinematics and the radial velocity, one of the speed components, is derived from the Gaia RVS spectrum. High absolute radial velocity values are sensitive to be false positive. They are rare and as such they are more easily impacted than lower velocity stars, by contamination by very low SNR spurious measures. We here investigate a sample of 26 stars with Gaia absolute radial velocity in excess of 500 km/s with spectroscopic follow‐up observations with UVES. For all but one star the extreme radial velocity is confirmed and these stars are all metal‐poor and, as expected, enhanced in the elements. The complete chemical inventory confirm the large star‐to‐star scatter for the heavy elements and their on average larger ratio over iron with respect to the Sun, in agreement with the literature
The IDROGEN data acquisition system: Versatile data acquisition and picosecond synchronization
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Characterization of the solar wind context during the third Mercury flyby of BepiColombo
No full textInternational audienceContext. The interaction of the solar wind (SW) with the coupled magnetosphere-exosphere-surface of Mercury is complex. Charged particles released by the SW can precipitate along planetary magnetic field lines on specific areas of the surface of the planet. The processes responsible for the particle precipitation strongly depend on the orientation of the interplanetary magnetic field (IMF) upstream of Mercury.Aims. During the third Mercury flyby (MFB3) by BepiColombo, the properties of the SW inferred from BepiColombo observations of a highly compressed magnetosphere corresponded to those of a very dense plasma embedded in a slow SW. The Mercury Electron Analyzer (MEA) measured continuous high-energy electron fluxes in the nightside dawn sector of the compressed magnetosphere. In order to constrain further studies related to the origin of these populations, we aim to firmly confirm the initial inferences and detail the SW properties throughout MFB3.Methods. We took advantage of a close radial alignment between Parker Solar Probe (PSP) and Mercury. We monitored the activity of the Sun using SOHO coronagraphs and we used a potential field source surface model to estimate the location of the magnetic footpoints of PSP and BepiColombo on the photosphere of the Sun. We propagated the plasma parameters and the IMF measured by PSP at BepiColombo, to check if the plasma impacted Mercury.Results. We show that during MFB3, PSP and BepiColombo connected magnetically to the same region at the solar surface. The slow SW perturbation first measured at PSP propagated to Mercury and BepiColombo, as was confirmed by similarly elevated plasma densities measured at PSP and BepiColombo. The IMF orientation stayed southward during the whole MFB3.Conclusions. Our results provide strong constraints for future studies of the magnetospheric structure and dynamics during MFB3, including tail reconnection, electron and ion energization, and subsequent plasma precipitation onto the surface of Mercury
Particle acceleration and multi-messenger radiation from ultra-luminous X-ray sources: A new class of Galactic PeVatrons
No full textInternational audienceSuper-Eddington accretion onto stellar-mass compact objects powers fast outflows in ultra-luminous X-ray sources (ULXs). Such outflows, which can reach mildly relativistic velocities, are often observed forming bubble structures. Wind bubbles are expected to develop strong wind termination shocks, which are sites of great interest for diffusive shock acceleration. We developed a model of diffusive shock acceleration in the wind bubbles powered by ULXs. We find that the maximum energy in these objects can easily reach the PeV range, promoting winds from ULXs as a new class of PeVatrons. We specialized our model in the context of the Galactic source SS 433 and show that high-energy protons in the bubble might explain the highest energy photons (>100 TeV) and their morphology recently observed by LHAASO. In this paper, we discuss the detectability of such a source in neutrinos, and we analyze the possible radio counterpart of ULXs focusing on the case of W50, the nebula surrounding SS 433. Finally, we discuss the possible contribution of Galactic ULXs to the cosmic-ray flux at the knee, concluding that their role could be significant only if one of these sources, currently undetected, were sufficiently close