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Fully-heavy baryons in vacuum and hot QCD medium
No full textInternational audienceWe study the properties of fully-heavy baryons in the vacuum and the hot QCD medium, which is created in relativistic heavy-ion collisions. Masses and wave functions of , , , and up to the second radial excited states are obtained by solving the three-body Schrödinger equation with Hyperspherical Harmonics method. With parameters completely fixed by fitting quarkonium boundstates in vacuum, we predicted the masses for , , and states of fully-heavy baryons. We also computed the temperature dependence of baryon masses and the thermal widths in a hot QCD medium. These properties are important to precise study of fully-heavy baryon production in heavy ion collisions
Optimised solid-phase extraction of At: Activity balance of At, At and Po after wet chemistry target dissolution
No full textInternational audienceSeveral studies have illustrated the significant increase in the production yield of cyclotron produced At-211 by irradiating targets at higher beam energies, highlighting that this approach warrants consideration. Recently published data also confirms the importance of the Bi-209(alpha,x)Po-210 reaction in addition to the increasing At-210 production at higher energies, stressing the importance of determining the total Po-210 activity on irradiated targets and the validation of radiochemical separation of Po-210 from astatine as an impurity. In this work, two experiments were performed: (i) the dissolution of irradiated Bi-targets to validate the calculated At-211, At-210 and Po-210 activities on target and (ii) the radiochemical separation of astatine by extraction chromatography to determine the activity balance of At-211, At-210 and Po-210 after target processing. The calculated At-211, At-210 and Po-210 activities were validated on targets irradiated at the Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark. At-211 and At-210 activities were determined by gamma spectrometry, whereas the Po-210 activity was measured by liquid scintillation counting (LSC) after target dissolution with concentrated nitric acid. The activity balance during target processing and extraction chromatography was established using targets irradiated at Arronax, Nantes, France. Targets were characterised after the dissolution with an in-house developed dissolution unit. Dissolution yield, extraction yield and separation capability were assessed by determining At-211, At-210 and Po-210 activities at every step. The results show that more than 88% of the total Po-210 activity in targets irradiated at approximate to 28.8 MeV is attributable to the direct production of Po-210. This amounts to about 53% at energies of 29.8 MeV. A maximal discrepancy of 21% was found when comparing the total measured activity to the total calculated Po-210. Activity balance calculations show a mean decay-corrected dissolution yield of 88.9% +/- 9.5% and an extraction yield of 87.56% +/- 11.4% (n = 5) of At-211/At-210 resulting in an overall yield of 77.8% +/- 10.5% (n = 5). In addition, the radiochemical separability was confirmed by removing >95% of the previously formed Po-210 before extraction. This work confirms the important underestimation of the total Po-210 component on irradiated targets at 28.8 and 29.8 MeV when calculating solely from At-210 measurements. In addition, the validation measurements indicate that calculations can be used to estimate the total Po-210 activity. The experimental setup of target dissolution and extraction chromatography presented a very good yield. It allowed the safe isolation and management of Po-210, leaving At-210 as the only source for future ingrowth of Po-210. This finding is an important step in moving beyond the conventional approach of irradiating Bi-targets at limited incident energies
Exploring nuclear structure with multiparticle azimuthal correlations at the LHC
No full textInternational audienceUnderstanding nuclear structure provides essential insights into the properties of atomic nuclei. In this paper, details of the nuclear structure of Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in XeXe collisions at a center-of-mass energy per nucleon pair TeV with the ALICE detector at the LHC. The results are compared with those from PbPb collisions at TeV for a baseline, given that the Pb nucleus is not deformed. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of and a nuclear quadrupole deformation parameter of provides a better description of the presented flow measurements. These studies represent an important step towards a thorough exploration of the imaging power of nuclear collisions at ultrarelativistic energy and the search for the imprint of nuclear structure on various flow observables in heavy-ion collisions at the LHC. The findings demonstrate the potential of nuclear structure studies at the TeV energy scale and highlight that the LHC experiments can complement existing low-energy experiments on nuclear structure studies
Contributions aux développements instrumentaux de la caméra XEMIS2, aux mesures embarquées de l'ionisation et de la scintillation
No full textThe work described in this thesis focuses on the evolution of nuclear medical imaging, from fundamental imaging techniques to current innovations, with a particular focus on the XEMIS2 camera. This liquid xenon Compton camera is designed for 3-gamma imaging of small, low-activity animals. The main objective of XEMIS2 is to localize in three dimensions a radiopharmaceutical labeled with a specific radionuclide, such as Scandium-44, while reducing the administered activity without compromising image quality. The thesis then focuses on the development and performance of the XEMIS2 camera. It covers the operational principles of the liquid xenon time projection chambers (LXeTPCs), the use of the Frisch grid to improve the performance of the ionization chambers, and the complex process of calibrating the scintillation signals in XEMIS2 using the Time over Threshold (TOT) method. Efforts to optimize calibration results are also discussed. By summarizing these technological and methodological advances, the thesis provides a historical perspective and a prospective analysis of the potential impact of these technologies on medical diagnostics and research.Les travaux décrits dans cette thèse sont centrés sur l'évolution de l'imagerie médicale nucléaire, des techniques d'imagerie fondamentales aux innovations actuelles, avec un focus particulier sur la caméra XEMIS2. Cette caméra Compton au xénon liquide est conçue pour l'imagerie 3-gamma des petits animaux à faible activité. L'objectif principal de XEMIS2 est de localiser en trois dimensions un radiopharmaceutique marqué avec un radionucléide spécifique, tel que le Scandium-44, tout en réduisant l'activité administrée sans compromettre la qualité de l'image.La thèse se concentre ensuite sur le développement et les performances de la caméra XEMIS2. Elle couvre les principes opérationnels des chambres de projection temporelle au xénon liquide (LXeTPCs), l'utilisation de la grille de Frisch pour améliorer les performances des chambres d'ionisation, et le processus complexe de la calibration des signaux de scintillation dans XEMIS2 en utilisant la méthode Time over Threshold (TOT). Les efforts d'optimisation des résultats de calibration sont également abordés. En résumant ces avancées technologiques et méthodologiques, la thèse offre une perspective historique et une analyse prospective des impacts potentiels de ces technologies sur les diagnostics médicaux et la recherche
Azimuthal anisotropy of jet particles in p-Pb and Pb-Pb collisions at = 5.02 TeV
No full textInternational audienceThe azimuthal anisotropy of particles associated with jets (jet particles) at midrapidity is measured for the first time in p-Pb and Pb-Pb collisions at = 5.02 TeV down to transverse momentum (p) of 0.5 GeV/c and 2 GeV/c, respectively, with ALICE. The results obtained in p-Pb collisions are based on a novel three-particle correlation technique. The azimuthal anisotropy coefficient v in high-multiplicity p-Pb collisions is positive, with a significance reaching 6.8σ at low p, and its magnitude is smaller than in semicentral Pb-Pb collisions. In contrast to the measurements in Pb-Pb collisions, the v coefficient is also found independent of p within uncertainties. Comparisons with the inclusive charged-particle v and with AMPT calculations are discussed. The predictions suggest that parton interactions play an important role in generating a non-zero jet-particle v in p-Pb collisions, even though they overestimate the reported measurement. These observations shed new insights on the understanding of the origin of the collective behaviour of jet particles in small systems such as p-Pb collisions, and provide significant stringent new constraints to models.[graphic not available: see fulltext
Measurement of neutrino oscillation parameters with the first six detection units of KM3NeT/ORCA
No full textInternational audienceKM3NeT/ORCA is a water Cherenkov neutrino detector under construction and anchored at the bottom of the Mediterranean Sea. The detector is designed to study oscillations of atmospheric neutrinos and determine the neutrino mass ordering. This paper focuses on an initial configuration of ORCA, referred to as ORCA6, which comprises six out of the foreseen 115 detection units of photo-sensors. A high-purity neutrino sample was extracted, corresponding to an exposure of 433 kton-years. The sample of 5828 neutrino candidates is analysed following a binned log-likelihood method in the reconstructed energy and cosine of the zenith angle. The atmospheric oscillation parameters are measured to be , and at 68% CL. The inverted neutrino mass ordering hypothesis is disfavoured with a p-value of 0.25
Investigating the interaction of uranium(VI) with diatoms and their bacterial community: A microscopic and spectroscopic study
No full textInternational audienceDiatoms and bacteria play a vital role in investigating the ecological effects of heavy metals in the environment. Despite separate studies on metal interactions with diatoms and bacteria, there is a significant gap in research regarding heavy metal interactions within a diatom-bacterium system, which closely mirrors natural conditions. In this study, we aim to address this gap by examining the interaction of uranium(VI) (U(VI)) with Achnanthidium saprophilum freshwater diatoms and their natural bacterial community, primarily consisting of four successfully isolated bacterial strains (Acidovorax facilis, Agrobacterium fabrum, Brevundimonas mediterranea, and Pseudomonas peli) from the diatom culture. Uranium (U) bio-association experiments were performed both on the xenic A. saprophilum culture and on the four bacterial isolates. Scanning electron microscopy and transmission electron microscopy coupled with spectrum imaging analysis based on energy-dispersive X-ray spectroscopy revealed a clear co-localization of U and phosphorus both on the surface and inside A. saprophilum diatoms and the associated bacterial cells. Time-resolved laser-induced fluorescence spectroscopy with parallel factor analysis identified similar U(VI) binding motifs both on A. saprophilum diatoms and the four bacterial isolates. This is the first work providing valuable microscopic and spectroscopic data on U localization and speciation within a diatom-bacterium system, demonstrating the contribution of the co-occurring bacteria to the overall interaction with U, a factor non-negligible for future modeling and assessment of radiological effects on living microorganisms
JUNO Sensitivity to Invisible Decay Modes of Neutrons
No full textInternational audienceWe explore the bound neutrons decay into invisible particles (e.g., or ) in the JUNO liquid scintillator detector. The invisible decay includes two decay modes: and . The invisible decays of -shell neutrons in will leave a highly excited residual nucleus. Subsequently, some de-excitation modes of the excited residual nuclei can produce a time- and space-correlated triple coincidence signal in the JUNO detector. Based on a full Monte Carlo simulation informed with the latest available data, we estimate all backgrounds, including inverse beta decay events of the reactor antineutrino , natural radioactivity, cosmogenic isotopes and neutral current interactions of atmospheric neutrinos. Pulse shape discrimination and multivariate analysis techniques are employed to further suppress backgrounds. With two years of exposure, JUNO is expected to give an order of magnitude improvement compared to the current best limits. After 10 years of data taking, the JUNO expected sensitivities at a 90% confidence level are and
« Optique » : Etat des lieux à Subatech
No full textNational audienceRecensement dans chaque laboratoire de l'IN2P3, et ici dans le cas de Subatech (Laboratoire de physique subatomique et des technologies associées), des outils de simulations, des expérimentations, des compétences, des applications, des coûts et besoins, du personpower et des difficultés dans le domaine de l'optique