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Precision measurement of CP violation and branching fractions in decays and search for the rare decay
No full textInternational audienceAn analysis of the decays and is performed using proton--proton collision data collected by the LHCb experiment at a center-of-mass energy of 13TeV, corresponding to an integrated luminosity of 5.4fb. The CP asymmetries are determined to be and , and the branching-fraction ratio is measured to be , where the first uncertainties are statistical and the second systematic. These results are the most precise measurements of these quantities to date. A search for the rare decay is also performed. No significant signal is observed, and the upper limit on the product of the branching-fraction ratio and the fragmentation-fraction ratio is set to be 0.015 (0.016) at the 90% (95%) confidence level
Identification of natural and anthropogenic sources of geogenic radionuclides by using a multi-isotope tracing approach
No full textInternational audienceEnvironmental monitoring programs of nuclear legacy sites,formerly producing U-enriched materials, are mainly based onthe interpretation of radionuclide concentrations in soils andsediments sampled downstream from these sites. However, thevariations of these concentrations can be very low in upstreamand downstream sampling locations. In addition, the differentgeological origins of soils and sediments can lead to differentgeochemical background values, which can be attributedwrongly to anthropogenic sources. It is therefore important to usegeochemical tracers for accurately deciphering natural andanthropogenic radionuclide sources. This information isimportant for a better understanding of transport mechanisms ofthese substances in the critical zone and improving the evaluationof site management strategies.The methodology proposed aims to provides tools fordiscriminating anthropogenic radioactive sources linked toformer U mining activities, with regard to those originating fromthe natural weathering and erosion of rocks. This approach wasperformed according to a multi-isotope tracing approach,including the determination of (226Ra/228Ra) and (234U/238U)Activity Ratios (ARs) combined with the knowledge of the other238U decay series nuclide disequilibria and Pb stable isotoperatios.Applied to a former U-mining-influenced watershed and lake,these isotopic tools reveal the existence of anthropogenicsignatures in surface environments, several kilometersdownstream from the mining source, several decades after theend of site rehabilitation operations. The integration of theseresults into the chronology of downstream lake sediment depositsshowed that even if U contents remained twice the localgeochemical background, these deposits sampled in a lakerecorded that a part of U has been brought as dissolved speciesfrom the site into the sedimentary column. Moreover, theanalyses of older lake sediment deposits indicated a clearsignature of radiogenic Pb (i. e. Pb from U ores) associated tosignificant 230Th activities, indicating the past transport of Udecay series-enriched particles. Overall, this study emphasizesthe high potential of multi-isotope tracing approaches fordocumenting the origin of geogenic radionuclides in the criticalzone. These results yield further mechanistic explanations for theobserved evolution of U concentration and speciation previouslyreported from mineralogical and spectroscopic analyses of theselake sediments
Observation of two nuclear recoil peaks induced by neutron capture on AlO
No full textInternational audienceWe report the observation of two nuclear recoil peaks induced by neutron capture on aluminum in a cryogenic AlO detector developed by the NUCLEUS collaboration for the detection of reactor neutrinos via coherent elastic neutrino-nucleus (CEvNS) process. Data collected at the Technical University of Munich in 2024 with a Cf source reveal a main recoil line at 1145 eV from single- de-excitation of Al and a newly observed structure near 575 eV originating from several two- cascades. The latter constitutes the first direct measurement of a nuclear recoil line induced by multi- cascades. It is predicted by our simulations when the recoiling nucleus has time to stop before the emission of the next -ray in the cascade. These results demonstrate the potential performance of the CRAB (Calibration Recoil for Accurate Bolometry) method for in situ nuclear recoil calibration and highlight the importance of accurately modeling recoil stopping and nuclear de-excitation times in cryogenic detectors of CEvNS and dark matter interactions
Uncertainty Principle and Angular Momentum Generation in Microscopic Fission Models
No full textInternational audienceThe generation of angular momentum (intrinsic spin) in fission fragments has recently attracted renewed attention. While several microscopic approaches reproduce the spin distribution qualitatively using projection techniques, the physical origin of the fragments' angular momentum in density functional theory remains unclear. In this work, we investigate the mechanisms responsible for the spin distribution of fission fragments within a microscopic TDDFT framework. We compare spin distributions obtained from projection operators with those predicted by a simple expression derived from the uncertainty relation between angle and angular momentum, where angular fluctuations are estimated using a Monte Carlo sampling of nucleon positions. We find that a large portion of the spin distribution obtained from projection methods can be explained by the uncertainty principle. Our results thus show that, within microscopic approaches, the spin of fission fragments originates primarily from quantum uncertainty associated with their orientation angle with respect to the fission axis, mainly due to quadrupole deformation and, to a lesser extent, octupole deformation
DIFFÉRENCIATION PAR SPECTROSCOPIE RAMAN DES ÉTATS DE VIABILITÉ DE BACILLUS CEREUS EXPOSÉ À UN STRESS SALIN OU DÉSINFECTANT
No full textInternational audienceIntroduction et ObjectifsBacillus cereus est un pathogène alimentaire largement répandu dans l'environnement et susceptible de contaminer diverses filières agroalimentaires, notamment les produits de la pêche et de l'aquaculture. En France, cette bactérie a été classée en 2014 comme la seconde cause d'infection alimentaire. Outre sa capacité à sporuler, B. cereus est capable d'entrer dans un autre état de dormance appelé état viable non cultivable (VNC), indétectable par les méthodes conventionnelles basées sur la croissance bactérienne. La technique PMA-qPCR a été développée pour contourner cette limite, mais elle reste peu sensible (seuil de détection d'environ 10³-10⁴ bactéries). Récemment, la microspectroscopie Raman a émergé comme une méthode innovante pour discriminer à l'échelle de la cellule unique, les cellules viables cultivables (VC), VNC et mortes. L'objectif de cette étude était d'évaluer la capacité de la spectroscopie Raman à distinguer les cellules VNC de B. cereus des autres états de viabilité.Matériel et MéthodesDes cultures planctoniques de B. cereus ont été incubées pendant 24h dans un milieu TSB, puis exposées pendant 20 min soit à de l'eau (témoin), soit à une solution saline (NaCl 15%), soit à un des deux désinfectants industriels choisis pour l'étude : l'un à base de triamines et l'autre de peroxyde d'hydrogène. Les populations VC, VNC et mortes ont été quantifiées par méthode culturale (UFC), qPCR et PMA-qPCR. Les spectres Raman ont été acquis sur cellules uniques après traitements. Une analyse en composantes principales (ACP) combinée à un clustering par HDBSCAN a été réalisée pour déterminer la capacité de la méthode à discriminer les différents états de viabilité préalablement quantifier par (PMA)-qPCR et UFC.Résultats, Discussion et ConclusionLes résultats obtenus indiquent qu'à partir de l'analyse de la région dite de “fingerprint” (de 700 à 1800 cm-1) des spectres Raman de B. cereus, il est possible de différencier les états de viabilité au sein d'une population stressés. De plus, une analyse approfondie des spectres a montré que les bactéries VNC présentent un profil distinct, montrant des modifications majeures dans leurs compositions moléculaires
Wilson loops in ABJM theory reloaded
No full textInternational audienceWe present a new technique for computing supersymmetric Wilson loops in the ABJM theory via supersymmetric localization, valid for arbitrary values of the rank of the gauge group and the Chern-Simons level . The approach relies on an operator representation of the Wilson loops within the Fermi gas formalism in terms of the resolvent of a certain integral operator previously encountered in the computation of the ABJM partition function on the round three-sphere. By deriving a set of nontrivial relations for this resolvent, we obtain exact expressions for the generating functions of Wilson loops in terms of the partition function. For large , these expressions reproduce the weak-coupling expansion of the Wilson loops, and in the large- limit at fixed they match previously obtained high-precision numerical results. This analysis also resolves the longstanding discrepancy between numerical data and the semiclassical expression for the BPS Wilson loop
Fano and Reflexive Polytopes from Feynman Integrals
No full text61 pages. List of representative of Feynman graphs leading to Fano and Reflexive polytopes is on this repository: https://github.com/pierrevanhove/ReflexiveFanoPolytope
Operando detection of lithium plating and stripping in fast charging Li-ion cells with a reference electrode
No full textInternational audienceUnderstanding degradation mechanisms in Li-ion cells is essential for advancing fast-charging technologies. One of the primary limitations of fast charging is the risk of lithium plating, driven by the negative electrode potential. In this study, a reference electrode was integrated into 30 mAh pouch cells to investigate aging under various charging regimes. This three-electrode setup allowed us to monitor the potential of both electrodes, with a particular focus on the negative electrode. By coupling operando data with post-mortem analysis, we linked the cell's electrical behavior to physical phenomena occurring within the cell. During fast charging at 2C, changes in the incremental capacity profile (ICA) were observed and correlated with a critical threshold in the negative electrode potential, measured using the reference electrode. Post-mortem analysis confirmed that these changes are indicative of lithium plating. Furthermore, an additional current during the potentiostatic phase of the charge was identified, correlating with a rise in the potentials of both electrodes. This current bump is interpreted as evidence of a lithium stripping process. These findings highlight the importance of monitoring the negative electrode potential using a reference electrode to detect and mitigate the risk of lithium plating during fast charging, contributing to the optimization of battery performance and safety
The Devil Lies in the Details: Small Structural and ChemicalChanges in Iron Oxide Pigments Largely Alter the BiologicalOutcomes in Macrophages
No full textInternational audienceBecause of their technical qualities, such as resistance to fading and to high temperatures, mineral pigments are still widely used. Among mineral pigments, iron oxide pigments represent a widely used class, because of their diversity of shades (from yellow to red to brown to black) and low toxicity compared to heavy metals-based pigments. However, low toxicity does not mean the absence of adverse effects. We thus investigated the biological effects of two different subtypes of Pigment Red 101, i.e., hematite, produced by two different processes, namely a wet precipitation process and a calcination process. Macrophages were chosen as a target cell type because they represent the main scavenger cell type that is in charge of handling particulate materials in the body. During this comparison, we realized that the calcined pigment was contaminated from the start by bacterial endotoxins, which induced intense inflammatory responses and biased the comparison. After depyrogenation, the calcined pigment proved to dissolve to a higher extent in macrophages, but to show less intense adverse effects (e.g., alteration of the mitochondrial transmembrane potential, oxidative stress and inflammatory responses) than the precipitated pigment in a recovery exposure mode, allowing us to investigate delayed effects of the pigments. Thus, despite their identical pigment number, pigments differing in their structure and in their synthesis induce different responses from living cells, even if administrated in equivalent amounts. This should be taken into account for some applications, such as tattooing. Moreover, endotoxin contamination should also be checked to increase workers’ and users’ safety
Tracing the horizon of tetragonal-to-monoclinic distortion in pressurized trilayer nickelate La4Ni3O10
No full textInternational audienceThe crux of understanding the superconducting mechanism in pressurized Ruddlesden-Popper nickelates hinges on elucidating their structural phases. Under ambient conditions, the trilayer nickelate La4Ni3O10 stabilizes in a twinned monoclinic structure with space group P21/c. Upon heating, it undergoes a structural transition to the tetragonal I4/mmm phase at Ts ~ 1030 K, while a second transition associated with the onset of density-weave (DW) ordering emerges upon cooling below TDW ~ 135 K. Here from pressure-temperature x-ray diffraction on high quality flux-grown single crystals we unequivocally demonstrate a direct tetragonal-to-monoclinic transition with no trace of intermediate orthorhombic Bmab phase. Ab initio density-functional theory calculations as a function of pressure fully corroborate the experimental observations. The transition unfolds as a 2-fold superstructure due to the emergence of commensurate superlattice reflections and can be progressively suppressed from 1030 K down to 20 K under 14 GPa. No discernible structural distortions associated with DW ordering are detected down to 20 K at ambient pressure. This is in contrast to Raman measurements that reveal the appearance of additional phonon modes below 130 K, implying a further reduction in symmetry from monoclinic P21/c and thus indicating the presence of a third structural phase associated with the DW ordering in La4Ni3O10