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Equation of state and elasticity of brucite at high temperatures and pressures from classical atomistic simulations
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Modified Korteweg-de Vries Equation as a System with Benign Ghosts
No full textInternational audienceWe consider the modified Korteweg-de Vries equation, , and explore its dynamics in {\it spatial} direction. Higher derivatives bring about the {\it ghosts}. We argue that these ghosts are benign, i.e. the classical dynamics of this system does not involve a blow-up. This probably means that also the associated quantum problem is well defined
Reactor rate modulation oscillation analysis with two detectors in Double Chooz
No full textInternational audienceA θ oscillation analysis based on the observed antineutrino rates at the Double Chooz far and near detectors for different reactor power conditions is presented. This approach provides a so far unique simultaneous determination of θ and the total background rates without relying on any assumptions on the specific background contributions. The analysis comprises 865 days of data collected in both detectors with at least one reactor in operation. The oscillation results are enhanced by the use of 24.06 days (12.74 days) of reactor-off data in the far (near) detector. The analysis considers the interactions up to a visible energy of 8.5 MeV, using the events at higher energies to build a cosmogenic background model considering fast-neutrons interactions and Li decays. The background-model-independent determination of the mixing angle yields sin(2θ) = 0.094 ± 0.017, being the best-fit total background rates fully consistent with the cosmogenic background model. A second oscillation analysis is also performed constraining the total background rates to the cosmogenic background estimates. While the central value is not significantly modified due to the consistency between the reactor-off data and the background estimates, the addition of the background model reduces the uncertainty on θ to 0.015. Along with the oscillation results, the normalization of the anti-neutrino rate is measured with a precision of 0.86%, reducing the 1.43% uncertainty associated to the expectation.[graphic not available: see fulltext
Feasibility and physics potential of detecting B solar neutrinos at JUNO
No full textInternational audienceThe Jiangmen Underground Neutrino Observatory (JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background U and Th in the liquid scintillator can be controlled to 10 g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If eV , JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3 (2 ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle. Moreover, JUNO can simultaneously measure using B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of reported by solar neutrino experiments and the KamLAND experiment
Description théorique de la dynamique des quarkonia dans le plasma de quarks et de gluons au moyen d'une approche de type équation maîtresse quantique
No full textQuantum chromodynamics (QCD) predicts the existance of a state of matter called the Quark-Gluon Plasma (QGP) at extreme temperature and density, which can be produced in heavy ion collisions. One of the QGP observables is the so-called quarkonia (heavy quark-antiquark bound states) suppression which is defined by a smaller production of quarkonia states in presence of QGP compared to the production in absence of plasma.In recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma , using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here a quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the system reduced density matrix.This thesis investigates the dynamics of quarkonium states by resolving a quantum master equation based on the approach of Blaizot & Escobedo. More precisely, this equation is resolved numerically directly for the first-time in both a static and a cooling QGP. The populations of quarkonium states over time are studied and the validity of semi-classical approximations leading to Langevin equations is investigated.La Chromodynamique Quantique (QCD) prédit l'existence d'un état de la matière appelé Plasma de Quarks et de Gluons (PQG) dans des conditions extrêmes de température et de pression, qui peut être produit lors de collisions d'ions lourds. Une observable du PQG est la suppression des quarkonia (états liés de quark-antiquark lourds), qui est définie par une plus faible production de ces états en présence de PQG par rapport à la production en l'absence de plasma.Ces dernières années, un effort significatif a été réalisé d'un point de vue théorique vers une description dynamique des quarkonia au sein du Plasma de Quarks et de Gluons, à l'aide du formalisme des systèmes quantiques ouverts. Dans ce cadre, il est possible d'obtenir une description en temps réel d'un système quantique (ici un quarkonium) en interaction avec un bain thermique (le PQG) en étudiant la matrice densité réduite du système.Cette thèse étudie la dynamique d'états quarkonium en résolvant une équation maîtresse quantique basée sur l'approche de Blaizot & Escobedo. Plus précisément, cette équation est résolue numériquement directement pour la première fois dans le cas d'un PQG statique et dans le cas d'un PQG se refroidissant. Les populations d'états quarkonium sont étudiées et la validité d'approximations semi-classiques amenant à des équations de Langevin est examinée
Mesures de sections efficaces d'ionisation et analyses d'objets du patrimoine avec des faisceaux d'ions légers aux énergies des accélérateurs médicaux
No full textThe development of proton therapy and cyclotrons for the production of radioisotopes for medicine has opened up a multitude of high-energy accelerators for ion beam analysis techniques. The high-energy PIXE method is developed at the ARRONAX cyclotron with proton beams, but also alpha particles at energies up to 70 MeV. The use of a high-energy beam allows the analysis of thick objects while limiting the damage aspect. Firstly, measurements of ionisation cross sections were carried out. They allowed to validate the RECPSSR model for elements with an atomic number Z ≥ 42 and to optimise a fitting function for elements whose values are poorly reproduced by the model. In a second phase, two applications of the PIXE method at high energy were carried out on the collections of the Dobrée Museum in Nantes. One of the studies concerned the analysis of seal matrices in order to determine their composition and to be able to classify them. The other study was on heavy silver coins from the 16th century, where the objective was to find the trace elements (Gold and Indium) allowing the provenance of the silver ore to be traced.Le développement de la protonthérapie et des cyclotrons de productions de radio-isotopes pour la médecine permet d’ouvrir aux techniques d’analyse par faisceaux d’ions une multitude d’accélérateurs de plusieurs dizaines de MeV. La méthode PIXE à haute énergie est développée au cyclotron ARRONAX avec des faisceaux de protons, mais aussi des particules alpha à des énergies pouvant atteindre 70 MeV. L’utilisation d’un faisceau de haute énergie permet l’analyse d’objet épais tout en limitant l’aspect d’endommagement.Dans un premier temps, des mesures de sections efficaces d’ionisation ont été réalisées. Elles ont permis de valider le modèle RECPSSR pour les éléments avec un numéro atomique Z ≥ 42 et d’optimiser une fonction d’ajustement pour les éléments dont les valeurs sont mal reproduites par le modèle. Dans un second temps, deux applications de la méthode PIXE à haute énergie ont été réalisées sur les collections du Musée Dobrée à Nantes. L'une des études a concerné l'analyse de matrices de sceaux afin de déterminer la composition et de pouvoir ensuite les classifier. L'autre étude était sur des pièces d'argent lourdes du XVIe siècle, où l'objectif était de retrouver les éléments traces (Or et Indium) permettant de retracer la provenance du minerai d'argent
Freeze-in produced dark matter in the ultra-relativistic regime
No full textInternational audienceWhen dark matter particles only feebly interact with plasma constituents in the early universe, they never reach thermal equilibrium. As opposed to the freeze-out mechanism, where the dark matter abundance is determined at , the energy density of a feebly interacting state builds up and increases over . In this work, we address the impact of the high-temperature regime on the dark matter production rate, where the dark and Standard Model particles are ultra-relativistic and nearly light-like. In this setting, multiple soft scatterings, as well as processes, are found to give a large contribution to the production rate. Within the model we consider in this work, namely a Majorana fermion dark matter of mass accompanied by a heavier scalar with mass splitting which shares interactions with the visible sector, the energy density can be dramatically underestimated when neglecting the high-temperature dynamics. We find that the overall effective and high-temperature contributions to dark-matter production give (20\%) corrections for () to the Born production rate with in-vacuum masses and matrix elements. We also assess the impact of bound-state effects on the late-time annihilations of the heavier scalar, in the context of the super-WIMP mechanism
Investigation on boron and iodine behavior during nuclear glass vapor hydration
No full textInternational audienceUnderstanding the durability of nuclear glass in the vapor phase is essential for evaluating the long-term safety of the nuclear glass. This work studies the vapor hydration of borosilicate and iodine-bearing glass at 90 °C and relative humidity at 99%. Hydration kinetics was monitored by analyzing the boron and iodine released during the vapor hydration process. It is found that boron becomes more easily released after iodine being added to the glass matrix. The results related to boron release and retention indicate the possible transformation of tetrahedral [4]B to trigonal [3]B on the hydrated glass surface, which may enhance the release of boron in the form of boric acid afterward. Release of iodine occurred but at a far lesser extent than boron with 92% of iodine retained in the alteration layer, thus opening good perspectives with regard to the disposal of high-level waste containing iodine
How to create giant Dzyaloshinskii–Moriya interactions? Analytical derivation and ab initio calculations on model dicopper(II) complexes
No full textInternational audienceThis paper is a theoretical “proof of concept” on how the on-site first-order spin–orbit coupling (SOC) can generate giant Dzyaloshinskii–Moriya interactions in binuclear transition metal complexes. This effective interaction plays a key role in strongly correlated materials, skyrmions, multiferroics, and molecular magnets of promising use in quantum information science and computing. Despite this, its determination from both theory and experiment is still in its infancy and existing systems usually exhibit very tiny magnitudes. We derive analytical formulas that perfectly reproduce both the nature and the magnitude of the Dzyaloshinskii–Moriya interaction calculated using state-of-the-art ab initio calculations performed on model bicopper(II) complexes. We also study which geometrical structures/ligand-field forces would enable one to control the magnitude and the orientation of the Dzyaloshinskii–Moriya vector in order to guide future synthesis of molecules or materials. This article provides an understanding of its microscopic origin and proposes recipes to increase its magnitude. We show that (i) the on-site mixings of 3d orbitals rule the orientation and magnitude of this interaction, (ii) increased values can be obtained by choosing more covalent complexes, and (iii) huge values (∼1000 cm−1) and controlled orientations could be reached by approaching structures exhibiting on-site first-order SOC, i.e., displaying an “unquenched orbital momentum.