HAL Mines Nantes
Not a member yet
7271 research outputs found
Sort by
Coupled baryon, electric charge and strangeness fluctuations in heavy-ion collisions
No full textInternational audienceWe present for the first time quantitative results for the coupled dynamics of second order fluctuations in the three conserved charges of QCD based on stochastic diffusion equations for a Bjorken-type expanding hadronic medium. We show that the fluctuations deviate from local equilibrium expectations which can result in important phenomenological consequences for the interpretation of experimental data
On exactly solvable ghost-ridden systems
No full textInternational audienceWe discuss exactly solvable systems involving integrals of motion with higher powers of momenta. If one of these integrals is chosen for the Hamiltonian, we obtain a higher-derivative system involving ghosts, i.e. a system whose Hamiltonian is not bounded neither from below, nor from above. However, these ghosts are benign: there is no collapse and unitarity is not violated. As an example, we consider the 3-particle Toda periodic chain, with the cubic invariant I chosen for the Hamiltonian. The classical trajectories exhibit regular oscillations, and the spectrum of the quantum Hamiltonian is discrete running from minus to plus infinity. We also discuss the classical dynamics of a perturbed system with the Hamiltonian H = I + v, where v is an oscillator potential. Such a system is not exactly solvable, but its classical trajectories exhibit not regular, but still benign behaviour without collapse. This means that also the corresponding quantum problem is well defined. The same observation can be made for exactly solvable (1+1)-dimensional field theories involving an infinite number of conservation laws: any of them can be chosen for the Hamiltonian. We illustrate this for the Sine-Gordon and KdV models. In the latter case, the Lagrangian and standard integrals of motion involve higher spatial rather than temporal derivatives. But one can always interchange x and t, after which we obtain a system with benign ghosts
Jet-associated deuteron production in pp collisions at = 13 TeV
No full textInternational audienceDeuteron production in high-energy collisions is sensitive to the space–time evolution of the collision system, and is typically described by a coalescence mechanism. For the first time, we present results on jet-associated deuteron production in pp collisions at s=13 TeV, providing an opportunity to test the established picture for deuteron production in events with a hard scattering. Using a trigger particle with high transverse-momentum (pT>5 GeV/c) as a proxy for the presence of a jet at midrapidity, we observe a measurable population of deuterons being produced around the jet proxy. The associated deuteron yield measured in a narrow angular range around the trigger particle differs by 2.4–4.8 standard deviations from the uncorrelated background. The data are described by PYTHIA model calculations featuring baryon coalescence
In-medium effects in strangeness production in heavy-ion collisions at (sub)threshold energies
No full textInternational audienceWe study the in-medium effects in strangeness production in heavy-ion collisions at (sub)threshold energies of (1–2)A GeV based on the microscopic Parton-Hadron-String Dynamics (PHSD) transport approach. The in-medium modifications of the antikaon (K¯=K−,K¯0) properties are described via the self-consistent coupled-channel unitarized scheme based on a SU(3) chiral Lagrangian which incorporates explicitly the s and p waves of the kaon-nucleon interaction. This scheme provides the antikaon potential, spectral functions, and reaction cross sections as well as their dependence on baryon density, temperature, and antikaon momentum in the nuclear medium, which are incorporated in the off-shell dynamics of the PHSD. The in-medium modification of kaons (K=K+,K0) are accounted via the kaon-nuclear potential, which is assumed to be proportional to the local baryon density. The manifestation of the medium effects in observables is investigated for the K and K¯ rapidity distributions, pT spectra, the polar and azimuthal angular distributions, and directed (v1) and elliptic (v2) flows in C+C, Ni+Ni, and Au+Au collisions. We find—by comparison to experimental data from the KaoS, FOPI, and HADES Collaborations—that the modifications of (anti)kaon properties in nuclear matter are necessary to explain the data in a consistent manner. Moreover, we demonstrate the sensitivity of kaon observables to the equation of state of nuclear matter
Atomistic computer simulations of the cement degradation mechanisms in the context of geological carbon sequestration
No full textInternational audienc
Atomistic computer simulation of the structure and properties of iodide-containing hydrocalumite (AFm phase)
No full textInternational audienc
Equations of state and elasticity of brucite and portlandite at high temperatures and pressures from classical atomistic simulations
No full textInternational audienc
Simulations and background estimate for the DAMIC-M experiment
No full textInternational audienceDAMIC-M (Dark Matter in CCDs at Modane) is a near-future experiment aiming to search for low-mass dark matter particles through their interactions with the silicon nucleus or electrons in the bulk of charge-coupled devices (CCDs). With respect to its predecessor DAMIC at SNOLAB, DAMIC-M will have a 25 times larger detector mass and will achieve sub-electron readout noise thanks to the use of the so-called skipper CCDs. With these novelties, DAMIC-M will be sensitive to WIMPS with masses below 10 GeV and it will be leading the search of MeV-scale hidden sector candidates and eV-scale hidden photons. To achieve these results, DAMIC-M requires a radiogenic background rate of a fraction of decays/keV/kg/day. Thus, an extensive campaign of innovation of the detector technology and design is ongoing. Simulations are being exploited to optimize the detector design and drive the material selection and handling. This proceedings provides a comprehensive overview of the explored detector designs, the corresponding estimated backgrounds, and the strategies for its mitigation
Prospects of studying the production of hypernuclei in heavy-ion interactions at the NICA collider at JINR
No full textInternational audienceNew acceleration complex NICA (Nuclotron-based Ion Collider fAcility) as well as MultiPurpose Detector (MPD) is underway at Joint Institute for Nuclear Research (Dubna, Russia) for the study of heavy ion collisions. Strangeness and hypernuclei production is presently under active experimental and theoretical investigation and is of particular interest of the NICA/MPD program. We combine several dynamical transport models and the MST cluster finding procedure to calculate the production of light nuclei and hypernuclei in heavy-ion collisions at NICA energies. The emphasis will be put on the NICA prospects for the study of the production of hypernuclei and detector performance in the reconstruction of hypernuclei species
Radiation exposure of microorganisms living in radioactive mineral springs
No full textInternational audienceThe TIRAMISU collaboration gathers expertise from biologists, physicists, radiochemists and geologists within the Zone-Atelier Territoires Uranifères (ZATU) in France to study the response of microorganisms living in naturally radioactive mineral springs. Mineral springs are isolated ecosystems, extremely stable over geological time scales, which display different physicochemical and radiological parameters compared to their surroundings. Water and sediment samples collected in 27 mineral springs of the volcanic Auvergne region (Massif Central, France) have been analyzed for their microbial biodiversity and radionuclide content. Among the microorganisms present, diatoms (a microalgae species), widely used as environmental bioindicators of water quality, have shown to display an exceptional abundance of teratogenic forms in the most radioactive springs studied (radon activity up to 3700 Bq/L). The current work presents a first assessment of the dose received by the diatoms inhabiting naturally radioactive mineral springs. The radiological risk for microorganisms living in freshwater environments was estimated using the ERICA tool. Most of the sampled mineral springs were highly above the risk threshold of 10 mGy/h due to the large concentrations of radium in the sediments (up to 50 Bq/g). The complete radiological data on water and sediments are used as inputs to Monte Carlo simulations at micro- (GATE) and nano- (Geant4-DNA) scale in order to assess the direct and indirect damages on the diatom DNA