HAL Mines Nantes
Not a member yet
7271 research outputs found
Sort by
Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant
No full textInternational audienceRadioactive Cs-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) are a potential health risk through inhalation. Little has been documented on the occurrence of CsMPs, particularly their occurrence inside buildings. In this study, we quantitatively analyze the distribution and number of CsMPs in indoor dust samples collected from an elementary school located 2.8 km to the southwest of FDNPP. The school had remained deserted until 2016. Then, using a modified version of the autoradiography-based “quantifying CsMPs (mQCP) method,” we collected samples and determined the number of CsMPs and Cs radioactive fraction (RF) values of the microparticles (defined as total Cs activity from CsMPs/bulk Cs activity of the entire sample). The numbers of CsMPs ranged from 653 to 2570 particles/(g dust) and 296–1273 particles/(g dust) on the first and second floors of the school, respectively. The corresponding RFs ranged between 6.85 – 38.9% and 4.48–6.61%, respectively. The number of CsMPs and RF values in additional outdoor samples collected near the school building were 23–63 particles/(g dust or soil) and 1.14–1.61%, respectively. The CsMPs were most abundant on the school's first floor near to the entrance, and the relative abundance was higher near the stairs on the second floor, indicating a likely CsMP dispersion path through the building. Additional wetting of the indoor samples combined with autoradiography revealed that indoor dusts had a distinct absence of intrinsic, soluble Cs species, such as CsOH. These combined observations indicate that a significant amount of poorly soluble CsMPs were likely contained in initial radioactive airmass plumes from the FDNPP and that the microparticles penetrated buildings. CsMPs could still be abundant at the location, with locally high Cs activity in indoor environments near to openings
Detecting nuclear mass distribution in isobar collisions via charmonium
No full textInternational audienceThe collective properties of final state hadrons produced in the high statistics Ru+Ru and Zr+Zr collisions at are found to be significantly different. Such differences were argued to be precise probes of the difference in nucleon distribution in the isobar nuclei. We investigate the production in the isobar collision via a relativistic transport approach. By comparing the isobar systems according to equal centrality bin and equal multiplicity bin, we find that the yield ratio of is sensitive to the differences in both the number of binary collisions and the medium evolution. Besides, the elliptic flow of is qualitatively different from the light hadrons, and the ratio between Ru+Ru and Zr+Zr collisions is sensitive to the medium evolution. The charmonium production provides an independent probe to study the nucleon distribution in the isobar system
Thermodynamics of aerosols during a molten core-concrete interaction at Fukushima Daiichi Unit 2 estimated conditions
No full textInternational audienceSeveral radioactive releases from the containment took place during all the events leading up to FukushimaDaiichi endstate. Radionuclides released into the environment may differ in their composition or chemical formdepending on the unit involved in the discharge and depending on the course of the accident. These differencesmay result from the path of the radionuclides from the core to the environment (e.g. through suppression poolwater) and from the chemical and physical properties within the reactor core and the containment. On March14th and 15th 2011, spherical glassy Cs-bearing microparticles (type-A CsMP) were collected for the first time.These microparticles might result from molten core-concrete interaction (MCCI) inside Unit 2, where the Zircaloyfrom the fuel cladding interacted with the SiO2 of the concrete pedestal at high temperature. The result of thisinteraction is a significant release of silica-rich gases or aerosols from the melt pool, which condense in colderlocations. Calculations using ThermoCalc with OECD/NEA database TAF-ID version 11 were performed on thethermodynamics of vaporization during an MCCI to find correlations between the chemical and physical propertiesof the reactor atmosphere and the chemical composition of type-A CsMP. Data from ORIGEN2 andMELCOR calculations were used to estimate the core melt and atmosphere composition at the assumed time ofthe reactor pressure vessel failure. The vapour temperature at which type-A CsMP may have condensed in thecontainment has been evaluated. Using Fe/Si, U/Si and Cs/Si ratios in the observed CsMP as an indicator forvapour composition, this suggests that type-A CsMP originate from condensation of vapours around2000 2200 ◦C from a low oxidised composition of corium, rich in zirconium and poor in stainless steel
Phase Transitions in Particle Physics -- Results and Perspectives from Lattice Quantum Chromo-Dynamics: Results and Perspectives from Lattice Quantum Chromo-Dynamics
No full textInternational audiencePhase transitions in a non-perturbative regime can be studied by ab initio Lattice Field Theory methods. The status and future research directions for LFT investigations of Quantum Chromo-Dynamics under extreme conditions are reviewed, including properties of hadrons and of the hypothesized QCD axion as inferred from QCD topology in different phases. We discuss phase transitions in strong interactions in an extended parameter space, and the possibility of model building for Dark Matter and Electro-Weak Symmetry Breaking. Methodological challenges are addressed as well, including new developments in Artificial Intelligence geared towards the identification of different phases and transitions
On a deep connection between factorization and saturation: new insight into modeling high-energy proton-proton and nucleus-nucleus scattering in the EPOS4 framework
No full textInternational audienceFollowing very elementary time-scale arguments, we know that multiple nucleon-nucleon scatterings in high-energy nucleus-nucleus (AA) collisions or multiple partonic scatterings in proton-proton (pp) collisions must happen in parallel. However, a parallel scattering formalism does not automatically lead to inclusive cross sections showing factorization in pp or binary scaling in AA scatterings. We will report on new ideas (leading to EPOS4), which will provide some new understanding of a deep connection between four basic concepts in pp and AA collisions: parallel scattering, energy conservation, factorization, and saturation. Missing one will spoil the whole picture. From a practical point of view, we can compute within the EPOS4 framework parton distribution functions (EPOS PDFs) and use them to compute inclusive pp cross sections. So for the first time, we may compute inclusive jet production (for heavy or light flavors) at very high transverse momentum (p_t) and at the same time in the same formalism study flow effects at low p_t in high-multiplicity pp events, making EPOS4 a full-scale "general purpose event generator". We discuss applications, essentially multiplicity dependencies (of particle ratios, mean p_t, charm production) which are very strongly affected by the saturation issues discussed in this paper
Coordination and thermodynamic properties of aqueous protactinium(V) by first-principle calculations
No full textInternational audienceProtactinium (Z = 91) is a very rare actinide with peculiar physico-chemical properties. Indeed, although one may naively think that it behaves similarly to either thorium or uranium by its position in the periodic table, it may in fact follow its own rules. Because of the quite small energy gap between its valence shells (in particular the 5f and 6d ones) and also the strong influence of relativistic effects on its properties, it is actually a challenging element for theoretical chemists. In this article, we combine experimental information, chemical arguments and standard first-principle calculations, complemented by implicit and explicit solvation, to revisit the stepwise complexation of aqueous protactinium(V) with sulfate and oxalate dianionic ligands (SO42- and C2O42-, respectively). From a methodological viewpoint, we notably conclude that it is necessary to at least saturate the coordination sphere of protactinium(V) to reach converged equilibrium constant values. Furthermore, in the case of single complexations (i.e. with one sulfate or oxalate ligand bound in the bidentate fashion), we show that it is necessary to maintain the coordination of one hydroxyl group, thought of in the [PaO(OH)]^3+ precursor, to obtain coherent complexation constants. Therefore, we predict that this hydroxyl group is maintained in the formation of 1:1 complexes while we confirm that it is withdrawn when coordinating three sulfate or oxalate ligands. Finally, we stress that this work is a first step toward the future use of theoretical predictions to elucidate the enigmatic chemistry of protactinium in solution
Measurement of the non-prompt D-meson fraction as a function of multiplicity in proton-proton collisions at = 13 TeV
No full textInternational audienceThe fractions of non-prompt (i.e. originating from beauty-hadron decays) D and D mesons with respect to the inclusive yield are measured as a function of the charged-particle multiplicity in proton-proton collisions at a centre-of-mass energy of = 13 TeV with the ALICE detector at the LHC. The results are reported in intervals of transverse momentum (p) and integrated in the range 1 < p< 24 GeV/c. The fraction of non-prompt D and D mesons is found to increase slightly as a function of p in all the measured multiplicity intervals, while no significant dependence on the charged-particle multiplicity is observed. In order to investigate the production and hadronisation mechanisms of charm and beauty quarks, the results are compared to PYTHIA 8 as well as EPOS 3 and EPOS 4 Monte Carlo simulations, and to calculations based on the colour glass condensate including three-pomeron fusion.[graphic not available: see fulltext
Measurement of the production of (anti)nuclei in p–Pb collisions at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>8.16</mn><mspace width="0.25em"/><mtext>TeV</mtext></math>
No full textInternational audienceMeasurements of (anti)proton, (anti)deuteron, and (anti)3He production in the rapidity range −1<y<0 as a function of the transverse momentum and event multiplicity in p–Pb collisions at a center-of-mass energy per nucleon–nucleon pair sNN=8.16TeV are presented. The coalescence parameters B2 and B3, measured as a function of the transverse momentum per nucleon and of the mean charged-particle multiplicity density, confirm a smooth evolution from low to high multiplicity across different collision systems and energies. The ratios between (anti)deuteron and (anti)3He yields and those of (anti)protons are also reported as a function of the mean charged-particle multiplicity density. A comparison with the predictions of the statistical hadronization and coalescence models for different collision systems and center-of-mass energies favors the coalescence description for the deuteron-to-proton yield ratio with respect to the canonical statistical model
Measurement of beauty-strange meson production in Pb–Pb collisions at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>5.02</mn><mspace width="0.25em"/><mrow><mi mathvariant="normal">TeV</mi></mrow></math> via non-prompt <math altimg="si2.svg"><msubsup><mrow><mi mathvariant="normal">D</mi></mrow><mrow><mi mathvariant="normal">s</mi></mrow><mrow><mo linebreak="badbreak" linebreakstyle="after">+</mo></mrow></msubsup></math> mesons
No full textInternational audienceThe production yields of non-prompt Ds+ mesons, namely Ds+ mesons from beauty-hadron decays, were measured for the first time as a function of the transverse momentum (pT) at midrapidity (|y|<0.5) in central and semi-central Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV with the ALICE experiment at the LHC. The Ds+ mesons and their charge conjugates were reconstructed from the hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the 4<pT<36GeV/c and 2<pT<24GeV/c intervals for the 0–10% and 30–50% centrality classes, respectively. The measured yields of non-prompt Ds+ mesons are compared to those of prompt Ds+ and non-prompt D0 mesons by calculating the ratios of the production yields in Pb–Pb collisions and the nuclear modification factor RAA. The ratio between the RAA of non-prompt Ds+ and prompt Ds+ mesons, and that between the RAA of non-prompt Ds+ and non-prompt D0 mesons in central Pb–Pb collisions are found to be on average higher than unity in the 4<pT<12GeV/c interval with a statistical significance of about 1.6σ and 1.7σ, respectively. The measured RAA ratios are compared with the predictions of theoretical models of heavy-quark transport in a hydrodynamically expanding QGP that incorporate hadronisation via quark recombination
Measurements of azimuthal anisotropies at forward and backward rapidity with muons in high-multiplicity p–Pb collisions at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>8.16</mn></math> TeV
No full textInternational audienceThe study of the azimuthal anisotropy of inclusive muons produced in p–Pb collisions at sNN=8.16 TeV, using the ALICE detector at the LHC is reported. The measurement of the second-order Fourier coefficient of the particle azimuthal distribution, v2, is performed as a function of transverse momentum pT in the 0–20% high-multiplicity interval at both forward (2.03<yCMS<3.53) and backward (−4.46<yCMS<−2.96) rapidities over a wide pT range, 0.5<pT<10 GeV/c, in which a dominant contribution of muons from heavy-flavour hadron decays is expected at pT>2 GeV/c. The v2 coefficient of inclusive muons is extracted using two different techniques, namely two-particle cumulants, used for the first time for heavy-flavour measurements, and forward–central two-particle correlations. Both techniques give compatible results. A positive v2 is measured at both forward and backward rapidities with a significance larger than 4.7σ and 7.6σ, respectively, in the interval 2<pT<6 GeV/c. Comparisons with previous measurements in p–Pb collisions at sNN=5.02 TeV, and with AMPT and CGC-based theoretical calculations are discussed. The findings impose new constraints on the theoretical interpretations of the origin of the collective behaviour in small collision systems