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Total absorption <math><mi>γ</mi></math>-ray spectroscopy of the <math><mi>β</mi></math> decays of <math><mmultiscripts><mi mathvariant="normal">Y</mi><mprescripts/><none/><mrow><mn>96</mn><mtext>gs</mtext><mo>,</mo><mi>m</mi></mrow></mmultiscripts></math>
No full textInternational audienceThe β decays of the ground state (gs) and isomeric state (m) of Y96 have been studied with the total absorption γ-ray spectroscopy technique at the Ion Guide Isotope Separator On-Line facility. The separation of the 8+ isomeric state from the 0− ground state was achieved thanks to the purification capabilities of the JYFLTRAP double Penning trap system. The β-intensity distributions of both decays have been independently determined. In the analyses the deexcitation of the 1581.6 keV level in Zr96, in which conversion electron emission competes with pair production, has been carefully considered and found to have significant impact on the β-detector efficiency, influencing the β-intensity distribution obtained. Our results for Y96gs (0−) confirm the large ground state to ground state β-intensity probability, although a slightly larger value than reported in previous studies was obtained, amounting to 96.6−2.1+0.3% of the total β intensity. Given that the decay of Y96gs is the second most important contributor to the reactor antineutrino spectrum between 5 and 7 MeV, the impact of the present results on reactor antineutrino summation calculations has been evaluated. In the decay of Y96m (8+), previously undetected β intensity in transitions to states above 6 MeV has been observed. This shows the importance of total absorption γ-ray spectroscopy measurements of β decays with highly fragmented deexcitation patterns. Y96m (8+) is a major contributor to reactor decay heat in uranium-plutonium and thorium-uranium fuels around 10 s after fission pulses, and the newly measured average β and γ energies differ significantly from the previous values in evaluated databases. The discrepancy is far above the previously quoted uncertainties. Finally, we also report on the successful implementation of an innovative total absorption γ-ray spectroscopy analysis of the module-multiplicity gated spectra, as a first proof of principle to distinguish between decaying states with very different spin-parity values
Projet BePAT : BeaQuant, un autoradiographe numérique au service de la production de radionucléides pour des applications en médecine nucléaire
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High energy ion beam monitoring: X-rays Bremsstrahlung production cross section measurements for carbon target
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3D-Representations for studying deep-sea coral habitats in the Lacaze-Duthiers Canyon, from geological settings to individual specimens
No full textInternational audienceThe Lacaze-Duthiers Canyon is located in the western Mediterranean Sea and is long known for hosting cold-water coral colonies in the canyon head region at depths ranging from 250 to 550 m. In 2019 during the CALADU cruise, three kinds of 3D-reconstructions were applied to better understand the distribution of coral colonies, their habitat and their skeleton morphologies. The canyon's flanks were mapped using a hull-mounted echosounder and an ROV multibeam echosounder. Digital terrain models were built with resolutions of 5 and 1 m and examined in three dimensions. ROV bathymetric data collected on the canyon's flanks made it possible to highlight a series of sub-parallel structures identified as lithified sedimentary strata along which coral colonies grow. Coral assemblages were explored at four locations and photographic images were assembled using structure from motion techniques to build photogrammetric models. Coral assemblages reconstructed in 3D enabled geo-localizing and recreating coral colonies on 16 models over a total area of 4370 m2. Two colonial species, Madrepora oculata and Desmophyllum pertusum were plotted and reported on bathymetric models to interpret their location at the scale of the canyon. The coordinates and depth of the colonies were used to calculate the vertical distribution (limited to our small bathymetric exploration, between 339 and 214 m depth) and density of populations (up to 4.3 colonies per m2). The spatial coverage of the 16 assemblages measured between 100 and 600 m2 each. The sizes of the colonies were measured to analyze the population structures of both species (mean sizes of 28 cm for D. pertusum and 18 cm for M. oculata, maximum sizes 1 m and 0.5 m, respectively, bushes 2.5 m long). In addition, lost fishing gears were quantified, longlines measured and their densities calculated (0.16 m/m2, up to 0.30 m/m2). An area with exuberant orange colonies of D. pertusum was discovered for the first time in the Lacaze-Duthiers Canyon. Five deep-sea scleractinian species were collected and micro-tomographic scans computed to view their intrinsic skeleton organization. Micro-CT scans of M. oculata, D. pertusum, Desmophyllum dianthus, Caryophyllia smithii, and Dendrophyllia cornigera enabled longitudinal and transversal cuts, highlighting morphological criteria for species identification and the multidirectional examination of specimens. We observed a thin canal connecting calices along the axis of D. pertusum colonies, and separate calices along the axis of M. oculata colonies
Antisymmetric Exchange in a Real Copper Triangular Complex
No full textInternational audienceThe antisymmetric exchange, also known as the Dzyaloshinskii-Moriya interaction (DMI), is an effective interaction that may be at play in isolated complexes (with transition metals or lanthanides, for instance), nanoparticles, and highly correlated materials with adequate symmetry properties. While many theoretical works have been devoted to the analysis of single-ion zero-field splitting and to a lesser extent to symmetric exchange, only a few ab initio studies deal with the DMI. Actually, it originates from a subtle interplay between weak electronic interactions and spin-orbit couplings. This article aims to highlight the origin of this interaction from theoretical grounds in a real tri-copper(II) complex, capitalizing on previous methodological studies on bi-copper(II) model complexes. By tackling this three-magnetic-center system, we will first show that the multispin model Hamiltonian is appropriate for trinuclear (and likely for higher nuclearity) complexes, then that the correct application of the permutation relationship is necessary to explain the outcomes of the ab initio calculations, and finally, that the model parameters extracted from a binuclear model transfer well to the trinuclear complex. For a more theory-oriented purpose, we will show that the use of a simplified structural model allows one to perform more demanding electronic structure calculations. On this simpler system, we will first check that the previous transferability is still valid, prior to performing more advanced calculations on the derived two-magnetic-center model system. To this end, we will explain in detail the physics of the DMI in the copper triangle of interest, before advocating further theory/experiment efforts
Quenching factor measurements of neon nuclei in neon gas
No full textInternational audienceThe NEWS-G collaboration uses spherical proportional counters (SPCs) to search for weakly interacting massive particles (WIMPs). In this paper, we report the first measurements of the nuclear quenching factor in neon gas at 2 bar using an SPC deployed in a neutron beam at the TUNL facility. The energy-dependence of the nuclear quenching factor is modeled using a simple power law: αEnrβ; we determine its parameters by simultaneously fitting the data collected with the detector over a range of energies. We measured the following parameters in Ne:CH4 at 2 bar: α=0.2801±0.0050 (fit) ±0.0045 (sys) and β=0.0867±0.020 (fit) ±0.006 (sys). Our measurements do not agree with expected values from SRIM or Lindhard theory. We demonstrated the feasibility of performing quenching factor measurements at sub-keV energies in gases using SPCs and a neutron beam
Production of K and in pp and Pb-Pb collisions at TeV
No full textInternational audienceThe production of K and mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum () distributions of K and mesons have been measured at midrapidity (|y|<0.5) up to GeV in inelastic pp collisions and for several Pb-Pb collision centralities. The collision centrality and collision energy dependence of the average transverse momenta agree with the radial flow scenario observed with stable hadrons, showing that the effect is stronger for more central collisions and higher collision energies. The ratio is found to be suppressed in Pb-Pb collisions relative to pp collisions: this indicates a loss of the measured K signal due to rescattering of its decay products in the hadronic phase. In contrast, for the longer-lived mesons, no such suppression is observed. The nuclear modification factors () of K and mesons are calculated using pp reference spectra at the same collision energy. In central Pb-Pb collisions for p_{\rm T} > 8 GeV, the values of K and are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The values at high for K and mesons are in agreement within uncertainties for and 2.76 TeV
Measurements of the ionization efficiency of protons in methane
No full textInternational audienceThe amount of energy released by a nuclear recoil ionizing the atoms of the active volume of detection appears "quenched" compared to an electron of the same kinetic energy. This different behavior in ionization between electrons and nuclei is described by the Ionization Quenching Factor (IQF) and it plays a crucial role in direct dark matter searches. For low kinetic energies (below ), IQF measurements deviate significantly from common models used for theoretical predictions and simulations. We report measurements of the IQF for proton, an appropriate target for searches of Dark Matter candidates with a mass of approximately 1 GeV, with kinetic energies in between and in of methane. We used the Comimac facility in order to produce the motion of nuclei and electrons of controlled kinetic energy in the active volume, and a NEWS-G SPC to measure the deposited energy. The Comimac electrons are used as reference to calibrate the detector with 7 energy points. A detailed study of systematic effects led to the final results well fitted by with and . In agreement with some previous works in other gas mixtures, we measured less ionization energy than predicted from SRIM simulations, the difference reaching at $2~\mathrm{keV}
First study of the two-body scattering involving charm hadrons
No full textInternational audienceThis Letter presents the first measurement of the interaction between charm hadrons and nucleons. The two-particle momentum correlations of and pairs are measured by the ALICE Collaboration in high-multiplicity pp collisions at . The data are compatible with the Coulomb-only interaction hypothesis within (1.1-1.5). Considering an attractive nucleon(N) strong interaction, in contrast to most model predictions which suggest an overall repulsive interaction, slightly improves the level of agreement. This measurement allows for the first time an estimation of the 68% confidence level interval for the isospin inverse scattering length of the state , assuming negligible interaction for the isospin channel