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Investigating the role of strangeness in baryon–antibaryon annihilation at the LHC
No full textInternational audienceAnnihilation dynamics plays a fundamental role in the baryon–antibaryon interaction (B–B‾) at low-energy and its strength and range are crucial in the assessment of possible baryonic bound states. Experimental data on annihilation cross sections are available for the p–p‾ system but not in the low relative momentum region. Data regarding the B–B‾ interaction with strange degrees of freedom are extremely scarce, hence the modeling of the annihilation contributions is mainly based on nucleon–antinucleon (N–N‾) results, when available. In this letter we present a measurement of the p–p‾, p–Λ‾⊕p‾–Λ and Λ–Λ‾ interaction using correlation functions in the relative momentum space in high-multiplicity triggered pp collisions at s=13 TeV recorded by ALICE at the LHC. In the p–p‾ system the couplings to the mesonic channels in different partial waves are extracted by adopting a coupled-channel approach with recent χEFT potentials. The inclusion of these inelastic channels provides good agreement with the data, showing a significant presence of the annihilation term down to zero momentum. Predictions obtained using the Lednický–Lyuboshits formula and scattering parameters obtained from heavy-ion collisions, hence mainly sensitive to elastic processes, are compared with the experimental p–Λ‾⊕p‾–Λ and Λ–Λ‾ correlations. The model describes the Λ–Λ‾ data and underestimates the p–Λ‾⊕p‾–Λ data in the region of momenta below 200 MeV/c. The observed deviation indicates a different contribution of annihilation channels to the two systems containing strange hadrons
Beta spectrum shape studies for the predictions of the antineutrino spectrum from reactors
No full textInternational audienceNuclear reactors antineutrino measurements at short baselines do not fully agree with model predictions calculated with the Conversion Method. An alternative method to calculate the antineutrino spectra is theSummation Method. Both methods require the shapes of beta spectra as inputs. For that reason a new setup to measure the shape of the beta spectrum of relevant fission products for the calculation of the antineutrino spectra of reactors has been developed. Some preliminary measurements performed at IGISOL with isotopically clean beams are presented in this contribution
A closed fuel cycle option using the MSFR concept with chloride salts and the U/Pu cycle
No full textInternational audienceThis paper proposes a concept of molten salt fast reactor (MSFR) using chloride salts and U/Pu cycle as solution to close the fuel cycle. It is making use of the available materials currently unused or even considered as waste: depleted uranium (depU) and transuranic elements (TRUs). Its fuel is a NaCl-depUCl3-(TRUs)Cl3 salt with an additional fertile blanket made of NaCl-depUCl3-(ex−MOXPu)Cl3, to increase the breeding ratio of the system while improving the Pu isotopic vector of the spent MOx fuel. TRUs can come from various sources: spent MOx and/or spent UOx fuels, breeded plutonium; or the reactor can start with enriched uranium instead of TRUs.To take full advantages of the liquid fuel features, MSFRs are associated with a reprocessing unit allowing for on-site refuelling and reprocessing without stopping the reactor. Principle diagrams of reprocessing for the chloride MSFR are proposed. Impacts of reprocessing flowrates on neutronics and mass management are discussed. Results of neutronic depletion calculations for mass flowrates of input and output matters are presented.Finally, preliminary studies of French deployment scenarios will be proposed, to assess the possibilities of adding the reactor to the current fleet of PWRs from a resource perspective
Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection
No full textInternational audienceExperiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of . In this regime, ionization signals from small-angle Compton scatters of environmental -rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23eV. A skipper charge-coupled device (CCD) with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a Am -ray source over several months. Features associated with the silicon K, L, and L-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5keV. The data are in better agreement with calculations originally developed for X-ray absorption spectroscopy
Chemistry and speciation of protactinium – a first principles study
No full textNational audienceIt is of fundamental interest to understand and predict the chemistry of rare radioelements. In this work, we focus on protactinium (Z = 91), an element that is sandwiched in between thorium and uranium in the periodic table. Protactinium may naturally occur in environment (protactini-um-231 results from the decay of naturally occurring uranium-235) and also appear in thorium-based nuclear fuel cycles. From a chemical point of view, protactinium is a crossing point in the actinide series [1] and its chemistry is hard to predict [2,3]. We hypothesize that relativistic quantum chemistry should allow us to understand the enigmatic chemistry of protactinium and even predict it. For our first study, we have chosen to focus on the coordination sphere of protactinium and on the computation of equilibrium constants for experimentally known systems [3–5]. The occur-rence of 1:1, 1:2 and 1:3 complexes of protactinium(V) with sulfate and oxalate ligands is thus studied by means of quantum mechanical calculations, in particular based on density functional theory. The solvent effects, inherent to solution chemistry, are introduced by means of a polariz-able continuum model [6] and the explicit treatment of water molecules (micro solvation).The coordination sphere of protactinium has been obtained by geometry optimizations per-formed both in the gas phase and in solution. It involves an oxygen atom from the Pa=O mono-oxo bond and also oxygen atoms from the bidentate ligands, and in some cases from additional water molecules. The computation of equilibrium constants and comparison with experimental data is more subtle. First, only apparent constants were experimentally determined. Since the oc-currence of a mono-oxo bond was confirmed by EXAFS [5] even in the case of the 1:3 complex with oxalate ligands (corresponding to the stronger complexation), we hypothesize that this bond is also present in all the studied complexes. Second, number of explicitly treated water molecules should not be randomly chosen, it should ideally (i) lead to saturation of the coordination sphere of protactinium and (ii) be sufficient to stabilize the anionic ligands. We find that adding CN+1 water molecules is enough to satisfy both conditions in all the six studied complexes. By doing so and computing ligand-exchange equilibrium constants, we reproduce well the experimental trends for the exchange of 2 and 3 ligands, while the exchange of only one ligand (1:1 complex-es) is still hard to reproduce from computations.We report recent progress concerning the basic chemistry of protactinium. We have shown that its coordination sphere may include up to 8 oxygen atoms (from the original mono-oxo bond and from ligand and solvent molecule complexation) and find an approximate way of determin-ing trends in equilibrium constants, opening the way for future predictions.[1]Wilson R. et al. (2018) Nat. Commun. 9, 622.[2]Wilson R. (2012) Nat. Chem. 4, 586.[3]Le Naour C. et al. (2019) Radiochim. Acta, 107, 979-991.[4]Le Naour C. et al. (2005) Inorg. Chem. 44, 9542.[5]Mendes M. et al. (2010) Inorg. Chem. 49, 9962-9971.[6]Barone et al. (1997) J. Chem. Phys. 107, 3210-3221.<br
In-medium effects in <math><mi>ϕ</mi></math> meson production in heavy-ion collisions from subthreshold to relativistic energies
No full textInternational audienceWe investigate the hidden strange ϕ meson production in heavy-ion collisions from subthreshold (Ekin≈1A GeV) to relativistic (Ekin≈21A TeV) energies as well as its coupling to the open strange mesons (kaons, antikaons) and their productions. Our study is based on the off-shell microscopic parton-hadron-string dynamics (PHSD) transport approach which is applicable for the dynamical description of strongly interacting hadronic and partonic degrees-of-freedom created in heavy-ion collisions. Implementing novel meson-baryon and meson-hyperon production channels for ϕ mesons, calculated within a T-matrix coupled-channel approach based on the extended SU(6) chiral effective Lagrangian model, along with the collisional broadening of the ϕ-meson in-medium spectral function, we find a substantial enhancement of ϕ meson production in heavy-ion collisions, especially at sub- and near-thresholds. This allows us to describe the experimentally observed strong enhancement of the ϕ/K− ratio at low energies without including hypothetical decays of heavy baryonic resonances to ϕ as in alternative approaches. Moreover, we show that in spite of a stronger contribution from enhanced ϕ to K− production, the majority of the experimental data for different A+A systems at low energies favor the scenario with in-medium modifications of the kaon and antikaon properties in the hot and dense environment. Moreover, we study the influence of the final-state interactions of K,K¯ mesons on the reconstruction of ϕ's by the invariant-mass method
Clinical research in radiation oncology: how to move from the laboratory to the patient?
No full textInternational audienceTranslational research in radiation oncology is undergoing intense development. An increasingly rapid transfer is taking place from the laboratory to the patients, both in the selection of patients who can benefit from radiotherapy and in the development of innovative irradiation strategies or the development of combinations with drugs. Accelerating the passage of discoveries from the laboratory to the clinic represents the ideal of any translational research program but requires taking into account the multiple obstacles that can slow this progress. The ambition of the RadioTransNet network, a project to structure preclinical research in radiation oncology in France, is precisely to promote scientific and clinical interactions at the interface of radiotherapy and radiobiology, in its preclinical positioning, in order to identify priorities for strategic research dedicated to innovation in radiotherapy. The multidisciplinary radiotherapy teams with experts in biology, medicine, medical physics, mathematics and engineering sciences are able to meet these new challenges which will allow these advances to be made available to patients as quickly as possible
Comparison of heavy ion transport simulations: Ag+Ag collisions at = 1.58 AGeV
No full textInternational audienceWe compare the microscopic transport models UrQMD, PHSD, PHQMD, and SMASH to make predictions for the upcoming Ag+Ag data at ~GeV (~GeV) by the HADES collaboration. We study multiplicities, spectra and effective source temperatures of protons, , , the , and the within these models. Despite variations in the detailed implementation of the dynamics in the different models, the employed transport approaches all show consistent multiplicities of the bulk of investigated hadrons. The main differences are in the production, which is treated differently between UrQMD/SMASH on one side employing high mass resonance states with explicit decays to in contrast to PHSD/PHQMD which account only non-resonant production channels. A comparison of the spectra, summarized by effective source temperatures, shows that all models provide similar source temperatures around ~MeV, and show substantial radial flow on the order of even for such a small system
Impact of fully coherent energy loss on heavy meson production in pA collisions
No full textInternational audienceHadron production in proton-nucleus (pA) collisions was previously shown to be suppressed by medium-induced fully coherent energy loss (FCEL). We show that the quenching of D and B mesons in pPb collisions at the LHC due solely to FCEL is, at least, on par with other nuclear effects such as gluon shadowing or saturation. This is consistent with previous findings for both quarkonium and light hadron production in pA collisions, emphasising that FCEL effects need to be included for a reliable understanding of hadron production measurements in pA collisions