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Dilepton production at NLO and intermediate invariant-mass observables
No full textInternational audienceThe thermal QCD dilepton production rate is calculated at next-to-leading order in the strong coupling and at finite baryon chemical potential. The two-loop virtual photon self-energy is evaluated using finite temperature field theory and combined consistently with the self-energy in the Landau-Pomeranchuk-Migdal regime. We present new results for a dense baryonic plasma. The rates are then integrated using (3+1)-dimensional fluid-dynamical simulations calibrated to reproduce hadronic experimental results obtained at RHIC at energies ranging from those of the Beam Energy Scan to GeV. We elaborate on the ability for dileptons to relay information about the plasma baryonic content and temperature
The force-force correlator at the hard thermal scale of hot QCD
No full textInternational audienceHigh-energy particles traversing the Quark-Gluon plasma experience modified (massive) dispersion, although their vacuum mass is negligible compared to the kinetic energy. Due to poor convergence of the perturbative series in the regime of soft loop momenta, a more precise determination of this effective mass is needed. This paper continues our investigation on the factorisation between strongly-coupled infrared classical and perturbative ultraviolet behavior. The former has been studied non-perturbatively within EQCD by determining a non-local operator on the lattice. By computing the temperature-scale contribution to the same operator in 4D QCD at next-to-leading order (NLO), we remove the ultraviolet divergence of the EQCD calculation with an opposite infrared divergence from the hard thermal scale. The result is a consistent, regulator-independent determination of the classical contribution where the emergence of new divergences signals sensitivities to new regions of phase space. We address the numerical impact of the classical and NLO thermal corrections on the convergence of the factorised approach and on the partial applicability of our results to calculations of transport coefficients
Core-corona procedure and microcanonical hadronization to understand strangeness enhancement in proton-proton and heavy ion collisions in the EPOS4 framework
No full textInternational audienceThe multiplicity dependence of multi-strange hadron yields in proton-proton and lead-lead collisions at several TeV allows to study the transition from very big to very small systems, in particular, concerning collective effects. We investigate this, employing a core-corona approach based on new microcanonical hadronization procedures in the EPOS4 framework, as well as new methods allowing to transform energy-momentum flow through freeze-out surfaces into invariant mass elements. We try to disentangle effects due to ``canonical suppression'' and ``core-corona separation'', which will both lead to a reduction of the yields at low multiplicity
Is 70 Zn(d,x) 67 Cu the best way to produce 67 Cu for medical applications ?
No full textInternational audienceA study of the production of 67Cu while limiting the production of 64Cu, its main contaminant, was performed. The 70Zn(d,x) reaction was identified to achieve high purity. 70Zn-enriched electrodeposited targets were fabricated to measure cross-sections and determine yields
The ionization yield in a methane-filled spherical proportional counter
No full textInternational audienceSpherical proportional counters (SPCs) are gaseous particle detectors sensitive to single ionization electrons in their target media, with large detector volumes and low background rates. The \mbox{NEWS-G} collaboration employs this technology to search for low-mass dark matter, having previously performed searches with detectors at the Laboratoire Souterrain de Modane (LSM), including a recent campaign with a 135 cm diameter SPC filled with methane. While in situ calibrations of the detector response were carried out at the LSM, measurements of the mean ionization yield and fluctuations of methane gas in SPCs were performed using a 30 cm diameter detector. The results of multiple measurements taken at different operating voltages are presented. A UV laser system was used to measure the mean gas gain of the SPC, along with and aluminum-fluorescence calibration sources. These measurements will inform the energy response model of future operating detectors
First polarisation measurement of coherently photoproduced J/ in ultra-peripheral PbPb collisions at = 5.02 TeV
No full textInternational audienceThe first measurement of the polarisation of coherently photoproduced J/ mesons in ultra-peripheral PbPb collisions, using data at TeV, is presented. The J/ meson is measured via its dimuon decay channel in the forward rapidity interval using the ALICE detector at the CERN LHC. An event sample corresponding to an integrated luminosity of 750 5% (syst) is analysed. Hadronic activity is highly suppressed since the interaction is mediated by a photon. The polar and azimuthal angle distributions of the decay muons are measured, and the polarisation parameters , , are extracted. The analysis is carried out in the helicity frame. The results are found to be consistent with a transversely polarised J/. These values are compared with previous measurements by the H1 and ZEUS experiments. The polarisation parameters of coherent J/ photoproduction in PbPb collisions are found to be consistent with the -channel helicity conservation hypothesis
Recent theoretical developments in quarkonia production in relativistic heavy ion collisions
No full textInternational audienceQuarkonium is a golden probe of the heavy ion collisions, which has attracted much attention from both experimental and theoretical sides. In this paper, I will review the recent developments on quarkonium thermal properties and its real-time evolution in heavy ion collisions from the theoretical side
Production de Pb-203 dédiée à l'imagerie médicale
No full textInternational audienceLe plomb-212 (t1/2 = 10,6 h) et le plomb-203 (t1/2 = 51,9 h) peuvent être utilisés comme une paire d'isotopes pour des applications théranostiques en médecine nucléaire. Pb-212 peut être obtenu à partir de la décroissance du thorium-232 et est utilisé pour l'alpha-thérapie [1] alors que Pb-203 peut être produit par irradiation de protons ou de deutérons sur une cible de thallium et permet la tomographie à émission monophotonique (TEMP).La production actuelle de Pb-203 utilise des Tl naturels, Tl-203 enrichi ou Tl-205 enrichi bombardés par un faisceau de protons à une énergie en-dessous de 24 MeV. Cette énergie ne peut être délivrée au GIP ARRONAX. Nous avons alors examiné d’autres voies de production et Pb-203 peut être produit en utilisant un faisceau de deutérons à une énergie de 31 MeV [2] [3]. Pour produire Pb-203 à l’échelle industrielle, un dépôt de Tl-205 enrichi d’une surface de 14 cm2 et d’épaisseur de 40 µm est fabriqué par une technique appelée électrodéposition. C’est une technique qui permet de réduire les cations Tl+ en Tl sur la plaque en or en appliquant les courants entre deux électrodes. Pendant le tir, la cible est inclinée d'un angle de 15° afin d’optimiser la production et elle est refroidie grâce à la circulation de l’eau. Après le tir, la cible est envoyée à l’enceinte blindée pour réaliser les séparations chimiques. Deux résines appelés résine Pb sont utilisées pour à la fois recycler la matière première, Tl-205, et obtenir un produit purifiée contenant Pb-203 dans une solution d’acétate d’ammonium 1 mol/l à pH 5. Depuis septembre 2023, Pb-203 est produit une fois par mois pour une durée de tir de 1h à 1h30 et à une intensité de 60 μA à 70 µA. Au temps de calibration (TC) qui est fixé 2 jours après le tir, la pureté de Pb-203 était supérieure à 99,5% et toutes les radio-impuretés étaient en dessous de la limite de détection de γ-spectrométrie, à l'exception de Pb-201 (moins de 0,5%). En outre, au TC, en moyenne 1500 MBq d'activité de Pb-203 était produite. Cette activité peut être augmentée en augmentant la durée de tir. Le rendement de la séparation chimique de Pb-203 variait de 80% à 90%. Dans la solution purifiée de Pb-203, tous les métaux qui sont susceptibles d’être présents dans la solution (Tl, Pb, Fe, Ni, Au) étaient en dessous de la limite de détection de ICP-OES. Parallèlement, le rendement de la récupération de Tl-205 était supérieur à 90%, ce qui lui permet de recycler plusieurs mois après la décroissance complète de Tl-202. En outre, le radiomarquage a été testé avec le peptide DOTATATE utilisant 250 MBq de Pb-203 par 100 μg de peptide, comparable aux conditions des essais cliniques. Les premiers résultats ont montré que la pureté radiochimique à la fin de la synthèse était de 99% et que la stabilité de l'environnement réactif après 12 heures, 24 heures et 96 heures était supérieure à 98%.Toutes ces valeurs sont prometteuses pour la production à l’échelle industrielle de Pb-203 de haute pureté, et les résultats seront discutés au cours de ma présentation. Notre spécification du produit Pb-203 sera également montrée.[1]B. L. McNeil et al., “Production, purification, and radiolabeling of the 203Pb/212Pb theranostic pair,” EJNMMI radiopharm. chem., vol. 6, no. 1, p. 6, Feb. 2021, doi: 10.1186/s41181-021-00121-4.[2]T. Sounalet et al., “Manufacture of Tl targets by electrodeposition for the study of excitation functions of 203Pb,” EPJ Web Conf., vol. 285, p. 09001, 2023, doi: 10.1051/epjconf/202328509001.[3]T. Sounalet, A. Guertin, F. Haddad, K. Kamalakannan, and E. Nigron, “Production of 203Pb from enriched 205Tl using deuteron beams,” Applied Radiation and Isotopes, p. 111190, Jan. 2024, doi: 10.1016/j.apradiso.2024.111190
Radiation stability and durability of magnesium phosphate cement for radioactive reactive metals encapsulation
No full textInternational audienceThe encapsulation of Radioactive Reactive Metallic Waste (RRMW) in ordinary Portland cement poses significant challenges due to its incompatibility with the alkaline environment of the matrix. To address this issue, magnesium phosphate cements (MPC) emerge as potential solutions for the safe and effective immobilisation of RRMWs. The radiation stability and durability of an optimised formulation have been examined for samples irradiated up to 1000 kGy, in particular concerning the leaching behaviour of the three main constituents of the cement hydration products, and on four artificially added elements used to simulate radionuclides commonly found in radioactive waste (caesium, strontium, europium, and cobalt). The mortars exhibited excellent leaching behaviour and a high mechanical resistance, even after irradiation, freeze-thaw cycles, and water immersion. No significant radiation-induced effects were observed in the mineralogical and microstructural properties of the mortars, thus supporting their stability at the examined doses. Having verified the compliance with the main Italian waste acceptance criteria, the results of this research represent an encouraging step for the future implementation of MPCs for RRMWs conditioning