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Measurements of the groomed and ungroomed jet angularities in pp collisions at = 5.02 TeV
No full textInternational audienceThe jet angularities are a class of jet substructure observables which characterize the angular and momentum distribution of particles within jets. These observables are sensitive to momentum scales ranging from perturbative hard scatterings to nonperturbative fragmentation into final-state hadrons. We report measurements of several groomed and ungroomed jet angularities in pp collisions at = 5.02 TeV with the ALICE detector. Jets are reconstructed using charged particle tracks at midrapidity (|η| < 0.9). The anti-k algorithm is used with jet resolution parameters R = 0.2 and R = 0.4 for several transverse momentum {p}_{\mathrm{T}}^{\mathrm{ch}} ^{jet} intervals in the 20–100 GeV/c range. Using the jet grooming algorithm Soft Drop, the sensitivity to softer, wide-angle processes, as well as the underlying event, can be reduced in a way which is well-controlled in theoretical calculations. We report the ungroomed jet angularities, λ, and groomed jet angularities, λ, to investigate the interplay between perturbative and nonperturbative effects at low jet momenta. Various angular exponent parameters α = 1, 1.5, 2, and 3 are used to systematically vary the sensitivity of the observable to collinear and soft radiation. Results are compared to analytical predictions at next-to-leading-logarithmic accuracy, which provide a generally good description of the data in the perturbative regime but exhibit discrepancies in the nonperturbative regime. Moreover, these measurements serve as a baseline for future ones in heavy-ion collisions by providing new insight into the interplay between perturbative and nonperturbative effects in the angular and momentum substructure of jets. They supply crucial guidance on the selection of jet resolution parameter, jet transverse momentum, and angular scaling variable for jet quenching studies.[graphic not available: see fulltext
BeaQuant, un autoradiographe numérique au service de la production de radionucléides pour des applications en médecine nucléaire
No full textInternational audienceOne of the main difficulties in the development of radionuclides in nuclear medicine is related to the optimization of their production. As these are, in most cases, produced using a nuclear reactor or a particle accelerator, it is important to define optimal production methods in order to obtain a final product with the highest possible isotopic and chemical purity. In addition to production and distribution challenges, incomplete identification and spectroscopic characterization can sometimes be a limiting factor in determining the full potential of a radionuclide. This is particularly the case for heavy Auger radionuclides (Z>40) where the number of Auger electrons emitted remains a theoretical value [1].The BePAT project aims to demonstrate that it is possible to overcome these limitations by using a digital autoradiograph. Thus, through the exploratory study of the theragnostic β+/Auger couple, iridium, 187 and 189, we want to show that it is possible to identify and distinguish contaminants efficiently. Indeed, the production of these radionuclide with an alpha beam and a natural rhenium foil is inevitably accompanied by the production of contaminants that are difficult to separate chemically, such as iridium, 188 and 190.In parallel, part of the project will focus on the possibility of performing localized α-spectrometry of irradiated targets. While waiting to be able to acquire elements heavier than bismuth again, the project will also focus on astatine-211, the production of which is well-mastered at the GIP ARRONAX site located in Saint-Herblain.[1] D. Filosofov, E. Kurakina, et V. Radchenko, « Potent candidates for Targeted Auger Therapy : Production and radiochemical considerations », Nucl. Med. Biol., vol. 94‑95, p. 1‑19, mars 2021, doi : 10.1016/j.nucmedbio.2020.12.001Funding : Plan de relance - ANR-21-PRRD-0027-0
Revealing the nature of neutrinos with XENON direct dark matter detector and future perspectives
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One-dimensional complex potentials for quarkonia in a quark–gluon plasma
No full textInternational audienceMaster equations of the Lindblad type have recently been derived to describe the dynamics of quarkonium states in the quark–gluon plasma. Because their full resolution in three dimensions is very challenging, the equations are often reduced to one dimension. The main ingredient of these equations is the complex potential that describes the binding of the heavy quark-antiquark pairs and their interactions with the medium. In this work, we propose a one-dimensional complex potential parameterized to reproduce at best two key properties – the temperature-dependent masses of the eigenstates and their decay widths – of a three-dimensional lattice QCD inspired potential. Their spectral decompositions are calculated to check their compatibility with the positivity of the master equations
Comments on noncommutative quantum mechanical systems associated with Lie algebras
No full textInternational audienceWe consider quantum mechanics on the noncommutative spaces characterized by the commutation relations where are the structure constants of a Lie algebra. We note that this problem can be reformulated as an ordinary quantum problem in a commuting momentum space. The coordinates are then represented as linear differential operators . Generically, the matrix represents a certain infinite series over the deformation parameter : . The deformed Hamiltonian, describes the motion along the corresponding group manifolds with the characteristic size of order . Their metrics are also expressed into certain infinite series in , with having the meaning of vielbeins. For the algebras and , it has been possible to represent the operators in a simple finite form. A byproduct of our study are new nonstandard formulas for the metrics on all the spheres , on the corresponding projective spaces and on
Sorption properties of activated carbons for the capture of methyl iodide in the context of nuclear industry
No full textInternational audienceIn the present study, some commercially available activated carbons were evaluated towards the methyl iodide (CH3I) capture in the context of nuclear industry. A specific methodology was implemented in order to establish structure-activity relationships between adsorbent characteristics and its adsorption behavior towards CH3I. On the one hand, the investigated adsorbents were characterized by a combination of physico-chemical techniques. On the other hand, CH3I retention performance from batch sorption tests under different conditions (temperature and relative humidity) was studied using an original experimental setup. In this work, two conditions were investigated: (i) T = 35°C, R.H. = 26 % ([H2O] ∼15,000 ppmv); (ii) T = 75°C, R.H. = 30 % ([H2O] ∼130,000 ppmv). Different trends were obtained depending on the investigated scenario. At ambient conditions (i), CH3I adsorption performance was affected after KI/TEDA impregnation because of partial pore blockage phenomena induced by the of impregnants presence within the microporosity. However, TEDA impregnation was found to be required to enhance the trapping stability and to capture CH3I with superior efficiency at higher temperature (ii)
Strengthened erosion resistance of compacted bentonite by layered double hydroxide: A new electrostatic interaction-based approach
No full textInternational audienceFor the geological repository of high-level radioactive waste (HLW) built in granitic host rock，the control of buffer material (compacted bentonite) erosion and subsequent loss caused by groundwater in granite fissures is an unresolved problem of major concern. We propose here new insight into enhancing the erosion resistance of compacted bentonite by means of its electrostatic interaction with oppositely-charged layered double hydroxide (LDH). The interaction between bentonite and LDH was studied by dropwise addition of colloidal LDH into colloidal bentonite suspension, during which the variation in electrical conductivity, zeta potential and particle size proved a strong interaction between these two materials. Interestingly, in addition to their aggregation, intercalated structures of LDH and montmorillonite were found in the composite (BEN@LDH) by a combined characterization of X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM), and were confirmed by density functional theory (DFT) calculation. Colloid generation of compacted BEN@LDH under ultrasonic conditions is negligible comparing with that of compacted bentonite, indicating a significantly higher erosion resistance. Besides, a small amount of LDH by mechanically mixing with bentonite (mass ratio 1:99) can also effectively improve the erosion resistance of compacted bentonite. Moreover, BEN@LDH displayed stronger retention performance towards U(VI) and Se(IV) than bentonite under near-neutral/weakly alkaline conditions. Our results indicate that LDH is a promising additive in compacted bentonite, and this approach may be extended to common geotechnical structures built with clays and soils
Multiplicity dependence of charged-particle jet production in pp collisions at
No full textInternational audienceThe multiplicity dependence of jet production in pp collisions at the centre-of-mass energy of is studied for the first time. Jets are reconstructed from charged particles using the anti- algorithm with resolution parameters R varying from 0.2 to 0.7. The jets are measured in the pseudorapidity range and in the transverse momentum range . The multiplicity intervals are categorised by the ALICE forward detector V0. The differential cross section of charged-particle jets are compared to leading order (LO) and next-to-leading order (NLO) perturbative quantum chromodynamics (pQCD) calculations. It is found that the data are better described by the NLO calculation, although the NLO prediction overestimates the jet cross section below . The cross section ratios for different R are also measured and compared to model calculations. These measurements provide insights into the angular dependence of jet fragmentation. The jet yield increases with increasing self-normalised charged-particle multiplicity. This increase shows only a weak dependence on jet transverse momentum and resolution parameter at the highest multiplicity. While such behaviour is qualitatively described by the present version of PYTHIA, quantitative description may require implementing new mechanisms for multi-particle production in hadronic collisions