SUBA-Jet: a new Model for Jets in Heavy Ion Collisions

International audienceWe present a new model for jet quenching in a quark gluon plasma (QGP). The jet energy loss has two steps. The initial jet parton with a high virtuality loses energy by a perturbative vacuum parton shower modified by medium interactions until it becomes on shell. Subsequent energy loss originates from elastic and radiative collisions with the medium constituents. Coherency of the radiative collisions is achieved by starting with virtual gluons that act as field dressing of the initial jet parton. These are formed according to a Gunion-Bertsch seed. The QCD version of the LPM effect is obtained by increasing the phase of the virtual gluons through elastic scatterings with the medium. Above a phase threshold, the virtual gluons will be formed and can produce coherent radiation themselves. The model has been implemented in a Monte Carlo code and is validated by successfully reproducing the BDMPS-Z prediction for the energy spectrum of radiated gluons in a static medium. Results for the more realistic case, in which the assumptions of the BDMPS-Z approach are released, are also shown. We investigate the influence of various parameters on the energy spectrum and the transverse momentum distribution, such as the in-medium quark masses, the energy transfer in the recoil process, and the phase accumulation criteria, especially for low and intermediate energy gluons

Longitudinal ternary fission

International audienceThe longitudinal ternary fission is studied using the generalized liquid drop model. The proximity energy and the charge and mass asymmetries are taken into account. Spherical parent and daughter nuclei are considered. The shape sequence selected to simulate the quasimolecular three-body shapes is built from different but connected elliptic half lemniscatoids. The potential barriers are much lower when the central fragment is the smallest one and particularly when it is an α particle. The 2α emission can be described as a particular prolate fission with emission of two particles at the tips of the deformed nucleus. The associated potential barriers are high and thin

Methodology for small animals targeted irradiations at conventional and ultra-high dose rates 65 MeV proton beam

International audienceAs part of translational research projects, mice may be irradiated on radiobiology platforms such as the one at the ARRONAX cyclotron. Generally, these platforms do not feature an integrated imaging system. Moreover, in the context of ultra-high dose-rate radiotherapy (FLASH-RT), treatment planning should consider potential changes in the beam characteristics and internal movements in the animal. A patient-like set-up and methodology has been implemented to ensure target coverage during conformal irradiations of the brain, lungs and intestines. In addition, respiratory cycle amplitudes were quantified by fluoroscopic acquisitions on a mouse, to ensure organ coverage and to assess the impact of respiration during FLASH-RT using the 4D digital phantom MOBY. Furthermore, beam incidence direction was studied from mice µCBCT and Monte Carlo simulations. Finally,in vivo dosimetry with dose-rate independent radiochromic films (OC-1) and their LET dependency were investigated. The immobilization system ensures that the animal is held in a safe and suitable position. The geometrical evaluation of organ coverage, after the addition of the margins around the organs, was satisfactory. Moreover, no measured differences were found between CONV and FLASH beams enabling a single model of the beamline for all planning studies. Finally, the LET-dependency of the OC-1 film was determined and experimentally verified with phantoms, as well as the feasibility of using these filmsin vivoto validate the targeting. The methodology developed ensures accurate and reproducible preclinical irradiations in CONV and FLASH-RT without in-room image guidance in terms of positioning, dose calculation and in vivo dosimetry

ALICE luminosity determination for Pb−-Pb collisions at sNN=5.02\sqrt{s_{\mathrm{NN}}} = 5.02 TeV

International audienceLuminosity determination within the ALICE experiment is based on the measurement, in van der Meer scans, of the cross sections for visible processes involving one or more detectors (visible cross sections). In 2015 and 2018, the Large Hadron Collider provided Pb–Pb collisions at a centre-of-mass energy per nucleon pair of √s$_{NN}$ = 5.02 TeV. Two visible cross sections, associated with particle detection in the Zero Degree Calorimeter (ZDC) and in the V0 detector, were measured in a van der Meer scan.This article describes the experimental set-up and the analysis procedure, and presents the measurement results. The analysis involves a comprehensive study of beam-related effects and an improved fitting procedure, compared to previous ALICE studies, for the extraction of the visible cross section. The resulting uncertainty of both the ZDC-based and the V0-based luminosity measurement for the full sample is 2.5%. The inelastic cross section for hadronic interactions in Pb–Pb collisions at √s$_{NN}$ = 5.02 TeV, obtained by efficiency correction of the V0-based visible cross section, was measured to be 7.67 ± 0.25 b, in agreement with predictions using the Glauber model

Relationships between absorbed dose and proton energy with bremsstrahlung spectra for in vivo dosimetry of preclinical hadrontherapy

International audienceContext: The ARRONAX cyclotron preclinical platform was upgraded to enable irradiations of mice with 70 MeV proton beams [1]. Currently, radiochomic films are used for online comparison with the simulated dose distribution after the irradiation but do not provide online verification. Hence, this study proposes to use the bremsstrahlung X-rays emitted by the medium as an in vivo dosimetry method. Previous studies have demonstrated the feasibility of using the bremsstrahlung yield to monitor the delivered dose at the entrance of a several-mm-thick PMMA phantom using a silicon drift detector SDD, with maximal intrinsic efficiency on the range 1-10 keV [2]. In addition, Ralite et al. have shown the yield's dependence on the beam energy and, therefore, the possibility of monitoring the incident beam energy.Material and Methods: In this work, an additional CdTe detector was used to detect X-ray energy up to 100 keV to access a broader spectrum, enabling a precise quantification of the main components of the bremsstrahlung, the Quasi Free Electron Bremsstrahlung (QFEB) (up to 37 keV for 70 MeV protons) and the Secondary Electron Bremsstrahlung (SEB) (mainly under 100 keV). Several calibrated tissue substitute cylinders (solid water, breast, lungs, bone - Gammex-RMI, WI, USA) were irradiated to investigate the spectrum dependencies on medium density and effective atomic number with proton energy. The information on dose and energy have been simulated with the code Monte Carlo GATE. The diameter of the cylinders is 28 mm, mimicking the mouse size, and the beam spot was 10 mm. The cylinders were positioned on a motorized translational axis in the beam propagation direction, and the detectors were shielded with lead to scan in depth by 5 mm slices.Results: Spectra at different depths and in various materials were acquired with both detectors. The method's sensitivity to dose was studied, and despite medium auto-attenuation, the bremsstrahlung X-rays were detected even in the Bragg peak region. Moreover, several characteristics of the bremsstrahlung spectrum (mean energy, FWHM, etc.) were studied to establish a direct link with the beam energy in the medium and its chemical composition.Conclusion and perspectives: This work is a comprehensive experimental study of bremsstrahlung spectra dependencies, for preclinical in vivo dosimetry verification. Analytical and Monte Carlo simulations will be used to optimize experimental set-up and to provide information on absorbed dose maps in mice, in relation to bremsstrahlung spectra, allowing the online comparison with treatment planning in a preclinical context.[1] M. Evin et al.,« Methodology for small animals targeted irradiations at conventional and ultra-high dose rates 65 MeV proton beam », Physica Medica, vol. 120, p. 103332, avr. 2024, doi: 10.1016/j.ejmp.2024.103332.[2] F. Ralite et al., « Bremsstrahlung X-rays as a non-invasive tool for ion beam monitoring », NIM-B, vol. 500-501, p. 76-82, août 2021, doi: 10.1016/j.nimb.2021.05.013

Investigating the interaction of uranium(VI) with diatoms and their bacterial community: A microscopic and spectroscopic study

International audienceDiatoms and bacteria play a vital role in investigating the ecological effects of heavy metals in the environment. Despite separate studies on metal interactions with diatoms and bacteria, there is a significant gap in research regarding heavy metal interactions within a diatom-bacterium system, which closely mirrors natural conditions. In this study, we aim to address this gap by examining the interaction of uranium(VI) (U(VI)) with Achnanthidium saprophilum freshwater diatoms and their natural bacterial community, primarily consisting of four successfully isolated bacterial strains (Acidovorax facilis, Agrobacterium fabrum, Brevundimonas mediterranea, and Pseudomonas peli) from the diatom culture. Uranium (U) bio-association experiments were performed both on the xenic A. saprophilum culture and on the four bacterial isolates. Scanning electron microscopy and transmission electron microscopy coupled with spectrum imaging analysis based on energy-dispersive X-ray spectroscopy revealed a clear co-localization of U and phosphorus both on the surface and inside A. saprophilum diatoms and the associated bacterial cells. Time-resolved laser-induced fluorescence spectroscopy with parallel factor analysis identified similar U(VI) binding motifs both on A. saprophilum diatoms and the four bacterial isolates. This is the first work providing valuable microscopic and spectroscopic data on U localization and speciation within a diatom-bacterium system, demonstrating the contribution of the co-occurring bacteria to the overall interaction with U, a factor non-negligible for future modeling and assessment of radiological effects on living microorganisms

Microvolume analysis of 226Ra by inductively coupled plasma mass spectrometry: Environmental applications to high-resolution profile of wetland soil pore waters

International audienceBackground: The release to the environment of natural radionuclides like 226Ra due to human activities haveraised concerns about human and ecosystem exposure. 226Ra’s resemblance to calcium and involvement inbiological processes accentuate the importance of understanding its geochemical behavior and migrationpathways. Soil and sediment pore waters provide valuable information but have proved to be challenging toanalyze, requiring to push the limits of current sample preparation and detection methods often not scaled forlow concentrated microvolumes of samples. A more efficient and accurate analytical method is therefore neededto get reliable data to support hydro-geochemical modeling.Results: We describe here a novel comprehensive approach for accurate 226Ra quantification in pore waters of awetland located downstream of the former Rophin uranium mine. In order to highlight the migration of 226Rabetween the different soil layers, microvolumes of soil pore waters were in situ sampled up to 50 cm depthemploying Diffusive Equilibrium in Thin-Films (DET) probes. The workflow included spiking DET extracts withan in-house 228Ra tracer, specific solid-phase extraction with 50 mg of AnaLig Ra-01® resin, and elution fractioncalcination. This process eliminated interferences and simplify the analysis matrix. Quantification relied onisotope dilution after measurement by ICP-MS hyphenated to a desolvator module and to a microsampler (150 µLinjection). The resulting 1 cm-high-resolution profile revealed unusual 226Ra enrichment with depth, signs of Ramobility from the solid contamination source. These elements are essential for assessing 226Ra distribution coefficients across soil horizons and subsequent wetland remobilization considerations.Significance and novelty: This first methodological advance for 226Ra constitutes a significant step to understand 226Ra behavior i.e., to quantify its activity level, fluxes inside of wetland soils or at the interface overlyingwaters/sediments. Its potential extension to studies involving other elements underscores its broader applicability in environmental research. The findings contribute to evidence-based decision-making for environmentalprotection and management, aiding in the preservation of ecological integrity and human health

Multi-particle cumulant J/psi v_{2} measurement in Pb--Pb with the ALICE experiment

National audienc

Higher-order symmetry plane correlations in Pb−-Pb collisions at sNN\sqrt{s_{\mathrm{NN}}} = 5.02 TeV

International audienceThe correlations between event-by-event fluctuations of symmetry planes are measured in Pb$-$Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian Estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the non-linear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information - independent of flow amplitudes - their usage in future model developments can further constrain the properties of the strongly-interacting matter created in ultrarelativistic heavy-ion collisions

Tracing the impact of former uranium mine sites using stable Pb isotopes: A review

International audienceTracing pollution originating from uranium (U) mining activities is a key challenge due to the diversity of U sources (geochemical background versus U-ore) and its daughter radionuclides. Among the available tracers that can be used to highlight the impact of these activities on the environment, the application of Pb stable isotopes is relevant. This paper is an overview of the use of Pb isotopes for tracing U-mining impacts due to mining and milling activities. For this purpose, this work outlines the different Pb isotope sources in the environment with a focus on the primary U-rich ores until the mineralized area. This information is an important prerequisite for the understanding of Pb fate during the physical and chemical processing of U-ores. Moreover, an important review regarding the Pb isotope composition of the different types of U mining waste is carried out. Finally, an additional part of analytical procedures including sample preparation and Pb isotopic analysis are also be presented