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Assessment of Heavy Metal Contamination of the Environment in the Mining Site of Ouixane (North East Morocco)
No full textInternational audienceThis study aims to assess the metallic contamination of soils and water resources in the environment of the Ouixane mining area (North East Morocco). Six metallic elements (Fe, Cu, Pb, Zn, Ni, and Cd) were analyzed by ICP-AES and ICP-MS. To evaluate the contamination of the soils, three contamination assessment methods were used as follows: enrichment factor (EF), pollution index (PI), and geo-accumulation index (Igeo). The results showed that the soils of the studied area are highly enriched in metallic elements Cd, Cu, Zn, and Pb. Thus, the enrichment factor (EF) revealed an anthropogenic contamination of the majority of studied soils with an extreme contamination by Cd (EFm = 59.29), Cu (EFm = 45.93), and Zn (EFm = 44.73). The results of PI revealed extreme contamination by Cu (PIm = 7.12) and considerable contamination by Zn (PIm = 5.61), Cd (PIm = 4.83), Fe (PIm = 3.09), and Pb (PIm = 3). The Igeo results showed strong contamination for most of the metallic elements and extreme accumulation for Cu and Zn in the Axara-Imnassen lake and the valley located downstream from the Ouixane deposit. Depressions and lakes are highly contaminated by heavy metals due to the leaching phenomenon of surrounding geological formations rich in sulfides. The significant leaching of metallic elements (Cu, Pb, Zn, Ni…) led to significant acid mine drainage (AMD). On the other hand, the geochemistry of the water samples revealed the transfer of metallic pollutants to the water resources which become very acidic locally. Using the contamination degree index (Cd), surface water was found to be highly contaminated by heavy metals (Cd > 3) compared to well water (1 < Cd < 3). Contamination assessment indices combined with the geographic information system (GIS) have been used successfully to identify the most polluted sites
Pseudorapidity distributions of charged particles as a function of mid- and forward rapidity multiplicities in pp collisions at = 5.02, 7 and 13 TeV
No full textInternational audienceThe multiplicity dependence of the pseudorapidity density of charged particles in proton–proton (pp) collisions at centre-of-mass energies , 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range (). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval . The multiplicity dependence of the pseudorapidity density of charged particles is measured with mid- and forward rapidity multiplicity estimators, the latter being less affected by autocorrelations. A detailed comparison with predictions from the PYTHIA 8 and EPOS LHC event generators is also presented. The results can be used to constrain models for particle production as a function of multiplicity in pp collisions
Search for signatures of sterile neutrinos with Double Chooz
No full textInternational audienceWe present a search for signatures of neutrino mixing of electron anti-neutrinos with additional hypothetical sterile neutrino flavors using the Double Chooz experiment. The search is based on data from 5 years of operation of Double Chooz, including 2 years in the two-detector configuration. The analysis is based on a profile likelihood, i.e. comparing the data to the model prediction of disappearance in a data-to-data comparison of the two respective detectors. The analysis is optimized for a model of three active and one sterile neutrino. It is sensitive in the typical mass range for mixing angles down to . No significant disappearance additionally to the conventional disappearance related to is observed and correspondingly exclusion bounds on the sterile mixing parameter as a function of are obtained
The influence of iodide on glass transition temperature of high‐pressure nuclear waste glasses
No full textInternational audienceThe glass transition temperature (Tg) is a key parameter to investigate for application in nuclear waste immobilization in borosilicate glasses. Tg for several glasses containing iodine (I) has been measured in order to determine the I effect on Tg. Two series of glass composition (ISG and NH) containing up to 2.5 mol% I and synthesized under high pressure (0.5 to 1.5 GPa) have been investigated using differential scanning calorimetry (DSC). The I local environment in glasses has been determined using X‐ray photoelectron spectroscopy and revealed that I is dissolved under its iodide form (I−). Results show that Tg is decreased with the I addition in the glass in agreement with previous results. We also observed that this Tg decrease is a strong function of glass composition. For NH, 2.5 mol% I induces a decrease of 24°C in Tg, whereas for ISG, 1.2 mol% decreases the Tg by 64°C. We interpret this difference as the result of the I dissolution mechanism and its effect on the polymerization of the boron network. The I dissolution in ISG is accompanied by a depolymerization of the boron network, whereas it is the opposite in NH. Although ISG corresponds to a standardized glass, for the particular case of I immobilization it appears less adequate than NH considering that the decrease in Tg for NH is small in comparison to ISG
Assessment of strategy robustness under disruption of objective in dynamic fuel cycle studies
No full textInternational audienceThe future of nuclear power depends on the interests and decisions. To take the relevant deep uncertainty into account, a new methodology of robustness analysis of fuel cycle strategies has been developed. The method has been applied to the French cycle, considering the future deployment of fast reactor as the pre-selected objective and an uncertain change, called disruption, towards a new objective: the minimization of transuranic inventories without fast reactor. The status of plutonium is contradictory in two cases. Two approaches of identifying robust strategies were tested, which correspond respectively to the static and adaptive robustness assessment. One identifies static strategies in a pre-disruption scenario, which achieve acceptable outcomes for both objectives. The other takes a trajectory pursuing the pre-selected objective and, in case of disruption, adapts it for the new objective. The comparison of two approaches indicates the temporality of adaptation relative to immediate actions under the uncertain disruptio
First measurement of the ||-dependence of coherent photonuclear production
No full textInternational audienceThe first measurement of the cross section for coherent J/ψ photoproduction as a function of |t| , the square of the momentum transferred between the incoming and outgoing target nucleus, is presented. The data were measured with the ALICE detector in ultra-peripheral Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV with the J/ψ produced in the central rapidity region |y|<0.8 , which corresponds to the small Bjorken- x range (0.3−1.4)×10−3 .The measured |t| -dependence is not described by computations based only on the Pb nuclear form factor, while the photonuclear cross section is better reproduced by models including shadowing according to the leading-twist approximation, or gluon-saturation effects from the impact-parameter dependent Balitsky–Kovchegov equation. These new results are therefore a valid tool to constrain the relevant model parameters and to investigate the transverse gluonic structure at very low Bjorken- x
Performance of CVD diamond detectors for single ion beam-tagging applications in hadrontherapy monitoring
No full text14 pages, 9 figuresInternational audienceIn the context of online ion range verification in particle therapy, the CLaRyS collaboration is developing Prompt-Gamma (PG) detection systems. The originality in the CLaRyS approach is to use a beam-tagging hodoscope in coincidence with the gamma detectors to provide both temporal and spatial information of the incoming ions. The ion range sensitivity of such PG detection systems could be improved by detecting single ions with a 100 ps (sigma) time resolution, through a quality assurance procedure at low beam intensity at the beginning of the treatment session. This work presents the investigations led to assess the performance of Chemical Vapor Deposition (CVD) diamond detectors to fulfill these requirements. A 90Sr beta source, 68 MeV protons, 95 MeV/u carbon ions and a synchrotron X-ray pulsed beam were used to measure the time resolution, single ion detection efficiency and proton counting capability of various CVD diamond samples. An offline technique, based on double-sided readout with fast current preamplifiers and used to improve the signal-to-noise ratio, is also presented. The different tests highlighted Time-Of-Flight resolutions ranging from 13 ps (Sigma) to 250 ps (Sigma), depending on the experimental conditions. The single 68 MeV proton detection efficiency of various large area polycrystalline (pCVD) samples was measured to be >96% using coincidence measurements with a single-crystal reference detector. Single-crystal CVD (sCVD) diamond proved to be able to count a discrete number of simultaneous protons while it was not achievable with a polycrystalline sample. Considering the results of the present study, two diamond hodoscope demonstrators are under development: one based on sCVD, and one of larger size based on pCVD. They will be used for the purpose of single ion as well as ion bunches detection, either at reduced or clinical beam intensities
Measurement of the Cross Sections of and Baryons and of the Branching-Fraction Ratio BR()/BR() in pp collisions at 13 TeV
No full textInternational audienceThe pT-differential cross sections of prompt charm-strange baryons Ξc0 and Ξc+ were measured at midrapidity (|y|<0.5) in proton-proton (pp) collisions at a center-of-mass energy s=13 TeV with the ALICE detector at the LHC. The Ξc0 baryon was reconstructed via both the semileptonic decay (Ξ-e+νe) and the hadronic decay (Ξ-π+) channels. The Ξc+ baryon was reconstructed via the hadronic decay (Ξ-π+π+) channel. The branching-fraction ratio BR(Ξc0→Ξ-e+νe)/BR(Ξc0→Ξ-π+)=1.38±0.14(stat)±0.22(syst) was measured with a total uncertainty reduced by a factor of about 3 with respect to the current world average reported by the Particle Data Group. The transverse momentum (pT) dependence of the Ξc0- and Ξc+-baryon production relative to the D0 meson and to the Σc0,+,++- and Λc+-baryon production are reported. The baryon-to-meson ratio increases toward low pT up to a value of approximately 0.3. The measurements are compared with various models that take different hadronization mechanisms into consideration. The results provide stringent constraints to these theoretical calculations and additional evidence that different processes are involved in charm hadronization in electron-positron (e+e-) and hadronic collisions
Corrélations angulaires azimutales entre les mésons D*+ et les hadrons chargés dans les collisions proton-proton à 13 TeV avec l'expérience ALICE au LHC
No full textCollisions of heavy-ions at ultra-relativistic speeds allow for the creation of a new state of matter where quarks and gluons are deconfined in the so-called Quark-Gluon Plasma (QGP). It is believed that such a state of matter was present in our Universe a few microseconds after the Big Bang. The QGP properties are studied by means of probes. Heavy quarks (charm and beauty) are among the most suitable probes since, due to their large masses, are produced early in the collision and therefore they witness the full evolution of the system while losing energy in the QGP via collisional and radiative processes. The measurements of heavy quarks production and of their azimuthal correlation with lighter particles in small systems (proton-proton and proton-ion collisions) constitute a stringent test of perturbative Quantum Chromodynamics (pQCD) and a mandatory reference for the heavy-ion measurements in order to disentangle cold and hot nuclear matter effects. In this manuscript, we investigate the azimuthal correlations of charmed mesons (D*, D⁰, D⁺) with charged particles. The study is performed on real data and simulation for different collision energies. The proton-proton data used were collected by the ALICE Collaboration at CERN Large Hadron Collider while the simulation studies are performed with PYTHIA8 and EPOS3/EPOS@sHQ event generators. By means of correlation studies, we aim to shed light on the heavy-quarks production mechanisms setting constraints to pQCD calculations. At the same time, we build the necessary reference for future D mesons correlation studies in heavy-ion collisions targeted to investigate charm and beauty in medium energy loss.Les collisions d'ions lourds à des vitesses ultra-relativistes permettent la création d'un nouvel état de la matière où les quarks et les gluons sont déconfinés dans ce qu'on appelle le Plasma Quark-Gluon (QGP). On pense qu'un tel état de la matière était présent dans notre Univers quelques microsecondes après le Big Bang. Les propriétés QGP sont étudiées au moyen de sondes. Les quarks lourds (charme et beauté) sont parmi les sondes les plus appropriées car, en raison de leurs masses importantes, sont produits tôt dans la collision et par conséquent, ils témoignent à la pleine évolution du système tout en perdant de l'énergie dans le QGP via des processus collisionnels et radiatifs. Les mesures de la production de quarks lourds et de leur corrélation azimutale avec des particules plus légères dans de petits systèmes (collisions proton-proton et proton-ion) constituent un test rigoureux de Chromodynamique Quantique perturbatrice (pQCD) est une référence obligatoire pour les mesures d'ions lourds afin de démêler les effets de la matière nucléaire froide et chaude. Dans ce manuscrit, nous étudions les corrélations azimutales de mésons charmés (D*, D⁰, D⁺) avec des particules chargées. L'étude est réalisée sur des données réelles et une simulation pour différentes énergies de collision. Les données proton-proton utilisées ont été collectées par la collaboration ALICE au CERN Large Hadron Collider tandis que les études de simulation sont réalisées avec les générateurs d'événements PYTHIA8 et EPOS3/EPOS@sHQ. Au moyen d'études de corrélation, nous visons à faire la lumière sur les mécanismes de production de quarks lourds imposant des contraintes aux calculs de pQCD. Dans le même temps, nous construisons la référence nécessaire pour les futures études de corrélation des mésons D dans les collisions d'ions lourds visant à étudier le charme et la beauté dans la perte d'énergie moyenne
Quarkonium dynamics inside the Quark-Gluon Plasma using open quantum systems
No full textInternational audienceIn recent years, a significant theoretical effort has been made towards a dynamical description of quarkonia inside the Quark-Gluon Plasma (QGP), using the open quantum systems formalism. In this framework, one can get a real-time description of a quantum system (here the quarkonium) in interaction with a thermal bath (the QGP) by integrating out the bath degrees of freedom and studying the system reduced density matrix. We investigate the real-time dynamics of a correlated heavy quark-antiquark pair inside the QGP using a quantum master equation previously derived from first QCD principles in [4]. The full equation is directly resolved in 1D to lessen computing costs and is used for the first time to gain insight on the dynamics in both a static and evolving medium following a Björken-like temperature evolution