HAL Mines Nantes
Not a member yet
7271 research outputs found
Sort by
Measurements of dihadron correlations relative to the event plane in Au+Au collisions at GeV
No full textInternational audienceDihadron azimuthal correlations containing a high transverse momentum ( ) trigger particle are sensitive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium, i.e. jet-quenching. Previous measurements revealed a strong modification to dihadron azimuthal correlations in Au+Au collisions with respect to p+p and d+Au collisions. The modification increases with the collision centrality, suggesting a path-length or energy density dependence to the jet-quenching effect. This paper reports STAR measurements of dihadron azimuthal correlations in mid-central (20%-60%) Au+Au collisions at GeV as a function of the trigger particle's azimuthal angle relative to the event plane, . The azimuthal correlation is studied as a function of both the trigger and associated particle . The subtractions of the combinatorial background and anisotropic flow, assuming Zero Yield At Minimum (ZYAM), are described. The correlation results are first discussed with subtraction of the even harmonic (elliptic and quadrangular) flow backgrounds. The away-side correlation is strongly modified, and the modification varies with , with a double-peak structure for out-of-plane trigger particles. The near-side ridge (long range pseudo-rapidity correlation) appears to drop with increasing while the jet-like component remains approximately constant. The correlation functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluctuations. It is found that the triangular flow, while responsible for the majority of the amplitudes, is not sufficient to explain the -dependence of the ridge or the away-side double-peak structure. The dropping ridge with could be attributed to a -dependent elliptic anisotropy; however, the physics mechanism of the ridge remains an open question. Even with a -dependent elliptic flow, the away-side correlation structure is robust. These results, with extensive systematic studies of the dihadron correlations as a function of , trigger and associated particle , and the pseudo-rapidity range , should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions
The ARRONAX platform for proton FLASH irradiation: From beam production to the target
No full textInternational audienc
Proton beam dosimetry at ultra high dose rates: evaluation of the usability and the dose rate dependency of various radiochromic films
No full textInternational audienc
Mesure de la production des mésons ϒ dans les collisions proton–proton et Pb–Pb à √s_(NN) = 5.02 TeV avec l'expérience ALICE au LHC
No full textUltrarelativistic heavy-ion collisions lead to the emergence of an extreme state of matter, the quark-gluon plasma or QGP. Formed at the early stage of the collision, quarkonia, resonances of two quarks of the same heavy flavour, interact with the medium throughout its evolution. Depending on the intensity of the mechanisms at play, the pairs are dissociated and the final-state production rate is thus suppressed. The measurement of this suppression offers a privileged access to QGP features. In particular, the production of quarkonia in heavy-ion collisions is commonly advertised as a key observable of the modification of the strong interaction. This thesis is devoted to the study of the Υ production in Pb–Pb collisions at √sNN = 5.02 TeV at the LHC. The Υ(nS) mesons are reconstructed via their decay into muon pairs detected by the ALICE muon spectrometer. The results indicate a strong suppression of the Υ(1S) production, increasing from peripheral towards more central collisions. For the first time, the Υ(2S) excited state can be measured at forward rapidity in nucleus–nucleus collisions. The comparison with predictions by phenomenological models allows to interpret the measurements and to constrain the suppression mechanisms of quarkonia.Les collisions d’ions lourds ultra-relativistes mène à l’émergence d’un état extrême de la matière, le plasma de quarks et de gluons ou QGP. Formés aux premiers instants de la collision, les quarkonia, résonances de deux quarks de même saveur lourde, interagissent avec le milieu tout au long de son évolution. Selon l’intensité des mécanismes en jeu, les paires sont dissociées et le taux de production est donc supprimé. La mesure de cette suppression offre un accès privilégié aux caractéristiques du QGP. En particulier, la production de quarkonia dans les collisions d’ions lourds est communément avancée comme une observable clé de la modification de l’interaction forte.Cette thèse porte sur l’étude de la production du méson Υ en collisions Pb–Pbà √sNN = 5.02 TeV au LHC. Les mésons Υ(nS) sont reconstruits à travers leur désintégration en paire de muons détectés parle spectromètre à muon d’ALICE. Les résultats montrent une forte suppression de la production de Υ(1S), augmentant des collisions périphériques aux plus centrales. L’état excité Υ(2S) est pour la première fois mesuré à rapidité avant dans des collisions noyau–noyau. La comparaison avec des prédictions de modèles phénoménologiques permettent d’interpréter les mesures et de contraindre les mécanismes de suppression des quarkonia
Chapter 2. Atomistic modeling of clays and related nanoporous materials with ClayFF force field
No full textThe paper is based on the material of two invited lectures given by the author at the AIPEASchool for Young Scientists “Computational Modeling In Clay Mineralogy”, Granada, Spain, July2017, and the Workshop “Argilla Studium-2019”, Moscow, Russia, November 2019International audienceThe Chapter is based on the material of two invited lectures given by the author at the AIPEA School for Young Scientists “Computational Modeling In Clay Mineralogy”, Granada, Spain, July 2017, and the Workshop “Argilla Studium-2019”, Moscow, Russia, November 2019
Radio-detection of neutrino-induced air showers: the influence of topography
No full textInternational audienceNeutrinos of astrophysical origin could be detected through the electromagnetic radiation of the particle showers induced in the atmosphere by their interaction in the Earth. This applies in particular for tau neutrinos of energies E > 10 16 eV following Earth-skimming trajectories. The ∼1° beaming of the radio emission in the forward direction however implies that the radio signal will likely fly above a detector deployed over a flat site and would therefore not be detected
Beta-decay studies for applied and basic nuclear physics
No full textInternational audienceIn this review we will present the results of recent -decay studies using the total absorption technique that cover topics of interest for applications, nuclear structure and astrophysics. The decays studied were selected primarily because they have a large impact on the prediction of (a) the decay heat in reactors, important for the safety of present and future reactors and (b) the reactor electron anti-neutrino spectrum, of interest for particle/nuclear physics and reactor monitoring. For these studies the total absorption technique was chosen, since it is the only method that allows one to obtain -decay probabilities free from a systematic error called the Pandemonium effect. The total absorption technique is based on the detection of the cascades that follow the initial decay. For this reason the technique requires the use of calorimeters with very high detection efficiency. The measurements presented and discussed here were performed mainly at the IGISOL facility of the University of Jyväskylä (Finland) using isotopically pure beams provided by the JYFLTRAP Penning trap. Examples are presented to show that the results of our measurements on selected nuclei have had a large impact on predictions of both the decay heat and the anti-neutrino spectrum from reactors. Some of the cases involve -delayed neutron emission thus one can study the competition between - and neutron-emission from states above the neutron separation energy. The -to-neutron emission ratios can be used to constrain neutron capture (n,) cross sections for unstable nuclei of interest in astrophysics. The information obtained from the measurements can also be used to test nuclear model predictions of half-lives and Pn values for decays of interest in astrophysical network calculations. These comparisons also provide insights into aspects of nuclear structure in particular regions of the nuclear chart
Pion-kaon femtoscopy and the lifetime of the hadronic phase in PbPb collisions at = 2.76 TeV
No full textInternational audienceIn this paper, the first femtoscopic analysis of pion–kaon correlations at the LHC is reported. The analysis was performed on the Pb–Pb collision data at sNN=2.76 TeV recorded with the ALICE detector. The non-identical particle correlations probe the spatio-temporal separation between sources of different particle species as well as the average source size of the emitting system. The sizes of the pion and kaon sources increase with centrality, and pions are emitted closer to the centre of the system and/or later than kaons. This is naturally expected in a system with strong radial flow and is qualitatively reproduced by hydrodynamic models. ALICE data on pion–kaon emission asymmetry are consistent with (3+1)-dimensional viscous hydrodynamics coupled to a statistical hadronisation model, resonance propagation, and decay code THERMINATOR 2 calculation, with an additional time delay between 1 and 2 fm/ c for kaons. The delay can be interpreted as evidence for a significant hadronic rescattering phase in heavy-ion collisions at the LHC
Investigation on the injection of the Arronax Cyclotron 70XP
No full textInternational audienceA 70 MeV cyclotron is being used at the Arronax GIP (Interest Public Group), France, for various types of R&D on nuclear, biological and chemical reactions with beams and radioisotopes production. In order to adapt its usage for experiments and users demands of high peak intensity, above an equivalent average of a few µA, the injection is being adapted. Several studies are thus being performed in this section. These include the newly installed chopper-based system and the injection collimator. This paper details the various studies, specifically the signal purity obtained in the pulsed mode. A mode particularly adapted for flash irradiation
