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Anisotropic flow and flow fluctuations of identified hadrons in Pb–Pb collisions at = 5.02 TeV
No full textInternational audienceThe first measurements of elliptic flow of π, K, , , , ϕ, , and using multiparticle cumulants in Pb–Pb collisions at = 5.02 TeV are resented. Results obtained with two- (v{2}) and four-particle cumulants (v{4}) are shown as a function of transverse momentum, p, for various collision centrality intervals. Combining the data for both v{2} and v{4} also allows us to report the first measurements of the mean elliptic flow, elliptic flow fluctuations, and relative elliptic flow fluctuations for various hadron species. These observables probe the event-by-event eccentricity fluctuations in the initial state and the contributions from the dynamic evolution of the expanding quark–gluon plasma. The characteristic features observed in previous p-differential anisotropic flow measurements for identified hadrons with two-particle correlations, namely the mass ordering at low p and the approximate scaling with the number of constituent quarks at intermediate p, are similarly present in the four-particle correlations and the combinations of v{2} and v{4}. In addition, a particle species dependence of flow fluctuations is observed that could indicate a significant contribution from final state hadronic interactions. The comparison between experimental measurements and CoLBT model calculations, which combine the various physics processes of hydrodynamics, quark coalescence, and jet fragmentation, illustrates their importance over a wide p range.[graphic not available: see fulltext
Bottomonium production in pp and heavy-ion collisions
No full textInternational audienceWe study bottomonium production in pp collisions as well as in heavy-ion collisions, using a quantal density matrix approach. The initial bottom (anti)quarks are provided by the PYTHIA event generator. We solve the Schrödinger equation for the pair, identifying the potential with the free energy, calculated with lattice QCD, to obtain the temperature dependent density matrix as well as the dissociation temperature. The formation of bottomonium is given by projection of the bottomonium density matrix onto the density matrix of the system. With this approach we describe the rapidity and transverse momentum distribution of the (1S) and (2S) in pp collisions at 5.02 TeV extending a similar calculation for the charmonium states. We employ the Remler formalism to study the production in heavy ion collisions in which the heavy quarks scatter elastically with partons from the quark gluon plasma (QGP). The elastic scattering of heavy (anti)quark in QGP is realized by the dynamical quasi-particle model (DQPM) and the expanding QGP is modeled by PHSD. We find that a reduction to 20 % of the scattering cross section for a (anti)bottom quark with a QGP parton reproduces the experimental data. This suggests that due to color neutrality the scattering cross section of the small system with a parton is considerably smaller than twice the bottom-parton scattering cross section
Investigation of <math><mrow><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></mrow></math> interactions via femtoscopy in Pb-Pb collisions at <math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>=</mo><mn>2.76</mn></mrow></math> TeV at the CERN Large Hadron Collider
No full textInternational audienceFemtoscopic correlations of nonidentical charged kaons (K+K−) are studied in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision sNN=2.76 TeV by ALICE at the CERN Large Hadron Collider. One-dimensional K+K− correlation functions are analyzed in three centrality classes and eight intervals of particle-pair transverse momentum. The Lednický and Luboshitz interaction model used in the K+K− analysis includes the final-state Coulomb interactions between kaons and the final-state interaction through a0(980) and f0(980) resonances. The mass of f0(980) and coupling were extracted from the fit to K+K− correlation functions using the femtoscopic technique. The measured mass and width of the f0(980) resonance are consistent with other published measurements. The height of the ϕ(1020) meson peak present in the K+K− correlation function rapidly decreases with increasing source radius, qualitatively in agreement with an inverse volume dependence. A phenomenological fit to this trend suggests that the ϕ(1020) meson yield is dominated by particles produced directly from the hadronization of the system. The small fraction subsequently produced by final-state interactions could not be precisely quantified with data presented in this paper and will be assessed in future work
Interaction between carbon steel and low-pH bentonitic cement grout in anoxic, high temperature (80°C) and spatially heterogeneous conditions
No full textInternational audienceAnoxic corrosion processes impacting carbon steel samples for both intimate and imperfect metal/ low-pH bentonitic cement grout (BCG) contacts were studied at 80 °C. SEM, XRD and µ-Raman spectroscopy analyses supported by geochemical modelling allowed a full characterization of the corrosion mechanism. Steel in direct contact with BCG suffered from localized corrosion (pits measuring up to 160 µm in depth after 150 days of exposure) principally triggered by the presence of HS-. Depending on silicate and sulphide ingress from the BCG towards the interface, neoformed magnetite may be converted to iron silicates and/or iron sulphides
Critical net-baryon fluctuations in an expanding system
No full textInternational audienceIn this work we study the consequences of a longitudinal Bjorken expansion and a Hubble-like temperature cooling scenario on a 1+1D non-linear model of the diffusive dynamics of fluctuations in the net-baryon density. The equilibrium behavior of the fluctuations is fully encoded in the temperature dependence of the susceptibilities on the crossover side both in the vicinity of the assumed location of the critical point and at vanishing baryo-chemical potential in-line with lattice QCD calculations. We demonstrate the great sensitivity of the fluctuation observables on the dynamics, in particular on the diffusion length and the freeze-out conditions. While the critical signals are visible and the critical region is broadened by the expansion, a too small diffusion length can strongly reduce the amplitude of the signals. We propose to search for significant anti-correlations of baryons at intermediate rapidity experimentally and to map out the rapidity dependence of the fourth-order cumulant, which in the presence of a critical point (and only in its presence) has a pronounced minimum at intermediate rapidities
JUNO Sensitivity on Proton Decay Searches
No full textInternational audienceThe Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is years, competitive with the current best limits on the proton lifetime in this channel
New experimental ideas at the LHC regarding coherent photo-production in overlap with hadronic interaction and the link with potential QGP studies : "Imaging of Heavy Ion Collisions"
No full textInternational audienceNew experimental ideas at the LHC regarding coherent photo-production in overlap with hadronic interaction and the link with potential QGP studies : "Imaging of Heavy Ion Collisions
Bacterial Diversity Downstream from a Former Uranium mine and in Waters from Naturally Radioactive Mineral Sources: Potential Role on Uranium Migration in the Environment
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Technical Report on Selective Laser Ionization
No full textThe SMILES project (Mass Separation Coupled with Laser Ionization for Environmental and Health Applications) aims to quantify, purify or separate isotopes for health and environmental applications using the laser ionization technique coupled with mass separation.This report focuses specifically on laser beam resonant ionization which was first demonstrated and experimented at the LNPI (Leningrad Nuclear Physics Institute) in 1988 and which selectively and efficiently promotes atoms into their excited and ionized states by photoionization.We are particularly interested in the performance that instruments, using this technique, can achieve:-A high selectivity: isobaric deletions are greater than 108, only due to multi-step optical transitions, and greater than > 1013 by combining laser ionization with mass separation. Indeed, laser ionization is selective according to the atomic number Z while the application of an electromagnetic field ensures the separation of the isotopes according to their mass A, the combination of the two thus making it possible to isolate a given isotope (Z, A) with great precision.-An ionization efficiency between 10-3 and 10-1 that is due to the high optical cross-section values that generate high ionization and excitation probabilities.-A high sensitivity that can reach detection limits of fg, and even ag.For the SMILES project, the experimental set-up, as a whole, will have to adapt to the diversity of samples encountered within a large community of users in various disciplinary fields (environment, medicine, physics, chemistry…). The experiments planned will first concern the analysis of stable isotopes or very low activities radioisotopes at the ultra-trace scale. A first list of elements of interest has already been established: Stable Cu-(63/65), Er, Pb, Am, Pu, Ra-226/Ra-228 (but also interest in a Ra-228 source), Pb-210, Th-230, U-236,...The primary aim of this report is to define the technical requirements for the selective laser ionization device of the SMILES project by presenting initial specifications of the selective laser ionization system as it will be implemented.After presenting two possible configurations of the experimental set-up, the various elements of this system will be reviewed: pump laser, Ti:Sapphire cavities, frequency conversion units, optical paths, system control such as laser diagnostics, spatial and temporal overlapping of laser pulses,… as well as the main technical characteristics of the future "Laser room”.Finally, a series of “open questions” is addressed to the expert committee in order to validate and improve the technical solutions to be implemented for the SMILES selective laser ionization system
Atomistic simulation of glass alteration using the Monte Carlo method
No full textInternational audienceAs glass used to confine the long-lived radionuclides arising from spent nuclear fuel are intended to be stored definitively in a deep geological repository, it is important to predict the glass dissolution rate when being in contact with underground water. Indeed, this material alteration rate is directly linked to the release of the radioelements into the environment, thus the safety of the disposal. For the development of a predictive model, the first step is to determine the preponderant elementary mechanisms originating the glass alteration.More and more sophisticated stochastic approaches based on Monte Carlo algorithms have been developed in previous years to try to capture these elementary mechanisms and determine the rate limiting once depending on the glass composition and the alteration conditions. This presentation starts with a history of these developments from the very first model proposed by M. Aertsens around 1995 until the one currently under development.The first attempt to simulate nuclear glass alteration using a Monte Carlo approach is due by M. Aertsens from Mol in Belgium. An ordered SiO2-Na2O network in contact with water was built to simulate the glass alteration and a set of probabilities were introduced to represent the release of Si into the solution and the Na+-H+ exchange mechanisms. Unfortunately, this method was limited because of a too-long computational time.Then a refined algorithm was developed at CEA Marcoule [1,2]. The glass compositions considered were more complex (up to five oxides SiO2-B2O3-Na2O-CaO-ZrO2) and the glass structure was still represented by an ordered network in contact with water. A larger set of probabilities was used to simulate the hydrolysis of glass formers (Si, Al). One Si or one Al ion in contact with water was released into the solution with a probability depending on the local degree of polymerization of its site. The B ions were immediately released in the solution when in contact with water. Using this more sophisticated algorithm, it has been possible to reproduce with good agreement some experimental results, such as the behavior of B, a glass dissolution tracer, for a series of SiO2-B2O3-Na2O glasses altered at different S/V ratios, or the strengthening effect of ZrO2.Later, S. Kerisit at PNNL [3] continued to improve the Monte Carlo method first by adding Al2O3 to the glass composition, then by considering the boroxols rings effect. He developed his own code, before a new collaboration with CEA started. He observed a non-linear impact of Al2O3 on the glass alteration and an acceleration of the glass alteration with the number of boroxol rings.CEA and PNNL codes were later compared successfully during A. Jan thesis [3]. One of the main objectives of this thesis was to use these Monte Carlo codes to try to reproduce the increase of glass alteration after irradiation of the material by heavy ions. But it has not been possible to trigger the Monte Carlo probabilities to reproduce the experimentally observed radiation effects. From this work, it has been concluded that other important elementary mechanisms were still missing.For this reason, a new Monte Carlo algorithm is currently in development. The main difference with the previous CEA and PNNL codes is the possibility for water to diffuse inside the glass (this has never been considered so far) and the possibility to represent the alteration layer ripening. Thanks to these new options, it should be possible to represent more precisely both the radiation effects on glass alteration, along with the so called residual rate. The first results obtained with this refined Monte Carlo method will be presented for a series of SiO2-B2O3-Al2O3-Na2O glasses.[1] C. Cailleteau, F. Angeli, F. Devreux, S. Gin, J. Jestin, P. Jollivet, O. Spalla, Nat. Mater. 7 (2008) 978-983.[2] F. Devreux, A. Ledieu, P. Barboux, Y. Minet, J. Non-Cryst. Solids 343 (2004) 13-25.[3] S. Kerisit, E.M. Pierce, Geochim. Cosmochim. Acta 75 (2011) 5296-5309.[4] A. Jan, J.-M. Delaye, S. Gin, S. Kerisit, J. Non-Cryst. Solids 519 (2019) 6-13