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A study by molecular dynamics of the energies of hydrolysis and reformation of chemical bonds in aluminosilicate glasses
No full textInternational audienceUnderstanding the elementary mechanisms at the origin of glass alteration is very important in the nuclear field because in France nuclear glasses are intended to be stored in a deep geological repository. Consequently, they must be highly resistant to the underground water in order to limit the release of radioelements into the environment. One way to extrapolate the long term behavior of nuclear glasses is to build models based on the elementary mechanisms.In this presentation, a study was performed to better understand the mechanisms of bond hydrolysis and reformation around the Si and Al atoms in SiO2-Al2O3-CaO glasses in contact with water will be detailed.Firstly a diffuse charge reactive potential (DCRP) was developed using a Force Matching technique to reproduce ab initio calculations. This potential has been further refined to better reproduce the experiments [1].Then this potential has been used to measure the hydrolysis and reformation energies around the Si atoms in pure silica and around the Si and Al atoms in different SiO2-Al2O3-CaO glasses. It was observed that there is a strengthening effect on the Si-O bonds when Al2O3 is added to the glass. Indeed, the Si-O bonds average hydrolysis energy increases from 1.22eV in pure silica to 1.34eV in an aluminosilicate glass. In parallel, it was observed that the Al-O bonds average hydrolysis energy is lower (0.49eV). Moreover, reforming bonds around the Si atoms in aluminosilicate glasses is easier than in pure silica. This effect of Al on the Si-O hydrolysis energies were qualitatively confirmed experimentally [2].When more complex glasses containing both CaO and Na2O are considered, a non linear effect is evidenced, i.e. the Si-O bonds hydrolysis energy presents a minimum in glasses where CaO and Na2O are mixed. From this observation, it was concluded that the average hydrolysis energy of Si-O in a SiO2-Al2O3-CaO-Na2O glass results from both a chemical effect (the impact of Al) and a topological effect (the level of disorder).[1] T. Mahadevan, A. Baroni, M. Taron, S. Gin, J. Du, J.-M. Delaye, Journal of Non-Crystalline Solids 592 (2022) 121746.[2] K. Damodaran, J.-M. Delaye, A. G. Kalinichev, S. Gin, Acta Materialia, 225 (2022) 117478
KM3NeT broadcast optical data transport system
No full textInternational audienceThe optical data transport system of the KM3NeT neutrino telescope at the bottom of the Mediterranean Sea will provide more than 6000 optical modules in the detector arrays with a point-to-point optical connection to the control stations onshore. The ARCA and ORCA detectors of KM3NeT are being installed at a depth of about 3500 m and 2500 m, respectively and their distance to the control stations is about 100 kilometers and 40 kilometers. In particular, the two detectors are optimised for the detection of cosmic neutrinos with energies above about 1 TeV (ARCA) and for the detection of atmospheric neutrinos with energies in the range 1 GeV–1 TeV (ORCA). The expected maximum data rate is 200 Mbps per optical module. The implemented optical data transport system matches the layouts of the networks of electro-optical cables and junction boxes in the deep sea. For efficient use of the fibres in the system the technology of Dense Wavelength Division Multiplexing is applied. The performance of the optical system in terms of measured bit error rates, optical budget are presented. The next steps in the implementation of the system are also discussed
Low-energy Calibration of XENON1T with an Internal Ar Source
No full textInternational audienceA low-energy electronic recoil calibration of XENON1T, a dual-phase xenon time projection chamber, with an internal Ar source was performed. This calibration source features a 35-day half-life and provides two mono-energetic lines at 2.82 keV and 0.27 keV. The photon yield and electron yield at 2.82 keV are measured to be (32.30.3) photons/keV and (40.60.5) electrons/keV, respectively, in agreement with other measurements and with NEST predictions. The electron yield at 0.27 keV is also measured and it is (68.0) electrons/keV. The Ar calibration confirms that the detector is well-understood in the energy region close to the detection threshold, with the 2.82 keV line reconstructed at (2.830.02) keV, which further validates the model used to interpret the low-energy electronic recoil excess previously reported by XENON1T. The ability to efficiently remove argon with cryogenic distillation after the calibration proves that Ar can be considered as a regular calibration source for multi-tonne xenon detectors
Interaction between carbon steel and low-pH bentonitic cement grout in anoxic and heterogeneous conditions at 80°C
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R2D2 TPC: first Xenon results
No full textInternational audienceRadial time projection chambers (TPC), already employed inthe search for rare phenomena such as light Dark Matter candidate,could provide a new detection approach for the search ofneutrinoless double beta decay (ββ0ν). The assessment ofthe performances of such a detector for ββ0ν search isindeed the goal of the Rare Decays with Radial Detector (R2D2)R&D. Promising results operating a spherical TPC with argon up to1 bar have been published in 2021. Supplementary measurements wererecently taken extending the gas pressure range up to 3 bar. Inaddition, a comparison between two detector geometries, namelyspherical (SPC for spherical proportional counter) and cylindrical(CPC for cylindrical proportional counter), was performed. Using arelatively simple gas purification system the CPC detector was alsooperated with xenon at 1 bar: an energy resolution of 1.4%full-width at half-maximum was achieved for drift distances up to17 cm. Much lower resolution was observed with the SPC. Theseresults are presented in this article
Probing the Chiral Magnetic Wave with charge-dependent flow measurements in Pb-Pb collisions at the LHC
No full textInternational audienceThe Chiral Magnetic Wave (CMW) phenomenon is essential to provide insights into the strong interaction in QCD, the properties of the quark-gluon plasma, and the topological characteristics of the early universe, offering a deeper understanding of fundamental physics in high-energy collisions. Measurements of the charge-dependent anisotropic flow coefficients are studied in Pb-Pb collisions at center-of-mass energy per nucleon-nucleon collision 5.02 TeV to probe the CMW. In particular, the slope of the normalized difference in elliptic () and triangular () flow coefficients of positively and negatively charged particles as a function of their event-wise normalized number difference, is reported for inclusive and identified particles. The slope is found to be larger than zero and to have a magnitude similar to , thus pointing to a large background contribution for these measurements. Furthermore, can be described by a blast wave model calculation that incorporates local charge conservation. In addition, using the event shape engineering technique yields a fraction of CMW () contribution to this measurement which is compatible with zero. This measurement provides the very first upper limit for , and in the 10-60% centrality interval it is found to be 26% (38%) at 95% (99.7%) confidence level
Measurement of the <math display="inline"><mrow><mi>J</mi><mo>/</mo><mi>ψ</mi></mrow></math> Polarization with Respect to the Event Plane in Pb-Pb Collisions at the LHC
No full textInternational audienceWe study the polarization of inclusive J/ψ produced in Pb-Pb collisions at sNN=5.02 TeV at the LHC in the dimuon channel, via the measurement of the angular distribution of its decay products. We perform the study in the rapidity region 2.5<y<4, for three transverse momentum intervals (2<pT<4, 4<pT<6, 6<pT<10 GeV/c) and as a function of the centrality of the collision for 2<pT<6 GeV/c. For the first time, the polarization is measured with respect to the event plane of the collision, by considering the angle between the positive-charge decay muon in the J/ψ rest frame and the axis perpendicular to the event-plane vector in the laboratory system. A small transverse polarization is measured, with a significance reaching 3.9σ at low pT and for intermediate centrality values. The polarization could be connected with the behavior of the quark-gluon plasma, formed in Pb-Pb collisions, as a rotating fluid with large vorticity, as well as with the existence of a strong magnetic field in the early stage of its formation
Inclusive quarkonium production in pp collisions at TeV
No full textInternational audienceThis article reports on the inclusive production cross section of several quarkonium states, , , , , and , measured with the ALICE detector at the LHC, in \pp collisions at TeV. The analysis is performed in the dimuon decay channel at forward rapidity (). The measured cross sections, assuming unpolarized quarkonia, are: b, b, nb, nb, and nb, where the first (second) uncertainty is the statistical (systematic) one. The transverse-momentum () and rapidity () differential cross sections for , , , and the -to- cross section ratios are presented. For the first time, the cross sections of the three states, as well as the one as a function of and , are measured at TeV at forward rapidity. These measurements also significantly extend the reach with respect to previously published results. A comparison with ALICE measurements in pp collisions at , 7, 8, and 13 TeV is presented and the energy dependence of quarkonium production cross sections is discussed. Finally, the results are compared with the predictions from several production models
Transverse momentum broadening from NLL BFKL to all orders in pQCD
No full textInternational audienceWe study, to all orders in perturbative QCD, the universal behavior of the saturation momentum controlling the transverse momentum distribution of a fast parton propagating through a dense QCD medium with large size . Due to the double logarithmic nature of the quantum evolution of the saturation momentum, its large asymptotics is obtained by slightly departing from the double logarithmic limit of either next-to-leading log (NLL) BFKL or leading order DGLAP evolution equations. At fixed coupling, or in conformal SYM theory, we derive the large expansion of up to order . In QCD with massless quarks, where conformal symmetry is broken by the running of the strong coupling constant, the one-loop QCD -function fully accounts for the universal terms in the expansion. Therefore, the universal coefficients of this series are known exactly to all orders in