HAL Mines Nantes
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Neutral to charged kaon yield fluctuations in Pb – Pb collisions at <math altimg="si1.svg"><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi mathvariant="normal">NN</mi></mrow></msub></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after">=</mo><mn>2.76</mn></math> TeV
No full textInternational audienceWe present the first measurement of event-by-event fluctuations in the kaon sector in Pb – Pb collisions at sNN=2.76 TeV with the ALICE detector at the LHC. The robust fluctuation correlator νdyn is used to evaluate the magnitude of fluctuations of the relative yields of neutral and charged kaons, as well as the relative yields of charged kaons, as a function of collision centrality and selected kinematic ranges. While the correlator νdyn[K+,K−] exhibits a scaling approximately in inverse proportion of the charged particle multiplicity, νdyn[KS0,K±] features a significant deviation from such scaling. Within uncertainties, the value of νdyn[KS0,K±] is independent of the selected transverse momentum interval, while it exhibits a pseudorapidity dependence. The results are compared with HIJING, AMPT and EPOS–LHC predictions, and are further discussed in the context of the possible production of disoriented chiral condensates in central Pb – Pb collisions
Unmoderated molten salt reactors design optimisation for power stability
No full textInternational audienceThe critical region of unmoderated molten salt reactors consists in a cavity filled with a liquid fuel. The lack of internal structure implies a complex flow structure of the circulating fuel salt. A preliminary core shape optimization has been performed during the EVOL European project to limit recirculation and hotspots. This optimization was based on a Reynolds Averaged Navier Stokes (RANS) approach, but the latter only provides time-averaged values for velocity and temperature. However, the power stability is sensitive to thermal fluctuations induced by the flow turbulence itself, even at steady state without pump flow rate or heat extraction variation. This phenomenon is studied using a Detached Eddies Simulation approach to solve the turbulence in the reactor and get a time dependent temperature distribution and then the reactivity fluctuations. A new geometry is proposed to limit the total power fluctuations from 7.5% for the preconceptual EVOL geometry down to 1.2%
Damping signatures at JUNO, a medium-baseline reactor neutrino oscillation experiment
No full textInternational audienceWe study damping signatures at the Jiangmen Underground Neutrino Observatory (JUNO), a medium-baseline reactor neutrino oscillation experiment. These damping signatures are motivated by various new physics models, including quantum decoherence, ν decay, neutrino absorption, and wave packet decoherence. The phenomenological effects of these models can be characterized by exponential damping factors at the probability level. We assess how well JUNO can constrain these damping parameters and how to disentangle these different damping signatures at JUNO. Compared to current experimental limits, JUNO can significantly improve the limits on τ/m in the ν decay model, the width of the neutrino wave packet σ, and the intrinsic relative dispersion of neutrino momentum σ.[graphic not available: see fulltext
Double-weak decays of <math><mmultiscripts><mi>Xe</mi><mprescripts/><none/><mn>124</mn></mmultiscripts></math> and <math><mmultiscripts><mi>Xe</mi><mprescripts/><none/><mn>136</mn></mmultiscripts></math> in the XENON1T and XENONnT experiments
No full textInternational audienceWe present results on the search for two-neutrino double-electron capture (2νECEC) of Xe124 and neutrinoless double-β decay (0νββ) of Xe136 in XENON1T. We consider captures from the K shell up to the N shell in the 2νECEC signal model and measure a total half-life of T1/22νECEC=(1.1±0.2stat±0.1sys)×1022yr with a 0.87kgyr isotope exposure. The statistical significance of the signal is 7.0σ. We use XENON1T data with 36.16kgyr of Xe136 exposure to search for 0νββ. We find no evidence of a signal and set a lower limit on the half-life of T1/20νββ>1.2×1024yrat90%CL. This is the best result from a dark matter detector without an enriched target to date. We also report projections on the sensitivity of XENONnT to 0νββ. Assuming a 275kgyr Xe136 exposure, the expected sensitivity is T1/20νββ>2.1×1025yrat90%CL, corresponding to an effective Majorana mass range of 〈mββ〉<(0.19–0.59)eV/c2
High energy ion beam analysis of cultural heritage objects, a study of provenance and manufacturing techniques
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Geological disposal of fuel debris? Comparison of the interaction of fuel debris and of spent nuclear fuel with water
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Calculation of two-proton radioactivity and application to and emissions
No full textInternational audienceThe 2p radioactivity half-lives have been calculated within a tunneling process through the potential barrier determined from the original version of the generalized liquid drop model and quasimolecular shapes. The sparse experimental data on the 2p radioactivity half-lives of the O12, Ne16, Mg19, Fe45, Ni48, Zn54, and Kr67 nuclei are roughly reproduced when taking into account the Q2pexp value. An analytic formula is provided to obtain rapidly these different half-lives. Using the Q2p values extracted from the recent Nubase2020 table, extrapolations to other perhaps possible 2p emitters are proposed. Within the same approach, formulas to determine the Be9, Li6,7, He3,6, and H2,3 decay half-lives at low excitation energy are also provided
Experimental study of the Ca+ Ca reactions at 35 MeV/nucleon
No full textInternational audienceIn this article we investigate Ca+Ca peripheral and semi-peripheral reactions at 35 MeV/nucleon. Data were obtained using the unique coupling of the VAMOS high acceptance spectrometer and the INDRA charged particle multidetector.The spectrometer allowed high resolution measurement of charge, mass and velocity of the cold projectile-like fragment (PLF), while the INDRA detector recorded coincident charged particles with nearly acceptance.The measured isotopic composition of the PLF identified in VAMOS and the average light charged particle (LCP) multiplicities are promising observables to study the isospin diffusion.The detection of the PLF in coincidence with LCP allows the reconstruction of the mass, charge and excitation energy of the associated initial quasi-projectile nuclei (QP), as well as the extraction of apparent temperatures.We investigate the suitability of the isoscaling method with the PLF and the experimental reconstructed QP.The extracted and isoscaling parameters present a dependence on the considered system combination that could justify their use as a surrogate for isospin asymmetry in isospin transport studies.The reconstruction of the QP allows to observe an evolution of the with the size of the QP, the latter being consistent with a strong surface contribution to the symmetry energy term in finite nuclei. This leads to the conclusion that the reconstruction of the primary source is mandatory for the study of the symmetry energy term based on the isoscaling method for such reactions