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Search Results: 1 - 10 of 219510 matches for " C. Jollet "
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A new anti-neutrino detection technique based on positronium tagging with plastic scintillators
G. Consolati,D. Franco,C. Jollet,A. Meregaglia,A. Minotti,S. Perasso,A. Tonazzo
Physics , 2015, DOI: 10.1016/j.nima.2015.06.021
Abstract: The main signature for anti-neutrino detection in reactor and geo-neutrino experiments based on scintillators is provided by the space-time coincidence of positron and neutron produced in the Inverse Beta Decay reaction. Such a signature strongly suppresses backgrounds and allows for measurements performed underground with a relatively high signal-to-background ratio. In an aboveground environment, however, the twofold coincidence technique is not sufficient to efficiently reject the high background rate induced by cosmogenic events. Enhancing the positron-neutron twofold coincidence efficiency has the potential to pave the way future aboveground detectors for reactor monitoring. We propose a new detection scheme based on a threefold coincidence, between the positron ionization, the ortho-positronium (o-Ps) decay, and the neutron capture, in a sandwich detector with alternated layers of plastic scintillator and aerogel powder. We present the results of a set of dedicated measurements on the achievable light yield and on the o-Ps formation and lifetime. The efficiencies for signal detection and background rejection of a preliminary detector design are also discussed.
Measurement of ortho-Positronium Properties in Liquid Scintillators
S. Perasso,G. Consolati,D. Franco,S. Hans,C. Jollet,A. Meregaglia,A. Tonazzo,M. Yeh
Physics , 2013, DOI: 10.1088/1748-0221/9/03/C03028
Abstract: Pulse shape discrimination in liquid scintillator detectors is a well-established technique for the discrimination of heavy particles from light particles. Nonetheless, it is not efficient in the separation of electrons and positrons, as they give rise to indistinguishable scintillator responses. This inefficiency can be overtaken through the exploitation of the formation of ortho-Positronium (o-Ps), which alters the time profile of light pulses induced by positrons. We characterized the o-Ps properties in the most commonly used liquid scintillators, i.e. PC, PXE, LAB, OIL and PC + PPO. In addition, we studied the effects of scintillator doping on the o-Ps properties for dopants currently used in neutrino experiments, Gd and Nd. Further measurements for Li-loaded and Tl-loaded liquid scintillators are foreseen. We found that the o-Ps properties are suitable for enhancing the electron-positron discrimination.
Characterization of positronium properties in doped liquid scintillators
G. Consolati,D. Franco,S. Hans,C. Jollet,A. Meregaglia,S. Perasso,A. Tonazzo,M. Yeh
Physics , 2013, DOI: 10.1103/PhysRevC.88.065502
Abstract: Ortho-positronium (o-Ps) formation and decay can replace the annihilation process, when positron interacts in liquid scintillator media. The delay induced by the positronium decay represents either a potential signature for anti-neutrino detection, via inverse beta decay, or to identify and suppress positron background, as recently demonstrated by the Borexino experiment. The formation probability and decay time of o-Ps depend strongly on the surrounding material. In this paper, we characterize the o-Ps properties in liquid scintillators as function of concentrations of gadolinium, lithium, neodymium, and tellurium, dopers used by present and future neutrino experiments. In particular, gadolinium and lithium are high neutron cross section isotopes, widely used in reactor anti-neutrino experiments, while neodymium and tellurium are double beta decay emitters, employed to investigates the Majorana neutrino nature. Future neutrino experiments may profit from the performed measurements to tune the preparation of the scintillator in order to maximize the o-Ps signature, and therefore the discrimination power.
Mass hierarchy discrimination with atmospheric neutrinos in large volume ice/water Cherenkov detectors
Franco, D.;Jollet, C.;Kouchner, A.;Kulikovskiy, V.;Meregaglia, A.;Perasso, S.;Pradier, T.;Tonazzo, A.;Van Elewyck, V.
High Energy Physics - Phenomenology , 2013,
Abstract: Large mass ice/water Cherenkov experiments, optimized to detect low energy (1-20 GeV) atmospheric neutrinos, have the potential to discriminate between normal and inverted neutrino mass hierarchies. The sensitivity depends on several model and detector parameters, such as the neutrino flux profile and normalization, the Earth density profile, the oscillation parameter uncertainties, and the detector effective mass and resolution. A proper evaluation of the mass hierarchy discrimination power requires a robust statistical approach. In this work, the Toy Monte Carlo, based on an extended unbinned likelihood ratio test statistic, was used. The effect of each model and detector parameter, as well as the required detector exposure, was then studied. While uncertainties on the Earth density and atmospheric neutrino flux profiles were found to have a minor impact on the mass hierarchy discrimination, the flux normalization, as well as some of the oscillation parameter (\Delta m^2_{31}, \theta_{13}, \theta_{23}, and \delta_{CP}) uncertainties and correlations resulted critical. Finally, the minimum required detector exposure, the optimization of the low energy threshold, and the detector resolutions were also investigated.
Mass hierarchy discrimination with atmospheric neutrinos in large volume ice/water Cherenkov detectors
D. Franco,C. Jollet,A. Kouchner,V. Kulikovskiy,A. Meregaglia,S. Perasso,T. Pradier,A. Tonazzo,V. Van Elewyck
Physics , 2013, DOI: 10.1007/JHEP04(2013)008
Abstract: Large mass ice/water Cherenkov experiments, optimized to detect low energy (1-20 GeV) atmospheric neutrinos, have the potential to discriminate between normal and inverted neutrino mass hierarchies. The sensitivity depends on several model and detector parameters, such as the neutrino flux profile and normalization, the Earth density profile, the oscillation parameter uncertainties, and the detector effective mass and resolution. A proper evaluation of the mass hierarchy discrimination power requires a robust statistical approach. In this work, the Toy Monte Carlo, based on an extended unbinned likelihood ratio test statistic, was used. The effect of each model and detector parameter, as well as the required detector exposure, was then studied. While uncertainties on the Earth density and atmospheric neutrino flux profiles were found to have a minor impact on the mass hierarchy discrimination, the flux normalization, as well as some of the oscillation parameter (\Delta m^2_{31}, \theta_{13}, \theta_{23}, and \delta_{CP}) uncertainties and correlations resulted critical. Finally, the minimum required detector exposure, the optimization of the low energy threshold, and the detector resolutions were also investigated.
Generation of Projector Augmented-Wave atomic data: a 71 elements validated table in the XML format
Fran?ois Jollet,Marc Torrent,Natalie Holzwarth
Physics , 2013, DOI: 10.1016/j.cpc.2013.12.023
Abstract: A Projector Augmented Wave (PAW) atomic data file is needed to be generated for each element, and plays in the PAW method the role of the pseudopotential file for norm-conserving (NC) or ultra-soft (US) plane wave calculations. In this paper, we present a review on how to obtain these data as well as results concerning their accuracy, their transferability and their efficiency for bulk solids. Following \cite{Lejaeghere}, we propose a new criterium to test PAW atomic data and we provide a new table written in a XML format potentially readable by every PAW electronic structure code.
A non-conventional neutrino beamline for the measurement of the electron neutrino cross section
A. Berra,S. Cecchini,F. Cindolo,C. Jollet,A. Longhin,L. Ludovici,G. Mandrioli,N. Mauri,A. Meregaglia,A. Paoloni,L. Pasqualini,L. Patrizii,F. Pupilli,M. Pozzato,M. Prest,G. Sirri,F. Terranova,E. Vallazza,L. Votano
Physics , 2015,
Abstract: Absolute neutrino cross section measurements at the GeV scale are ultimately limited by the knowledge of the initial $\nu$ flux. In order to evade such limitation and reach the accuracy that is needed for precision oscillation physics ($\sim 1$%), substantial advances in flux measurement techniques are requested. We discuss here the possibility of instrumenting the decay tunnel to identify large-angle positrons and monitor $\nu_e$ production from $K^+ \rightarrow e^+ \nu_e \pi^0$ decays. This non conventional technique opens up opportunities to measure the $\nu_e$ CC cross section at the per cent level in the energy range of interest for DUNE/HK. We discuss the progress in the simulation of the facility (beamline and instrumentation) and the ongoing R&D.
Solar neutrino detection in a large volume double-phase liquid argon experiment
D. Franco,C. Giganti,P. Agnes,L. Agostino,B. Bottino,S. Davini,S. De Cecco,A. Fan,G. Fiorillo,C. Galbiati,A. M. Goretti,E. V. Hungerford,Al. Ianni,An. Ianni,C. Jollet,L. Marini,C. J. Martoff,A. Meregaglia,L. Pagani,M. Pallavicini,E. Pantic,A. Pocar,A. L. Renshaw,B. Rossi,N. Rossi,Y. Suvorov,G. Testera,A. Tonazzo,H. Wang,S. Zavatarelli
Physics , 2015,
Abstract: The direct search for dark matter WIMP particles through their interaction with nuclei at the "neutrino floor" sensitivity, where neutrino-induced coherent scattering on nuclei starts contributing to the background, requires detectors capable of collecting exposures of the order of 1~ktonne yr free of background resulting from beta and gamma decays and cosmogenic and radiogenic neutrons. The same constraints are required for precision measurements of solar neutrinos elastically scattering on electrons. Two-phase liquid argon time projection chambers (LAr TPCs) are prime candidates for the ambitious program to explore the nature of dark matter. The large target, high scintillation light yield and good spatial resolution in all three cartesian directions concurrently allows a high precision measurement of solar neutrino fluxes. We studied the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). Such a detector could measure the CNO neutrino rate with 5 sigma sensitivity, and significantly improve the precision of the 7Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector. Measurements with ~2%, ~10% and ~15% precision for 7Be, pep, and CNO neutrinos, respectively, are possible.
Plane-wave based electronic structure calculations for correlated materials using dynamical mean-field theory and projected local orbitals
B. Amadon,F. Lechermann,A. Georges,F. Jollet,T. O. Wehling,A. I. Lichtenstein
Physics , 2008, DOI: 10.1103/PhysRevB.77.205112
Abstract: The description of realistic strongly correlated systems has recently advanced through the combination of density functional theory in the local density approximation (LDA) and dynamical mean field theory (DMFT). This LDA+DMFT method is able to treat both strongly correlated insulators and metals. Several interfaces between LDA and DMFT have been used, such as (N-th order) Linear Muffin Tin Orbitals or Maximally localized Wannier Functions. Such schemes are however either complex in use or additional simplifications are often performed (i.e., the atomic sphere approximation). We present an alternative implementation of LDA+DMFT, which keeps the precision of the Wannier implementation, but which is lighter. It relies on the projection of localized orbitals onto a restricted set of Kohn-Sham states to define the correlated subspace. The method is implemented within the Projector Augmented Wave (PAW) and within the Mixed Basis Pseudopotential (MBPP) frameworks. This opens the way to electronic structure calculations within LDA+DMFT for more complex structures with the precision of an all-electron method. We present an application to two correlated systems, namely SrVO3 and beta-NiS (a charge-transfer material), including ligand states in the basis-set. The results are compared to calculations done with Maximally Localized Wannier functions, and the physical features appearing in the orbitally resolved spectral functions are discussed.
Possible background reductions in double beta decay experiments
R. Arnold,C. Augier,J. Baker,A. Barabash,O. Bing,V. Brudanin,A. J. Caffrey,E. Caurier,K. Errahmane,A. -I. Etienvre,J. L. Guyonnet,F. Hubert,Ph. Hubert,C. Jollet,S. Jullian,O. Kochetov,V. Kovalenko,D. Lalanne,F. Leccia,C. Longuemare,Ch. Marquet,F. Mauger,H. W. Nicholson,H. Ohsumi,F. Piquemal,J-L. Reyss,X. Sarazin,Yu. Shitov,L. Simard,I. Stekl,J. Suhonen,C. S. Sutton,G. Szklarz,V. Timkin,V. Tretyak,V. Umatov,L. Vala,I. Vanyushin,V. Vasilyev,V. Vorobel,Ts. Vylov
Physics , 2003, DOI: 10.1016/S0168-9002(03)00992-6
Abstract: The background induced by radioactive impurities of $^{208}\rm Tl$ and $^{214}\rm Bi$ in the source of the double beta experiment NEMO-3 has been investigated. New methods of data analysis which decrease the background from the above mentioned contamination are identified. The techniques can also be applied to other double beta decay experiments capable of measuring independently the energies of the two electrons.
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