WorldCat Identities

Laboratoire de physique subatomique et de cosmologie (Grenoble)

Overview
Works: 129 works in 132 publications in 2 languages and 220 library holdings
Roles: Other, Editor, 981
Publication Timeline
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Most widely held works by Laboratoire de physique subatomique et de cosmologie (Grenoble)
Mesure de la production inclusive de jets chargés dans les collisions Pb-Pb à 5.02TeV avec l'expérience ALICE auprès du LHC by Hiroki Yokoyama( )

1 edition published in 2018 in English and held by 2 WorldCat member libraries worldwide

La physique nucléaire de haute énergie a pour objet l'étude des propriétés du Plasma de Quarks et de Gluons (PQG), un nouvel état de la matière composée de quarks et de gluons asymptotiquement libres. Selon les calculs de la ChromoDynamique Quantique (CDQ) sur réseau, une transition de la matière nucléaire vers un PQG doit se produire pour des densités d'énergie au-delà de ~ 1 GeV/fm3 (correspondant à une température ~ 150 - 200 MeV). De telles conditions extrêmes de température et de densité d'énergie sont réalisées en laboratoire en utilisant des collisions ions lourds aux énergies ultra-relativistes. Le PQG ainsi créé est cependant si fugace qu'il ne peut être étudié que par des sondes internes produites au sein même de la collision mais à des échelles de temps bien inférieures à celle du PQG. Ces sondes dites dures vont alors être modifiée suite à leur interaction avec le PQG, de cette modification s'ensuit l'inférence des propriétés de transport du PQG.Cette thèse porte sur la mesure des jets comme sondes dures du PQG, elle s'articule selon deux axes complémentaires : le développement d'un nouvel algorithme de déclenchement calorimétrique de l'expérience ALICE pour le Run 2 du LHC afin d'efficacement sélectionner les événements contenant une gerbe électromagnétique, ainsi que la mesure de la production inclusive de jets chargés dans les collisions Pb-Pb à l'énergie la plus élevée à ce jour de 5.02 TeV auprès du LHC. Un des défis majeurs de la mesure des jets dans les collisions d'ions lourds consiste à séparer les jets de l'événement sous-jacent. L'approche retenue dans ce travail repose sur une évaluation événement par événement de l'amplitude de cet événement sous-jacent qui est alors soustraite des jets reconstruits. Les fluctuations résiduelles de ce bruit de fond sont par la suite corrigées par une méthode de déconvolution adaptée. Enfin, afin de réduire au maximum la contamination du bruit de fond combinatoire, une coupure de 5 GeV/c sur l'impulsion transverse du constituant prééminent est appliquée.La mesure des facteurs de modification nucléaire des jets montrent une très forte suppression que l'on attribue à la perte d'énergie des partons dans le PQG. Dans ce travail de thèse, une étude phénoménologique de cette manifestation qualifiée "d'étouffement des jets" à partir d'une observable originale, est présentée. Cette étude met en évidence plusieurs résultats fondamentaux : une perte d'énergie constante dans le domaine d'impulsion transverse de jet mesuré (jusqu'à 100 GeV/c), plus prononcée qu'à plus basse énergie et montrant une dépendance quadratique avec la longueur de parcours dans le milieu suggérant la prépondérance d'une perte d'énergie des partons par radiation de gluons
La co-magnétométrie mercure pour la mesure du moment électrique dipolaire du neutron : optimisation et application au test de l'invariance de Lorentz by Stéphanie Roccia( )

2 editions published in 2009 in French and held by 2 WorldCat member libraries worldwide

In this thesis, magnetometry is studied in the context of the neutron Electric Dipole Moment (nEDM) measurement with the RAL/Sussex/ILL spectrometer. In particular, the pre-existing mercury co-magnetometer has been modeled and optimized to be used in the next nEDM measurement at the Paul Scherrer Institut (Villigen Suisserland) in 2010-2012. Using data taken at the Institut Laue-Langevin (Grenoble, France), the complementarity between external cesium magnetometry and mercury co-magnetometry has been studied, bringing two results : - a best way to control systematics due to the co-magnetometer - a limit on the neutron anomalous couplings that violates Lorentz invariance
Mesure des corrélations photon-hadron auprès de l'expérience ALICE au LHC pour l'étude du plasma de quarks et de gluons by Astrid Vauthier( )

1 edition published in 2017 in French and held by 2 WorldCat member libraries worldwide

The quantum chromodynamics (QCD), the theory used at present to describe the strong interaction, predicts the existence of a phase transition, at very high temperature and/or density, towards a state of nuclear matter where quarks and gluons are deconfined : the Quark-Gluon Plasma (QGP). Such a medium can be produced in laboratory, and the measurement of its properties allows to give a new perspective on the mechanisms of interactions between the constituents as well as to test the QCD in unexplored domains.Ultra-relativistic heavy ion collisions delivered by the accelerator LHC at CERN allow to obtain the thermodynamical conditions necessary for the QGP to be formed. By means of a diversified instrumentation, the ALICE experiment allows to reach a large number of observables allowing to characterize the QGP. Among these, the measurement of the fragmentation of the partons (quarks and gluons) allows to study in detail the mechanisms of energy loss in the medium and its redistribution in the final state, and can also be compared with theoretical calculations, based on QCD, that model the interaction of an energetic parton with the QGP which is passing through.The work presented in this manuscript is articulated around the study of the fragmentation function via the measurement of the photon-hadron correlations in proton-proton and proton-Lead collisions. At first, a work on energy calibration of the ALICE experiment's electromagnetic calorimeter was realized, along with the characterization of the uncertainties of this calibration. Secondly, the photon-hadron correlations, whose main difficulty is the identification of the direct photons, were studied. The results obtained in both systems of collisions demonstrate the feasibility of the analysis which can be easily widened to the peripheral Lead-Lead collisions. Finally, this work shows that the dominant uncertainties of the measurement will be reducible with the new data delivered by the LHC
Détermination de sections efficaces pour la production de champs neutroniques monoénergétiques de basse énergie by Vincent Lamirand( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

The response of a neutron detector, defined as the reading of the device per unit of incident fluence or dose, varies with neutron energy. The experimental determination of this variation, i.e. of the response function of this instrument, has to be performed by facilities producing monoenergetic neutron fields. These neutrons are commonly produced by interaction between accelerated ions (proton or deuteron) onto a thin target composed of a reactive layer deposited on a metallic backing. Using the 7Li(p,n), 3H(p,n), 2H(d,n) and 3H(d,n) reactions, monoenergetic neutrons are obtained between 120 keV and 20 MeV in the ion beam direction (0°).To reach lower neutron energies, the angle of the measuring point with respect to the ion beam direction can be increased. However, this method presents several problems of neutron energy and fluence homogeneities over the detector surface, as well as an important increase of the scattered neutron contribution. Another solution is to investigate other nuclear reactions, as 45Sc(p,n) allowing to extend the neutron energy range down to 8 keV at 0°.A complete study of this reaction and its cross section has been undertaken within the framework of a scientific cooperation between the laboratory of neutron metrology and dosimetry (IRSN, France), two European national metrological institutes, the National Physical Laboratory (UK) and the Physikalisch-Technische Bundesanstalt (Germany), and IRMM, the Institute for Reference Materials and Measurements (EC).In parallel, other possible reactions have been investigated: 65Cu(p,n), 51V(p,n), 57Fe(p,n), 49Ti(p,n), 53Cr(p,n) and 37Cl(p,n). They were compared in terms of neutron fluence and minimum energy of the produced neutrons
Mesure de la section efficace de production du single top en voie-t en utilisant des arbres de décision avec ATLAS à sqrt(s)=7TeV by Jin Wang( )

1 edition published in 2012 in French and held by 2 WorldCat member libraries worldwide

This thesis presents a measurement of the cross section of t-channel single top-quark production using 1.04~fb^{-1} data collected by the ATLAS detector at the LHC with proton-proton collision at center-of-mass sqrt(s)=7TeV. Selected events contain one lepton, missing transverse energy, and two or three jets, one of them b-tagged. The background model consists of multijets, W+jets and top-quark pair events, with smaller contributions from Z+jets and diboson events. By using a cut and count method based on the distribution of a multivariate discriminant constructed with the boosted decision trees, the cross section of t-channel single top-quark production is measured: sigma_{t}= 97.3^{+30.7}_{-30.2}~pb, which is in good agreement with the prediction of the Standard Model. Assuming that the top-quark-related CKM matrix elements obey the relation |Vtb|>>|Vts|, |V_td|, the coupling strength at the W-t-b vertex is extracted from the measured cross section, |Vtb| = 1,23^{+0,20}_{-0,19}. If it is assumed that |Vtb|<1, a lower limit of |Vtb|>0.61 is obtained at the 95% confidence level
Impact des combustibles sphere-pac innovants sur les performances de sûreté des réacteurs à neutrons rapides refroidis au sodium by Lena Andriolo( )

1 edition published in 2015 in English and held by 2 WorldCat member libraries worldwide

Les futurs réacteurs à neutrons rapides refroidis au sodium (RNR-Na) doivent remplir les critères GEN-IV à savoir présenter des qualités d'économie, de sûreté améliorée, de résistance à la prolifération et de minimisation des déchets. Ce projet de thèse est dédié à l'étude de l'impact des combustibles innovants (spécialement le combustible oxyde sphere-pac chargé en actinides mineurs) sur les performances de sûreté des RNR-Na dédiés à la transmutation.Le code de calcul SIMMER-III, développé à l'origine pour les phases avancées d'un accident grave, est utilisé pour les simulations. Ce code a été étendu dans le cadre de cette thèse afin d'améliorer la simulation de la phase primaire de l'accident, en introduisant le traitement des effets en réactivité liés à la dilatation du cœur et les spécificités du combustible sphere-pac (conductivité thermique, gap). Les transitoires complets (de la phase d'initiation aux phases avancées) sont simulés avec cette version étendue du code. Dans le cadre de cette thèse, les propriétés thermiques du combustible sphere-pac ont été modélisées et adaptées à SIMMER. Une méthodologie innovante tenant compte des effets en réactivité liés à la dilation thermique du cœur dans un maillage Eulérien et dans le cadre de la cinétique spatiale a ensuite été développée. A chaque pas de temps, les dimensions et densités dilatées sont calculées pour chaque cellule suite aux variations de températures. Des facteurs correctifs sont appliqués aux densités dilatées pour obtenir une configuration équivalente (en réactivité) ayant les dimensions non-dilatées et des densités modifiées. De nouvelles sections efficaces sont calculées à partir de ces densités et l'effet en réactivité lié à la dilatation est calculé. Les résultats sont prometteurs pour des dilatations uniformes et non-uniformes. Des limitations dans le cas de dilatations non-uniformes ont été identifiées et des calculs neutroniques ont été effectués en vue de futurs développements SIMMER. Les résultats préliminaires sont encourageants. Enfin, deux cœurs RNR-Na, issus du précédent projet CP-ESFR, ont été modélisés avec des combustibles sphere-pac : le Working Horse et le CONF2 (présentant un plénum sodium élargi pour une diminution de l'effet de vide sodium). Des analyses de sûreté ont été effectuées afin de fournir une première évaluation du comportement du combustible sphere-pac comparé au combustible pastille. Les deux options sont analysées en situation nominale et accidentelle (accident de perte de débit primaire) en début de vie du cœur et après irradiation. Les analyses révèlent deux phases à considérer en début de vie pour le combustible sphere-pac. Au démarrage du réacteur, ce combustible n'est pas restructuré et sa conductivité thermique est très inférieure à celle du combustible pastille. Après quelques heures sous irradiation, il se restructure suite aux importants gradients de température, ce qui améliore sa conductivité. Il se comporte alors de façon similaire au combustible pastille. Ce travail a également permis d'évaluer le comportement accidentel du cœur CONF2 qui subit un transitoire doux, prouvant que le large plénum sodium prévient efficacement de larges insertions de réactivité positive. Cependant, avec l'ajout d'américium ou suite à l'irradiation, des excursions de puissance et de réactivité plus prononcées sont observées. Ce travail a permis de démontrer que le combustible sphere-pac ne semble pas causer de problèmes de sûreté spécifiques comparé au combustible pastille, dans les conditions de simulations actuelles. La prise en compte des effets en réactivité liés à la dilatation du cœur avec cette version étendue de SIMMER retarde et réduit le potentiel énergétique lors d'un accident. Les analyses confirment également l'action atténuante du plénum sodium sur les transitoires conduisant à la vidange du sodium du coeur. Le comportement du combustible sphere-pac dans ces conditions ouvre une perspective à son utilisation en RNR-Na
Recherche de manifestations de dimensions supplémentaires dans le canal diphoton avec l'expérience ATLAS au LHC by Bảo Trân Lê( )

1 edition published in 2013 in French and held by 2 WorldCat member libraries worldwide

This thesis summarizes a search for manifestations of Large Extra Dimensions (LED) using 4.91fb-1 of data collected in 2011 by the Atlas detector at the LHC collider at CERN. In 2011, the LHC has provided proton-proton collisions at a center-of-mass energy of sqrt(s) = 7 TeV. LED can potentially solve the so-called hierarchy problem, i.e. large apparent difference between two fundamental scales of the Standard Model (SM), the electroweak and the Planck scales. In the context of the ADD model (named after the authors N. Arkani-Hamed, S. Dimopoulos and G. Dvali) of LED, the effects of quantum gravity become much stronger than in the SM; possibly large enough to be observed at the LHC. There are two possibilities of graviton production in proton-proton collisions: direct graviton production and virtual graviton exchange. In this thesis, we present a search for the manifestation of extra dimensions via the effect of virtual graviton exchange on the di-photon final state. The di-photon invariant mass spectrum is studied and found to be in good agreement with SM background expectation. We set limits on the fundamental Planck scale of the ADD model using two different methods: a counting experiment and an analysis of the shape of the di-photon mass spectrum. The counting experiment yields limits between 2.62 and 3.92 TeV at 95% CL, depending on the number of extra dimensions and the theoretical formalism used. The shape analysis yields slightly more stringent limits: the lower limits on the fundamental Planck scale improve by a factor of 1.04
New heavy resonances : from the electroweak to the planck scale by Florian Lyonnet( )

1 edition published in 2014 in English and held by 2 WorldCat member libraries worldwide

The principle of local gauge invariance is a pillar of modern particle physics theories and in the SM relies on the ad-hoc gauge group structure SU(3)_c x SU(2)_L x U(1)_Y. Extending this gauge group is very well motivated in a Grand Unified Theory (GUT) perspective in which the SM is the low-energy limit of a more fundamental theory based on a larger gauge group like SO(10) or E(6). Indeed, the symmetry breaking (SB) of the underlying GUT gauge group, down to the SM one, leaves some additional group factors unbroken, such as U(1) or SU(2). In this spirit, we focus in this manuscript on the phenomenology of extended gauge group models and on the new heavy neutral and charged resonances, generically called Z' and W' predicted by these.In this manuscript we present different aspects of the phenomenology of the G(221) models. After reviewing these extensions, we present a public tool, [email protected], that aims at automating the calculation of RGEs at two-loop for arbitrary gauge theories and exemplify its use with the G(221) models. In a second part, we present our results for the calculation of the QCD corrections to the electroweak top-pair production as well as their implementation in a general purpose Monte Carlo generator allowing for a consistent matching of next-to-leading order (NLO) matrix elements with parton shower algorithms, the POWHEG BOX. We then review the status of our calculation of the QCD corrections to the electroweak single-top production. Finally, we present a different aspect of the phenomenology of new heavy resonances, Z', W' by studying their impact on the interaction of ultra-high energy neutrinos in the atmosphere. For definiteness we consider the Pierre Auger Observatory, which is sensible to showers initiated by neutrinos of extreme energies up to 10E12 GeV
Mg2Si, Mg2(Si,Sn) et barrières de diffusion déposées en couches minces par co-pulvérisation assistée par plasma micro-onde pour des applications thermoélectriques pour l'automobile by Codrin Prahoveanu( )

1 edition published in 2015 in English and held by 2 WorldCat member libraries worldwide

In this thesis are presented the deposition of thin films by microwave plasma-assisted cosputtering and their characterization within the context of thermoelectric applications. The aims of the work are split into two categories: the investigation of Mg2Si and Mg2(Si,Sn) thin films in terms of their potential to be implemented in a miniaturized thermoelectric module and the inquiry of materials which may act as diffusion barriers at the interface between Mg2Si-based thermoelements and the brazing joints used in the preparation of electrical contacts. In the first part of the work, thin films of Mg2(Si,Sn) solid solutions with a stoichiometry close to Mg2Si0.4Sn0.6 have been deposited on various substrates. The thermomechanical properties of these films have been investigated with respect to their dependence on the deposition process and the nature of the substrate on which they are grown, while the thermal stability and reactivity with the substrates at intermediate temperatures based on their composition has been explored. Furthermore, the transport properties of Sb-doped Mg2Si thin films have been also characterized. This was done in the context of finding the evolution and dependence of the thermoelectric properties (Seebeck coefficient, electrical and thermal conductivities) to the level of texturing within the thin film. The second part of this thesis involves the deposition of diffusion barriers on bulk Bi-doped Mg2(Si,Ge) thermoelements in order to disrupt the diffusion and reactivity between the thermoelectric leg and the Al-Si alloy-based brazing joint and to obtain a chemically stable, low resistive electrical contact. With this objective, two options have been pursued. One is based on the deposition of gradient layers that are meant to gradually inverse the composition from the Mg2(Si,Ge) thermoelements to a top layer of Ni that is used in the deposition of the potential diffusion barrier. The other option concerns the deposition of a M/Ni bilayer on the TE legs, where M is a metallic layer (Ti, Ta, W or Cr). Overall, the work presented here offers a glimpse of the potential use of Mg2Si and Mg2(Si,Sn) thin films in the making of a miniaturized thermoelectric module and the efficiency of various materials as diffusion barriers in the industry of thermoeletrics
Recherche d'un neutrino stérile avec l'expérience STEREO : développement de l'électronique et identification des neutrinos by Thomas Salagnac( )

1 edition published in 2017 in French and held by 2 WorldCat member libraries worldwide

Since 2011, the re-evaluation of about twenty neutrino flux measurements at short distance from reactors suggests a deficit of about 7 % with respect to predictions. This anomaly has a 3 sigmas significance, as another similar anomaly which corresponds to the deficit of neutrinos emitted from intense source of beta-decay. These anomalies could be explain either by a bias in the flux prediction or by the existence of a new neutrino state, a light sterile neutrino, possibly mixing with the three neutrino states of the standard model. This new neutrino, with no ordinary weak interaction, could only be “visible” via the neutrino oscillation. The STEREO experiment goal is to answer the question of the sterile neutrino existence with mass around 1 eV, using neutrino flux emitted from the research reactor of the « Institut Laue-Langevin » (ILL) at Grenoble, France. To achieve this, the STEREO detector is segmented in 6 cells to measure a hypothetical distortion of the neutrino energy spectrum at different distances from the reactor (between 9 et 11m). Afters few years of detector construction and preparation, the STEREO experiment has started taking data in November 2016 with a first period over in Mars 2017. This thesis took place during two distinct phases of the STEREO experiment. A first part was dedicated to the characterisation and the validation of the electronics, during all its development process until its final conception. In this context, a method to measure the charge response linearity of photomultipliers and their bases, with a precision better than 1 %, has been developed, in order to fulfill the desired sensitivity to the light sterile neutrino hypothesis. This requirement on the precision has been validated by a statistical analysis of the experiment. The second part of the thesis was devoted to the analysis of the first data and more particularly to the identification of the different kinds of background and to the search of neutrino candidates
Caractérisation du secteur de Higgs et aspects du problème de la saveur by Jérémy Bernon( )

1 edition published in 2016 in English and held by 2 WorldCat member libraries worldwide

The Standard Model (SM) of particle physics stands as the most successful description of the fundamental interactions between elementary particles. The discovery of a Higgs boson, at a mass of 125 GeV, in July 2012 at the Large Hadron Collider (LHC), marked its ultimate confirmation. However, various observational and theoretical problems lie in the heart of the SM, with the majority of them linked to the Higgs sector. Being a scalar, the Higgs boson is subject to very large radiative corrections and this ultimately leads to the electroweak hierarchy problem. One of the main goals of the LHC program is to precisely probe the Higgs sector, in order to characterize the mechanism at the origin of the breaking of the electroweak symmetry and test possible solutions to the hierarchy problem. The Higgs sector is also responsible for the generation of the fermion masses, as it induces the Yukawa couplings. The SM flavor sector is highly hierarchical and this leads to flavor puzzles in theories beyond the SM.The first part of this thesis is dedicated to the precise characterization of the Higgs sector. In particular, the public tool Lilith is presented, which allows to derive constraints on new physics models based on the Higgs measurements at colliders. It is then used to perform global fits of the Higgs couplings in the context of various scenarios. In the second part, the phenomenology of two-Higgs-doublet models is studied in the light of the results from the first run of the LHC. The so-called alignment limit is explored in detail, as well as the possible presence of light scalar states. Finally, in the last part of this thesis, the Minimal Flavor Violation hypothesis is introduced as a possible solution to the flavor puzzles beyond the SM. Enforcing it in the Minimal Supersymmetric Standard Model, the renormalisation group evolution of the baryonic R-parity violating couplings is then studied in detail
Spectrocopie gamma des noyaux 84, 86Se, 83As et 98Y by Floriane Drouet( )

1 edition published in 2014 in French and held by 2 WorldCat member libraries worldwide

The work presented in this thesis includes four gamma-ray spectroscopy studies of four nuclei produced by fission induced by 25 MeV protons, on a thick target of 238U. This experiment was realized at JYFL in Jyväskylä with the multi-detector JUROGAM II. In this manuscript a detailed spectroscopic study of nuclei : 84Se, 86 Se, 83 As and 98Y was performed. The first three nuclei are spherical and they are on or adjacent to the N =50 shell closure. Their studies provide a better understanding of the possible decrease in energy of this shell closure, and also of the interactions used in shell-model calculations. Eight new transitions have been assigned to these nuclei and these experimental results are in a relatively good agreement with the shell-model calculations. In the nucleus 98Y a coexistence of nuclear shapes is observed. While the low-energy states below 500keV have a spherical configuration, higher lying states are deformed. Five new transitions were discovered and added to the existing levels scheme, and two calculations using two collective models have been made. The first set of calculations has used the GICM model to reproduce the behavior of states below 500keV and the second set of calculations has used QPRM to reproduce the prolate deformed states, and permitted the assignment of a spherical shape to the isomer (10-)
Etude de la fragmentation des partons par mesure de corrélations photon-hadrons auprès de l'expérience ALICE au LHC by Nicolas Arbor( )

1 edition published in 2013 in French and held by 2 WorldCat member libraries worldwide

The strong interaction theory, Quantum Chromodynamic (QCD), predicts a new phase of nuclearmatter at very high temperature and/or very high density. This state is composed of deconfinedquarks and gluons known as the quark-gluon plasma (QGP). The measurement of its compositionand properties is a challenge for the nuclear physics of the 21st century and should lead to a betterunderstanding of the fundamental symetries and mechanisms related to the quarks confinement insidehadrons and the strong interaction generally.The Large Hadron Collider (LHC) accelerator at CERN (European Organization for NuclearResearch) allows to reach the thermodynamic conditions required to create the quark-gluon plasmausing ultra-relativistic heavy ion collisions (Pb). The ALICE experiment (A Large Ion ColliderExperiment) allows to access several probes to characterize the QGP through particles reconstructionand. Among these probes, high energy parton energy loss is used to access medium characteristicssuch as density or temperature. Parton energy loss is estimated from the modification of the energydistribution of hadrons produced by fragmentation.This thesis is dedicated to the photon-hadron correlations analysis in order to study the modificationof the parton fragmentation due to the quark-gluon plasma. First part of this thesis is devotedto the characterization of the electromagnetic calorimeter (EMCal), the central detector for energymeasurement and photon identification. The second part is dedicated to the photon-hadron correlationmeasurement, for the 7 TeV proton-proton collisions and 2.76 TeV Lead-Lead collisions. Animportant work has been done to improve the prompt photon identification, one of the key point ofthis analysis
Search for Dark Matter and Supersymmetry in the single photon events with the ATLAS detector by Mengqing Wu( )

1 edition published in 2015 in English and held by 2 WorldCat member libraries worldwide

This thesis presents the search for new physics in the final state containing a single photon and missing transverse momentum. The analysis is performed on 20.3fb-1 of proton-proton collisions data at a center-of-mass energy of 8 TeV collected by the ATLAS detector at the Large Hadron Collider. Given the good agreement of the data with the Standard Model pre- diction of such events, an upper limit to the visible cross section produced by new physics is derived. The observed limit at 95% confidence level is 3.64 fb.In this thesis, the results are also interpreted as limits in the parameter space of two new physics models. The first model is an effective field theory, inspired by Fermi-LAT results, in which dark matter particles couple to photons via a contact interaction vertex. Limits are set on the effective mass scale and depend on the postulated coupling constants. The limits set in this dark matter model provide an effective constraint in the parameter space of the theory compatible with the Fermi-LAT results. The second one is a simplified supersymmetric model describing squark pair production with their subsequent decay into a quark and a neutralino. The photon is emitted as initial or final state radiation and the spectrum is compressed, i.e. the mass difference between the squark and the neutralino is assumed to be small. Limits are set on the production cross-section; squark masses are excluded up to 250 GeV in the very compressed region. As the photon can be irradiated from the intermediate squark, this final state would eventually provide the possibility to probe the charge of the squark.A preliminary study has also been carried out to show the search sensitivity with 13 TeV data, which indicate that the limits presented in this thesis can already be improved by 10% with 5fb-1
Fonctionnalisation d'un fil métallique par croissance de films minces dans un magnétron cylindrique inversé by Thomas Le Coz( )

1 edition published in 2018 in French and held by 2 WorldCat member libraries worldwide

The work presented in this manuscript deals with the optimization of the process of deposition of thin films on a moving stainless steel wire. Two inverted cylindrical magnetrons (ICMs) are used to study different aspects of sputtering. At first, an analytical model allowing the evaluation of the thermal contributions to the heating of the substrate is confronted with series of measurements. The results obtained are conclusive but suffer from the inhomogeneity of the magnetic field, which is responsible for the localized loss of high energy secondary electrons. In order to limit the thermal contribution of the charges on the substrate, auxiliary anodes designed to recover the energy flow, are added to each end of the magnetrons. Their influence on the plasma distribution, the microstructure and the chemical composition of the coatings is then discussed. In a second part, the study of reactive sputter deposition with ICMs highlights the need to homogenize the magnetic field in the cathodes. A discussion is then conducted on the influence of the magnetic field on the distribution of deposition rates within the magnetrons and an analytical model, aimed at reproducing the deposition profiles, is developed on the basis of the results obtained. A parametric study (pressure, target - substrate distance, magnetic field strength) is also performed to determine optimal deposition conditions in an ICM. Finally, finite element modeling using commercial software closes the manuscript
Corrections mixtes QCD-EW au niveau NNLO à la production Drell-Yan de bosons Z et W by Zhaoting Pan( )

1 edition published in 2013 in English and held by 2 WorldCat member libraries worldwide

The thesis concerns the NNLO mixed QCD-EW corrections to the Drell-Yan (DY)production of Z andW bosons, via the following reactions: pp(p) Z+X to l + Xand pp to W + X to l + X. This is a fundamental process for an accurate testof the Standard Model (SM) at hadron colliders, since it has a large cross section, aclean experimental signature. In particular, the Drell-Yan production of Ws is important for an accuratedetermination (via transverse mass and pT distributions) of the W mass, mW, aninput parameter of the model. Because of all these reasons, an accurate and reliable theoretical prediction forthe cross section and the distributions of the Drell-Yan production mechanism, thatmeans control on the higher-order perturbative corrections, is demanded for physicsstudies at hadron colliders. In this thesis, we study the mixed QCD-EW corrections to Drell-Yan processes at the NNLO. From a technical point of view, the calculation of such a set of corrections would involve the calcu-lation of very complicated Feynman diagrams, The biggest contribution comes from the diagrams in which the decaying particle(Z or W boson) is nearly on-shell. Using the Cutkosky rules, we can re-write the integration over the phase-space of theinterference terms (one-loop 2 to 2 diagrams interfered with the tree-level 2 to 2 andtree 2 to 3 diagrams squared) in terms of a combination of integrals with propaga-tors having the right causality prescription and propagators with the opposite one.These integrals can be treated in the same way as the virtual corrections. This reduction is done using the \Laporta Algorithm", based onthe Integration-by-Parts Identities. The calculation of the MIs is performed using the method of differentialequations. As a result, we get the MIs expressed as a Laurent series ,where D is the dimension of the space-time, multiplying a factor which takes intoaccount the soft limit of the integral in D dimensions
Interpréter les recherches de nouvelle physique au LHC à l'aide de modèles simplifiés by Ursula Laa( )

1 edition published in 2017 in English and held by 2 WorldCat member libraries worldwide

The recent discovery of the Higgs boson completes the standard model of particle physics, but no compelling signal for physics beyond the standard model has been observed despite the numerous searches performed by experiments at the Large Hadron Collider (LHC). Nevertheless, the hierarchy problem and the observation of dark matter are compelling arguments to study theories predicting new states at the weak scale, and a main effort has been directed towards understanding the negative search results and their implications for such weak scale new physics scenarios. Simplified models have become a standard in the interpretation of LHC searches for supersymmetry (SUSY), aiming at maximal model independence. More recently a similar approach was adopted for the interpretation of dark matter searches. The success of this approach is due to the fact that the small set of free parameters relates to the observables in LHC searches in a clear way, allowing an efficient optimisation of search strategies. Moreover, generic models can be projected on a simplified model description giving an intuitive understanding of the constraints on the parameter space, and providing a fast test against LHC constraints. As the relation between generic model parameters and simplified models is generally not straightforward, sophisticated computational tools are required to facilitate such a projection.This thesis explores the various aspects of simplified model interpretations of LHC searches and how they can be used to understand the results and bridge the gap between theoretical descriptions and experimental observations. In particular the software tool SModelS is presented, a tool that automates the mapping of generic models onto SUSY-like simplified model components, and that allows direct tests against corresponding experimental limits in the included database. Under certain assumptions SModelS can be used to constrain a wide class of new physics models with a dark matter candidate. These assumptions and some explicit tests are discussed in detail, followed by studies of (non-minimal) supersymmetric models using SModelS for the fast evaluation of constraints from SUSY searches. These studies highlight the capacity as well as the limitations of using simplified model results to study generic models. Finally regarding simplified models for dark matter searches, scenarios with a spin-2 mediator are studied in detail
Analyse des données de l'expérience AMS-02 pour la propagation du rayonnement cosmique dans la cavité solaire et la Galaxie by Alexandre Ghelfi( )

1 edition published in 2016 in French and held by 2 WorldCat member libraries worldwide

Le rayonnement cosmique, mis en évidence par Viktor Hess en 1912, est composé de particules chargées, créées et possiblement accélérées dans les restes de supernova, et qui se propagent dans la Galaxie. La mesure des flux du rayonnement cosmique permet de mettre des contraintes sur leurs sources et leur transport, mais aussi de se pencher sur le problème de la matière sombre.C'est pour répondre à ces questions qu'a été construit le détecteur AMS-02, mis en place sur la station spatiale internationale depuis mai 2011. Ce détecteur de haute précision mesure l'ensemble des flux de particules du rayonnement cosmique.Le travail proposé dans cette thèse consiste à estimer le flux de protons avec le détecteur AMS-02. L'accent est mis sur la déconvolution des effets de la réponse en énergie du détecteur sur les flux et sur la caractérisation du flux obtenu à haute énergie (au-dessus de 200 GeV/n) avec la mise en évidence d'une cassure spectrale.D'autre part, le soleil émet un plasma qui interagit avec les particules du rayonnement cosmique, modifiant les flux issus de la propagation dans la Galaxie. Cette modification évolue dans le temps en suivant le cycle d'activité solaire et est appelée modulation solaire. Dans ce cadre, nous avons obtenu une nouvelle détermination robuste des flux interstellaires de protons et d'hélium en nous basant sur les données récentes du rayonnement cosmique (incluant AMS-02). Les niveaux de modulation solaire obtenus sont validés avec une seconde analyse réalisée à partir des données des moniteurs à neutrons, détecteurs au sol, qui permettent d'établir des séries en temps du paramètre de modulation depuis les années 50
Design and implementation of an application specific multi-channel stimulator for electrokinetically-driven microfluidic devices by Jose Gomez Quinones( )

1 edition published in 2011 in French and held by 2 WorldCat member libraries worldwide

This dissertation presents the design and implementation of a 16-channel sinusoidal generator to stimulate microfluidic devices that use electrokinetic forces to manipulate particles. The generator has both, independent frequency and independent amplitude control for each channel. The stimulation system is based upon a CMOS application specific (ASIC) device developed using 0.35¦Ìm technology. Several generator techniques were compared based on frequency range, total harmonic distortion (THD), and on-chip area. The best alternative for the microfluidic applications is based in a triangle-to-sine converter and presents a frequency range of 8kHz to 21MHz, an output voltage range of 0V to 3.1VPP, and a maximum THD of 5.11%. The fabricated device, has a foot- print of 1560¦Ìm¡Á2030¦Ìm. The amplitude of the outputs is extended using an interface card, achieving voltages of 0V to 15VPP. The generator functionality was tested by performing an experimental set-up with particle trapping. The set-up consisted of a micromachined channel with embedded electrodes configured as two electrical ports located at different positions along the channel. By choosing specific amplitude and frequency values from the generator, different particles suspended in a fluid were simultaneously trapped at different ports. The multichannel stimulator presented here can be used in many microfluidic experiments and devices where particle trapping, separation and characterization is desired
Nouvelles méthodes de modélisation neutronique des réacteurs rapides de quatrième Génération by Philippe Jacquet( )

1 edition published in 2011 in French and held by 2 WorldCat member libraries worldwide

Les critères de sureté qui régissent le développement de coeurs de réacteurs dequatrième génération implique l'usage d'outils de calcul neutronique performants. Unepremière partie de la thèse reprend toutes les étapes de modélisation neutronique desréacteurs rapides actuellement d'usage dans le code de référence ECCO. La capacité desmodèles à décrire le phénomène d'autoprotection, à représenter les fuites neutroniques auniveau d'un réseau d'assemblages combustibles et à générer des sections macroscopiquesreprésentatives est appréciée sur le domaine des réacteurs rapides innovants respectant lescritères de quatrième génération. La deuxième partie de ce mémoire se consacre à lamodélisation des coeurs rapides avec réflecteur acier. Ces derniers nécessitent ledéveloppement de méthodes avancées de condensation et d'homogénéisation. Plusieursméthodes sont proposées et confrontées sur un problème de modélisation typique : le coeurZONA2B du réacteur maquette MASURCA
 
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Alternative Names
Laboratoire de physique subatomique et cosmologie (Grenoble)

LPSC

UMR 5821

UMR5821

Unité Mixte de Recherche 5821

Languages
French (12)

English (9)