One-nucleon halo nuclei are exotic nuclei which can be seen as a core around which orbits a loosely-bound valence nucleon. They are usually studied through reactions such as elastic scattering and breakup. The ratio method has been developed as a tool to study one-neutron halo nuclei at high energies. It consists of the ratio of angular cross sections, breakup and elastic scattering, which removes most of the sensitivity to the reaction mechanism and to the reaction model. In the simple recoil excitation and breakup (REB) model, the ratio simplifies to a form factor dependent solely on the wave function of the projectile. By measuring this observable and comparing it to the REB form factor, i.e. in the ratio method, more detailed information on the structure of the halo could be obtained. For neutron-halo nuclei at high energy, the ratio observable obtained from accurate CDCC and DEA theoretical calculations follows its REB prediction. I study the extension of this method to lower energies of the reaction which could make the measurement appropriate to facilities such as SPIRAL2 (GANIL, Caen, France) and ReA12 at FRIB (Michigan State University) and to proton halos. This is done by comparing the REB form factor to dynamical calculations of the ratio. The reactions investigated are the reaction of 11Be, the archetypical one-neutron halo nucleus, on 12C, 40Ca and 208Pb targets at 20 MeV/nucleon and of 8B, the archetypical one-proton halo nucleus, on 12C, 58Ni and 208Pb targets at44 MeV/nucleon.For these reactions, the adiabatic assumption is no longer valid due to the effect of the Coulomb interaction. This effect is mainly visible at forward angle for 11Be and is aggravated for 8B by the fact that the halo is charged. The ratio works less well than for neutron-halos at intermediate and high energies. Nevertheless, the ratio is shown to be very sensitive to the orbital angular momentum l0 in which the halo is bound and its binding energy E0, i.e. the single-particle structure of the projectile. Variations of l0 and E0 induce visible changes in shape and in magnitude (up to several orders) of the ratio. Also, the agreement of the ratio with its REB prediction is best when the projectile is loosely-bound and for low l0, i.e. for s and p waves. The validity of the method is not affected by the use of energy ranges—or bins— in the projectile continuum. These tend to increase the cross section without changing the agreement of the ratio with its REB prediction. The applicability of the method is finally explored at high energy for proton-rich nuclei 17F, 25Al and 27P. I show that the ratio method works the latter since this nucleus is bound by a mere 0.870 MeV in the s-wave. For the other nuclei, although the agreement of the ratio with its REB prediction is less good than for neutron-halo nuclei at high energy, it still provides estimates of nuclear-structure features, such as l0 and E0 and could be applied in what can be called an approximate application of the ratio method. Heavy nuclei exhibit a neutron skin, i.e. a thin layer around the nucleus where only neutrons are found. The thickness of the skin is highly correlated with the slope of the symmetry energy. The process of coherent neutral-pion photoproduction is used to extract the nuclear density and hence the neutron-skin thickness of heavy nuclei. In order to analyse recent data on the photoproduction on 12C, 40,48Ca, 116, 120, 124Sn and 208Pb, I build a reaction code. My model uses the formalism of Kerman, McManus and Thaler (KMT) which allows to build the photoproduction matrix on a nucleus from the ones describing the elementary process on a single nucleon. Within the impulse approximation, the photoproduction is seen as the coherent sum of the photoproduction on each of the nucleons. In the plane wave impulse approximation (PWIA), no rescattering of the pion is considered after its production and the cross section is directly proportional to the Fourier transform of the density. Such process is taken into account at the distorted wave impulse approximation (DWIA) by considering a potential simulating the pion-nucleus interaction and built from the KMT formalism.The agreement of my model with the data is good, especially for 208Pb. The distortion has a significant impact on the photoproduction process. The sensitivity of the process to the density of the target is analysed by performing the calculations with several different densities calculated in different structure models. The distortion has the effect of deteriorating this sensitivity. In the particular case of a 208Pb target, the impact of variations of the neutron-skin thickness of around 0.1 fm on the photoproduction cross section is ten times smaller than the size of the error bars on the experimental data. These results, although less dramatic, hold for the tin targets, for which preliminary data exists. In the light of these results, the coherent neutral-pion photoproduction process does not seem to be suited in the study of the neutron-skin thickness. This conclusion goes in contrast to the results of recent measurements on 208Pb, for which the method was shown to be sensitive to fine details of the density. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

This dissertation documents the results of two related efforts. Firstly, a model of nucleon-nucleon (NN) interactions is developed based on scalar field theory. Secondly, the relativistic 2-body Bethe-Salpeter equation (BSE) is generalized to handle inelastic processes in the ladder approximation. Scalar field theory describes the behavior of scalar particles, particles with spin 0. In the present work scalar field theory is used to describe NN interactions mediated by pion exchange. The scalar theory is applied to nucleons despite the fact that nucleons are fermions, spin 1/2 particles best described by fourcomponent Dirac spinor fields. Nevertheless, the scalar theory is shown to give a good fit to experiment for the total cross sections for several reactions [1]. The results are consistent with more elaborate spinor models involving one boson exchange (OBE). The results indicate that the spin and isospin of nucleons can to some extent be ignored under certain conditions. Being able to ignore spin and isospin greatly reduces the complexity of the model. A limitation of the scalar theory is that it does not distinguish between particle and anti-particle. Consequently one must decide how to interpret the s-channel diagrams generated by the theory, diagrams which involve particle creation and annihilation. The issue is resolved by extending the scalar theory to include electric charge, and formulating NN interactions in terms of complex scalar fields, which are able to describe both particles and anti-particles. A generalized Bethe-Salpeter equation (GBSE) is developed to handle inelastic processes in the ladder approximation. The GBSE, formulated using the scalar theory, is new, and introduces a systematic method for analyzing families of coupled reactions. A formalism is developed centered around the amplitude matrix M' defined for a given Lagrangian. M' gives the amplitudes of a family of reactions that arise from the Lagrangian. The formalism demonstrates how these amplitudes, to 2nd order, segregate into independent groups of coupled BSE's. The GBSE formalism is applied to the coupled BSE (CBSE) of Faassen and Tjon (FT) [2] for the reaction N+N->N+Delta, showing that the CBSE is missing a coupling channel, and in the expansion, under counts ladder diagrams. A proof is given of the equivalence of the series of ladder diagrams generated by M' and the S-matrix. A section on future work discusses several projects for further development and application of the GBSE.

The ESSnuSB will produce a high intensity neutrino super beam based on the 3 ms long proton pulses at 14 Hz from the ESS linac. With the use of a conventional normal-conducting van der Meer horn, to collect pions from the neutrino target, these 3 ms pulses will have to be compressed to of the order of 1 microsecond in order to avoid overheating of the magnet current conductors. Since this pulse compression requires costly extensions to the accelerator complex a prototype design of an alternative normal-conducting hadron collector scheme that could be operated in DC mode has been studied. The magnet has been implemented in the simulation software FLUKA and extensive research has been made to analyse and maximise the flux of charged pions inside and downsteam of the magnet. Further simulations have been made to asses the flux of on-target neutrinos from the alternative collector scheme in comparison to the corresponding flux of a van der Meer horn. Simulation results from the comparison show that the alternative magnet greatly improved the neutrino flux of a bare source but not to the extent necessary to replace the magnetic horn. A conclusion is presented on the future possibilities of an optimized design that can improve the neutrino flux.

The scalar mesons have caused much debate amongst hadronic physicists for many years. Even today the number of scalars is hotly contested, and there is almost no agreement on the composition of any of the experimentally observed states, except perhaps for the K*(_0) (1430). This thesis attempts to shed light on both of these problems via the application of analyticity to two different quantities. Recently a number of authors have proposed the existence of a light, strange, scalar meson known as the k. We perform a direct search of the best available πK scattering data to determine whether or not this resonance exists. This is done by constructing contour integrals from these data and determining the number of poles present inside the contour. We do not need to model either the internal dynamics of the state nor the form of the background scattering. The number of poles found tells us the number of resonances present and their positions allow us to estimate the resonance parameters. We find that there is only one resonance in scalar πK scattering below 1800 MeV and this is identified with the established K*(_0)(1430). We find no evidence for the k. Secondly, applying Cauchy's Theorem to the vacuum polarisation function leads to a relation between experimental and theoretical integrals known as a Finite Energy Sum Rule (FESR). FESRs are used to explore the scalar, isoscalar non-strange current and allow us to determine which of the experimentally observed scalar, isoscalar mesons is most likely to be the uũ + dd state. We find that the lightest scalar, isoscalar uũ dd state is not the fo(980) as suggested by some authors, but is rather the light, broad object known as the fo(400 - 1200). We are also able to estimate the average light quark mass and find m(_q)(l GeV(^2)) = 4.7 ± 0.9 MeV which is consistent with the recent estimates of this quantity from unquenched lattice QCD.

Universiẗat, Diss., 2002--Münster (Westfalen). / Dateiein im PS-Format.

L’étude présentée est consacrée à l’usinabilité de la fonte à graphite vermiculaire. Celle-ci se situe entre la fonte à graphite lamellaire et la fonte à graphite sphéroïdale par rapport à la forme du graphite constituant ce matériau. Elle est utilisée depuis plus de cinq ans dans les blocs moteurs diesel afin d’améliorer les performances et de diminuer les rejets atmosphériques pour respecter les nouvelles normes Européennes. Pour évaluer l’usinabilité d’un matériau, il faut s’étalonner par rapport à un matériau de référence. Dans notre cas, la fonte à graphite vermiculaire a été comparée à la fonte à graphite lamellaire. Des essais de tractions ont permis d’obtenir les propriétés mécaniques du lot de matière utilisé pour la campagne d’essais d’usinage ; ceci, afin de se situer dans la gamme de ce type de fonte. Les plaquettes d’usinage ont été caractérisées par nano-indentation. Les revêtements PVD et CVD ont subit des essais de micro-rayure afin de caractériser leur adhésion sur leurs substrats respectifs. La mise en place d’un plan d’expérience a permis de limiter le nombre de plaquettes d’usinage prototypes à réaliser. Des essais tribologiques de type pion/disque ont révélé des pistes exploitables pour la compréhension des phénomènes de frottement et d’usures mis en jeu lors de l’usinage de la fonte à graphite vermiculaire. / This study deals with machinability of compacted graphite iron. This material is in-between grey cast iron and nodular cast iron due to the graphite particle shape. It is used for manufacturing diesel engine blocks so as to increase performances and reduce carbon emissions to comply with Euro 5 norm. It is necessary to compare one material to a reference material to evalute machinability criterium. In our case, compacted graphite iron has been compared to grey cast iron. Tensile tests have given us mechanical properties of our test pieces batch used for machining tests. It helped us to qualify the material in its own material range. Inserts have been characterized by nanoindentation. PVD and CVD coatings were benchmarked in microscratch way to determine their respective adhesion to theirs substrates A design of experiment has been setted up so as to reduce number of inserts protypes to be manufactured. Pin on disk tribologic tests gave few hints to have a better understanding of friction phenomena and wear during compacted graphite iron machining.

No description available.

L'objet de cette thèse est de présenter une nouvelle mesure de la masse du pion en utilisant la spectroscopie X de l'hydrogène pionique et des résultats de spectroscopie de l'argon et du soufre héliumoïdes. La nouvelle masse du pion a été mesurée avec une précision 30% supérieure à la moyenne mondiale actuelle, c'est-à-dire égale à 1.7 ppm. Elle a été obtenue par spectroscopie de Bragg des transitions 5 -> 4 de l'azote pionique en utilisant les prédictions théoriques de QED. Je présente le calcul de la structure hyperfine et celui de la correction de recul du noyau pour les atomes pioniques au moyen d'une nouvelle méthode de perturbation de l'équation Klein-Gordon.Le spectromètre utilisé pour cette mesure a été caractérisé grâce aux transitions relativistes des atomes héliumoïdes produits dans un nouveau type de source d'ions à résonance cyclotronique des électrons. Les spectres haute statistique de ces ions permettent de mesurer les énergies de transition avec une précision de quelques ppm, ce qui permet de tester, avec un degré de précision jamais atteint, les prédictions théoriques. L'émission de rayons-X des atomes pioniques et des ions multichargés peut ainsi être utilisée pour la définition de nouveaux étalons de rayons-X de quelques keV.

L'expérience de physique nucléaire GRAAL installée à Grenoble auprès du synchrotron européen (ESRF) produit, par rétrodiffusion Compton, un faisceau de gammas polarisés linéairement ou circulairement. <br /><br />Les caractéristiques d'un tel faisceau rendent possible l'étude des réactions de photoproduction de mésons pseudoscalaires (pion, eta, kaon) dont certains aspects théoriques sont explicités dans le cadre de cette thèse. <br /><br />Une description précise des programmes d'analyse permet de comprendre le traitement complet des informations depuis l'acquisition des données jusqu'à la présentation des premiers résultats expérimentaux sur l'asymétrie Sigma du faisceau pour les réactions gamma + p -> p + X (X = pi, eta) dans le domaine d'énergie situé entre 700 et 1100 MeV. <br /><br />Des méthodes d'extraction des observables de polarisation de la réaction gamma + p -> K+ + Lambda ont été mises au point à partir de la simulation Monte Carlo. La reproduction précise des trois observables de simple polarisation (P, Sigma, T) et des quatre observables de double polarisation faisceau-recul (Ox, Oz, Cx, Cz), pour un ensemble de données correspondant à 100000 réactions gamma + p -> K+ + Lambda, montre que ces quantités peuvent être mesurées dans l'expérience GRAAL.

Dans ce travail de thèse, nous présentons quatre expériences, portant soit sur l'étude d'ions lourds hydrogenoïdes ou héliumoïdes, soit sur celle d'atomes exotiques, et qui se sont déroulées au Gesellschaft für Scherionenforchung (GSI) et à l'Institut Paul Scherrer (PSI).<br /><br />Dans la première partie de ce manuscrit, nous décrivons, tout d'abord, un spectromètre à cristal courbe et en transmission, couplé à un détecteur germanium sensible en position. Cet ensemble, dédié à la mesure de l'énergie de photons X entre 50 et 100 keV et qui est destiné à être monté sur l'accélérateur du GSI, nous permettra, dans les années avenirs, de gagner un ordre de grandeur sur la précision de la mesure du déplacement de Lamb du niveau fondamental de l'uranium hydrogénoïde, afin de tester la QED en champ coulombien fort. Ensuite, nous détaillons une expérience qui nous permettra de donner bientôt une nouvelle valeur de la masse du pion chargé avec une incertitude relative de 1 ppm. Elle est basée sur une spectroscopie X de l'azote pionique, effectuée au PSI. Pour celle-ci nous utilisons un montage composé d'une trappe anticyclotronique, d'un spectromètre de Bragg en réflexion, possédant un cristal sphérique et d'un détecteur CCD refroidit. Ce dispositif permet également de tester la QCD et la théorie des perturbations chirales, par une mesure des transitions radiatives de l'hydrogène pionique.<br /><br />La seconde partie est consacrée à une description d'une mesure la durée de vie d'un niveau métastable de l'or héliumoïde, grâce à une expérience de temps de vol, qui se déroule au GSI. Nous donnons, pour la toute première fois pour un Z si élevé, une valeur précise de cette durée de vie, qui constitue un test important de la théorie relativiste à n-corps.