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Dissertations / Theses on the topic 'Nuclear structure physics'
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1
Seely, Jason (Charles Jason). "Precise measurement of the nuclear dependence of structure functions in light nuclei." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39559.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.Includes bibliographical references (leaves 171-174).
The EMC effect has been with us for over 20 years. During this time, the nuclear dependence of the structure functions, and therefore the underlying quark distributions, has been studied with much success. However, the bulk of the experimental effort has been to measure the effect in heavy nuclei where it has the same zBj dependence and differs only in magnitude. Calculations predict large differences in both the magnitude and zBj-dependence of the EMC effect in 3He and 4He and precise measurements of the EMC effect in these nuclei could be used to distinguish between existing models. E03-103 measured the inclusive electron scattering cross-section on 1H, 2H, 3He, and 4He, as well as the heavier targets Be, C, Cu, and Au. This thesis describes the experiment in detail and presents results for 3He, 4He, and carbon. These data provide the first measurement of the EMC effect in 3He above xBj > 0.4, and improve upon the existing measurement of the effect in 4He.
by Jason Seely.
Ph.D.
2
Bissey, François René Pierre. "Structure functions in the three nucleon system /." Title page, contents and abstract only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phb6228.pdf.
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James, Jessica. "Nuclear structure effects in atomic parity non-conservation." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259953.
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Abidin, Zainul. "Hadron structure from holographic QCD." W&M ScholarWorks, 2010. https://scholarworks.wm.edu/etd/1539623570.
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The AdS/CFT correspondence relates a strongly coupled gauge theory in four dimensional space-time with a weakly coupled gravity theory in five dimensional space-time. This correspondence provides a way to access the strongly coupled regime of a gauge theory via a perturbative approach in its gravity dual theory. In this dissertation, the gravity dual of Quantum Chromodynamics (QCD) is discussed. The so-called bottom-up approach (AdS/QCD) successfully reproduces the low energy observables at 10-20% accuracy.;An AdS/QCD model with two flavors of quarks is considered, assuming isospin symmetry. Pions and rho mesons masses and decay constants are obtained. We calculate the stress tensor, or energy-momentum tensor, form factors. Mesons appear strikingly more compact measured by the gravitational form factor than by the electromagnetic form factor.;Extension of the model to three flavors of quarks, incorporating quarks with differing masses (including the strange quark), is also considered. Dynamical properties of mesons such as electromagnetic form factors, strangeness-changing form factors, and gravitational form factors are obtained from 3-point function calculations. The results agree well with experimental data (when available) and with calculations from other methods (when available).;Electromagnetic and gravitational form factors for baryons are calculated, in a scheme where the baryons are treated as independent particles in AdS space. The form factors were calculated both in the case of so called hard-wall and soft-wall model. The simplest fermion Lagrangian for the five dimensional curved space does not contribute to the F2 form factor unless one adds a Pauli term, which also contributes to the F1 form factor.
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Hopkins, P. J. B. "Nuclear cluster structure and electron scattering." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376916.
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Papanicolopoulos, Chrysanthos Dionisios. "Shape coexistence in odd-mass nuclei near Z = 82 closed shell : a study of the excited states of [superscript]185Au in the [beta]/Ec decay of [superscript]185Hg." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/30333.
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Mohammed, Mustafa Mohammed. "Nuclear structure studies of 159Er up to high spin." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/6815/.
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In the current work a detailed spectroscopic investigations of the gamma-decays from the excited states of the rare-earth nucleus 159Er has been performed to study the structural properties up to possible ultrahigh spins. The nucleus of 159Er had been populated by the reaction 116Cd(48Ca,5n ) at beam energy of 215-MeV in an experiment at Argonne National Laboratory using the Gammashphere array. Following a hypercube analysis of the collected data, new rotational bands were observed and the previously reported bands were extended up to possible spin through observation of new gamma-ray transitions in coincidence with the existing sequences. Possible angular intensity-ratio, B(M1)/B(E2)-ratios, measurements have been performed to confirm the nature of previously observed transitions and to assign multipolarites of the new ones. The band structures are discussed within the framework of cranked shell model calculations, revealing a diverse range of quasiparticle configurations. At spins of around 50¯h, there is evidence for a change from dominant prolate collective motion in the yrast band and its signature partner to oblate non-collective structures via the mechanism of band termination. A possible strongly deformed triaxial band occurs at these high spins, which indicate collectivity beyond 50¯h. The high-spin structures of data are interpreted within the framework of cranked Nilsson-Strutinsky calculations.
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Bednar, Kyle D. "The Partonic Structure of the Nucleon, Pion, and Kaon." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1574292072566539.
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Oginni, Babatunde M. "Study Of Nuclear Level Densities From Evaporation Of Compound Nuclei Of Mass Numbers 61, 64, 65, And 82." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1241791753.
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Hadinia, Baharak. "In-beam Study of Extremely Neutron deficient Nuclei Using the Recoil-Decay Tagging Technique." Doctoral thesis, KTH, Kärnfysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4596.
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The low-lying structures of the extremely neutron-deficient nuclei 106Te, 107Te, 110Xe, 170Ir and 172Au have been investigated experimentally. Prompt gamma rays emitted in fusion-evaporation reactions were detected by the Jurogam HPGe array. The gamma rays were assigned to specific reaction channels using the recoil-decay tagging technique provided by the gas-filled separator RITU and the GREAT focal-plane spectrometer. The experimental set-up and the technique used to extract the information from the experimental data are described in detail. Results were interpreted in terms of the nuclear shell model and Total Routhian Surface calculations. In addition, decay studies on 170Ir, 172Au and 164Re led to the discovery of new alpha-decay branches in these nuclei.QC 20100730
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BARFIELD, ARIEL FOOTE. "CONFIGURATION MIXING AND OCTUPOLE STUDIES OF NUCLEI WITHIN THE INTERACTING BOSON MODEL." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/188141.
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The Interacting Boson Model (IBM) has been very successful in describing the collective properties of nuclei. This work concerns two systematic applications of the model, one involving configuration mixing, and the other involving octupole bands. The even isotopes of mercury are of special interest because of the coexistence of two sets of bands, of very different character, in the lighter nuclei. The neutron-proton IBM (IBM-2) with configuration mixing provides a good description, both of states built on the normal ground state and of those associated with a proton pair excitation across the Z = 82 closed-shell gap. Eleven isotopes are studied, ranging from the middle of the neutron shell to very near the doubly closed shell at ²⁰⁸Pb. The same Hamiltonian is used for all the nuclei studied, with parameters which are constant or smoothly varying. There have been extensive IBM studies of low-lying positive parity bands, which are based on the ground state and the quadrupole degree of freedom. The present work comprises the first systematic IBM study of the corresponding negative parity bands, which are based on the octupole degree of freedom. In this model, an f boson is coupled to a positive parity core, described by the usual s and d bosons. This is done within the original IBM framework, called IBM-1, which does not include separate neutron and proton degrees of freedom. The IBM octupole model is presented and the phenomenology is explored, both for the full model, and for the SU(3) limit of the model. Calculated energy spectra and B(E3) transition rates are presented for nine deformed rare-earth nuclei. There is good agreement with available experimental data for these nuclei. It is shown that nuclei for which the two lowest octupole bands are K = 2 and 0 cannot be described within the present model. In this case, it appears that separate neutron and proton octupole degrees of freedom are necessary. The exchange term in the Hamiltonian is shown to arise from a neutron-proton octupole-octupole interaction. A consistent octupole model is developed and successfully applied to the nucleus ¹⁶⁸Er.
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Ikin, Peter Jonathon Christopher. "Data analysis techniques for triggerless data streams in nuclear structure physics." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427039.
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Harding, Peter Alan. "On-line studies of nuclear structure and relaxation mechanisms." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358608.
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Keeling, P. R. "Spin and structure of '1'2C-'1'2C resonances." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379972.
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Maragni, Elisabeth de Castro Caparelli. "A Dependência do Calibre nos Cálculos Modelo do Fator de Forma Transverso Elétrico em Núcleos Complexos." Universidade de São Paulo, 1996. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-26022014-151850/.
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Neste trabalho estudamos a dependência do calibre nos cálculos modelo do fator de forma transverso elétrico para núcleos complexos. Foram consideradas as diferentes prescrições que procuram levar parcialmente em consideração os efeitos da corrente de dois corpos, no cálculo do fator de forma transverso elétrico, através dos vínculos impostos pela equação da continuidade. Quando os estados nucleares satisfazem a equação de Schrödinger e a corrente a equação da continuidade as prescrições coincidem. Entretanto, em geral, essas condições não são satisfeitas, surgindo assim as diferenças entre elas, que pode ser interpretada como uma dependência do calibre no cálculo do fator de forma transverso elétrico, Nosso objetivo neste trabalho é mostrar a importância, em núcleos complexos) da dependência do calibre oriunda da violação da equação de Schrödinger pelas funções de onda modelo. Nós fazemos uma análise para verificar sua origem e, para demonstrar sua importância quantitativa, comparamos cálculos do fator de forma na TDA e na RPA, para estados coletivos de paridade negativa no 16 ANTPOT O e 40 ANTPOT Ca. Esta comparação mostra uma considerável diminuição da dependência do calibre quando passamos da TDA para RPA.In this work we study the gauge dependence of mode) calculations of transverse electric form factors in complex nuclei. We consider the different prescriptions that try to take partially into account the effects of the two-body current, in the calculation of the transverse electric form factor, through the continuity equation constraints. When the nuclear states obey the Schrodinger equation and the current density the continuity equation, the prescriptions coincide. However, in general, these two conditions are not satisfied and therefore they differ which can be seen as a gauge dependence in the calculation of the transverse electric form factor. Our aim is to show the importance in complex nuclei, of the gauge dependence that comes from the violation of the Schrödinger equation by the model wave functions. We perform an analysis to identify its origin and, to give evidences of its quantitative importance, we compare TDA and RPA calculations of transverse electric form factors for collective states of negative parity in 160 and 46Ca. This comparison shows that the gauge dependence diminishes considerably in RPA.
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Dimarco, Alejandro Javier. "O Papel da Estrutura Nuclear nas Taxas de Decaimento Beta e Captura de Elétrons na Pré-Supernova." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-27022014-150737/.
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Neste trabalho calculamos taxas de captura de elétrons e decaimento beta no estágio de pré-supernova, para espécies nucleares da camada fp que são fundamentais nessa etapa da evolução estelar. Enfatizamos as transições entre estados de baixa energia. No cálculo dos elementos de matriz nucleares foram utilizados modelos microscópicos. Dados experimentais e densidades de níveis foram empregados na construção da função de partição nuclear. Foi avaliado o impacto de nossos cálculos nas abundâncias isotópicas e na derivada temporal da fração de elétrons, comparando o nossos resultados com cálculos mais simples. Concluímos de nosso trabalho que um cálculo mais detalhado das taxas de captura de elétrons e decaimento beta dando ênfase nas transições entre ~estados de baixa energia, pode conduzir a variações importantes nas predições sobre o posterior colapso e explosão da supernova.ln this work we carry out calculations of electron capture and beta decay rates, at presupernova stages, from several nuclei of the fp region that are important in this stages of stellar evolution. We emphasize transitions between low energy states. The nuclear matrix elements was calculated using microscopic models. We used experimental data and level densities in the construction of the nuclear partition function. We estimated the influence of ours calculations in the isotopic abundances and in the temporal variation of the electron fraction. We compared ours results with nives calculations. We conclude that a more detailed calculation of the electron capture and beta decay rates giving emphasize to the transition between low energy states can lead importants variations to predictions about the subsequent collapse and supernova explosion.
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Ukita, Gilberto Mitsuo. "Espalhamento inelástico de deuterons nos isótopos de ANTPOT.94,98 Mo." Universidade de São Paulo, 1998. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-28022014-115433/.
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eng Distribuições angulares, referentes ao espalhamento inelástico de dêuterons nos isótopos de ANTPOT 94,98 Mo e à excitação dos primeiros estados coletivos 2 POT.+ E 3 POT.-, foram obtidas com dêuterons incidentes de 13,2 MeV e 16,0 MeV, utilizando o acelerador Pelletron da Universidade de São Paulo. Os dêuterons emergentes da reação foram analisados por um espectrógrafo magnético tipo polo-partido de Enge e registrados em placas de emulsão posicionadas na sua superfície focal. As seções de choque diferenciais, na energia incidente de 13,2 MeV, foram medidas em 18 ângulos de espalhamento, detalhando, particularmente para as excitações quadrupolares de ambos os isótopos, a região de máxima interferência nuclear-coulombiana (CNI) e também aquela onde a excitação nuclear predomina. A análise foi feita na aproximação de Born com ondas distorcidas e potencial óptico deformado (DWBA-DOMP), utilizando parâmetros ópticos globais. O ajuste das previsões sobre as medidas de CNI com dêuterons, que interagem isoescalarmente com o núcleo, foi realizado pelo método dos mínimos quadrados, permitindo a extração dos parâmetros correlacionados delta POT.N IND.L e C = delta POT.C IND.L/DELTAPOT.N IND.L , com suas incertezas experimentais, onde deltaPOT.N IND.L é o comprimento de deformação nuclear e deltaPOT.C IND.L., o comprimento de deformação de carga. Esses parâmetros possibilitaram, dentro dos modelos adotados, a determinação da razão dos momentos quadrupolares e octupolares das distribuições de nêutrons e prótons,M IND.n/M IND.p, bem como os respectivos valores das probabilidades reduzidas de transição elétrica, B(EL), e isoescalar, B(ISL). O parâmetro C, que é diretamente proporcional à [B(EL)/B(ISL)] POT.1/2, foi obtido com precisão da ordem de 2% para as excitações quadrupolares e de aproximadamente 7% para as octopolares, para ambos os isótopos, nos estudos de CNI aqui apresentados. ) Os resultados experimentais indicam, de forma coerente, que as transições para os estados 2 POT.+ IND.1 e 3 POT.- IND.1nos núcleos de ANTPOT 94 Moe ANTPOT 98 Mo são mais influenciadas pelos prótons do que pelos nêutrosn, em relação à previsão do modelo coletivo homogêneo N/Z.eng Experimental angular distributions for deuteron inelastic scaterring by 94,98Mo excitating the first 2+ and 3- collective states were obtained using the deuteron beam of the São Paulo Pelletron accelerator, at incident energies of 13.2 MeV and 16.0 MeV. The ejectiles of the reactions were momentum analyzed by an Enge split-pole magnetic spectrograph and detected in nuclear emulasion plates exposed at the focal plane. The differential cross sections, corresponding to the incident energy of 13.2 MeV, were measured for both isotopes at 18 scattering angles, detailing, in particular for the quadrupolar excitations, not only the region of maximum Coulomb-nuclear interference (CNI), but also the region where the nuclear interaction is predominant. The analysis was performed in the framework of the collective distorted wave Born approximation (DWBA) within a deformed optical model potential (DOMP) approach, using well tested global optical model parameters for deuterons. Since the deuteron is a projectile of isoscalar character, the fit of the DWBA-DOMP predictions to the CNI measurements, by means of the least squares method, allowed the simultaneous extractions of the correlated parameters NL and C= CL/NL, with their experimental uncertainties, where NL and CL are, respectively, the nuclear (mass) and charge deformation lengths. These experimental quantities yielded, within the adopted models, values of the ratio Mn/Mp for the quadrupolar and octupoular moments of the neutron and proton distributions, and also for the corresponding electric [B(EL)] and isoscalar [B(ISL)] reduced transition probabilities. The C parameters, which are proportional to the ratio [B(EL)/B(ISL)]1/2, were determined in the present CNI studies, for both 94,98Mo, within a 2% statistical uncertainty level for the 2+1 excitations and within ~ 7% for the 3-1 ones. The experimental results reveal, in a consistent way for both isotopes, protons to contribute more than neutrons to the first quadrupolar and octupolar excitations, with respect to the homogeneous collective model expectation of N/Z.
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Núñez, Juan Antonio Alcántara. "Estruturas rotacionais quadrupolares elétricas e dipolares magnéticas nos núcleos de 105Rh e 108Pd." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-24022014-142835/.
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As estruturas dos núcleos de ANTPOT. 105 Rhe de ANTPOT 108.Pd foram estudadas usando a reação ANTPOT. 100 Mo(ANTPOT. 11 Bxalfaypzn) na energia incidente de 43 MeV. Foram realizadas as medidas de coincidências gama-gama, gama-gama- multiplicidade de partículas carregadas e das correlações angulares utilizando o espectrômetro gama formado por 4 detectores HPGe e o sistema ancilar de detectores de partículas carregadas. No núcleo de ANTPOT. 105 Rh foi observada pela primeira vez a banda gama, indicando a existência de trixialidade em baixo spin, e uma nova estrutura baseada no orbital intruso (431)1/2 POT. +. Duas estruturas formadas por uma quasi-próton, pig IND. 9/2 e pi[301]1/2 POT. -, foram estendidas, e em ambos casos foram observadas as duas signatures. Quatro bandas de dipolo magnético foram observadas em alto spin, sendo três delas de paridade negativa e com características similares: muito regulares, alinhamento quase constante e valores de B(M1)/B(E2) relativamente grandes. Duas destas bandas são aproximadamente degeneradas em energia de excitação, e podem ser consideradas como parceiras quirais com uma configuração pig IND. 9/2 vh IND. 11/2 v(g IND. 7/2, d IND. 5/2). No núcleo de ANTPOT. 108 Pd foram observadas pela primeira vez as duas signatures da banda de configuração negativa vh IND. 11/2 v(g IND. 7/2, d IND. 5/2), e uma banda com intensidade relativa baixa, à qual pode ser atribuída uma configuração de paridade positiva (vh IND. 11/2) POT. 2. A interpretação dos resultados experimentais foi feita no contexto de Cranked Shell Model e de Total Routhian Surfaces.The structures of the 105Rh and 108Pd nuclei have been studied by the in-beam heavy-ion fusion-evaporation reaction 100Mo (11B, xaypzn) at 43 MeV incident energy. -, charged particle -- coincidences and angular correlation were measured using the spectrometer formed by four HPGe detectors and the charge-particle ancillary detector system. In 105Rh, a -vibration band was observed for the first time indicating the existence of triaxiality at low spin. A new structure based on the intruder [431]1/2+ próton orbital was identified. The structures based on one quase-proton, g9/2 and [301]1/2-, were extended, showing the two signatures partners. Four magnetic dipole bands have also been observed at high spin, three of which have negative parity and have similar characteristics: they are very regular, present nearly Constant alignments, and large values of B (M1)/B(E2) ratios. Two of them are nearly degenerate in excitation energy and could be chiral partners with , g9/2 x h 11/2 x (9 7/2 , d 5/2) configuration. Also, in 108Pd the both signatures partners of h 11/2 x (9 7/2 , d 5/2) configuration and one structure for the first time. Experimental results were interpreted within the framework of Cranked Shell Model and Total Routhian Surfaces.
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Allegro, Paula Rangel Pestana. "Estrutura nuclear do 64Cu." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26112008-105333/.
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Este trabalho tem como principal interesse o estudo das propriedades do núcleo ímpar-ímpar 64Cu utilizando técnicas de espectroscopia de raios em linha. Para o estudo deste núcleo, foi realizada no acelerador Pelletron (Modelo 8-UD, tipo TANDEM) da Universidade de São Paulo a reação de fusão-evaporação 51V(16O, 2pn)64Cu com energia de feixe incidente igual a 70 MeV, utilizando-se um alvo de 4,4 mg/cm2 de 51V com um backing de 7,0 mg/cm2 de Au. As medidas de coincidência das partículas carregadas evaporadas e da radiação gama foram feitas utilizando-se o espectrômetro de raios SACI-PERERE, composto por quatro detectores de GeHP com supressores Compton e 11 detectores E-E de partículas carregadas. Dez novas transições pertencentes ao núcleo 64Cu e um novo estado excitado foram identificados, porém somente uma transição foi posicionada no esquema de níveis conhecido do 64Cu devido principalmente à baixa estatística. Utilizando-se a técnica DCO (Correlações angulares de radiação emitida por estados orientados), determinou-se a multiporaridade de algumas transições pertencentes ao núcleo 64Cu. A descrição do núcleo 64Cu foi feita através do Modelo de Camada em Larga Escala. Para previsões deste modelo, utilizou-se o código Antoine e as interações residuais GXPF1 e fpg, desenvolvidas para as camadas pf e pfg, respectivamente. Os resultados obtidos com este modelo mostram que os estados excitados do núcleo 64Cu podem ser descritos como excitações do tipo partícula-buraco e são caracterizados por funções de onda com alto grau de mistura de configurações.The main goal of this work is a study of the odd-odd nucleus 64Cu using in-beam gamma-ray spectroscopy. For this study, the fusion-evaporation reaction 51V(16O, 2pn)64Cu at 70 MeV bombarding energy has been performed with the 8-UD Pelletron TANDEM accelerator of the Universidade de São Paulo. The target consisted of a 4.4 mg/cm2 foil of 51V with a 7.0 mg/cm2 Au backing. Gamma-ray and evaporated charged particle coincidences were measured with the SACI-PERERE -ray spectrometer, composed of 4 Comptonsuppressed GeHP and an ancillary system of 11 E-E plastic phoswich scintillators. Ten new -rays and a new excited state have been assigned to 64Cu. Due to low statistics, only one transition could be placed in the known level scheme of 64Cu. The gammaray multipolarities were determined using the Directional Correlations of -rays from Oriented States of Nuclei (DCO) technique. The results were compared with Shell Model calculations using the Antoine code with the GXPF1 and fpg effective interactions, developed for use in the pf shell and pfg shell, respectively. The results obtained with this model have shown that the 64Cu excited states could be described by particle-hole excitations and these states are characterized by wave functions with configuration mixing.
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Ndayishimye, Joram. "Alpha cluster structure and scattering in 20Ne, 44Ti, 94Mo, 136Te and 212Po." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6484.
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Thesis (MSc)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: We investigate the nuclei 20Ne, 44Ti, 94Mo, 136Te and 212Po using a model of an α-cluster orbiting a closed shell core. A purely phenomenological cluster-core potential is found to provide a successful description of the spectra, B(E2↓) transition strengths, and α-decay rates of the low-lying positive parity states of these nuclei. We then use the same potential as the real part of an optical model potential to describe the α elastic scattering by 16O, 40Ca, 90Zr and 208Pb. The experimental differential cross-section data are reasonably well reproduced with the imaginary potential depth as the only free parameter. The special case of the 8Be system is also analysed.
AFRIKAANSE OPSOMMING: Ons ondersoek die kerne 20Ne, 44Ti, 94Mo, 136Te en 212Po deur gebruik te maak van ’n model waar ’n α-bondel om ’n kern met ’n geslote skil wentel. ’n Suiwer fenomenologiese bondelkern potentiaal is gevind wat die energie spektra, B(E2 ↓) oorgangs sterktes, en α-verval tempo vir laagliggende positiewe pariteitstoestande vir hierdie kerne beskryf. Ons gebruik dieselfde potentiaal as die reele deel van die optiese potentiaal om die alpha elastiese verstrooiing deur die kerne 16O, 40Ca, 90Zr en 208Pb te beskryf. Die eksperimentele differensiele kansvlak data word redelik goed gereprodukseer met slegs die imaginere potensiaal diepte as die enigste vrye parameter. Die spesiale geval van 8Be is ook ondersoek.
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Cresswell, Alan James. "Studies of nuclear structure using heavy ion-induced transfer reactions." Thesis, University of Liverpool, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240215.
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Rotival, Vincent. "Fonctionnelles d'energie non-empiriques pour la structure nucleaire." Phd thesis, Université Paris-Diderot - Paris VII, 2008. http://tel.archives-ouvertes.fr/tel-00409482.
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La methode de la fonctionnelle de la densite d'energie (EDF) est un outil de choix pour l'etude de la structure nucleaire a basse energie, car elle permet des calculs de noyaux finis aussi bien pour des systemes stables connus experimentalement dont les proprietes sont reproduites avec une bonne precision, que pour des noyaux qui ne peuvent encore etre produits mais sont predits theoriquement. Dans la premiere partie de cette these, une nouvelle methode quantitative est introduite pour caracteriser l'existence et les proprietes des halos dans les noyaux moyens et lourds, ainsi que pour etudier l'impact des correlations d'appariement ou du choix de la fonctionnelle d'energie sur leur formation. Il apparait que la solidite de ces resultats est limitee par le faible pouvoir predictif des fonctionnelles utilisees jusqu'a present qui sont ajustees sur des donnees experimentales. Dans la seconde partie de ce memoire, nous entreprenons la construction de fonctionnelles non-empiriques qui reposent sur un nouveau paradigme pour les forces nucleon-nucleon dans le vide, a savoir les interactions low-momentum engendrees par l'application des methodes du groupe de renormalisation. Ces potentiels a coeur mou sont utilises comme point de depart d'une strategie a long terme faisant le lien entre les techniques modernes de resolution du probleme a N corps et les methodes EDF. Nous donnons ainsi des perspectives pour construire differentes realisations d'un modele non-empirique d'interaction incluant les effets de milieu a differents niveaux d'approximation et pouvant etre traite dans les codes dedies a la structure nucleaire. Dans ce memoire, la premiere etape de ce travail est initiee par l'ajustement d'une representation operatorielle des forces low-momentum dans le vide realise au moyen d'un algorithme parallele d'intelligence artificielle. Les premiers resultats mettent en valeur la possibilite d'incorporer la physique necessaire a la structure de basse energie dans ce vertex gaussien.
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Güven, Haşim Zahid. "Nuclear Physics in Neutron Stars : Study of Superfluidity in Hypernuclei and Constraining the Nuclear Equation of State." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP041.
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Dans cette thèse nous avons d’abord étudié l’effet du paring Lambda sur les propriétés des hypernoyaux dans le formalisme Hartree-Fock Bogoliubov. La fonctionnelle de Skyrme SLy5 est utilisée dans le canal nucleon-nucleon alors que 3 fonctionelles fittées sur les calculs microscopiques Brueckner Hartree-Fock sont utilisées dans le canal Nλ : DF-NSC89, DF-NSC97a et DF-NSC97f. Ces fonctionnelles décrivent la séquence des énergies de liaison expérimentales à un lambda, des hypernoyaux légers aux hypernoyaux lourds. Dans le cas du canal Lambda-Lambda, nous avons utilisé la prescription empirique EmpC, ajustée à 1 MeV sur l’énergie expérimentale de liaison dans le 6HeLL. A l’aide de cette approche de la fonctionnelle de la densité, plusieurs noyaux ont été étudiés, avec des couches nucléoniques fermées et des couches ouvertes en Lambda. Une interaction d’appariement Lambda-Lambda est introduite, dont la magnitude est ajustée pour être consistante avec la valeur maximale des prédictions BCS pour le gap d’appariement Lambda dans la matière hyperonique. Nous donnons ainsi une valeur maximale pour la prédiction du gap d’appariement Lambda et ses effets dans les hypernoyaux. Nous avons montré que les effets de l’appariement LL dépendent de l’hypernoyau considéré. L’énergie correspondante de condensation est de l’ordre de 3 MeV au maximum, ce qui entraine de faibles corrections sur les distributions de densité et la structure en couches. De manière générale, nous avons trouvé que l’appariement Lambda-Lambda peut être important si l’écart en énergie entre les couches est plus petit que 3 MeV. A cette condition, l’appariement Lambda peut impacter les densité et les énergies de liaison. En résumé, il est montré que l’effet de l’appariement relié aux Lambda peut être en général négligé dans la plupart des hypernoyaux, sauf pour les ceux ayant un écart typique dans le spectre à une particule plus petit que 3 MeV autour du niveau de Fermi. De plus, les conditions sur à la fois les énergies de Fermi et les moments angulaire orbitaux atténuent l’appariement nucleon-Lambda pour la plupart des hypernoyaux.La deuxième partie de la thèse est dévolue aux équations d’état dans les étoiles à neutrons. Nous avons confronté les valeurs des déformabilité de marée extraites de l’évènement d’onde gravitationnelle GW170817, aux contraintes issues de la physique nucléaire à l’aide d’une approche semi-agnostique pour l’équation d’état de la matière dense. Nous avons utilisé les statistiques Bayesienne pour combiner les données de physique nucléaire à basse densité, comme les prédictions ab initio provenant des interactions chirales EFT ou la résonance géante monopolaire isoscalaire, et les contraintes astrophysiques des étoiles à neutrons, comme leur masse maximale, ou la fonction densité de probabilité de la déformabilité de marée obtenue de l’événement GW170817. Les fonctions postérieures de densité de probabilité sont marginalisées sur plusieurs paramètres nucléaires empiriques (Lsym, Ksym, Qsat et Qsym), et aussi sur des grandeurs observationnelles des étoiles à neutrons comme la masse et le rayon à 1.4 masses solaires, ou la pression à deux fois la densité de saturation P(2nsat). Les correlations entre Lsym et Ksym, et entre KSat et Qsat sont aussi analysées. Une tension importante entre les données observationnelles d’ondes gravitationnelles et les inputs de physique nucléaire est trouvée pour les distributions marginales de probabilité de Lsym et R1.4. Ceci pourrait être une indication d’une transition de phase de nucléons vers des particules plus exotiques dans le coeur des étoiles à neutrons. Nous trouvons aussi qu’augmenter la précision sur la détermination de la déformabilité de marée à partir des ondes gravitationnelles, ou sur Mc à partir de la résonance géantes monopolaire, devrait aboutir à une meilleure détermination de Ksat et QsatIn this thesis, we first investigated the effect of Lambda pairing on the ground state properties of hypernuclei within the Hartree-Fock-Bogoliubov formalism. The SLy5 Skyrme functional is used in the NN channel, while for N-Lambda channel we employ three functionals fitted from microscopic Brueckner-Hartree-Fock calculations: DF-NSC89, DF-NSC97a and DF-NSC97f. These functionals reproduce the sequence of single-Lambda experimental binding energies from light to heavy hypernuclei. For the Lambda-Lambda channel, we used the empirical prescription EmpC, calibrated to 1 MeV on the experimental bond energy in 6He_LL. Based on this density-functional approach, several nuclei have been studied with nucleon closed-shells and Lambda open-shells. A Lambda-Lambda pairing interaction is introduced, which magnitude is calibrated to be consistent with the maximum BCS predictions for the Lambda pairing gap in hypernuclear matter. In this way, we provide an upper bound for the prediction of the Lambda pairing gap and its effects in hypernuclei. We have shown that the effects of the Lambda-Lambda pairing depends on hypernuclei. The condensation energy is predicted to be about 3~MeV as a maximum value, yielding small corrections on density distributions and shell structure. Generally, we found that Lambda-Lambda pairing could be active if the energy gap between shells is smaller than 3~MeV. Under this condition, Lambda pairing could impact densities and binding energies. Since only a weak spin-orbit interaction is expected in the Lambda channel, Lambda states are highly degenerated and usually levels are distant by more than 3~MeV in energy. In summary, it is shown that the Lambda-related pairing effect can usually be neglected in most of hypernuclei, except for hypernuclei which have a single particle gap lower than 3~MeV around the Fermi level. In addition, conditions on both Fermi energies and orbital angular momenta are expected to quench the nucleon-Lambda pairing for most of hypernuclei.The second part of the thesis is devoted to equation of states in neutron stars. We confronted the tidal deformability values extracted from the gravitational event GW170817 to nuclear physics constraints within a semi-agnostic approach for the dense matter equation of state. We used Bayesian statistics to combine together low density nuclear physics data, such as the ab-initio predictions based on chiral EFT interactions or the isoscalar giant monopole resonance, and astrophysical constraints from neutron stars, such as the maximum mass of neutron stars or the probability density function of the tidal deformability obtained from the GW170817 event. The posteriors probability distribution functions are marginalized over several nuclear empirical parameters (Lsym, Ksym, Qsat and Qsym), as well as over observational quantities such as the 1.4Msun radius R1.4 and the pressure at twice the saturation density P(2n_sat). The correlations between Lsym and Ksym and between Ksat and Qsat are also further analyzed. It is found that there is a marked tension between the gravitational wave observational data and the nuclear physics inputs for the Lsym and R1.4 marginal probability distributions. This could be a hint for nucleons to more exotic particles phase transition inside of the core of neutron stars. We also conclude that increasing the accuracy on the determination of tidal deformability from the gravitational wave, as well as Mc from the isoscalar giant monopole resonance, will lead to a better determination of Ksat and Qsat
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Nieminen, John Matti. "Superdeformation : a tool to study fusion-evaporation reactions /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/NQ42868.pdf.
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Steffens, Fernando Monti. "The spin and flavour structure of the nucleon /." Title page, contents and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09PH/09phs817.pdf.
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Thesis (Ph. D.)--University of Adelaide, Dept. of Physics and Mathematical Physics, 1996?Copies of author's previously published articles inserted. Includes bibliographical references (leaves 189-206).
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Barros, Cristian Javier Caniu. "Alpha Particles in Effective Field Theory." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-13012015-131131/.
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In this thesis we work on the problem of the two-alpha-particle system using a halo/- cluster effective field theory (EFT). Our goal is to address the alpha-alpha scattering observables and its low-energy resonance identified as the ground state of Beryllium-8. In this work we start with an EFT in which the degrees of freedom are the alpha particles interacting via momentum-dependent contact forces. These, in contrast to forces that are energy-dependent, are more useful in extending the theory to systems with more than two alpha particles. Additionally, momentum-dependent forces allow us to address causal restrictions on scattering observables, known as the Wigners causality bound. We present our EFT calculations for the alpha-alpha system.Nesta tese, nós trabalhamos sobre o problema do sistema de duas partículas alfa utilizando uma teoria de campos efetiva. O nosso objetivo é abordar os observáveis e a ressonância do sistema alfa-alfa de baixa energia identificada como o estado fundamental do berílio-8. Neste trabalho nós começamos com uma teoria de campo efetiva em que os graus de liberdade são as partículas alfa interagindo via forças de contato dependentes do momento. Estes, em contraste com as forças que são dependentes da energia, são mais úteis na extensão da teorias para sistemas com mais de duas partículas alfa. Além disso, forças dependentes do momento nos permitem abordar restrições causais nos observáveis, conhecidas como causalidade de Wigner. Nós apresentamos nossos cálculos para o sistema alfa-alfa.
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Mortuza, Muhammad Golam. "A nuclear magnetic resonance investigation of the structure of some alkali silicate glasses." Thesis, University of Warwick, 1989. http://wrap.warwick.ac.uk/55507/.
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The potential for the use of MAS and static NMR in the investigation of alkali silicate and alkali phosphosilicate glasses and glass ceramics is the main theme of this thesis. MAS NMR of binary lithium silicate glasses containing 24-29 mol% Li20 shows that their structure follows the constrained distribution model. However addition of Li20 in excess of 29 mol% causes deviation from the model and a concentration dependent disproportionation of Q3 to Q4+Q2 occurs. This is observable from MAS NMR in combination with static NMR results. The devitrification of these glasses produces two polymorphs of lithium disilicate. The structural changes during heat treatment occur aNve the glass transition temperature and are observed from the Si chemical shift and full width at half maximum. The static Li spectra for the crystallised samples exhibit a Pake doublet indicative of the presence of Li pairs. The effect of paramagnetic impurity from 0-0.8 mol% on the 29Si T1 relaxation times in Na20.2SiO2 base glasses is discussed. The heat treatment of the sodium disilicate glasses shows a -, ß-, Y- and 6- Na2Si2O5 as the devitrification products depending upon heat treatment. A way of estimating the unknown Si-O-Si mean bond angle of the polymorphs is presented. The effect of the addition of 0-70 moll P205 to alkali disilicate glasses is described. Small amounts of P205 (1-10 mol%) in the glasses results in the scavenging of alkali metal ions by phosphate groups. In sodium and potassium disilicates the phosphate groups resemble orthophosphate and pyrophosphate but only orthophosphate like units are formed in lithium disilicate glasses. As a consequence of the scavenging, the silicate network partially repolymerises. A structural model for the disilicates with (1-10) moll P2OS is presented. For larger concentrations of P205 (>10 mol%) in sodium disilicate glasses only metaphosphate species are observed and phosphorus occurs as next nearest neighbour of silicon. However this arrangement gradually changes to Si-O-Si bond with - 25 moll P 05 and the length of metaphosphate chain increases. On addition oft greater than about 30 mol% P205 some of the network silicon changes radically from its conventional four coordination to six coordination. Both the tetrahedral and octahedral environments of silicon at these concentrations are characteristic of mainly Si-O-P bonds. The six coordinated silicon occupies a SiPZO7 like environment. The proportion of "SiP2O7" depends upon the alkali content and the cooling rate. The cooling rates cause structural relaxation and are used to measure fictive temperature. This gives an estimate of the change of enthalpy for the conversion of one mole of six coordinated silicon from four coordinated silicon. The 29Si T1 relaxation times in alkali silicate glass, glass ceramics and alkali phosphosilicates are presented. The T1 in sodium disilicate glasses as a function of MnO content is a single exponential but a two component T1 is observed after heat treatment. The single component relaxation times for the disilicate composition range becomes two component as the Na20 content is reduced. The Tl values in all the lithium silicate glasses, glass ceramics and alkali phosphosilicate systems are two component. The conversion of single component exponential to two component because of heat treatment or Na20 content could be due to either nucleation or glass-in-glass phase separation. Thus the possibilities for obtaining new information about phase separation in glasses are also briefly discussed with the help of TEM micrographs.
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Filho, Zwinglio de Oliveira Guimarães. "Energias de raios gama padrões: suas covariâncias e relações com as constantes fundamentais." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-02072012-153200/.
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Este trabalho apresenta o procedimento que desenvolvemos e empregamos para determinar os valores a serem adotados para as energias de um conjunto de raios gama comumente utilizados como padrões de calibração, bem como sua respectiva matriz de covariância, esta obtida pela primeira vez. A matriz de covariância entre as energias destes padrões revelou muitos casos de correlações com valores absolutos maiores que 0,8, correlações estas que precisam ser corretamente consideradas para não comprometer a qualidade das análises efetuadas com o uso daquelas energias. No procedimento desenvolvido foi considerada a relação entre as energias dos raios gama (em múltiplos de eV) e as constantes fundamentais das quais dependem: h, e, c e o parâmetro de rede do Silício (aSi), o que possibilitou atualizar os resultados para as constantes fundamentais recomendadas de 2002. Uma metodologia para a inclusão de novos resultados experimentais ao conjunto de padrões de modo a preservar sua auto-consistência também foi desenvolvida neste trabalho. Este método considera adequadamente as covariâncias e atualiza todo o conjunto de padrões para incorporar as novas informações experimentais em uma única etapa. Por fim, utilizamos as metodologias de análise desenvolvidas e o conjunto de padrões aqui recomendados para analisar dados de medidas dos raios gama do decaimento do 233U e, assim, estudar a adequação de três diferentes modelos de estrutura nuclear para o 229Th, bem como as energias de excitação dos estados nucleares. A energia do primeiro estado excitado do 229Th, um estado metaestável de energia inferior a 10 eV, foi determinada com base naqueles diferentes modelos.This work presents the procedure which we have developed and employed to determine the values to be adopted for the energies of a set of gamma-rays in common use as calibration standards, publishing for the fist time their respective covariance matrix. Several correlations with absolute values exceeding 0.8 were found, revealing the necessity of considering correctly the covariance matrix in any analysis to be done with the use of these standards in order not to interfere with the quality of the analysis. The procedure here presented considers correctly the relation between the gamma-ray energies (given in eV) and the fundamental constants h, e, c, and the lattice parameter (aSi), allowing the updating of the set with respect to the 2002 recommended values for those constants. A methodology for the inclusion of new experimental results in the set of standards, in a way which preserve its selfconsistency, was also developed in this work. In this method the updating of the whole set of standards is performed in a single step, while considering adequately the covariances. Finally, the standard set recommended here and the methodology developed in this work were employed to analyze data of gamma-rays measurement which follow the 233U decay and therewith to decide about the adequacy of three different nuclear structure models for 229Th and the excitation energy of its nuclear states. The energy of the first excited state of 229Th, a meta-stable state of less than 10 eV, was determined taking into account those different models.
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Svensson, Carl Edward. "Collectivity in A ~ 60 nuclei : superdeformed and smoothly terminating rotational bands /." *McMaster only, 1998.
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Toufen, Dennis Lozano. "Sistema para medida de estados isoméricos." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26022009-112321/.
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Com o objetivo de permitir a detecção e a medida de estados isoméricos com meias vidas na faixa de 10 ns a 10 s sem a utilização de feixe pulsado, desenvolveu-se um sistema, batizado de SISMEI (SIStema de Medida de Estados Isoméricos). Este sistema utiliza principalmente a técnica de coincidência atrasada entre partículas carregadas e raios . No SISMEI há uma separação espacial entre a região do alvo, onde as partículas carregadas são emitidas, e a região do stopper, onde os raios atrasados são emitidos, permitindo assim uma diminuição do fundo estatístico. Para o teste do SISMEI foram realizadas duas experiências com a reação de fusão evaporação 46Ti(11B,1p2n)54Fe, Efeixe=30MeV e Efeixe=33MeV. Nestas experiências o estado isomérico conhecido 10+ do 54Fe (T1/2=364(7) ns) foi medido, sendo o resultado encontrado (T1/2 = 375(16) ns) compatível com o conhecido. Utilizando o espectro de tempo do estado isomérico 10+ do 54Fe como calibração, mediu-se a meia vida do estado isomérico 5/2+ do 19F (T1/2=89,3(10) ns) e a meia vida encontrada (T1/2=100(36) ns) é compatível com o valor conhecido. O sistema também foi capaz de identificar transições que populam o estado isomérico 10+ através da técnica de coincidência - atrasada. O Modelo de Camadas de Larga Escala foi utilizado para interpretar o estado isomérico 10+ do 54Fe. Este modelo foi capaz de reproduzir bem os valores experimentais de energia do nível e da probabilidade de transição reduzida B(E2), desde que seja utilizado um número suficiente de partículas livres na camada pf.A system, called SISMEI (Isomeric State Measurement System), was developed for the detection and measurement of isomeric states with half-lives in the range of 10 ns to 10 s without the use of a pulsed beam. This system mainly uses the technique of charged particles and -ray delayed coincidences. In SISMEI, the statistical background is reduced by the separation between the target region, where charged particles are evaporated, and the \"stopper\" region, where the delayed -rays are emitted. SISMEI was tested in two experiments with the reaction 46Ti (11B, 1p2n) 54Fe, Ebeam = 30 MeV and Ebeam = 33 MeV. In these experiments, the experimental lifetime of the 54Fe nucleus 10+ isomeric state was T1/2 = 375 (16) ns, which is consistent with the known experimental value (T1/2 = 364(7) ns). Using the 54Fe 10+ isomeric state time spectrum as calibration, the half life of the 19F 5/2+ state was measured. The experimental lifetime (T1/2 = 100 (36) s) is consistent with the known value (T1/2 = 89.3 (10) ns). The results also indicate that the system is capable of identifying the transitions to the isomeric state through the delayed - coincidence method. The 54Fe nucleus 10+ isomeric state was calculated in the framework of the Large Scale Shell Model. The energy and B (E2) experimental values were very well reproduced for a sufficient number of free particles in the full pf shell.
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Griffiths, Austyn Glyn. "Nuclear orientation studies of isotopes far from stability." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:d8bdd79d-9621-46c3-be82-3a13d1d629cb.
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Low Temperature Nuclear Orientation (LTNO) is an important technique in the study of nuclei far from stability. The theory of LTNO and its applications to the measurement of static nuclear moments and other quantities of spectroscopic interest are reviewed. Among the nuclei off the line of stability those in the A ~ 75 region are of considerable interest, exhibiting large quadrupole deformations, triaxiality and shape coexistence. LTNO measurements performed on neutron deficient bromine isotopes have yielded the static magnetic dipole moments of the nuclei 72g,72m,74m,75,76,77Br, Spectroscopic information on 72-77Se and also identified the ground state spin of 73Br as l/2‾ Existing odd A and odd-odd particle-rotor computer codes have been extended in order to include a Variable Moment of Inertia (VMI) asymmetric rotational core. The formalism necessary for this modification is developed. The measured magnetic moments are interpreted within the framework of this particle - VMI rotor model. It is shown that the systematic reduction in the moments of the odd A nuclei 75-81Br characterizes the transformation of the prolate ground state configuration from largely π[301]3/2 in 79,81Br to almost pure π[312]3/2 in 75,77Br. This trend is fully consistent with the increase in deformation towards the lower masses suggested by the known electric quadrupole moments. In contrast, the ground state spin of 73Br can only be interpreted in terms of an oblate nuclear shape. This is the first evidence for the predicted prolate-oblate shape transition in the bromine nuclei. In addition the magnetic moment of 74Brm, by identifying a π[431]3/2ν[422]5/2 configuration, strongly suggests a positive parity assignment for the isomeric state. Finally, an experiment to search for possible T-violation effects in nuclear gamma decay is described. Using coincidence techniques, a measurement of the T-odd P-even quantity (I ‧ k x e)(I ‧ k)(I ‧ e) has lead to a limit on the T-violating phase angle between the E2 and Ml matrix elements associated with the 604 keV gamma transition in 192Pt of sin η = ±11(12) x 10-3.
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Beaumier, Michael John. "Probing the Spin Structure of the Proton Using Polarized Proton-Proton Collisions and the Production of W Bosons." Thesis, University of California, Riverside, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10181454.
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This thesis discusses the process of extracting the longitudinal asymmetry, $A_L
{W\pm}$, describing $W\rightarrow\mu$ production in forward kinematic regimes. This asymmetry is used to constrain our understanding of the polarized parton distribution functions characterizing $\bar{u}$ and $\bar{d}$ sea quarks in the proton. This asymmetry will be used to constrain the overall contribution of the sea-quarks to the total proton spin. The asymmetry is evaluated over the pseudorapidity range of the PHENIX Muon Arms, $2.1 < |\eta|2.6$, for longitudinally polarized proton-proton collisions at 510 GeV $\sqrt{s}$. In particular, I will discuss the statistical methods used to characterize real muonic $W$ decays and the various background processes is presented, including a discussion of likelihood event selection and the Extended Unbinned Maximum Likelihood fit. These statistical methods serve estimate the yields of $W$ muonic decays, which are used to calculate the longitudinal asymmetry.
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Bezuidenhout, Jacques. "Cross sections and analysing power energy-sharing distributions of valence (p,2p)-knockout from 208Pb with a projectile of 200MeV." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51668.
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Thesis (MSc)--Stellenbosch University, 2000.ENGLISH ABSTRACT: The aim of this work was to study the 208Pb(p,2p)207Tl quasi-free knockout process. The experimental data were measured at the National Accelerator Centre using incident polarised protons of 200 MeV. The two scattered particles, from the knockout reaction, were detected in coincidence and their energies were determined using a magnetic spectrometer and a solid state detector telescope. Cross section and analysing power energy distributions were extracted from the experimental measurements and these were compared with theoretical values for the Distorted Wave Impulse Approximation. The theoretical cross-section calculations predict the experimental cross-section distribution well for all combinations of distorting potentials and bound states that were investigated, both with regard to shape, as well as absolute magnitude. However the theoretical analysing power distributions did not agree with the experimental quantities. Therefore it is not clear whether the analysing power is a useful tool to extract information on the specifics of the quasi-free reaction mechanism. The spectroscopic factors were found to be consistent with the results obtained in previous studies, thereby inspiring confidence that the problem with the analysing power distribution is not ascribable to a possible deficiency in the experimental techniques exploited in this work.
AFRIKAANSE OPSOMMING: Die doel van die studie was om die kwasi vrye 208pb(p,2p )207TI verstrooingsproses te ondersoek. Die eksperimentele data is ingewin by die Nasionale Versnellingsentrum deur gebruik te maak van 'n 200 MeV gepolariseerde proton bundel. Die twee verstrooide deeltjies is in koïnsidens gemeet. Vir die metings is 'n magnetiese spektrometer en 'n vastetoestand detektorteleskoop gebruik. Die kansvlak- en analiseervermoë-energieverdelings is uit die eksperimentele data verkry en is vergelyk met die berekenings van die Vervormde Golf Impuls Benadering. Die teoretiese kansvlak berekening het die eksperimetele data goed voorspel, vir die verskillende parametrisering van potensiaal en gebonde toestande. Die berekeninge het goed ooreengestem met betrekking tot beide vorm en absolute grootheid. Die berekende analiseervermoë het egter nie goed met die eksperimentele data ooreengestem nie. Dit is dus nie duidelik of die analiseervermoë 'n handige instrument is om inligting oor die betrokke kwasi-vrye reaksie meganisme te bekom nie. Die spektroskopiese faktore was in ooreenstemming met resultate wat in vorige studies verkry is. Dit versterk vertroue dat die probleem met die analiseervermoë nie toegeskryf kan word aan die eksperimentele tegniek wat gebruik is nie.
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Francis, D. "Measurement of the nucleon structure function in deep inelastic muon-nucleon scattering." Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384355.
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Medina, Israel Ariel González. "Estudo de processos a energias médias e altas pelo método Monte Carlo." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-02102014-143638/.
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O trabalho de pesquisa está orientado ao estudo de processos nucleares em altas energias usando o modelo de cascata intranuclear desenvolvido no código CRISP. O estudo é realizado pela introdução de modificações no código CRISP, visando adaptá-lo à utilização em cálculos relacionados às reações nucleares onde a densidade de hádrons é quente e densa. Este estado é muito sensível às modificações no meio da distribuição dos mésons vetoriais $ho$ e $\\omega$, $\\phi$ e $J/\\Psi$. Em altas energias, o código CRISP incorpora os processos de fotoprodução de mésons vetoriais e os processos de interação no estado final destes mésons com o núcleo. A cascata intranuclear que se formará será processada de acordo com o modelo já utilizado no código, com as devidas correções que se fizerem necessárias. A nova extensão de CRISP é utilizada para estudar as fotorreações nucleares em altas energias e na análise de efeitos importantes como a multiplicidade de partículas secundários produzidas, o efeito de sombreamento, a fotoprodução sub-limiar de mésons, a distribução de massa dos méson gerados na matéria nuclear e a transparência. Usando o CRISP, as características do núcleo residual formado ao final da reação poderão ser determinadas e comparadas com os dados experimentais. A boa concordância entre estes e nossos resultados mostram o potencial do modelo CRISP nesta nova versão.We present recent improvements in the CRISP code for nuclear reactions simulation for study high energy nuclear reactions. In nuclear environment, at these energies, hadron density is hot, dense and very sensitive to the modification of vector meson distribution. The photoproduction of vector mesons $ho$ e $\\omega$, $\\phi$ and $J/\\Psi$ was included in the code, also the interaction of these mesons with the nucleus. Fotonuclear reactions are treated according the multicollisional model included in the CRISP code. Nuclear effects as shadowing, subthreshold production, Pauli Blocking, meson invariant mass distribution and transparency can be studied with this CRISP. The model describe in details all the features of the nucleus at the end of the nuclear reaction allowing compare some important quantities with experimental data. The agreement of the results with the data set is a prove of the potentialities of our code.
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Allegro, Paula Rangel Pestana. "Sistemática de núcleos ímpar-ímpar de Ga na região de massa A=60 - 70." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-17102014-143630/.
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Um dos modelos mais utilizados para a descrição de núcleos é o Modelo de Camadas em Larga Escala, que demonstrou grande acurácia na descrição detalhada de propriedades nucleares. Na região de massa A = 50 80, os orbitais 1g9/2 e 2d5/2 são fundamentais para a descrição de estados excitados com mudança de paridade e de estruturas deformadas, porém suas contribuições na descrição de estados excitados de núcleos com número de massa ímpar e núcleos duplamente ímpares perto da linha de estabilidade ainda estão por ser investigadas. Nesta tese, a importância dos orbitais 1g9/2 e 2d5/2 na formação dos estados excitados dos núcleos duplamente ímpares 64,66,68,70Ga é estudada sistematicamente, levando também em consideração a descrição dos isótopos de Zn, Ge e Ga com número de massa ímpar pelo Modelo de Camadas em Larga Escala. Propriedades dos estados excitados, como energia e vidas médias de alguns estados isoméricos, foram medidas experimentalmente para os isótopos 64,66,70Ga e para o núcleo 67Ge na Universidade de São Paulo, Brasil, e na Universidade Estadual da Florida, EUA, utilizando os espectrômetros de raios SACI-PERERE, SISMEI e FSU Clover Array e as reações de fusão-evaporação 58Ni(12C, xpynz)64Ga,67Ge, 55Mn(18O, xpynz)66,70Ga, 58Ni(11B, 2pn)66Ga e 51V(19F, p3n) 66Ga. Os resultados experimentais obtidos para estes núcleos, assim como os conhecidos na literatura para os núcleos 68Ga e de Zn, Ga e Ge com número de massa ímpar foram comparados com as previsões do Modelo de Camadas em Larga Escala utilizando cinco interações residuais: JUN45, FPG, FPG (Neutron Rich), JJ4b-SDI para a descrição de excitações para o orbital 1g9/2 e LNPS para excitações para o orbital 2d5/2. Foram identificadas 34 novas transições e 19 novos estados excitados pertencentes ao núcleo 67Ge, uma nova transição e um novo estado excitado para o núcleo 70Ga e foram confirmadas as transições e estados excitados previamente identificados em trabalhos anteriores para os núcleos 64,66Ga. As multipolaridades de algumas transições dos núcleos 64,66,70Ga e 67Ge foram determinadas utilizando a razão DCO (Correlações Direcionadas de Radiação Emitida por Estados Orientados). A meia vida medida do estado isomérico de energia igual a 1464,33 (15) keV, pertencente ao núcleo 66Ga, é igual a T1/2 = 58,1 (12) ns, enquanto que para o estado isomérico do núcleo 67Ge, de energia igual a 751,70 (6) keV, a meia vida medida foi de T1/2= 107,2 (23) ns. As interações efetivas JUN45 e FPG se mostraram mais adequadas para a descrição dos isótopos 64,66,68,70Ga, indicando que os estados de paridade negativa são formados preferencialmente pela ocupação de 1 nêutron no orbital 1g9/2. No caso dos núcleos mais ricos em nêutrons 68,70Ga, em que excitações de nêutrons provenientes da camada pf para o orbital 2d5/2 poderiam ocorrer, os resultados calculados com a interação LNPS mostraram que orbital 2d5/2 praticamente não é ocupado, apenas o orbital 1g9/2 é ocupado na camada gds.One of the most reliable models for describing nuclei is the Large Scale Shell Model, which has been shown to reproduce with very good accuracy detailed nuclear properties. In the A=50-80 mass region, the 1g9/2 and 2d5/2 orbitals are needed to describe the parity changes of the excited states and deformed structures, but the role of these two orbitals in the excited states of odd and odd-odd-mass nuclei near the stability line has still to be investigated. In this thesis, a systematic study is performed to determine the role of the 1g9/2 and 2d5/2 orbitals in the excited states of odd-odd 64,66,68,70Ga. This has been done in the framework of a systematic study of odd-mass Zn, Ga and Ge nuclei in the mass A= 60 -70 region by means of Large Scale Shell Model calculations. Nuclear properties of 64,66,70Ga and 67Ge nuclei, such as the energy of the excited states and the lifetime of isomeric states were measured at University of São Paulo, Brazil, and at Florida State University, USA, using the SACI-PERERE, SISMEI and FSU Clover Array -ray spectrometers and the 58Ni(12C, xpynz)64Ga,67Ge, 55Mn(18O, xpynz)66,70Ga, 58Ni(11B, 2pn)66Ga and 51V(19F, p3n) 66Ga fusionevaporation reactions. The obtained experimental results for those nuclei and the known values of 68Ga and odd-mass Zn, Ga, Ge were compared with the results of the Large Scale Shell Model using five different residual interactions: JUN45, FPG, FPG (Neutron Rich), JJ4b-SDI to describe excitations to the 1g9/2 orbital and LNPS to describe the excitations to the 2d5/2 orbital. Thirty-four new transitions and 19 new excited states were identified in the 67Ge nucleus, one new transition and an excited state were found in the 70Ga nucleus, while the excited states and transitions of 64,66Ga nuclei known in previous works were confirmed. The multipolarities of some transitions of 64,66,70Ga and 67Ge nuclei were determined by using the DCO ratios (Directional Correlations of -rays from Oriented States of Nuclei). The measured value for the half-life of the 66Ga 1464.33 (15) keV isomeric state is T1/2 = 58.1 (12) ns, while the measured value for the half-life of the 67Ge 751.70 (6) keV isomeric state is T1/2= 107.2 (23) ns. The JUN45 and FPG effective interactions give a good description of the excited states of the 64,66,68,70Ga isotopes and they have shown that the negative parity excited states were preferentially formed by the excitation of only one neutron to the 1g9/2 orbital. In the case of the more neutron rich 68,70Ga nuclei, where neutron excitations from the pf shell to the 2d5/2 could occur, the calculated results using the LNPS effective interaction have shown that the 2d5/2 orbital remains practically empty and only the 1g9/2 orbital is occupied in the gds shell.
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Wiedemann, Kenia Teodoro. "Propriedades de decaimento eletromagnético dos núcleos espelho 67As e 67Se." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-11052009-102216/.
Full textAbstract:
No presente trabalho foram feitos estudos das propriedades de decaimento eletromagnético do par de núcleos espelho mais pesado conhecido atualmente: 67As e 67Se. Esses núcleos foram produzidos através da reação de fusão-evaporação 32S+40Ca, com energia de feixe Ef = 90MeV. O experimento foi realizado nos Laboratórios Nacionais de Argonne, com o feixe fornecido pelo acelerador ATLAS. Os raios gama emitidos do decaimento dos núcleos residuais foram observados utilizando o espectrômetro de raios gama Gammasphere, em conjunto com o sistema de detecção de partículas carregadas Microball e o sistema de detecção de nêutrons Neutron Shell. Os esquemas de níveis obtidos mostraram-se bastante similares como é de se esperar para um par de núcleos espelho, e caracterizados por fortes transições dipolares elétricas E1 na desexcitação na sequência principal. No caso do núcleo de 67As, foram acrescentadas cinco transições gama e dois estados excitados ao esquema de níveis já conhecido. As multipolaridades de todas as transições novas foram determinadas através da técnica de análise ADO. O esquema de níveis do núcleo de 67Se foi ampliado até o momento angular (25/2+), a 5.560(1) MeV. Foram acrescentadas doze transições e oito estados excitados ao esquema de níveis já conhecido. As multipolaridades das transições já conhecidas foram determinadas e, das transições inseridas no esquema de níveis deste núcleo, cinco tiveram suas multipolaridades determinadas também pela técnica ADO. Do ponto de vista teórico, foram realizados cálculos de Modelo de Camadas em Larga Escala, utilizando o código Antoine, com diferentes interações residuais (KB3G, GXPF1 e fpg). Para a descrição dos estados de paridade positiva, foi utilizada a interação residual fpg, que permite a excitação de núcleons de valência até o orbital g9/2. Esta interação não prevê interação coulombiana entre os núcleons, e desta forma, os cálculos realizados para um par de núcleos espelho, apresenta resultados idênticos. Os cálculos realizados com a interação fpg para os estados de paridade positiva dos núcleos espelho de 67As e 67Se mostraram-se em bom acordo com os resultados experimentais, descrevendo as energias dos estados excitados de ambos os núcleos, com uma diferença máxima, em energia, de 500 keV. Diferenças observadas nas intensidades das transições dipolares magnéticas, M1, que depopulam os estados análogos 19/2(+), dos núcleos de 67As e 67Se foram discutidas em termos da contribuição dos termos isoescalar e isovetorial no operador de transição M1, e sustentam a hipótese de conservação na simetria de isospin. Para o estudo dos estados de paridade negativa, foram utilizadas duas interações residuais, levando em consideração a interação coulombiana entre os núcleons de valência: KB3G e GXPF1, ambas permitindo a descrição teórica de núcleos com núcleons de valência na camada pf . Ambas intera ções reproduziram razoavelmente bem as energias dos estados de paridade negativa para ambos os núcleos. A interação KB3G, entretanto, inverteu os momentos angulares do estado fundamental e do primeiro estado excitado do núcleo de 67As, enquanto a interação GXPF1, reproduziu bem a ordem dos momentos angulares dos estados de paridade negativa. A análise da diferença das energias dos estados análogos (MED) foi feita com a introdução de termos de correção nas energias de partícula única devido à interação órbita-órbita (Ell ) e spin-órbita (Els ), além de uma estimativa de um termo de quebra de simetria de isospin (VB). Os resultados mostraram que a introdução dos termos de correção propostos não permitiu reproduzir completamente os resultados experimentais, indicando que as estimativas teóricas devem ser melhoradas para essa região de massa. Foi observado que as transições E1, análogas, de 319 keV, proveniente do núcleo de 67As, e de 304 keV, proveniente do núcleo de 67Se, apresentaram intensidades bastante distintas, a saber: B(E1)319 keV = 8.6(6) × 106 u.W., e B(E1)319 keV = 2.6(8) × 106 u.W. Além deste resultado, os estados análogos 7/22 , populados por essas transições, foram os únicos a apresentar um pequeno desvio na descrição de suas funções de onda. Os resultados foram discutidos em termos de uma possível quebra de simetria de isospin.In the present work the electromagnetic decay properties of the mirror pair 67As and 67Se are investigated. The experiment was performed in the Argonne National Laboratory, and these nuclei were produced through the fusion-evaporation reaction 32S +40 Ca, with a 90 MeV beam provided by the ATLAS accelerator. The gamma rays emitted by the residual nuclei were observed using the Gammasphere spectrometer, with 72 HPGe detectors, and its ancillary system composed of the Microball and Neutron Shell systems, for charged particle and neutron detection, respectively. The obtained level schemes are very similiar, as expected for mirror nuclei, and characterized by strong E1 transitions in the main sequencies. Five new transitions and two new excited states were added to the already known 67As level scheme, and in the case of the 67Se nucleus, the level scheme was extended up to 5.56 MeV, and twelve new transitions and eight new excited states were added to the previously known level scheme. The multipolarities were obtained by ADO analysis, taking into account the geometry of the Gammasphere spectrometer. In the theoretical point of view, Large Scale Shell Model calculations were performed, using KB3G and GXPF1 residual interactions for the natural parity states description, including electromagnetic interactions among the valence nucleons. The fpg residual interaction, with no electromagnetic interaction among the valence nucleons, was used for the positive parity description. Diferences in the analogue states energies were discussed using arguments based on the role of the isospin quantum number in the electromagnetic decay properties. The GXPF1 residual interaction provided a better description of the nuclear states, and was assumed as the best theoretical description provider for the nuclear states of the mirror pair 67As and 67Se. The mirror energies dierences were investigated including the orbit-orbit (Ell ) and the spin-orbit (Els) corrections to the single particle energies, and an estimative of an isospin non-conserving term (VB). The results showed that the proposed corrections do not describe completely the mirror energy diferences of the natural parity states, for this mirror pair, which is the heaviest mirror pair known nowadays, indicating that improvements in the residual interactions are highly desirable for this mass region. There was observed diferences in the strengths of the 319 and 304 keV transitions, that depopulate the 9/2+ analogue states of the 67As and 67Se respectively, being B(E1)319 keV = 8.6(6) × 106 u.W., and B(E1)319 keV = 2.6(8) × 106 u.W. The diferences were discussed in terms of a possible charge symmetry breaking, supported by the theoretical results, that showed a slight diference in the wavefunctions, described by the occupation numbers, of the analogue states populated by these transitions.
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Lester, G. A. "A computing structure for data acquisition in high energy physics." Thesis, University of Salford, 1988. http://usir.salford.ac.uk/2168/.
Full textAbstract:
A review of the development of parallel computing is presented, followed by a summary of currently recognised types of parallel computer and a brief summary of some applications of parallel computing in the field of high energy physics. The computing requirement at the data acquisition stage of a particular set of high energy physics experiments is detailed, with reference to the computing system currently in use. The requirement for a parallel processor to process the data from these experiments is established and a possible computing structure put forward. The topology proposed consists of a set of rings of processors stacked to give a cylindrical arrangement, an analytical approach is used to verify the suitability and extensibility of the suggested scheme. Using simulation results the behaviour of rings and cylinders of processors using different algorithms for the movement of data within the system and different patterns of data input is presented and discussed. Practical hardware and software details for processing equipment capable of supporting such a structure as presented here is given, various algorithms for use with this equipment, e. g. program distribution, are developed and the software for the implementation of the cylindrical structure is presented. Appendices of constructional information and all program listings are included.
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Utley, Martin Lawrence. "A first study of the structure of the virtual photon at HERA." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321826.
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Burrows, Matthew. "Translationally Invariant Local Densities for Light Nuclei from No-Core-Shell-Model Calculations." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1477569906766884.
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Day, Iain J. "Real-time NMR of the transient states of proteins." Thesis, University of Oxford, 2004. http://ora.ox.ac.uk/objects/uuid:19b0637b-e28a-4d34-9016-ebfb5a507720.
Full textAbstract:
The work described in this thesis is concerned with the development and application of real-time photo-CIDNP (Chemically Induced Dynamic Nuclear Polarisation) to the study of protein structure and folding. Chapters 1 and 2 introduce the protein folding problem, and its study by NMR, then go on to elucidate the mechanisms behind the photo-CIDNP phenomenon. Chapter 3 applies photo-CIDNP spectroscopy to the study of a small cytochrome protein. The difficulties of performing these experiments on chromophore-containing proteins are discussed. Chapter 4 begins with the development of a rapid mixing device for use in real-time NMR and CIDNP studies. Experiments used to characterise the device are presented. This chapter then goes on to describe CIDNP pulse labelling experiments, used to investigate the surface structure of some molten globule states of two a-lactalbumins. This chapter concludes with an application of the rapid mixing device to the real-time refolding of hen egg white lysozyme. Chapter 5 extends the work of the previous chapter, studying the real-time refolding of bovine pancreatic ribonuclease A. Refolding studies are performed from different denaturing conditions, and the effects of sample heating during the real-time CIDNP experiment are discussed. Chapter 6 describes the use of illumination during an NMR experiment to study the conformational changes in a plant blue light receptor protein, phototropin. The structural changes are characterised with 2-dimensional NMR spectroscopy and photo-CIDNP. The kinetics of the ground state recovery are also investigated by real-time NMR spectroscopy. Chapter 7 uses calculated hyperfine coupling constants and a radical pair diffusion model from the literature to simulate the nuclear polarisation obtained for the amino acid tryptophan. Comparisons are made between theory and experiment. Chapter 8 describes the structural characterisation of a homologous series of de novo peptides, designed for subsequent use in EPR experiments when derivatised with a suitable spin label.
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Tommasini, Paolo Roberto Inglese. "Aproximação gaussiana para um sistema não-ideal de muitos bósons." Universidade de São Paulo, 1995. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-28022014-114504/.
Full textAbstract:
O estado fundamental e propriedades térmicas de um sistema de bosons não relativísticos interagentes por uma interação repulsiva de dois corpos, são investigados através de uma aproximação Gaussiana auto-consistente que consiste em escrevermos o operador densidade variacionalmente determinado como o funcional Gaussiano mais geral dos operadores de campo. Resultados a temperatura finita são obtidos, incluindo transições de fase, no contexto do ensemble grand-canônico. Através de truncamentos na aproximação Gaussiana completa podemos reproduzir resultados tradicionais de Bogolyubov e de Lee, Yang e Huang. A aproximação Gaussiana completa fornece uma fase condensada que é termodinamicamente instável e uma fase não condensada que não difere essencialmente de uma teoria livre quando forças de contato e um esquema de renormalização padrão são usados. Como alternativa, uma teoria dependente do cut-off no momento é desenvolvida para um sistema diluído de bosons interagentes. A aproximação Gaussiana gera um espectro de quasi-partículas que contém um gap na energia, em conflito com os resultados perturbativos. Para investigar o espectro de excitações na teoria efetiva, é desenvolvida uma formulação dependente do tempo e o regime de pequenas oscilações para os parâmetros variacionais é estudado. São obtidas então as mesmas energias utilizadas no cálculo das ocupações estáticas.The ground-state and thermal properties of a system of non-relativistic bosons interacting through repulsive two-body interactions are investigated using a self-consistent Gaussian mean-field approximation which consists in writing the variational determined density operator as the most general Gaussian functional of the quantized field operators. Finite temperature results are obtained, including phase transitions, in the grand canonical framework. Contact is made with the results of Bogolyubov and Lee, Yang and Huang in terms of particular truncations of the full Gaussian approximation. The full Gaussian approximation gives a condensate phase which is thermodinamically unstable and a non-condensate phase that does not differ essentially from a free phase when contact forces and standard renormalization scheme are used. As an alternative an effective cut-off dependent theory is developed for a dilute interacting bose system. The Gaussian approximation generates a quasi-particle spectrum having an energy gap, in conflict with perturbation theory results. In order to investigate the excitation spectrum of the effective theory, a time-dependent formulation is developed and the small oscillation regime for the variational parameter is studied. The same energies used in the calculus of the static occupations are obtained.
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Buck, Paul G. "Measurement of the photon structure function of low Q'2 using ALEPH detector." Thesis, Lancaster University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249810.
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Dursun, Serkan. "Nuclear structure of the N=88 isotones: the decay of 156Tm to 156Er." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37155.
Full textAbstract:
The N=88 nuclei lie in a transitional region of the nuclear chart. Collective structure and nuclear deformation for this region is commonly occurring. Previously, some of the nuclei having 88 neutrons have been well studied, e.g., 148Nd, 150Sm, 152Gd, 154Dy; however, 156Er has not. To be able to understand the nuclei in this region one needs to extract all the systematics of these deformed nuclei and the relations between them. The structure of 156Er is the main focus in this thesis and the work seeks understanding of the N=88 nuclei and systematics among them. To accomplish this task, 156Tm to 156Er beta decay was studied. Many new levels and gamma transitions have been added to the existing scheme. The significance for detailed decay scheme studies far from stability is also discussed.
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Hague, Tyler J. "Measurement of the EMC Effect of the Helium-3 Nucleus at Jefferson Lab." Kent State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=kent1587232156043952.
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Allmond, James Mitchell. "Studies of Triaxial Rotors and Band Mixing in Nuclei." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14604.
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Rigid rotor models were investigated with constraints from data for even-even nuclei. Specifically, from precision gamma-ray intensity measurements for 166-Er (from 166m-Ho and 166-Tm beta decays); from B(E2) systematics; and for 186,188,190,192-Os matrix element data.
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Fallot, Muriel. "Recherche de l'état à trois phonons dans le $^(40)$Ca." Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00002925.
Full textAbstract:
Ce travail porte sur l'étude des états de vibration collective du noyau : les résonances géantes et les états multiphonons. Ces derniers, constitués de plusieurs résonances géantes superposées, peuvent être excités par diffusion inélastique d'ions lourds près de l'angle d'effleurement. Aucun état à trois phonons collectif n'a été observé jusqu'à maintenant. Une expérience a été effectuée au GANIL dans le but d'observer l'état à trois phonons construit avec la Résonance Géante Quadrupolaire dans le $^(40)$Ca, avec la réaction $^(40)$Ca + $^(40)$Ca à 50 A.MeV. L'éjectile était identifié dans le spectromètre SPEG et les particules chargées légères étaient détectées dans les 240 scintillateurs CsI du multidétecteur 4 Pi INDRA. L'analyse de cette expérience confirme les résultats précédents concernant la Résonance Géante Quadrupolaire (RGQ) et l'état à deux phonons quadrupolaires dans le $^(40)$Ca. Pour la première fois, une branche importante de décroissance directe de la RGQ par particules alpha est mesurée. En appliquant la méthode dite de l'énergie manquante aux événements contenant trois protons mesurés en coïncidence avec l'éjectile, une décroissance directe révélant la présence d'un état à trois phonons est observée dans la région en énergie attendue pour une triple RGQ. Les mécanismes de réaction dans la voie inélastique sont également étudiés, en particulier, un mécanisme récemment découvert appelé towing mode. Pour la première fois le towing mode de particules alpha est observé.
Les énergies des états multiphonons dans le $^(40)$Ca et le $^(208)$Pb ont été calculées microscopiquement en incluant des anharmonicités. La base du calcul a été étendue aux états à trois phonons. Nos résultats montrent de grandes anharmonicités (plusieurs MeV), dues au couplage des états à trois phonons avec les états à deux phonons. L'extension de la base aux états à quatre phonons a été effectuée pour la première fois. Les résultats montrent que les états à deux phonons ne sont pas affectés par les états à quatre phonons. Quelques résultats préliminaires sur l'influence de ces derniers sur les états à trois phonons sont présentés.
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Simmons, Peter Mark. "A study of highly-deformed α-cluster structures in light nuclei." Thesis, University of Oxford, 1995. http://ora.ox.ac.uk/objects/uuid:37f984ce-da25-4e98-a843-5039c4f406ff.
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The inelastic scattering reaction 160+12C has been studied in the centre-of-mass energy region from 37.7 MeV to 51.4 MeV, in a search for evidence for a seven-alpha chain state in 28Si. The decay products were detected in coincidence at angular separations around 90° in the centre of mass using two position-sensitive strip detectors. Kinematic reconstruction of the quasi-three body final states yielded the differential cross-sections for the decay channels leading to excited states in 12C, 160 and 20Ne. The excitation functions measured for the 12 C(0+2)-12C(0+2)-U+03B1 and 12C(02)-8Be-8Be final states agree broadly between the three experiments that were performed, but contain no structure. Reaction channels have also been identified leading to the 8Be-20Ne* and 12C*-160* final states. The cross-sections for the 8Be-20Ne* decay channels, with the 20 Ne in its lowest excited states, have been compared with previous measurements and provide good agreement. However, none of the excitation functions for these channels contain any structure. The absence of structure in any of the final states, that were identified in this study, indicates that a 28Si chain state is probably not being observed. The same model, that predicts that the seven-alpha chain state should lie in this excitation region in 28Si, has also been used to assign a six alpha chain structure to a resonance at Ex=46.6 MeV in 24 Mg. These two results are compared, and possible reasons for the absence of evidence for a 28Si chain structure are discussed.
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Shotton, P. N. "A measurement of the proton structure functions in neutrino-hydrogen and antineutrino-hydrogen charged-current interactions." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355802.
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Rybak, Karolina. "Predictive power of nuclear mean-field theories for exotic-nuclei problem." Phd thesis, Université de Strasbourg, 2012. http://tel.archives-ouvertes.fr/tel-00864240.
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This thesis is a critical examination of phenomenological nuclear mean field theories, focusing on reliable description of levels of individual particles. The approach presented here is new in the sense that it not only allows to predict the numerical values obtained with this formalism, but also yields an estimate of the probability distributions corresponding to the experimental results. We introduce the concept of 'theoretical errors' to estimate uncertainties in theoreticalmodels. We also introduce a subjective notion of 'Predictive Power' of nuclear Hamiltonians, which is analyzed in the context of the energy spectra of individual particles. The mathematical concept of 'Inverse Problem' is applied to a realistic mean-field Hamiltonian. This technique allows to predict the properties of a system from a limited number of data. To deepen our understanding of Inverse Problems, we focus on a simple mathematical problem. A function dependent on four free parameters is introduced in order to reproduce 'experimental' data. We study the behavior of the 'fitted' parameters, their correlation and the associated errors. This study helps us understand the importance of the correct formulation of the problem. It also shows the importance of including theoretical and experimental errors in the solution.