Polarized nuclear Compton scattering on a proton target provides a test of low energy QCD. The beam-target asymmetries of a circularly polarized Bremsstrahlung photon beam on a transversely polarized butanol target (&Sigma2x) and on a longitudinally polarized butanol target (&Sigma2z), and the beam asymmetry of a linearly polarized Bremsstrahlung beam on an unpolarized hydrogen target (&Sigma3) are sensitive to the proton spin polarizabilities, third order terms in the energy expansion of the Compton scattering amplitude. This experiment consisted of the &Sigma2x measurement, both just below and above two-pion threshold.

Tagged photons from 81 to 116 MeV were used to measure elastic Compton scat- tering cross sections from deuterium and carbon targets at the MAX-lab facility in Lund. Scattered gamma rays were detected in three very large NaI(Tl) crystals with sufficient energy resolution to isolate deuterium elastic yields at scattering angles of 60°, 90°, 120° and 150°. Calculations indicate that back-angle Compton scattering on deuterium in this energy range is sensitive to the electric and magnetic polarizabilities of the nucleon. Results of this research were obtained with improved beam tagging system conditions compared to previous elastic Compton scattering experiments from deuterium.

In this work we present the first implementation of the incremental scheme for coupled cluster linear-response frequency-dependent dipole polarizabilities. The implementation is fully automated and makes use of the domain-specific basis set approach. The accuracy of the approach is determined on the basis of a test suite of 47 molecules and small clusters. The local approximation in the coupled cluster singles and doubles polarizability exhibits a mean error of 0.02% and a standard deviation of 0.32% when using a third-order incremental expansion. With the proposed approach, it is possible to compute polarizabilities with larger basis sets compared to the canonical implementation and thus it is possible to obtain higher total accuracy. The incremental scheme yields the smallest errors for weakly-bound and quasi-linear systems, while two- and three-dimensional (cage-like) structures exhibit somewhat larger errors as compared to the full test set. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Estimamos os valores das polarizabilidades dipolares elétrica e magnética do próton, levando em conta as contribuições das ressonâncias nucleônicas de menor massa: P33 (1236), P11 (1450), D13 (1525), S11(1550), e da ressonância mesônica &#949 (660). O valor obtido para a soma das polarizabilidades concorda bem com os dados experimentais. Por outro lado, o valor obtido para cada uma delas, que depende do valor não bem determinado da largura do decaimento &#949 &#8594 &#933 &#933, é compatível com os valores experimentais / We have estimated the values of electric and magnetic polarizabilities of the proton, taking into account the contributions of the low masses nucleon ressonances : P33 (1236), P11 (1450), D13 (1525), S11(1550) and the meson ressonance &#949 (660). The obtained value for the sumo f the polarizabilities is in good agreement with the experimental data. On the other hand, the value, of each polarizability, which depends on the not too well determined width decay &#949 &#8594 &#933 &#933, is compatible with experimental values

Estimamos os valores das polarizabilidades dipolares elétrica e magnética do próton, levando em conta as contribuições das ressonâncias nucleônicas de menor massa: P33 (1236), P11 (1450), D13 (1525), S11(1550), e da ressonância mesônica &#949 (660). O valor obtido para a soma das polarizabilidades concorda bem com os dados experimentais. Por outro lado, o valor obtido para cada uma delas, que depende do valor não bem determinado da largura do decaimento &#949 &#8594 &#933 &#933, é compatível com os valores experimentais / We have estimated the values of electric and magnetic polarizabilities of the proton, taking into account the contributions of the low masses nucleon ressonances : P33 (1236), P11 (1450), D13 (1525), S11(1550) and the meson ressonance &#949 (660). The obtained value for the sumo f the polarizabilities is in good agreement with the experimental data. On the other hand, the value, of each polarizability, which depends on the not too well determined width decay &#949 &#8594 &#933 &#933, is compatible with experimental values

Submitted by Erika Demachki (erikademachki@gmail.com) on 2015-02-02T18:46:20Z No. of bitstreams: 2 Dissertação - Orlando José Silveira Júnior - 2014.pdf: 1308675 bytes, checksum: 2e446ecac4945cf2b151a2a2a13cfb8f (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Erika Demachki (erikademachki@gmail.com) on 2015-02-03T15:47:07Z (GMT) No. of bitstreams: 2 Dissertação - Orlando José Silveira Júnior - 2014.pdf: 1308675 bytes, checksum: 2e446ecac4945cf2b151a2a2a13cfb8f (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-02-03T15:47:07Z (GMT). No. of bitstreams: 2 Dissertação - Orlando José Silveira Júnior - 2014.pdf: 1308675 bytes, checksum: 2e446ecac4945cf2b151a2a2a13cfb8f (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2014-02-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / In this work we report dynamic values for the (hyper)polarizabilities of lithium salt of pyridazine Li H3C4N2 including vibrational corrections. The electronic contributions were computed analytically at the single and double coupled cluster level (CCSD) through response theory, as implemented in the DALTON program, with the aug-cc-pVDZ basis set. The calculations for the vibrational corrections were carried out at the second-order Møller-Plesset level (MP2) by means of the perturbation theoretical method of Bishop and Kirtman and also using a variational approach proposed here. The results obtained for the zero-point vibrational average (zpva) corrections show that the two approaches lead practically to the same results, accounting for 2 and 6 % of the corresponding electronic contributions for polarizability and _rst hyperpolarizability, respectively. The results ob-tained show that, at the static limit, the pure vibrational corrections for the polarizability and _rst and second hyperpolarizabilities have the same order of magnitude of the corre-sponding electronic contributions. Comparisons between the results obtained through the two methods show that the perturbation theoretical method is not suitable to treat the system studied, whereas the variational methodology presented seems to be an alternative approach to treat anharmonic systems. / Neste trabalho nós apresentamos resultados dinâmicos para as (hiper)polarizabilidades do sal de lítio de piridazina Li H3C4N2 incluindo correções vibracionais. As contribuições eletrônicas foram calculadas analiticamente no nível coupled cluster com simples e duplas (CCSD) através da teoria de resposta, utilizando o conjunto de funções base aug-cc-pVDZ. Os cálculos para as correções vibracionais foram realizadas utilizando teoria de perturbação Møller-Plesset em segunda ordem (MP2) via método perturbativo de Bishop e Kirtman, e também utilizando um procedimento variacional proposto aqui. Os resultados obtidos para a correção da média vibracional de ponto-zero (zpva) mostram que os dois métodos levam aos mesmos resultados, contribuindo com 2 e 6 % dos correspondentes valores eletrônicos da polarizabilidade e primeira hiperpolarizabilidade. Os resultados obtidos mostram que, no limite estático, a correção vibracional pura para a polarizabili-dade e primeira e segunda hiperpolarizabilidades são da mesma ordem de magnitude que as correspondentes contribuições eletrônicas. Comparações entre os resultados obtidos através dos dois métodos mostram que o método perturbativo não é adequado para tratar o sistema estudado, enquanto que o procedimento variacional apresentado parece ser uma boa alternativa para tratar sistemas anarmônicos.

In this work we present the first implementation of the incremental scheme for coupled cluster linear-response frequency-dependent dipole polarizabilities. The implementation is fully automated and makes use of the domain-specific basis set approach. The accuracy of the approach is determined on the basis of a test suite of 47 molecules and small clusters. The local approximation in the coupled cluster singles and doubles polarizability exhibits a mean error of 0.02% and a standard deviation of 0.32% when using a third-order incremental expansion. With the proposed approach, it is possible to compute polarizabilities with larger basis sets compared to the canonical implementation and thus it is possible to obtain higher total accuracy. The incremental scheme yields the smallest errors for weakly-bound and quasi-linear systems, while two- and three-dimensional (cage-like) structures exhibit somewhat larger errors as compared to the full test set. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

abstract: In this thesis, I present the study of nucleon structure from distinct perspectives. I start by elaborating the motivations behind the endeavors and then introducing the key concept, namely the generalized parton distribution functions (GPDs), which serves as the frame- work describing hadronic particles in terms of their fundamental constituents. The second chapter is then devoted to a detailed phenomenological study of the Virtual Compton Scattering (VCS) process, where a more comprehensive parametrization is suggested. In the third chapter, the renormalization kernels that enters the QCD evolution equations at twist- 4 accuracy are computed in terms of Feynman diagrams in momentum space, which can be viewed as an extension of the work by Bukhvostov, Frolov, Lipatov, and Kuraev (BKLK). The results can be used for determining the QCD background interaction for future precision measurements. / Dissertation/Thesis / Doctoral Dissertation Physics 2016

This thesis presents a robust method for estimating the relaxations of a metallic object from its electromagnetic induction (EMI) response. The EMI response of a metallic object can be accurately modeled by a sum of real decaying exponentials. However, it is diffcult to obtain the model parameters from measurements when the number of exponentials in the sum is unknown or the terms are strongly correlated. Traditionally, the time constants and residues are estimated by nonlinear iterative search that often leads to unsatisfactory results. In this thesis, a constrained linear method of estimating the parameters is formulated by enumerating the relaxation parameter space and imposing a nonnegative constraint on the parameters. The resulting algorithm does not depend on a good initial guess to converge to a solution. Using tests on synthetic data and laboratory measurement of known targets the proposed method is shown to provide accurate and stable estimates of the model parameters.

The first aim of this thesis is to perform relativistic calculation of atomic and ionic polarizabilities and two-photon decay rates. Hydrogenic systems are treated by the Lagrange-mesh method. The extension to alkali-like systems is realized by means of a semiempirical-core-potential approach combined with the Lagrange-mesh method. The studied systems are partitioned into frozen-core electrons and an active valence electron. The core orbitals are defined by a Dirac-Hartree-Fock (DHF) calculation using the GRASP2K package. The valence electron is described by a Dirac-like Hamiltonian involving a core-polarization potential to simulate the core-valence electron correlation. Polarizabilities appear in a large number of fields and applications, namely in cold atoms physics, metrology and chemical physics. Two-photon transitions are part of a priori highly unlikely processes and are therefore called forbidden radiative processes. Experimental situations report decays from metastable excited states through these channels. Long lifetimes were measured for highly charged Be-like ions in recent storage-ring experiments, but their interpretation is problematic. The study of the competition between forbidden (one-photon beyond the dipole approximation, or multi-photon) and unexpected (hyperfine-induced or induced by external magnetic fields) radiative processes is all obviously relevant. The second aim of this thesis is to perform relativistic ab initio calculations of electronic isotope-shift (IS) factors by using the multiconfiguration DHF (MCDHF) method implemented in the RIS3/GRASP2K and RATIP program packages. Using the MCDHF method, two different approaches are adopted for the computation of electronic IS factors for a set of transitions between low-lying levels of neutral systems. The first one is based on the estimate of the expectation values of the one- and two-body nuclear recoil Hamiltonian for a given isotope, including relativistic corrections derived by Shabaev, combined with the calculation of the total electron densities at the origin. In the second approach, the relevant electronic factors are extracted from the calculated transition shifts for given triads of isotopes. These electronic quantities together with observed ISs between different pairs of isotopes provide the changes in mean-square charge radii of the atomic nuclei. Within this computational approach for the estimation of the mass- and field-shift factors, different models for electron correlation are explored in a systematic way to determine a reliable computational strategy, and to estimate theoretical error bars of the IS factors. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished