A search for squarks and gluinos in all hadronic final states in \sqrt(s) = 13 TeV proton-proton collisions using an integrated luminosity of 13.3 fb^-1 collected by the ATLAS detector at the LHC is presented. The search is the first to use Recursive Jigsaw Reconstruction, a technique to impose a particular decay tree interpretation on events. The decay tree is resolved using jigsaw rules, which define boosts between the relevant reference frames to define an uncorrelated basis of variables to describe the decay. The Recursive Jigsaw Reconstruction variables are used to define a set of selections with sensitivity to pair produced squarks and gluinos. No excess is observed over the Standard Model background. Results are interpreted in simplified models where squarks and gluinos are pair produced and decay to jets and the lightest supersymmetric particle. These limits substantially extend the region of supersymmetric phase space excluded by previous searches.

<p> A study of ground state binding energy values listed in the Atomic Mass Evaluation 2012 (AME2012) using an interpretive approach, as opposed to the exploratory methods of previous models, is presented. This model is based on a postulate requiring all protons to pair with available neutrons to form bound alpha clusters as the ground state for an <i>N = Z</i> core upon which excess neutrons are added. For each core, the trend of the binding energy as a function of excess neutrons in the isotopic chain can be fit with a three-term quadratic function. The quadratic parameter reveals a smooth decaying exponential function. By re-envisioning the determination of mass excess, the constant-term fit parameters, representing <i>N = Z</i> nuclei, reveal a near-symmetry around <i>Z</i> = 50. The linear fit parameters exhibit trends which are linear functions of core size. A neutron drip-line prediction is compared against current models. By considering the possibility of an alpha-cluster core, a new ground-state structure grouping scheme is presented; nucleon-nucleon pairing is shown to have a greater role in level filling. This model, referred to as the Alpha-Deuteron-Neutron Model, yields promising first results when considering root-mean-square variances from the AME2012.</p><p> The beta-decay of the neutron-rich isotope ⁷⁴Cu has been studied using three high-purity Germanium clover detectors at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. A high-resolution mass separator greatly improved the purity of the ⁷⁴Cu beam by removing isobaric contaminants, thus allowing decay through its isobar chain to the stable ⁷⁴Ge at the center of the LeRIBSS detector array without any decay chain member dominating. Using coincidence gating techniques, 121 gamma-rays associated with ⁷⁴Cu were isolated from the collective singles spectrum. Eighty-seven of these were placed in an expanded level scheme, and updated beta-feeding level intensities and log(<i> ft</i>) values are presented based on multiple newly-placed excited states up to 6.8 MeV. The progression of simulated Total Absorption gamma-ray Spectroscopy (TAGS) based on known levels and beta feeding values from previous measurements to this evaluation are presented and demonstrate the need for a TAGS measurement of this isotope to gain a more complete understanding of its decay scheme. </p>

Estudo dos movimentos atômicos do t-Butanol do Espalhamento de nêutrons lentos / Study of the atomic motions of the slow neutron scattering t-Butanol

Vidas médias de níveis mais baixos nas bandas de 1 e 3 quase-partículas em ANTPOT 133Ce foram medidas usando a técnica de distância de recuo e deslocamento Doppler RDDS. As amplitudes das transições E2 extraídas dos estados yrast de paridade negativa são bem descritas pelos modelos Rotor Triaxial + Quase-Partícula e geométrico. Os valores de B(M1) extraídos para os níveis na banda de 3 quase-partículas de paridade positiva estão consistentes com a atribuição da configuração Vh1l/2 (X) h 1l/2 (X) g7/2 para essa banda. Os níveis no 132,133Ce foram populados pela reação ANTPOT 120 Sn (ANTPOT 16 O,4n,3n) ANTPOT 132,133Ce na energia incidente de 70 MeV. O feixe foi fornecido pelo acelerador Tandem do Laboratório Pelletron. Os dados foram obtidos usando um detetor HP Ge (22% de eficiência, resolução de energia de 2.1keV) com supressão Compton BGO a 0° em relação ao feixe e um filtro de multiplicidades de 6 detetores 3\" x 3\" de NaI(Tl) num plano perpendicular ao plano da reação. O alvo foi produzido por evaporação ed ANTPOT 120 Sn metálico sobre um substrato fino de ouro voltado na direção de incidência do feixe, enquanto que o anteparo (stopper) foi produzido em chumbo. Os núcleos de recuo atingiram uma velocidade média de v= 0.008c. As medidas foram realizadas com um dispositivo plunger construído no Laboratório Pelletron. Os espectros foram obtidos para 13 diferentes distâncias alvo-stopper e foram normalizadas usando uma linha gama de 279 keV da excitação Coulombiana do substrato de Au. As distâncias de vôo alvo-stopper foram medidas usando a técnica de capacitância e também com um micrômetro de precisão. As vidas médias de estados de alto spin em ANTPOT 136 Pr, ímpar-ímpar, foram também medidas usando a reação ANTPOT. 123 Sb (ANTPOT 16 O,3n) na energia incidente de 65 MeV. Os espectros de raios gama foram adquirídos para 20 diferentes distâncias. O alvo foi confeccionado de ANTPOT 123 Sb de espessura de 1mg/cm², evaporado sobre um substrato de 2mg/cm² de Au. A análise mostra que a vida média do estado 8+ da banda yrast (h1l/2) (X) v(h 1l / 2) é de 1177 ± 64ps. Um limite superior para a vida média do estado 7- foi estabelecido em < 1ns. / Lifetimes of the low-lying levels in the one and three quasiparticle bands in 133Ce have been measured using the recoil-distance Doppler-shift technique RDDS. The E2 transition strengths extracted for the negative parity yrast states are well described by the Triaxial-Rotor-plus-Quasipartide and the geometrical model. The B(M1) values extracted for the levels in the positive parity 3 quasipartide band are consistent with the Vh11/2 X h 11/2 g7/2 configuration assignment to this band. Levels in 132,133Ce were populated by the 120Sn(16O,4n,3n)132,133Ce reaction at an incident energy of 70 MeV. The beam was provided by the Tandem accelerator of the Pelletron Laboratory. Data were obtained using a BGO Compton suppressed HPGe detector (22% efficiency, energy resolution 2.1 keV) at 0° to the beam and a multiplicity filter of six 3\" x 3\" NaI(TI) detectors in a plane perpendicular to the reaction plane. The target was produced by evaporation of enriched metallic 120Sn onto a thin Au backing which faced the incident beam, while the stopper was of lead. The recoil nuclei had an average velocity of v = 0.008c. The measurements were performed with a plunger device constructed in our laboratory. Spectra were obtained for 13 different target-stopper distances and were normalized using the 279 keV gamma line from the Coulomb excitation of the Au backing. The target-stopper flight distances were measured using the capacitance technique and also with a precision micrometer. Lifetimes of the high spin states in odd-odd 136Pr were also measured using the 123Sb(16O,3n) reaction at an incident energy of 65 MeV. Gamma spectra were collected at about 20 different distances. The target was of enriched 123Sb 1mg/cm2 thick, evaporated onto a Au 2mg/cm2 backing. Analysis shows that the lifetime of the 8+ state in the yrast band (h11 2Z) X V (h11/2) is 1177 ± 64ps. An upper limit for the 7- state was stablished in < 1ns.

São discutidas as hipóteses teóricas que levam à determinação da função distribuição que descreve o s elétrons dentro de um Órbitron. Comparando- se as medidas do espectro de energia dos íons feitas por Cybulska e Douglas com o espectro teórico concluído que os elétrons são adequadamente descritos supondo um estado de equilíbrio estatístico. É feita uma estimativa do tempo de relaxação que mostra que o tempo médio de permanência dos elétrons dentro do aparelho é suficiente para que se estabeleça equilíbrio térmico. É mostrado como é possível calcular de um modelo auto-consistente a modificação do potencial e da densidade quando é levado em conta a carga eletrônica espacial. O espectro de frequências medido por Troise é interpretado dentro do modelo estatístico considerando-se as frequências de vibrações coletivas do gás de elétrons dentro do Órbitron. / The theoretical assumptions that lead to the determination of the distribution function describiling the electrons in orbitrons are discussed. Comparing the ion energy spectrum measured by Çybulska with the theoretical spectrum it is concluded that the electrons are appropriately described if a state of statistical equilibrium is assumed. The relaxation time is estimated it is shown that the average time spent by the electrons inside the orbitron is sufficient for thermal equilibrium to attain. A self-consistent calculation of the potentical and the density is done taking the electronic charge into account The radio-frequencies spectrum measurement of Troise is interpreted on the basico of the statistical model, by considering the frequencies of the collective vibrations of the electron gas inside the orbitron.

RAZAO GIROMAGNETICA DE ESTADOS EXCITADOS DE 107,109AG / Giant-state race of excited states of \'ANTPOT.107,109 AG\'.

Neste trabalho as diversas propostas de \'\'Trajetórias Coletivas\" apresentadas na literatura foram derivadas a partir de uma análise local das equações dinâmicas de Hartree Fock Dependente do Tempo. Estas propostas foram comparadas e condições de validade obtidas para hamiltonianas semiclássicas que tem apenas termos de 2ª ordem nos momentos. Uma análise cuidadosa da parametrização de Determinantes de Slater permitiu- nos explorar as características geométricas da teoria de Hartree-Fock Dependente do tempo e construir as trajetórias num formalismo covariante. Esta análise foi aplicada a um modelo esquemático de três níveis SU(3). / In this work, the many proposals of Collective Paths\" that have appeared in literature, were derived through a local analysis of the Time Dependent Hartree Fock dynamics. Those proposals were compared and validity conditions obtained for Semiclassical Hamiltonians which have only quadratic terms in momenta. A careful analysis of the parametrization of Slater Determinants allowed us to exploit the geometrical features of the Time Dependent Hartree Fock Theory and construct the Paths in a covariant way. The analysis was applied to a three level model (SU(3)).

Optical trapping techniques have become an important and irreplaceable tool in many research disciplines for reaching non-invasively into the microscopic world and to manipulate, cut, assemble and transform micro-objects with nanometer precision and sub-micrometer resolution. Further advances in optical trapping techniques promise to bridge the gap and bring together the macroscopic world and experimental techniques and applications of Microsystems in areas of physics, chemistry and biology. In order to understand the optical trapping process and to improve and tailor experimental techniques and applications in a variety of scientific disciplines, an accurate knowledge of trapping forces exerted on particles and their dependency on environmental and morphological factors is of crucial importance. Furthermore, the recent trend in novel laser trapping experiments sees the use of complex laser beams in trapping arrangements for achieving more controllable laser trapping techniques. Focusing of such beams with a high numerical aperture (NA) objective required for efficient trapping leads to a complicated amplitude, phase and polarisation distributions of an electromagnetic field in the focal region. Current optical trapping models based on ray optics theory and the Gaussian beam approximation are inadequate to deal with such a focal complexity. Novel applications of the laser trapping such as the particle-trapped scanning near field optical microscopy (SNOM) and optical-trap nanometry techniques are currently investigated largely in the experimental sense or with approximated theoretical models. These applications are implemented using the efficient laser trapping with high NA and evanescent wave illumination of the sample for high resolution sensing. The proper study of these novel laser trapping applications and the potential benefits of implementation of these applications with complex laser beams requires an exact physical model for the laser trapping process and a nanometric sensing model for detection of evanescent wave scattering. This thesis is concerned with comprehensive and rigorous modelling and characterisation of the trapping process of spherical dielectric particles implemented using far-field and near-field optical trapping modalities. Two types of incident illuminations are considered, the plane wave illumination and the doughnut beam illumination of various topological charges. The doughnut beams represent one class of complex laser beams. However, our optical trapping model presented in this thesis is in no way restricted to this type of incident illumination, but is equally applicable to other types of complex laser beam illuminations. Furthermore, the thesis is concerned with development of a physical model for nanometric sensing, which is of great importance for optical trapping systems that utilise evanescent field illumination for achieving high resolution position monitoring and imaging. The nanometric sensing model, describing the conversion of evanescent photons into propagating photons, is realised using an analytical approach to evanescent wave scattering by a microscopic particle. The effects of an interface at which the evanescent wave is generated are included by considering the scattered field reflection from the interface. Collection and imaging of the resultant scattered field by a high numerical aperture objective is described using vectorial diffraction theory. Using our sensing model, we have investigated the dependence of the scattering on the particle size and refractive index, the effects of the interface on the scattering cross-section, morphology dependent resonance effects associated with the scattering process, and the effects of the incident angle of a laser beam undergoing total internal reflection to generate an evanescent field. Furthermore, we have studied the detectability of the scattered signal using a wide area detector and a pinhole detector. A good agreement between our experimental measurements of the focal intensity distribution in the back focal region of the collecting objective and the theoretical predictions confirm the validity of our approach. The optical trapping model is implemented using a rigorous vectorial diffraction theory for characterisation of the electromagnetic field distribution in the focal region of a high NA objective. It is an exact model capable of considering arbitrary amplitude, phase and polarisation of the incident laser beam as well as apodisation functions of the focusing objective. The interaction of a particle with the complex focused field is described by an extension of the classical plane wave Lorentz-Mie theory with the expansion of the incident field requiring numerical integration of finite surface integrals only. The net force exerted on the particle is then determined using the Maxwell stress tensor approach. Using the optical trapping model one can consider the laser trapping process in the far-field of the focusing objective, also known as the far-field trapping, and the laser trapping achieved by focused evanescent field, i.e. near-field optical trapping. Investigations of far-field laser trapping show that spherical aberration plays a significant role in the trapping process if a refractive index mismatch exists between the objective immersion and particle suspension media. An optical trap efficiency is severely degraded under the presence of spherical aberration. However, our study shows that the spherical aberration effect can be successfully dealt with using our optical trapping model. Theoretical investigations of the trapping process achieved using an obstructed laser beam indicate that the transverse trapping efficiency decreases rapidly with increasing size of the obstruction, unlike the trend predicted using a ray optics model. These theoretical investigations are in a good agreement with our experimentally observed results. Far-field optical trapping with complex doughnut laser beams leads to reduced lifting force for small dielectric particles, compared with plane wave illumination, while for large particles it is relatively unchanged. A slight advantage of using a doughnut laser beam over plane wave illumination for far-field trapping of large dielectric particles manifests in a higher forward axial trapping efficiency, which increases for increasing doughnut beam topological charge. It is indicated that the maximal transverse trapping efficiency decreases for reducing particle size and that the rate of decrease is higher for doughnut beam illumination, compared with plane wave illumination, which has been confirmed by experimental measurements. A near-field trapping modality is investigated by considering a central obstruction placed before the focusing objective so that the obstruction size corresponds to the minimum convergence angle larger than the critical angle. This implies that the portion of the incident wave that is passed through the high numerical aperture objective satisfies the total internal reflection condition at the surface of the coverslip, so that only a focused evanescent field is present in the particle suspension medium. Interaction of this focused near-field with a dielectric micro-particle is described and investigated using our optical trapping model with a central obstruction. Our investigation shows that the maximal backward axial trapping efficiency or the lifting force is comparable to that achieved by the far-field trapping under similar conditions for either plane wave illumination or complex doughnut beam illumination. The dependence of the maximal axial trapping efficiency on the particle size is nearly linear for near-field trapping with focused evanescent wave illumination in the Mie size regime, unlike that achieved using the far-field trapping technique.

<p>A new neutron time-of-flight spectrometer optimized for high count rate (TOFOR) has been developed for the JET research tokamak. TOFOR will measure the energy distribution of neutrons emitted from the d+d → ³He+n fusion reactions in deuterium plasma. It will serve as the principal neutron spectroscopy diagnostic of high fusion power plasmas produced by injection of radio frequency waves (RF) and neutral beams (NB). The objective is to study plasma effects of RF and NB injection, with regard to temperature rise of the bulk deuteron population and the characteristics of supra-thermal components manifesting themselves over an extended energy range and with large spectral intensity variations. </p><p>To meet the plasma diagnostic objectives, special demands have been put on the design and characterization of TOFOR which, to a great extent, has relied on extensive neutron transport calculations. These calculations were used to optimize the design and to determine the TOFOR neutron response function. For the response function, TOF spectra were simulated for 81 quasi mono-energetic neutron energies in the range 1 to 5 MeV.</p><p>This thesis presents new results on instrumental solutions on the problem to reach high count rates, leading to a factor of hundred improvement compared to earlier designs.</p><p>With regard to the analysis of measured TOF spectra, the determined response function was folded with models and fitted to measurement data. The general issue of the energy dependence of the response function is raised and its importance is illustrated with analysis of high-quality TOF spectra for NB and RF heated plasmas. Potential for future developments are identified in the use of hybrid cards able to provide digital infromation on both time and pulse height.</p>

A new neutron time-of-flight spectrometer optimized for high count rate (TOFOR) has been developed for the JET research tokamak. TOFOR will measure the energy distribution of neutrons emitted from the d+d → 3He+n fusion reactions in deuterium plasma. It will serve as the principal neutron spectroscopy diagnostic of high fusion power plasmas produced by injection of radio frequency waves (RF) and neutral beams (NB). The objective is to study plasma effects of RF and NB injection, with regard to temperature rise of the bulk deuteron population and the characteristics of supra-thermal components manifesting themselves over an extended energy range and with large spectral intensity variations. To meet the plasma diagnostic objectives, special demands have been put on the design and characterization of TOFOR which, to a great extent, has relied on extensive neutron transport calculations. These calculations were used to optimize the design and to determine the TOFOR neutron response function. For the response function, TOF spectra were simulated for 81 quasi mono-energetic neutron energies in the range 1 to 5 MeV. This thesis presents new results on instrumental solutions on the problem to reach high count rates, leading to a factor of hundred improvement compared to earlier designs. With regard to the analysis of measured TOF spectra, the determined response function was folded with models and fitted to measurement data. The general issue of the energy dependence of the response function is raised and its importance is illustrated with analysis of high-quality TOF spectra for NB and RF heated plasmas. Potential for future developments are identified in the use of hybrid cards able to provide digital infromation on both time and pulse height.