The cross sections for neutral current (NC) deep inelastic scattering (DIS) in e+p collisions with a longitudinally polarised positron beam are measured at high momentum transfer squared (Q2 > 185 GeV2) at the ZEUS detector at HERA. The HERA accelerator provides e+-p collisions at a centre-of-mass energy of 318 GeV, which allows the weak contribution to the NC process to be studied at high Q2. The measurements are based on a data sample with an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007. The single differential NC cross sections dsigma/dQ2, dsigma/dx and dsigma/dy and the reduced cross section are measured. The structure function xF3 is determined by combining the e+p NC reduced cross sections with the previously measured e-p measurements. The interference structure function xF 3^gamma,Z is extracted at Q2 = 1500 GeV2. The cross-section asymmetry between the positive and negative polarisation of the positron beam is measured and the parity violation effects of the electroweak interaction are observed. The predictions of the Standard Model of particle physics agree well with the measurements.

Die Off-Axis-Elektronenholographie ist eine interferometrische Methode zur experimentellen Bestimmung von relativen Phasenschiebungen einer Elektronenwelle. Der Zugang zu diesen Phasenschiebungen ermöglicht z.B. die Bestimmung von intrinsischen elektrischen und magnetischen Feldern eines Objektes im Nanometerbereich. Für eine quantitative Interpretation der Resultate ist die Kenntnis des Rauschens der holographisch rekonstruierten Größen von hoher Bedeutung. In dieser Arbeit wird ein allgemeiner Formalismus abgeleitet, der den Rauschtransfer vom detektierten Hologramm in die rekonstruierten Amplituden- und Phasenbilder beschreibt. Anhand zielgerichteter Experimente wird dieser Formalismus unter Berücksichtigung von gemessenen Rauscheigenschaften des Detektors verifiziert. Im Zuge dessen wird eine experimentelle Methode entwickelt, die es erlaubt, durch Serienaufnahmen und Mittelungsprozeduren das Signal-zu-Rauschverhältnis in den holographischen Resultaten bei gleichbleibender Ortsauflösung erheblich zu verbessern. Daran knüpft sich eine Vielzahl von Anwendungen an, welche in dieser Arbeit in Auszügen aufgeführt werden. Die Grundlage für all diese Experimente besteht in den Welleneigenschaften des Elektrons, welche in der Interferenzfähigkeit (Kohärenz) des Elektrons zum Ausdruck kommen. Elektronen, welche unelastisch an einem Objekt streuen, verlieren diese Eigenschaft und es stellt sich die Frage, ob aus diesem Verlust zusätzliche Informationen über den Streuprozess bzw. über das Objekt selbst gewonnen werden können. Eine Größe, die neben der Intensität auch die Kohärenz der Elektronen beschreibt, ist die reduzierte Dichtematrix. Das motiviert, die Methode der Off-Axis-Elektronenholographie in der Sprache der Dichtematrizen zu formulieren und eine allgemeine Übertragungstheorie für ein holographiefähiges Transmissionselektronenmikroskop abzuleiten. Diese Theorie umfasst alle bisher bekannten Phänomene im Rahmen der Elektronenholographie und bietet darüber hinaus neue instrumentelle Ansätze zur Optimierung des Signal-zu-Rausch-Verhältnisses und zur Überwindung auflösungsbegrenzender Aberrationen. Vor diesem Hintergrund wird weiterhin die Kohärenz von Elektronen mittels energiegefilterter Off-Axis-Elektronenholographie untersucht, welche unelastisch an Siliziumoberflächen streuen und charakteristische Oberflächenplasmonen anregen. Für die Interpretation der Resultate werden zwei Modelle für die Dekohärenz des Elektrons infolge der Wechselwirkung mit einer Objektoberfläche entwickelt und unter Berücksichtigung der Aberrationen des Energiefilters mit dem Experiment verglichen. / Off-axis electron holography provides access to the relative phase shift of an electron wave and allows the experimental determination of intrinsic electric and magnetic fields within an object at nanometre scale. A quantitative interpretation of the results requires the knowledge about the noise in the reconstructed data. In this work, a general formalism is derived describing the transfer of noise from an experimental hologram into reconstructed amplitude and phase images. Concerted experiments verify this formalism under consideration of measured noise properties of the detector. In this frame, a method based on series acquisition and averaging is developed to improve significantly the signal-to-noise ratio of the reconstructed amplitude and phase images at constant spatial resolution. The usefulnes of this method is demonstrated by selected experimental examples from the materials sciences. The capability to show interference, i.e. to be coherent, is a consequence of the electron's wave nature and provides the fundament for all applications of electron holography. By inelastic interaction with the object, the electron loses coherence and the question comes up, whether this loss mechanism contains additional information about the scattering process or even about the object itself. The reduced density matrix is introduced as a suitable quantity describing both intensity and coherence of scattered electrons. That motivates to formulate off-axis electron holography in the language of density matrices and to derive a general transfer theory for this quantity in a holography-dedicated transmission electron microscope. This theory reproduces all known phenomena related to off-axis electron holography and provides new instrumental approaches to improve the signal-to-noise ratio and to overcome resolution limiting aberrations. In this context, the coherence of electrons, which are inelastically scattered by silicon surfaces and have excited characteristic surface plasmons, is investigated by energy-filtered electron holography. For the interpretation of the experimental results, two models are developed for the decoherence of the electron by interaction with an object surface and are compared to the experiment under consideration of the aberrations of the energy-filter.

No description available.

The cross sections for neutral current (NC) deep inelastic scattering (DIS) in e+p collisions with a longitudinally polarised positron beam are measured at high momentum transfer squared (Q2 > 185 GeV2) at the ZEUS detector at HERA. The HERA accelerator provides e+-p collisions at a centre-of-mass energy of 318 GeV, which allows the weak contribution to the NC process to be studied at high Q2. The measurements are based on a data sample with an integrated luminosity of 135.5 pb-1 collected with the ZEUS detector in 2006 and 2007. The single differential NC cross sections dsigma/dQ2, dsigma/dx and dsigma/dy and the reduced cross section are measured. The structure function xF3 is determined by combining the e+p NC reduced cross sections with the previously measured e-p measurements. The interference structure function xF 3^gamma,Z is extracted at Q2 = 1500 GeV2. The cross-section asymmetry between the positive and negative polarisation of the positron beam is measured and the parity violation effects of the electroweak interaction are observed. The predictions of the Standard Model of particle physics agree well with the measurements.

doctoral thesis, Ph.D, University of California, Berkeley, Berkeley, CA. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55855" Gedik, Nuh. USDOE Director. Office of Science. Office of Basic Energy Sciences 05/20/2004. Report is also available in paper and microfiche from NTIS.

Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-01-21T10:32:45Z No. of bitstreams: 0 / Made available in DSpace on 2015-01-21T10:32:45Z (GMT). No. of bitstreams: 0 / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutorado em Tecnologia Nuclear) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:10/04206-4

A reação 10B+120Sn foi medida no Laboratório Aberto de Física Nuclear (LAFN) do Instituto de Física da Universidade de São Paulo, em energias próximas a barreira coulombiana (VB = 35 MeV). Distribuições angulares de espalhamento elástico e inelástico foram obtidas, e o canal de transferência de um nêutron do alvo para o projétil foi identificado. Além disso, foram feitas medidas utilizando a técnica de detecção em coincidências gamma-partícula no espectrômetro Saci-Perere (Sistema Ancilar de Cintiladores e Pequeno Espectrômetro de Radiação Eletromagnética com Rejeição de Espalhamento). Tais medidas possibilitaram a identificação do processo de fusão completa, a partir da detecção dos raios-gamma provenientes do núcleo composto 127Cs, formado pela absorção de toda carga do projétil pelo alvo, seguido da evaporação de nêutrons. Eventos relacionados ao processo de fusão incompleta, originados da quebra do projétil 10B, também foram identificados. Uma descrição teórica dos principais resultados experimentais foi realizada dentro do formalismo de canais acoplados, utilizando o potencial de São Paulo para descrever a parte real da interação nuclear entre os núcleos participantes da reação. / The 10B+120Sn reaction was measured at the \"Laboratório Aberto de Física Nuclear\" (LAFN, acronym in Portuguese) of the \"Instituto de Física da Universidade de São Paulo\", at energies around the Coulomb barrier (VB = 35 MeV). Angular distribuitions for the elastic and inelastic scattering were obtained, and the transfer channel of a neutron from the target to the projectile was also identified. Besides that, another set of measurements were carried out using the gamma-particle coincidence techinique with the ancillary system of scintillators and gamma-ray detectors Saci-Perere (acronym of \"Sistema Ancilar de Cintiladores e Pequeno Espectrômetro de Radiação Eletromagnética com Rejeição de Espalhamento\"). Such measurements have allowed the identification of the complete fusion process through the detection of gamma-rays coming from the compound nuclei 127Cs, formed by the absorption of the total projectile charge by the target, followed by the evaporation of neutrons. Events related to the incomplete fusion process, originated from the breakup of 10B, were also identified. A theoretical description of the main experimental results has been performed within the coupled channel formalism, using the São Paulo potential to represent the real part of the nuclear interaction between the two reacting nuclei.

Neste trabalho, estudamos a influência de canais de espalhamento inelástico no transporte eletrônico. Primeiramente, expomos o formalismo de Landauer usual para o cálculo da corrente elétrica em sistemas em que o espalhamento é puramente elástico. Como exemplo, calculamos a corrente para um potencial delta de Dirac a partir de suas probabilidades de transmissão. A amostra correspondente é aquela de uma camada muito fina com impurezas (não-magnéticas) contida em uma heterostrutura semicondutora. Mostramos que a distorção do potencial quântico devido à voltagem aplicada pode ser desprezada no cálculo da corrente elétrica, abaixo da energia de Fermi do emissor. Subsequentemente, acoplamos o potencial delta a um oscilador harmônico quântico para modelar a presença de fônons no sistema. Encontramos modos inelásticos de transmissão que se tornam acessíveis para energias cada vez maiores, múltiplas do quantum hω. Devido à conservação de probabilidade, a abertura de cada novo canal corresponde a bicos\" nas probabilidades de transmissão dos modos abaixo deste, em função da energia de incidência do elétron. No caso de uma delta atrativa, ressonâncias assimétricas com perfil de Fano são observadas. Adaptamos o formalismo de Landauer, incluindo canais inelásticos independentes. Seguindo um trabalho anterior de Emberly e Kirczenow (2000), mostramos que existe uma forma de se levar em conta possíveis coincidências nos estados de espalhamento finais aplicando o princípio de exclusão de Pauli. Isto leva as distribuições dos estados de espalhamento a estarem fora de equilíbrio, já que dependem umas das outras. Resolvendo o problema auto-consistentemente, somos capazes de obter a corrente elétrica a partir das probabilidades de transmissão do potencial quântico. Nossos resultados demonstram que as ressonâncias de Fano do potencial atrativo dão origem a uma diminuição da inclinação da corrente elétrica contra a voltagem aplicada, já que elétrons são presos\" ao potencial por um tempo infinito. Mostramos este efeito num regime de voltagens baixas em comparação com a energia de Fermi, para o qual desprezamos a distorção do potencial quântico devido à voltagem aplicada. Além disso, uma comparação com os resultados do formalismo de Landauer mostra que uma discrepância significativa é observada para o caso de o oscilador estar inicialmente excitado e fortemente acoplado ao elétron. / In this work, we study the influence of inelastic scattering channels in electronic transport. We first present the usual Landauer formalism, for calculating the electric current in systems where the scattering is purely elastic. As an example, we calculate the current for a Dirac delta potential from its transmission probabilities. The corresponding sample is that of a very thin layer with (non-magnetic) impurities within a semiconductor heterostructure. We show that the distortion of the quantum potential due to the applied voltage can be ignored in the calculation of an electric current below the Fermi energy of the emitter. Then we couple the delta potential to a quantum harmonic oscillator to model the presence of phonons in the system. We find inelastic transmission modes that become available for increasing energies, multiple of the quantum hω. Due to conservation of probability, the opening of each new channel corresponds to kinks\" in the transmission probabilities of lower modes as a function of the energy of the impinging electrons. In the case of an attractive delta potential, asymmetric resonances with a Fano-like profile are observed. We adapt the Landauer formalism by including the independent inelastic channels. Following a previous work by Emberly and Kirczenow (2000), we show that there is a way to take into account the possible coincidences in the final scattering states using Pauli\'s exclusion principle. This causes the distributions of the scattering states to be out of equilibrium, as they depend on each other. Solving the problem self-consistently, we are able to obtain the electric current from the transmission probabilities of the quantum potential. Our results demonstrate that the Fano resonances of the attractive potential gives rise to a decrease of the slope in the electric current versus the applied voltage, as the electrons are trapped\" in the potential for a finite amount of time. We have shown this effect in a low voltage regime with respect to the Fermi energy, for which we ignore the distortion of the quantum potential due to the applied voltage. Furthermore, a comparison with the results from the Landauer formalism shows that a significant discrepancy is seen for the oscillator initially in its excited mode and strongly coupled to the electron.

Cromodinâmica quântica, Espalhamento / Highly inelastic scattering proton electron in quantum chromodynamics

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