A Finite Hilbert Basis Set (FHBS) method to calculate the angular and energy distribution of ejected electrons in an ion-atom collision is presented. This method has been applied to the p + H collision at 20 keV impact energy. An interference effect between the exit channels, where electrons are guided out of the collision region by both the residual target proton and the projectile proton, is discovered. Experimental data appears to confirm this result.

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A Finite Hilbert Basis Set (FHBS) method to calculate the angular and energy distribution of ejected electrons in an ion-atom collision is presented. This method has been applied to the p + H collision at 20 keV impact energy. An interference effect between the exit channels, where electrons are guided out of the collision region by both the residual target proton and the projectile proton, is discovered. Experimental data appears to confirm this result.

Thesis (MSc (Physics))--University of Stellenbosch, 2008. / Experimental double differential cross sections and analyzing powers for the inclusive 93 Nb(p,α) r and 93 Nb(p, 3He) r reactions have been measured at an incident energy of 160 MeV. The results of this experiment, for emission angles ranging from 15º to 60º as well as previously measured data for 93 Nb(p,α) r at 100 MeV and 59Co(p,α) r at 100 and 160 MeV, have been compared with theoretical calculations based on a direct quasi-free α- cluster knockout mechanism. A computer code has been employed which calculates triple differential cross section and analysing power values using the distorted wave impulse approximation (DWIA). Inclusive double differential cross sections and analysing powers were calculated by integrating over the solid angle of the unobserved proton. It was found that the DWIA is limited in its ability to reproduce the experimental data. Some slight agreements have been observed in the region of large emission energies and small angles. This is consistent with the findings of previous studies based on a direct multi-step analysis which indicated that the first step knock-out reaction dominates in this region.

The top quark has been extensively studied since the Large Hadron Collider (LHC) began operating in 2010. The excellent performance of both the LHC and the Compact Muon Solenoid (CMS) detector has enabled complex analyses of many properties of the top quark. In this thesis inclusive and differential top pair (tt) production cross sections have been measured. Inclusive tt cross sections of 145.6 ± 8.2 (stat.) +38.1/28.3 (syst.) pb and 237.4 ± 1.9 (stat.) +20.4/-16.9 (syst.) pb were measured at 7 TeV and 8 TeV center-of-mass collision energies using luminosities of 1 fb⁻¹ and 19.7 fb⁻¹, respectively. These measurements were performed in the semi-leptonic channel by means of a maximum likelihood t of the lepton's pseudorapidity. The work in this thesis focuses specifically on the muon-plus-jets channel. The methods used for measuring the inclusive cross sections were built upon to measure differential cross sections with respect to event level observables. These observables include the missing transverse energy (Emiss T ) as well as some other kinematic distributions involving the jets, lepton and Emiss T in the decay. These results are unfolded to remove detector and selection effects and have uncertainties in the range of 3% to 15%. A low uncertainty is achieved by normalising the differential cross section using the total cross section. This leads to cancellations of some uncertainties. The results were compared with different Monte Carlo generators and with different input parameters. No significant deviations from predictions of the Standard Model were observed. This thesis also contains test beam results on CMS ECAL Endcap Lead Tungstate (PbWO4) crystals. These crystals had been damaged using various doses of proton irradiation. The damage for some crystals is expected to be roughly equivalent to 300 fb-1 of integrated luminosity at √s = 14 TeV. The energy resolution for these crystals was seen to reduce by close to a factor of 20.

The electron-electron coincidence (e,2e) technique yields complete kinematical information about the electron impact ionization process. The (e,2e) technique has been widely used to study dynamical effects in ionizing collisions with atomic targets, however studies of molecular ionization using this technique have been very limited. Recently further experimental studies of small molecules have been proposed, as the cross sections of small molecules are now computable using sophisticated theoretical approaches [77, 24]. This thesis presents dynamical investigations for the electron impact ionization of the molecular targets H2O and H2, employing the (e,2e) technique to experimentally measure the triple differential cross section (TDCS). The TDCS is defined as the probability that a bound electron will be ejected from the target atom or molecule (into a particular direction with a defined energy) and the initial electron will be scattered into a particular direction with a particular energy. All TDCSs presented within this thesis were performed using an electron coincidence spectrometer in the coplanar asymmetric geometry at intermediate incident electron energies. This thesis presents the electron impact ionization TDCSs of H2O. A series of measurements were performed using H2O in the vapour form. Measurements of the TDCS are presented for the 2a1 atomic-like orbital and the 1b2, 3a1 and 1b1 molecular orbitals at a common incident electron energy of 250eV, ejected electron energy of 10eV and scattering angle of -15o. The experimental TDCSs are compared with theoretical cross sections that were calculated by Champion et al [25, 26] using a distorted wave Born approach (DWBA). TDCS measurements for the single ionization of the hydrogen molecule, H2 were performed as in recent years there has been evidence that indicates the ejected electron angular distribution is perturbed due to Young-type interference effects. The oscillatory structure which is predicted in the cross section is due to the two-centred nature of the molecule [27, 29]. This thesis presents experimental TDCSs for the ionization of H2 which are compared to TDCSs of helium. A series of measurements for the TDCSs of H2 and He are presented at a common incident electron energy of 250eV and scattering angle of -15o, for a range of ejected electron energies between 10eV and 100eV. The experimental TDCSs are compared with two types of theoretical calculations.

A numerical analysis scheme has been developed to extract dynamic information from experimental images by the three-dimensional sliced fluorescence imaging method. The present scheme is based on a generalized framework in analyzing fluorescence images from the photo-initiated dynamic process. Specifically, image quality optimization, noise reduction and numerical fitting codes have been implemented in the present scheme to determine differential cross sections of the state-to-state inelastic collisions between CN(A 2£S) and He. These codes are indispensable in extracting state-to-state dynamic information from experimental images in any photo-initiated collision experiment, no matter it is executed in the beam or bulb environment.

Thesis--University of California, Berkeley. / Includes bibliographical references (p. 57). 23

Ce manuscrit présente une mesure de la section efficace de production des bosons W et de l'asymétrie de charge dans les collisions proton-proton avec l'expérience ATLAS à une énergie dans le centre de masse de 7 TeV. Ces mesures posent des contraintes sur la fraction d'impulsion des protons portée par les partons qui contribuent à la production des bosons W et donc elles permettent d'ameliorer notre compréhension des fonctions de distribution de partons. Dans l'analyse, les événements de signal sont sélectionnés dans le canal électronique W −→eν . Le calorimètre électromagnétique à Argon Liquide joue un rôle important pour la détection des électrons. L'auteur de cette thèse a travaillé sur la reconstruction en ligne de l'énergie dans les détecteurs à LAr. Un aspect important pour les mesures liées à la charge électrique, comme l'asymétrie de charge du boson W, est l'évaluation du taux de misidentification de la charge pour des électrons et des positons. Dans ce manuscrit, la section efficace de production de bosons W multipliée par le rapport de branchement est présentée de façon inclusive, en fonction de la pseudorapidité du lepton, et comme mesure différentielle en deux dimensions (c'est à dire en fonction de la pseudorapidité et de l'énergie transverse du lepton). La mesure de l'asymétrie de charge est aussi présentée en fonction de la pseudorapidité du lepton uniquement et en fonction de la pseudorapidité et de l'énergie transverse du lepton. Les données ont été enregistrées par l'expérience ATLAS en 2011 et correspondent à 4.7 fb−1 . / This document presents a measurement of the production cross section of W bosons and of its charge asymmetry in proton-proton collisions at a centre of mass energy of 7 TeV with the ATLAS detector. These measurements provide information on the momentum fraction of the protons carried by the partons contributing to the W production and therefore allow to better understand the parton distribution functions of the proton. The W candidate events are selected in the W −→ eν decay mode. The LAr electromagnetic calorimeter plays an important role in the detection of electrons and the author has worked on the on-line energy reconstruction in the LAr detectors. A subject which is treated in some detail is the evaluation of the charge misidentification rates for electrons and positrons. This is a key ingredient for charge related measurements such as the W charge asymmetry. In this document, the W production cross section times the branching ratio is studied inclusively, as a function of the lepton pseudorapidity and as a double differential measurement as a function of the lepton pseudorapidity and transverse energy. The charge asymmetry measurement is presented as a function of the lepton pseudorapidity and as a double differential measurement as well. The data were recorded by the ATLAS detector in 2011 and correspond to 4.7 fb−1 .

Thesis (PhD)--Stellenbosch University, 2012. / Please refer to full text for abstract.