Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

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During the summer 2014, the HADES collaboration had the opportunity to measure pion collisions with different nuclei. These measurements were done with two objectives. The first being the investigations of hadrons with strange quarks and their behaviour at normal nuclear density. The analysis of this will concentrate specifically on φ meson and Λ baryon production. The focus on properties of baryonic resonances in the region of N(1520) and N(1535) formed the second objective. Special emphasis is put on beam line detectors which use different particle detection techniques. In particular, the scintillator based Hodoscope and diamond based Start detector will be discussed. There is also presented the analysis of π + p elastic scattering which is important for normalisation of the cross section of the reactions of interest. The measured elastic scattering yields are compared with dedicated simulations and previously published data. 1

A search for the Higgs boson decaying to tau tau using 7.8 fb^-1 of pp collisions at 1.96 TeV collected with CDF II detector is presented. The search is sensitive to four production mechanisms of the Higgs boson: ggH, WH, ZH and VBF. Modes where one tau decay leptonically, and another decay, hadronically, are considered. Two novel techniques are developed and used in the search. A Probabilistic Particle Flow Algorithm is used for energy measurements of the hadronic tau candidates. The signal is discriminated from backgrounds by the Missing Mass Calculator, which allows for full invariant mass reconstruction of tau tau pair. The data are found to be consistent with the background only hypothesis. Therefore a 95% confidence level upper limit on the Standard Model Higgs boson cross section was set. At M_H=120 GeV/c^2 observed limit is 14.9 x sigma_SM x Br(H -> tau tau).

This thesis concerns the properties of two particles, the top quark and the tau lepton, the heaviest of the quarks and leptons, respectively, in the standard model of elementary particle physics. After a chapter introducing the standard model, the second concerns the tau lepton. Amongst all the quarks and leptons, the tau has the unique property that its polarisation can readily be measured at high energy colliders. We propose and develop new methods of using this unique property to search for new physics, such as Higgs bosons, and also for making an accurate measurement of the polarisation of taus produced via Z decay leading to a precision determination of the electroweak coupling. The third chapter of this thesis concerns the top quark. We perform the complete one- loop radiative corrections to the helicity amplitudes within the standard model. Even though the radiative corrections to top quark production and decay have already been calculated separately, our work makes it possible to combine the sequence of events by keeping full information on the correlations among final state particles.

We present searches for the leptonic decays B + → ℓ+nu and the lepton flavor violating decays B0 → ℓ+/-tau ∓, where ℓ = e, mu, with data collected by the BABAR experiment at SLAC. These searches utilize a technique in which we fully reconstruct the accompanying B¯ in Upsilon(4S) → BB¯ events, and look for a monoenergetic lepton in the signal B frame. The signal yield in the data is extracted from a fit to the signal lepton candidate momentum distribution in the signal B rest frame. Using a data sample of approximately 378 million BB¯ pairs (342 fb-1), we find no evidence of signal in any of the decay modes. Branching fraction upper limits of B (B+ → e +nu) < 5.2 x 10-6, B (B+ → mu+nu) < 5.6 x 10-6, B (B0 → e +tau-) < 2.8 x 10-5 and B (B0 → mu+tau -) < 2.2 x 10-5, are obtained at the 90% confidence level.

Thesis--Wisconsin. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1984. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 119-120).

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirement for the degree of Doctor of Philosophy. / The scope of the research reported in this thesis addresses some phenomena associated with lepton-photon processes resulting from the incidence of ultra-relativistic particles upon highly ordered crystalline materials. The study of channeling phenomena were extended to investigate coherent, correlated and strong field versions of the basic QED processes at much higher energies and at incident angles slightly larger than the channeling critical angle. (Abbreviation abstract) / Andrew Chakane 2019