The spin states of W bosons in e+e- -t W+W- -t q$tvc events recorded by the OPAL detector at LEP are determined by an analysis of the angular distributions of their d e cay products. This information is used to calculate polarised differential cross-sections and to search for CP-violating effects. Results are presented for W bosons produced in e+e- collisions with centre-of-mass energies between 183 GeV and 209 GeV. The average percentage of longitudinally polarised W bosons measured from the data is found to be (23.9 f 2.1 + 1.1)% compared to a Standard Model prediction of (23.9 f 0.1)%. All results are consistent with CP conservation.

Thesis (Ph. D.)--Florida State University, 2006. / Advisor: Susan K. Blessing, Florida State University, College of Arts and Sciences, Dept. of Physics. Title and description from dissertation home page (viewed Sept. 22, 2006). Document formatted into pages; contains xiv, 138 pages. Non-Latin script record Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Dept. of Physics, June 2000. / Includes bibliographical references. Also available on the Internet.

We consider the anomalous magnetic moment of the W boson, ĸ, from an experimental and from a theoretical point of view. In the first chapter,we consider five experiments where this parameter could in principle be measured. Our results show that the W pair-production remains the best process to measure ĸ. Single W production is very sensitive to ĸ, but it is plagued by very small cross-sections. Photon-electron colliders can also be valuable for measuring ĸ through single W production. In the second chapter, we consider a composite model where ĸ is essentially free. We found that it is impossible to rule out such a model from a single measurement of ĸ. We give detailed production rates for these processes. In the second half of the thesis, we set limits on the corrections to ĸ at the one loop level; first in the minimal SM and then in a two-Higgs-doublet model. The main results are that measured corrections of 0.1 would clearly indicate non-perturbative physics while the minimal SM can accommodate corrections up to 0.02. Possible extensions of the SM cannot increase this figure by much: unless one is willing to introduce several extra weakly interacting families, it remains that 75%, or more, of the corrections will arise from the minimal SM. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

This thesis presents measurements of charged current deep inelastic scattering cross sections in e+p collisions with longitudinally polarised positron beams. The measurements are based on data taken by the ZEUS detector at the HERA collider during the 2006-2007 run- ning period. The data sample has an integrated luminosity of 132 pb-1 and was taken at a centre-of-mass energy of 318 GeY. The total cross section has been measured at positive and negative values of the longitu- dinal polarisation of the positron beam (Pe). In addition, the single differential cross sections dδ / dQ2, dδ / dx and dδ / dy have been measured for Q2 > 200 Ge y2, also using both positively and negatively polarised positron beams. The reduced cross section has been measured in nine bins of Q2 in the kinematic range 280 < Q2 < 30000 Gey2 and 0.0078 < x < 0.42. The results are compared against the descriptions provided by the CTEQ6.6, MSTW 2008, HEARPDF1.0 and ZEUS-JETS PDFs. In general, the measured cross sections are well described by these predictions. Based on the measurement of the total cross section as a function of the polarisation of the positron beam, a lower limit on the mass of a hypothetical right-handed W boson has been extracted from the upper limit of the cross-section at Pe = -1. This limit is complementary to the limits obtained from direct searches (for example at CDF and D0) because the limit presented herein is for a space-like vV, whereas for direct searches, the limit on the mass of a time-like W boson is obtained. The results of this analysis have been published and have been included ill the determination of the HERAPDF theoretical prediction and also in HI and ZEUS combined results.

Este trabalho apresenta os resultados da primeira medida da secao de choque de producao W± e± utilizando dados de colisoes proton-proton com energia de centro de massa s = 13 TeV pelo detector ATLAS em dois regimes diferentes de operacao do Large Hadron Collider (LHC): um perodo de baixa luminosidade em que foram acumulados 81 pb1 de dados e que permitiram medir a secao de choque fiducial e total da producao de bosons W+ e W na regiao inclusiva (regiao de massa transversa acima de 50 GeV, abrangendo o pico de massa transversa do boson W) e um perodo de alta luminosidade em que foi obtido 76,6 fb1 de dados tornando acessvel a medida da secao de choque fiducial de producao de bosons W+ e W na regiao de alta massa transversa (regiao de massa transversa entre 130 GeV e 2,5 TeV). As secoes de choque medidas e as distribuicoes cinematicas referentes a energia transversa faltante (ETmiss ), massa transversa do boson W (mTW), pseudorapidez (), momento transverso (pTe) do eletron decorrente do decaimento do W e a diferenca entre o angulo azimutal () do eletron e da ETmiss sao consistentes com previsoes teoricas obtidas em NLO e normalizadas em NNLO, considerando-se as incertezas sistematicas, estatsticas e na luminosidade. / This work presents the results of the first W± e± production cross section measurements in the proton-proton collisions at the center of mass energy of s = 13 TeV obtained with the ATLAS detector in two different operation regimes: a low luminosity period when 81pb1 of data was accumulated allowing the measurement of the fiducial and total production cross section of W+ and W bosons in the inclusive region (region of transverse mass above 50 GeV, covering the transverse mass peak of the W boson) and a high luminosity period when 76,6 fb1 made accessible the high W boson transverse mass region (between 130 GeV and 2.5 TeV), allowing the measurement of the fiducial cross section of W+ and W boson production. The measured cross sections and the kinematic distributions for the missing transverse energy, (ETmiss), W boson transverse mass (mTW), the pseudorapidity (), the transverse momentum (pTe) of the electron originated from the W boson decay as well as the azimuthal angle difference () between the electron and the ETmiss are consistent with the theoretical predictions obtained at NLO and normalized to NNLO, considering the systematic, statistical and luminosity uncertainties.

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 .