A model is presented which consists of a dynamical scheme for reproducing the mass hierarchies observed in the quark sector. This is accomplished through new physics beyond the Standard Model, and does not rely upon the Higgs mechanism. By introducing a heavy fermion which couples to the quarks via the emission and reabsorption of a new boson, initially massless quarks are given their masses in a purely radiative fashion. The differences between up and down sector masses appear naturally as a result of generating the down mass matrix from corrections to the up mass matrix: accomplished via an anomalous flavour-changing coupling to the weak sector. Multipole type form-factors are inserted at each coupling, and introduce parameters which are varied to produce numerical fits to the quark masses, mixing angles and CP-violation parameter. Several extensions to the model are proposed and discussed.

The dominant term in the damping rate for quarks and transverse gluons at high momentum (p $ gg$ gT) is calculated within the framework of perturbative QCD at finite temperature. It is shown that the damping rate, $ gamma$, takes the form $ gamma$ = cg$ sp2$T log(1/g) with c = N/4$ pi$ for transverse gluons and c = (N$ sp2$-1)/(8$ pi$N) for quarks where N is the number of colours, g is the coupling constant, and T is the temperature. The sign and the gauge invariance of $ gamma$ are easily verifiable due to the simplicity of the argument. This result agrees with the more complicated (unpublished) calculations of Pisarski et al. but disagrees with those of Lebedev and Smilga.

A particular kind of gaseous particle detector, called resistive plate counter, has been built and tested with cosmic rays. It is composed of two parallel highly resistive electrode plates between which circulates an ionizing gas, and of capacitively coupled readout pads. The tests look at the pulse shape, efficiency, charge distribution, time delay, and time resolution of the counter. It is shown that these characteristics are dependent upon the voltage applied to the electrodes, the gas mixture ratio (argon/butane/freon), and the surface irregularities of the electrodes. The counter exhibits a 98% efficiency and a time resolution of approximately 1 ns. These results are consistent with published results for this type of counter.

This thesis describes the data acquisition error monitoring system developed for the 1993-94 physics run of the collider detector at Fermilab (CDF). It presents an overview of the CDF data acquisition system indicating the role that the error monitoring system plays in the experiment. It then describes the custom software and software packages used to meet the error monitoring requirements of the CDF data acquisition system.

$B sp pm$ mesons are reconstructed through the decay chain $B sp pm to chi sb{c}K sp pm, chi sb{c} to J/ psi gamma,$ and $J/ psi to mu sp+ mu sp-.$ Using data taken at the Collider Detector at Fermilab in $ bar pp$ collisions at $ sqrt{s}$ = 1.8 TeV during the 1988/89 run, we have seen the signal of the $B sp pm$ mesons from this decay channel although the statistics still need to be improved. By Monte Carlo methods, we also conclude that it is possible to resolve the individual $ chi sb{c1}$ and $ chi sb{c2}$ states by making higher photon energy cuts.

The production of the final states K$ sp+$K$ sp-$ and $ eta sp prime to pi sp+ pi sp- gamma$ in $ gamma gamma$ collisions has been measured using the ARGUS detector. The product $ Gamma sb{ gamma gamma}( eta sp prime)$Br$( eta sp prime to rho gamma)$ has been determined. The topological cross section for the production of charged kaon pairs in two-photon collisions has been measured and the $ gamma gamma$-widths and interference parameters for the tensor mesons f$ sb2$(1270), a$ sb2$(1320) and f$ sbsp{2}{ prime}$(1525) have been extracted. The helicity structure assumed for the K$ sp+$K$ sp-$ continuum contribution has a significant effect on the result. Upper limits have been obtained for the $ gamma gamma$-widths of the glueball candidate states f$ sb2$(1720) and X(2230).

The perturbative regime of Quantum Chromodynamics (QCD) is considered and certain aspects related with higher order corrections (HOC) are studied. Certain large correction terms in the perturbative expansion are determined, in particular for large transverse momentum $(p sb{T})$ direct photon production. The origin of these terms is specified and simple forms, called K-factors, are provided (soft gluon approach). / Furthermore, for processes initiated by 2 $ to$ 2 particle subprocesses the structure of the complete HOC is analyzed. It is shown that when structure functions and/or fragmentation functions are involved, there is a gauge invariant part that dominates HOC over a sizable kinematic range. Simple and general expressions are derived allowing an easy calculation of this part. Also, it is shown that, under certain approximations, this part reduces to the form of the simple K-factors. / Other aspects of HOC, in particular the dependence on the choice of scales, are considered. Using complete HOC, detailed analysis of recent and old data on large-$p sb{T}$ direct photon production is carried out. The dependence of the form of the gluon distribution on the choice of the scales (physical versus optimal scales) is discussed and it is concluded that appreciable ambiguity in this distribution still remains.

The formalism of effective potential method is first studied for usual field theory and extended to supersymmetric field theory. The specific case of supersymmetric quantum electrodynamics is then introduced. The superfields are shifted as required by Weinberg's method for the evaluation of effective potentials and superpropagators are derived with the method developed by Helayel-Neto for cases where supersymmetry is explicitly broken. Then, the one and two loop corrections to the effective potential may be calculated. These corrections are seen to be complex everywhere but at the minimum of the potential. Tile theory is then renormalized in a modified minimal substraction scheme and a finite expression is finally obtained for the effective potential. Thereon, the renormalized coupling constant and the $ beta$-function are calculated.

After a general review of Lie algebra theory, the generating function method describing the representations (or characters) of Lie algebras is introduced. The Demazure-Gaskell character formula for calculating a generating function is discussed in detail. / Using the concept of the depth of a weight i.e. the number of simple roots that are subtracted from the highest weight of a representation in order to arrive at a particular weight in that representation, the representations of affine Kac-Moody algebras are studied. The Demazure-Gaskell method is then applied to these representations, and the generating functions for the representations to finite depth are calculated. / Both complete representations and fully degenerate representations i.e. those whose highest weights contains only one non-zero weight component, are considered. Generating functions for complete and fully degenerate representations of affine Kac-Moody algebras are given.

This thesis presents the measurement of Ξ¯ and Σ(1385) strange baryons in deep inelastic scattering of 27.5 GeV positrons on 920 GeV protons with the ZEUS detector at HERA in the 1999--2000 run period. The kinematic range 20 < Q2 < 200 GeV 2, 0.0003 < x < 0.02, 0.04 < y < 0.7, and restricted kinematic regions in momentum pT and pseudorapidity eta for Ξ¯ and Σ, are used. This data set is suitable for the study of the strange content of the sea quarks inside the proton as well as the parton fragmentation process. The measured total cross sections of Ξ¯ and Σ(1385) baryons are compared with various Monte Carlo results generated with different strangeness suppression factors, and with a previous analysis which covered the 1997--2000 run period. The differential cross sections in bins of Q2, x, pT and η are also measured.