In this thesis we study two aspects of the lattice formulation of Quantum Chromodynamics (QCD). We first describe the study of baryons with one heavy and two light quarks. We compute the full spectrum for the ground state of the channels with quantum numbers <I>J<SUP>P</SUP></I> = <SUP>1</SUP>/<SUB>2</SUB> <SUP>+</SUP>, <SUP>3</SUP>/<SUB>2</SUB><SUP>+</SUP>, isospin <I>I </I>= 0,1 and strangeness <I>S </I>= 0, -1, -2. For the channel with quantum numbers <I>J<SUP>p </SUP></I>= <SUP>1</SUP>/<SUB>2</SUB><SUP>+ </SUP>we discuss the form factors for semileptonic decays of heavy baryons, compute the Isgur-Wise function and study its dependence on the light quark mass. In the second part of this thesis, we report the numerical results of a first study of a one-parameter family of covariant, non-perturbative gauge-fixing conditions. The gauge dependence of the gluon propagator is discussed.

No description available.

Results are presented of a lattice calculation of <I>f<SUB>B</SUB></I>, the leptonic decay constant of the <I>B</I> meson, and of <I>B<SUB>B</SUB></I>, the "bag-parameter" of <I>B</I><SUP>0</SUP>-<I>B‾</I><SUP>0</SUP>) mixing. All the calculations are performed with the heavy quark constituent of the <I>B</I> meson treated in the static approximation and with an Π(<I>a</I>)-improved fermion action used for the light quarks. The calculations are performed in the quenched approximation on a 24<SUP>3</SUP> x 48 lattice at <I>β</I> = 6.2. In simulating the behaviour of <I>B</I> mesons on the lattice, one of the most important technical issues is how to correctly isolate the ground state. This is particularly the case when the static approximation is used. Hence several smeared interpolating operators for the <I>B</I> meson are used in these calculations and the results using the various operators are presented and compared. The main findings are with the greatest uncertainty in the final results coming from one-loop perturbative matching of the lattice and continuum operators.

In this thesis two different aspects of Standard Model Higgs boson phenomenology at hadron colliders are addressed. A precise theoretical knowledge of production cross sections is needed in order to assist in the Higgs boson search efforts of the experimental community. Consequently, the next-to-leading-order electroweak corrections to Higgs boson production in association with a vector boson at hadron colliders have been calculated. Significant corrections were found, and theoretical uncertainties were analysed. In addition to production cross sections, a deep knowledge of background processes is also needed, especially at hadron colliders. The gluon-induced contributions to offshell W-boson pair production have been calculated. The invariant amplitude has been used to calculate the contribution from gluon initiated processes to the non-resonant W-boson pair production background to the Higgs boson search channel at the CERN LHC. These contributions are evaluated in the approximation of massless quarks circulating the loops. These results were used to study the effect of experimental cuts proposed to increase the signal to background ratio of the above mentioned search channel.

No description available.

In May 2003 PEP-II achieved instantaneous luminosities in excess of 6 x 10³³cm^-2s^-1, twice the design luminosity. To permit BABAR to operate in this challenging environment, development work on the data acquisition system continued after detector commissioning. A vital part of this process is understanding the performance of the data acquisition system. Considerable effort was invested in the design and implementation of an application capable of collecting performance statistics from hundreds of CPUs in the data acquisition system during data collection. The monitoring application and some examples of its operation are presented in this thesis.

No description available.

Quantum Chromodynamics (QCD) is the present theory of the strong interactions between quarks and gluons. To simulate QCD on a computer we need to discretise the field theory onto a space-time lattice. After outlining the standard Wilson action for lattice QCD, we describe the improved Clover fermion action with reduced discretisation errors. This thesis describes various techniques required to simulate lattice QCD and their implementation on the UKQCD Grand Challenge supercomputer Maxwell, which is a parallel computer consisting of 64 nodes. The ideas behind Monte Carlo (MC) simulation are introduced through their use to study spin systems in statistical physics. Various MC algorithms are outlined with particular emphasis on Stochastic Cluster MC and attempts to apply this to lattice gauge simulations. One of the best quantities to calculate in lattice QCD is the quark propagator. This requires the inversion of very large fermion matrices and takes an enormous amount of supercomputer time. We investigate a simple Red-Black preconditioning of the matrix and compare the performance of an Over-relaxed Minimal Residual inversion algorithm with various Conjugate Gradient algorithms. The quark propagators are calculated using Maxwell and we give details of our implementation of the inversion routines and the performance obtained. We present preliminary results from an investigation into the hadron mass spectrum. These are based on a sample of 9 gauge configurations on a 24<SUP>3</SUP> x 48 lattice at β = 6.2. There are descriptions of how lattice masses are calculated and of Wuppertal smearing, which is a technique that may be used to improve the signal. We conclude with a comparison of the spectrum of masses obtained from the Wilson fermion action and the Clover action.

No description available.

The breakup of 110.8 MeV <SUP>10</SUP>B has been studied for the reaction <SUP>10</SUP>B+ <SUP>58</SUP>Ni where kinematically complete measurements were obtained on the breakup channel p_<SUP>9</SUP>Be. In order to obtain data with high statistical quality and good accuracy the breakup fragments are detected in coincidence using large area silicon strip detectors in combination with a magnetic spectrometer. To assess the qualities and performances of the strip detectors, a preliminary experiment dealing with the breakup of <SUP>8</SUP>Be nuclei was performed and in which a new type of <SUP>8</SUP>Be detection system has been developed offering a very large effective solid angle. <SUP>8</SUP>Be nuclei, which are unstable, were produced in the <SUP>12</SUP>C(<SUP>9</SUP>Be,<SUP>8</SUP>Be) and <SUP>208</SUP>Pb(<SUP>9</SUP>Be,<SUP>8</SUP>Be) reactions with 90 MeV <SUP>8</SUP>Be projectiles. In the breakup of <SUP>10</SUP>B, evidence for the direct breakup mechanism in the <SUP>58</SUP>Ni(<SUP>10</SUP>B,<SUP>9</SUP>Be<SUB>g.s+</SUB> p) reaction has been obtained with possible contributions from the sequential mechanism through the <SUP>10</SUP>B excited states, 7.48 MeV and 7.75 MeV. A Coulomb excitation calculation for this reaction is presented and shown to be consistent with the shape, but not the magnitude of the energy spectra within the statistical accuracy of the data.