A description of SLAC experiment E154, a precision measurement of the neutron's longitudinal spin structure function $g\sbsp{1}{n},$ is presented. Deep inelastic electron scattering was used to measure the structure function in the kinematic range $0.014

In this thesis, we have explored the rich phenomenology of the chiral anomaly in order to further our understanding of this fascinating and unique aspect of quantum field theory. We studied a subset of anomalous processes viz., [special characters omitted], and [special characters omitted] with the explicit purpose of extending the current status of calculations in this sector. For this, we applied the N/D formalism, which exploits the unitarity and analyticity of the scattering amplitude, in order to provide a plausible extension of one-loop results into resonance dominated regions of phase space. In particular, we were able to account for vector meson exchange effects by demanding that the phase shifts of the N/D function reflect those appearing in [special characters omitted]-scattering. We also compared our results with calculations based on vector dominance models, for which purpose we adopted the hidden symmetry approach.

Nonperturbative methods in particle physics are introduced. Three nonperturbative approaches are used to extend chiral perturbation theory. Dispersive technique is used to address the asymptotic limit and structure of the pion form factor performing the matching with the constraints of perurbative QCD and chiral perurbation theory. Models of Bosonization technique are used to generate an effective action directly from QCD in order to predict the size of the low energy constants strictly from theory. A simple constituent quark model is also suggested to study the model dependence of [special characters omitted] non-leptonic hyperon decay amplitudes arising from isospin mixing. Finally, spin-dependent physics of monopoles are introduced to examine Montonen-Olive's electromagnetic duality conjecture by studying the long-range field of the different states in the N = 2 BPS monopole supermultiplet.

This document presents a new measurement of inclusive b semileptonic branching fractions [special characters omitted] and [special characters omitted]. The [special characters omitted] and [special characters omitted] are separated by a means that uses correlation between the final state lepton charge and that of its parent b quark as a constraint. Monte Carlo counts of electrons and muons are calibrated to the data using a newly developed technique based on pairs of mutually independent tests for each particle hypothesis separately. The data sample consists of about 550,000 hadronic Z decays collected at the SLD between 1993 and 1998. Upon analysis of electron and muon counts in 61602 hadronic event hemispheres tagged as containing either a b or a b¯, we report [special characters omitted][special characters omitted]

The method of modal field theory is a new development in the field of nonperturbative quantum field theory. This approach reduces a quantum field theory to a finite-dimensional quantum mechanical system by expanding field configurations in terms of free-wave modes. In this dissertation we apply this method to three-dimensional &phis;4 theory using two kinds of modal field approaches: a spherical partial wave expansion and a periodic-box mode expansion. The resulting modal-field quantum-mechanical systems are analyzed with the use of the diffusion Monte Carlo method and by calculating the spectrum and eigenstates of the Hamiltonian directly. In the latter approach we employ the recently introduced quasi-sparse eigenvector method which is designed to diagonalize infinite-dimensional yet very sparse matrices. We study the phase structure of three-dimensional &phis;4 theory, computing the critical coupling and the critical exponents ν and β. We also investigate the spectrum of low-lying energy eigenstates and find evidence of a nonperturbative state in the broken-symmetry phase of the theory.

We report the observation of charm final states produced in the single diffractive dissociative reactions (1) pp → pX(D*+ → (D 0 → K−π+)π +) and (2) pp → pX( D*− → (D¯ 0 → K+π−)π −). These results are based on the over 5 billion event data sample acquired by Fermilab experiment E690 during the fixed target run of 1991. In this run, an 800 GeV/c incident proton beam was used with a liquid hydrogen target. We measure cross sections of [0.209 ± 0.050[special characters omitted](syst)] μb and [0.196 ± 0.043[special characters omitted](syst)] μb for reactions (1) and (2), respectively. These results are compared with model predictions and results from other experiments. Our results are significantly lower than predictions based on the diffractive model of Ingelman and Schlein using a flat or a hard pomeron structure function.

We studied [special characters omitted] theory and the string sector of compact QED 3 using nonperturbative methods. The phase structure of two dimensional [special characters omitted] theory was studied using Modal Field methods. The critical coupling strength and the critical exponent β were determined for various values of the momentum cutoff and box sizes. The asymptotic value of the critical coupling was found to be 2.5 ± 0.2. The low energy spectrum of the string sector of compact QED3 on the lattice was studied using Diagonalization/Monte Carlo techniques for various lattice sizes. The lattice potential and the string tension for the axial and the diagonal strings were also studied.

Close studies of the solitonic solutions of D = 11 [special characters omitted] = 1 supergravity theory provide a deeper understanding of the elusive M-theory and constitute steps towards its final formulation. In this work, we propose the use of calibration techniques to find localized intersecting brane solutions of the theory. We test this hypothesis by considering Kähler and special Lagrangian calibrations. We also discuss the interpretation of some of these results as branes wrapped or reduced over supersymmetric cycles of Calabi-Yau manifolds and we find the corresponding solutions in D = 5 [special characters omitted] = 2 supergravity.

Flavor-changing neutral current transitions are forbidden at tree level in the Standard Model and can only occur via higher order diagrams. Since the amplitudes for such loops are dominated by the heaviest known particles, and non-SM effects are expected to contribute at the same order as the SM, such processes are an ideal place to look for new physics. We present a measurement of the inclusive branching fraction for the flavor-changing neutral current process B → Xsℓ+ℓ− with a sample of 81.9 fb−1, collected with the BABAR detector at the Stanford Linear Accelerator Center. The final state is reconstructed from e+e − or μ+μ− pairs and a hadronic system consisting of one K± or K s and up to two pions, with at most one π0 . We observe a signal of 40 ± 10(stat) ± 2(syst) events and extract a branching fraction [special characters omitted] (B → Xsℓ +ℓ−) = (5.6 ± 1.5(stat) ± 0.6(exp. syst) ± 1.1(model syst)) × 10−6 for mll > 0.2 GeV.

The time dependence of Bd - Bd mixing has been measured in b b events containing one or more kaons at the SLD experiment at the Stanford Linear Accelerator Center. A simultaneous measurement of the “right sign production fraction” of kaons from B d decays has also been made. The initial state B hadron flavor was determined using the large forward-backward asymetry provided by the polarized electron beam of the SLC in combination with a jet charge technique and information from the opposite hemisphere. From a sample of 400,000 Z0 events collected by the SLD experiment at SLC from 1996 to 1998, the kaon right sign production fraction has been measured to be 0.797 ± 0.022 and the mass difference between the two Bd eigenstates has been measured to be Δ md = 0.503 ± 0.028 ± 0.020 ps−1 .