This thesis reports the analysis of the e{sup +}e{sup -} {yields} e{sup +}e{sup -}K{sub S}{sup 0}K{sup {+-}}{pi}{sup {-+}} and e{sup +}e{sup -} {yields} e{sup +}e{sup -}K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} processes using the final dataset of the BABAR experiment located at the SLAC National Accelerator Laboratory. From previous measurements, the K{sub S}{sup 0}K{sup {+-}}{pi}{sup {-+}} final state is known to show a clear signal from the {eta}{sub c}(2S) particle. This c{bar c} state escaped detection for almost twenty years and its properties are still not well established on the experimental ground, while accurate predictions exist on the theoretical side. The e{sup +}e{sup -} {yields} e{sup +}e{sup -}K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} process is first studied in this thesis. An accurate determination of the {eta}{sub c}(2S) properties is obtained in the K{sub S}{sup 0}K{sup {+-}}{pi}{sup {-+}} decay mode. We also report the first observation of {eta}{sub c}(2S) and other charmonium states to the K{sup +}K{sup -}{pi}{sup +}{pi}{sup -}{pi}{sup 0} final state. The results of this thesis have been published in Physical Review D, and will be useful to test theoretical models describing the charmonium system. The thesis is organized in four chapters. The first one gives a brief introduction …

We have demonstrated that a bulk absorber coupled to a TES can serve as a good gamma-ray spectrometer. Our measured energy resolution of 70 eV at 60 keV is among the best measurements in this field. We have also shown excellent agreement between the noise predictions and measured noise. Despite this good result, we noted that our detector design has shortcomings with a low count rate and vulnerabilities with the linearity of energy response. We addressed these issues by implementation of an active negative feedback bias. We demonstrated the effects of active bias such as additional pulse shortening, reduction of TES change in temperature during a pulse, and linearization of energy response at low energy. Linearization at higher energy is possible with optimized heat capacities and thermal conductivities of the microcalorimeter. However, the current fabrication process has low control and repeatability over the thermal properties. Thus, optimization of the detector performance is difficult until the fabrication process is improved. Currently, several efforts are underway to better control the fabrication of our gamma-ray spectrometers. We are developing a full-wafer process to produce TES films. We are investigating the thermal conductivity and surface roughness of thicker SiN membranes. We are exploring alternative …

Over the past couple of decades, the Standard Model of high energy particle physics has clearly established itself as an invaluable tool in the analysis of high energy particle phenomenon. However, from a field theorists point of view, there are many dissatisfying aspects to the model. One of these, is the large number of free parameters in the theory arising from the Yukawa couplings of the Higgs doublet. In this thesis, we examine various issues relating to the Yukawa coupeng structure of high energy particle field theories. We begin by examining extensions to the Standard Model of particle physics which contain additional scalar fields. By appealing to the flavor structure observed in the fermion mass and Kobayashi-Maskawa matrices, we propose a reasonable phenomenological parameterization of the new Yukawa couplings based on the concept of approximate flavor symmetries. It is shown that such a parameterization eliminates the need for discrete symmetries which limit the allowed couplings of the new scalars. New scalar particles which can mediate exotic flavor changing reactions can have masses as low as the weak scale. Next, we turn to the issue of neutrino mass matrices, where we examine a particular texture which leads to matter independent neutrino …