Lepton-flavor mixing and K --> pi nu nu bar decays (open access)

Lepton-flavor mixing and K --> pi nu nu bar decays

The impact of possible sources of lepton-flavor mixing on K {yields} {pi}{nu}{bar {nu}} decays is analyzed. At the one-loop level lepton-flavor mixing originated from non-diagonal lepton mass matrices cannot generate a CP-conserving K{sub L} {yields} {pi}{sup 0}{nu}{bar {nu}} amplitude. The rates of these modes are sensitive to leptonic flavor violation when there are at least two different leptonic mixing matrices. New interactions that violate both quark and lepton universalities could enhance the CP-conserving component of {Lambda}(K{sub L} {yields} {pi}{sup 0}{nu}{bar {nu}}) and have a substantial impact. Explicit examples of these effects in the context of supersymmetric models, with and without R-parity conservation, are discussed.
Date: November 26, 2003
Creator: Grossman, Yuval; Isidori, Gino & Murayama, Hitoshi
Object Type: Article
System: The UNT Digital Library
The Minimal Supersymmetric Fat Higgs Model (open access)

The Minimal Supersymmetric Fat Higgs Model

We present a calculable supersymmetric theory of a composite"fat'" Higgs boson. Electroweak symmetry is broken dynamically through a new gauge interaction that becomes strong at an intermediate scale. The Higgs mass can easily be 200-450 GeV along with the superpartner masses, solving the supersymmetric little hierarchy problem. We explicitly verify that the model is consistent with precision electroweak data without fine-tuning. Gauge coupling unification can be maintained despite the inherently strong dynamics involved in electroweak symmetry breaking. Supersymmetrizing the Standard Model therefore does not imply a light Higgs mass, contrary to the lore in the literature. The Higgs sector of the minimal Fat Higgs model has a mass spectrum that is distinctly different from the Minimal Supersymmetric Standard Model.
Date: November 26, 2003
Creator: Harnik, Roni; Kribs, Graham D.; Larson, Daniel T. & Murayama, Hitoshi
Object Type: Article
System: The UNT Digital Library
Regional Grid Connection Project (open access)

Regional Grid Connection Project

OAK-B135
Date: November 26, 2003
Creator: Peter Hayes, PhD
Object Type: Report
System: The UNT Digital Library
Non-Contact Determination of Free Carrier Concentration in n-GaInAsSb (open access)

Non-Contact Determination of Free Carrier Concentration in n-GaInAsSb

GaSb-based semiconductors are of interest for mid-infrared optoelectronic and high-speed electronic devices. Accurate determination of electrical properties is essential for optimizing the performance of these devices. However, electrical characterization of these semiconductors is not straightforward since semi-insulating (SI) GaSb substrates for Hall measurements are not available. In this work, the capability of Raman spectroscopy for determination of the majority carrier concentration in n-GaInAsSb epilayers was investigated. Raman spectroscopy offers the advantage of being non-contact and spatially resolved. Furthermore, the type of substrate used for the epilayer does not affect the measurement. However, for antimonide-based materials, traditionally employed Raman laser sources and detectors are not optimized for the analysis wavelength range dictated by the narrow band gap of these materials. Therefore, a near-infrared Raman spectroscopic system, optimized for antimonide-based materials, was developed. Ga{sub 0.85}In{sub 0.15}As{sub 0.13}Sb{sub 0.87} epilayers were grown by organometallic vapor phase epitaxy with doping levels in the range 2 to 80 x 10{sup 17} cm{sup -3}, as measured by secondary ion mass spectrometry. For a particular nominal doping level, epilayers were grown both lattice matched to n-GaSb substrates and lattice-mismatched to SI GaAs substrates under nominally identical conditions. Single magnetic field Hall measurements were performed on the epilayers …
Date: November 26, 2003
Creator: Maslar, James E.; Hurst, Wildur S.; Wang, Christine A. & Shiau, Daniel A.
Object Type: Report
System: The UNT Digital Library
Optical Design for Extremely Large Telescope Adaptive Optics Systems (open access)

Optical Design for Extremely Large Telescope Adaptive Optics Systems

Designing an adaptive optics (AO) system for extremely large telescopes (ELT's) will present new optical engineering challenges. Several of these challenges are addressed in this work, including first-order design of multi-conjugate adaptive optics (MCAO) systems, pyramid wavefront sensors (PWFS's), and laser guide star (LGS) spot elongation. MCAO systems need to be designed in consideration of various constraints, including deformable mirror size and correction height. The y,{bar y} method of first-order optical design is a graphical technique that uses a plot with marginal and chief ray heights as coordinates; the optical system is represented as a segmented line. This method is shown to be a powerful tool in designing MCAO systems. From these analyses, important conclusions about configurations are derived. PWFS's, which offer an alternative to Shack-Hartmann (SH) wavefront sensors (WFS's), are envisioned as the workhorse of layer-oriented adaptive optics. Current approaches use a 4-faceted glass pyramid to create a WFS analogous to a quad-cell SH WFS. PWFS's and SH WFS's are compared and some newly-considered similarities and PWFS advantages are presented. Techniques to extend PWFS's are offered: First, PWFS's can be extended to more pixels in the image by tiling pyramids contiguously. Second, pyramids, which are difficult to manufacture, can …
Date: November 26, 2003
Creator: Bauman, B J
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Two-Phase Emission Detector for Measuring Coherent Neutrino-Nucleus Scattering (open access)

Two-Phase Emission Detector for Measuring Coherent Neutrino-Nucleus Scattering

Coherent scattering is a flavor-blind, high-rate, as yet undetected neutrino interaction predicted by the Standard Model. We propose to use a compact (kg-scale), two-phase (liquid-gas) argon ionization detector to measure coherent neutrino scattering off nuclei. In our approach, neutrino-induced nuclear recoils in the liquid produce a weak ionization signal, which is transported into a gas under the influence of an electric field, amplified via electroluminescence, and detected by phototubes or avalanche diodes. This paper describes the features of the detector, and estimates signal and background rates for a reactor neutrino source. Relatively compact detectors of this type, capable of detecting coherent scattering, offer a new approach to flavor-blind detection of man-made and astronomical neutrinos, and may allow development of compact neutrino detectors capable of nonintrusive real-time monitoring of fissile material in reactors.
Date: November 26, 2003
Creator: Bernstein, A & Hagmann, C A
Object Type: Article
System: The UNT Digital Library