Precise Electroweak Measurements at the Z0 Pole

Over the last decade, precise LEP and SLC measurements of electroweak coupling parameters at the Z0 pole have lead to tests of the Standard Model to unprecedented precision. This report presents a comprehensive review of these studies, including a review of relevant Z0 pole physics issues, facilities, instrumentation, and the measurements made. Global fits for the Higgs Boson mass and Z0-b coupling parameters are also presented.Comment: LaTex, 17 pages, 9 Postscript figures, uses ws-p8-50x6-00a.cls and epsfig.sty. Submitted to the Proceedings of the 1999 Conference on Physics in Collision, Ann Arbor, Michigan, June 24-26, 199

Magnetization Reversal in Ferromagnetic Spirals via Domain Wall Motion

Domain wall dynamics have been investigated in a variety of ferromagnetic nanostructures for potential applications in logic, sensing, and recording. We present a combination of analytic and simulated results describing the reliable field driven motion of a domain wall through the arms of a ferromagnetic spiral nanowire. The spiral geometry is capable of taking advantage of the benefits of both straight and circular wires. Measurements of the in-plane components of the spirals\u27 magnetization can be used to determine the angular location of the domain wall, impacting the magnetoresistive applications dependent on the domain wall location. The spirals\u27 magnetization components are found to depend on the spiral parameters: the initial radius and spacing between spiral arms, along with the domain wall location. The magnetization is independent of the parameters of the rotating field used to move the domain wall, and therefore the model is valid for current induced domain wall motion as well. The speed of the domain wall is found to depend on the frequency of the rotating driving field, and the domain wall speeds can be reliably varied over several orders of magnitude. We further demonstrate a technique capable of injecting multiple domain walls and show the reliable and unidirectional motion of domain walls through the arms of the spiral

Active optical frequency standard using sequential coupling of atomic ensembles

Recently, several theoretical proposals adressed the generation of an active optical frequency standard based on atomic ensembles trapped in an optical lattice potential inside an optical resonator. Using atoms with a narrow linewidth transition and population inversion together with a "bad" cavity allows to the realize the superradiant photon emission regime. These schemes reduce the influence of mechanical or thermal vibrations of the cavity mirrors on the emitted optical frequency, overcoming current limitation in passive optical standards. The coherence time of the emitted light is ultimately limited by the lifetime of the atoms in the optical lattice potential. Therefore these schemes would produce one light pulse per atomic ensemble without a phase relation between pulses. Here we study how phase coherence between pulses can be maintained by using several inverted atomic ensenbles, introduced into the cavity sequentially by means of a transport mechanism. We simulate the light emission process using the Heisenberg-Langevin approach and study the frequency noise of the intracavity field.Comment: 9 pages, 5 figure

Radioluminescence and photoluminescence of Th:CaF2_2 crystals

We study thorium-doped CaF$_2$ crystals as a possible platform for optical spectroscopy of the Th-229 nuclear isomer transition. We anticipate two major sources of background signal that might cover the nuclear spectroscopy signal: VUV-photoluminescence, caused by the probe light, and radioluminescence, caused by the radioactive decay of Th-229 and its daughters. We find a rich photoluminescence spectrum at wavelengths above 260 nm, and radioluminescence emission above 220 nm. This is very promising, as fluorescence originating from the isomer transition, predicted at a wavelength shorter than 200 nm, could be filtered spectrally from the crystal luminescence. Furthermore, we investigate the temperature-dependent decay time of the luminescence, as well as thermoluminescence properties. Our findings allow for an immediate optimization of spectroscopy protocols for both the initial search for the nuclear transition using synchrotron radiation, as well as future optical clock operation with narrow-linewidth lasers.Comment: 9 pages, 6 figure

Update on the Measurement of alpha_S with a 500 GeV Linear Collider

An update on the prospects for the precise measurement of the strong coupling constant alpha_S at a high energy Linear Collider via the three-jet rate is presented. In particular, the issue of the distribution of center-of-mass energies of the identified q-qbar event sample, which can affect the determination of \alpha_S at the scale Q^2=(500 GeV)^2$, is addressed.Comment: 4 pages, 3 figures, LaTex, requires epsfig and aipproc macro

Experimental studies on the formation of lunar surface features by gas emission - A preliminary report

Experimental data on lunar surface features caused by gas emissio

Prospects for a bad cavity laser using a large ion crystal

We propose to build a bad cavity laser using forbidden transitions in large ensembles of cold ions that form a Coulomb crystal in a linear Paul trap. This laser might realize an active optical frequency standard able to serve as a local oscillator in next-generation optical clock schemes. In passive optical clocks, large ensembles of ions appear less promising, as they suffer from inhomogeneous broadening due to quadrupole interactions and micromotion-relates shifts. In bad cavity lasers however, the radiating dipoles can synchronize and generate stable and narrow-linewidth radiation. Furthermore, for specific ions, micromotion-induced shifts can be largely suppressed by operating the ion trap at a magic frequency. We discuss the output radiation properties and perform quantitative estimations for lasing on the ${^3D_2} \rightarrow {^1S_0}$ transition in ${\rm ^{176}Lu^+}$ ions in a spherically-symmetric trap.Comment: 14 pages, 6 figure