Digital Commons Network^™

Search For Inclusive B→Sl+L-, S. Glenn, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for the effective flavor changing neutral-current decays b→sl⁺l^- using an inclusive method. We set upper limits on the branching ratios B(b→ se⁺e^-) < 5.7 X 10^-5, B(b→ sμ⁺μ^-) < 5.8 X 10^-5 and Bb→se⁺μ^-) < 2.2 3 10^-5 [at 90% confidence level (C.L.)]. Combing the dielectron and dimuon decay modes we find b→sl⁺l^-) < 4.2 X 10^-5 (at 90% C.L.).

Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, J. Paladino, Max B. Trueblood, H. Lilenfeld

Physics Faculty Research & Creative Works

Particle size and emission indices measurements for jet engines, primarily the Rolls Royce RB211 engines on a NASA 757 aircraft are reported. These data were used to estimate the fraction of fuel sulfur that was converted to particulates. These measurements were made in-situ with the sampling aircraft several kilometers behind the source. Some complimentary ground measurements on the same source aircraft and engines are also reported. Significant differences are seen between the ground observations and the in-situ observations, indicating that plume processes are changing the aerosol' s characteristics.

Observation Of The Radiative Decay D*+→D+Γ, J. Bartelt, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have observed a signal for the decay D^*+→D⁺γ at a significance of 4 standard deviations. From the measured branching ratio B(D^*+→D⁺γ)/ B(D^*+→ D⁺+pi⁰ = 0.055 ± 0.014 ± 0.010 we find B(D^*+→D⁺γ)= 0.017 ± 0.004 ± 0.003, where the first uncertainty is statistical and the second is systematic. We also report the highest precision determination of the remaining D^*+ branching fractions.

Thermoconvective Instability Of Paramagnetic Fluids In A Nonuniform Magnetic Field, J. Huang, D. D. Gray, Boyd F. Edwards

All Physics Faculty Publications

The effect of a static, nonuniform magnetic field on a laterally unbounded nonconducting paramagnetic fluid layer heated from below or above is studied using a linear stability analysis of the Navier-Stokes equations supplemented by Maxwell’s equations and the appropriate magnetic body force. Buoyancy-driven convection can be controlled by subjecting the layer to a nonuniform magnetic field. Theoretical predictions agree with experimental observations.

Deep Centers In N-Gan Grown By Reactive Molecular Beam Epitaxy, Z-Q. Fang, David C. Look, W. Kim, Z. Fan, A. Botchkarev, H. Morkoç

Physics Faculty Publications

Deep centers in Si-doped n-GaN layers grown by reactive molecular beam epitaxy have been studied by deep-level transient spectroscopy as a function of growth conditions. Si-doped GaN samples grown on a Si-doped n⁺-GaN contact layer at 800 °C show a dominant trap C₁ with activation energy E_T = 0.44 eV and capture cross-section σ_T = 1.3×10⁻¹⁵ cm⁻², while samples grown at 750 °C on an undoped semi-insulating GaN buffer show prominent traps D₁ and E₁, with E_T = 0.20 eV and σ_T = 8.4×10⁻¹⁷ cm …

High Mobility Algan/Gan Heterostructures Grown By Gas-Source Molecular Beam Epitaxy, L. K. Li, J. Alperin, W. I. Wang, David C. Look, Donald C. Reynolds

Physics Faculty Publications

We report on the growth of high electron mobility AlGaN/GaN heterostructures on sapphire substrates by gas-source molecular beam epitaxy (GSMBE) using ammonia as the nitrogen source. Improvements in structural, electrical, and optical properties of GaN and AlGaN layers have been made to achieve this goal. For the growth of AlGaN layers, the reflection high-energy electron diffraction revealed a twofold surface reconstruction, indicative of atomic smoothness of the film surface. High mobility two-dimensional electron gas has been achieved in both unintentionally doped (by piezoelectric effect induced by lattice mismatch strain) and modulation doped AlGaN/GaN heterostructures. The modulation-doped n+-Al_0.2Ga …

Particle Concentration Characterization For Jet Engine Emissions Under Cruise Conditions, Jonathan D. Paladino, Philip D. Whitefield, Donald E. Hagen, Alfred R. Hopkins, Max B. Trueblood

Chemistry Faculty Research & Creative Works

Airborne particle measurements during NASA project SUCCESS have shown that particle concentration profiles serve as good indicators of aircraft exhaust plume encounters. During exhaust plume penetrations there is a strong anticorrelation between the ratio of nonvolatile/total particulates and Nitrogen Oxide (NO) concentrations. an increase in fuel sulfur content was found to increase the total particle emission index, while the nonvolatile emission index remained unchanged. the EI's increased by a factor of 2.6 as the fuel sulfur increased from 70 - 700 ppm. the large particle size distribution (200-400 nm) was seen as a good long term indicator of an aircraft …

Particulate Sizing And Emission Indices For A Jet Engine Exhaust Sampled At Cruise, Donald E. Hagen, Philip D. Whitefield, Jonathan D. Paladino, Max B. Trueblood

Physics Faculty Research & Creative Works

Particle size and emission indices measurements for jet engines, primarily the Rolls Royce RB211 engines on a NASA 757 aircraft are reported. These data were used to estimate the fraction of fuel sulfur that was converted to particulates. These measurements were made in-situ with the sampling aircraft several kilometers behind the source. Some complimentary ground measurements on the same source aircraft and engines are also reported. Significant differences are seen between the ground observations and the in-situ observations, indicating that plume processes are changing the aerosol's characteristics.

New Limits For Neutrinoless Tau Decays, D. W. Bliss, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Neutrinoless 3-prong tau lepton decays into a charged lepton and either two charged particles or one neutral meson have been searched for using 4.79 fb^-1 of data collected with the CLEO II detector at Cornell Electron Storage Ring. This analysis represents an update of a previous study and the addition of six decay channels. In all channels the numbers of events found are compatible with background estimates and branching fraction upper limits are set for 28 different decay modes. These limits are either more stringent than those set previously or represent the first attempt to find these decays.

Search For Color-Suppressed B Hadronic Decay Processes At The Υ(4S) Resonance, B. Nemati, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

Using 3.1 fb^-1 of data accumulated at the Υ(4S) by the CLEO-II detector, corresponding to 3.3×10⁶ BB̅ pairs, we have searched for the color-suppressed B hadronic decay processes B⁰→D⁰ (D*⁰)X⁰, where X⁰ is a light neutral meson π⁰, ρ⁰, η, η′ or ω. The D*⁰ mesons are reconstructed in D*⁰→D⁰π⁰ and the D⁰ mesons in D⁰→K^-π⁺, K^-π⁺π⁰ and K …

Two-Body B Meson Decays To Η And Η′: Observation Of B→Η′K, B. H. Behrens, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

In a sample of 6.6 X 10⁶ produced B mesons we have observed decays B → η′K, with branching fractions Ɓ(B⁺ → η′K) = 6.5_-1.4^+1.5± 0.9) X 10^-5 and Ɓ(B⁰ → η′K⁰) = 4.7_-2.0^+2.7 ± 0.9) X 10^-5. We have searched with comparable sensitivity for 17 related decays to final states containing an η or η′ meson accompanied by a single particle or low-lying resonance. Our upper limits for these constrain theoretical interpretations of the B → η′K _signal.

X-Ray Spectroscopic Mapping Of Three Unusual Active Galaxies (Ngc 4258, Ngc 1097, And Ngc 1068), Jeremy Kotter '98

Honors Projects

One enigmatic class of objects whose structures are interesting and only recently explored are active galactic nuclei (AGN). These are galaxies in which massive black holes sit at the center and accrete matter. The term "active" refers to energetic processes which are not directly attributable to stars and which occur in the innermost portions of galaxies. Astrophysicists have developed general descriptions of AGN, but details about these objects remain incomplete. Notably, the thermal and ionization structures of AGN accretion disks and the geometries of the circum-source clouds which surround the black hole and comprise an important portion of the energy …

Measurement Of B(D0 → K-Π+) Using Partial Reconstruction Of B̅ → D*+Xℓ- Ν̅, M. Artuso, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We present a measurement of the absolute branching fraction for D⁰ → K^-π⁺ using the reconstruction of the decay chain B̅ → D*⁺Xℓ^- ν̅ where only the lepton and the low-momentum pion from the D*⁺ are detected. With data collected by the CLEO II detector at the Cornell Electron Storage Ring, we have determined Ɓ(D⁰ → K^-π⁺)= [3.81 ± 0.15(stat) ± 0.16(syst)]%.

Dynamic And Chemical Aspects Of The Mesospheric Na ‘Wall’ Event On 9 October 1993 During The Aloha Campaign, G. R. Swenson, J. Qian, J. M.C. Plane, P. J. Espy, Michael J. Taylor, D. N. Turnbull, R. P. Lowe

All Physics Faculty Publications

On October 9, 1993, observations were made from the National Center for Atmospheric Research Electra aircraft during a flight from Maui, Hawaii, toward a low-pressure system NW of the island, a flight of 7 hours in total. The leading edge (wall) of a bright airglow layer was observed 900 km NW of Maui at 0815 UT, which was traveling at 75 m s−1 toward the SE, reaching Haleakala, Maui, about 3.25 hours later [see Swenson and Espy, 1995]. An intriguing feature associated with the event was the large increase in the mesospheric Na column density at the wall (∼180%). The …

Material Evaluation By Pulsed Diode Laser Optoacoustics, Xiaodong Xu

Electrical & Computer Engineering Theses & Dissertations

Pulsed diode laser optoacoustic diagnostics were carried out to characterize solid sample materials. The apparatus developed is compact, portable, cost-effective and therefore very promising for both industrial as well as laboratory applications. To our knowledge, this is the first time that optoacoustic characterization and measurement have been performed with a diode laser. The method was successfully applied to measure the thickness of a multilayer structure non-intrusively. Internal cracks of the material were detected by this technique.

A theory for optoacoustic signal generation, propagation and detection is given. A numerical analysis technique is developed to solve for the expected signal. In …

Thermal Lattice Boltzmann Simulations Of Variable Prandtl Number Turbulent Flows, Min Soe, George Vahala, Pavol Pavlo, Linda L. Vahala, Hudong Chen

Electrical & Computer Engineering Faculty Publications

Thermal lattice Boltzmann (TLBE) models that utilize the single relaxation time scalar Bhatnagar, Gross, and Krook collision operator have an invariant Prandtl number. For flows with arbitrary Prandtl number, a matrix collision operator is introduced. The relaxation parameters are generalized so that the transport coefficients become density independent. TLBE simulations are presented for two-dimensional free decaying turbulence induced by a strongly perturbed double velocity shear layer for various Prandtl numbers.

Search For The Decay B→DS1+(2536)X, M. Bishai, Kenneth A. Bloom, Cleo Collaboration

Kenneth Bloom Publications

We have searched for the decay B→D_s1⁺ (2536)X and measured an upper limit for the inclusive branching fraction of B(B→D_s1⁺X) < 0.96% at the 90% confidence level. This limit is small compared with the total expected B→D‾^(*)D^(*) KX rate. Assuming factorization, the D_s1⁺ 1 decay constant is constrained to be f_Ds1⁺ < 114 MeV at the 90% confidence level, at least 2.5 times smaller than that of D_s.

The Effects Of Fabry-Perot Fringing On The Sensitivity Of A Wavelength Modulation Experiment, Patrick C. Shea

Electrical & Computer Engineering Theses & Dissertations

Parasitic Fabry-Perot etaloning plagues many experiments which use wavelength modulation spectroscopy. This fringing, which is an artifact that almost always appears in such experiments, arises from multiple reflections in the optical elements in the experimental apparatus. The etaloning plays a detrimental role and limits the ultimate sensitivity of wavelength modulation spectroscopy experiments. The research described in this thesis investigates this phenomenon. Experimental results are presented which show that when the Q-factor of the parasitic etalon is smaller that that of the absorption line being measured, significant improvement in the Signal to Fringe Noise Ratio can be obtained through the use …

Valence Intersubband Lasers With Inverted Light-Hole Effective Mass, Greg Sun, Y. Lu, Jacob B. Khurgin

Physics Faculty Publications

We propose a novel intersubband laser based on transition between the ground-state heavy-hole subband (HH1) and light-hole subband (LH1) in a k-space region where the light-hole effective mass is inverted. The laser structure can be electrically pumped with a simple quantum cascade scheme. Our calculation shows that with only a small fraction of the carrier population in the upper subband (LH1), it is possible to achieve population inversion between the two subbands locally in K space where the light-hole effective mass is inverted. Optical gain in excess of 150/cm can be achieved with a pumping current density on the …

Amplification Of High-Order Rainbows Of A Cylinder With An Elliptical Cross Section, James A. Lock, Charles L. Adler, Bradley R. Stone, Patrick D. Zajak

Physics Faculty Publications

The intensity of high-order rainbows for normally incident light and certain rotation angles of a cylinder with an elliptical cross section is greatly amplified with respect to the intensity for a circular cross-sectional cylinder. The amplification is due to a number of the internal reflections occurring past the critical angle for total internal reflection, and the effect is especially strong for odd-order rainbows, beginning with the third order. Experimentally, the fourth-and the fifth-order rainbows of a nearly elliptical cross-sectional glass rod were observed and analyzed. (C) 1998 Optical Society of America.

Rainbow Scattering By A Cylinder With A Nearly Elliptical Cross Section, Charles L. Adler, James A. Lock, Bradley R. Stone

Physics Faculty Publications

We both theoretically and experimentally examine the behavior of the first-and the second-order rainbows produced by a normally illuminated glass rod, which has a nearly elliptical cross section, as it is rotated about its major axis. We decompose the measured rainbow angle, taken as a function of the rod's rotation angle, into a Fourier series and find that the rod's refractive index, average ellipticity, and deviation from ellipticity are encoded primarily in the m = 0, 2, 3 Fourier coefficients, respectively. We determine these parameters for our glass rod and, where possible, compare them with independent measurements. We find that …

The Ultraviolet-Optical Albedo Of Broad Emission Line Clouds, Kirk Korista, Gary J. Ferland

Physics and Astronomy Faculty Publications

We explore the effective UV-optical albedos of a variety of types of broad emission line clouds, as well as their possible effects on the observed spectra of active galactic nuclei (AGNs). An important albedo source in moderately ionized ionization-bounded clouds is that which is due to neutral hydrogen: Rayleigh scattering of continuum photons off the extreme damping wings of Lyα. The photons resulting from this scattering mechanism may contribute significantly to the Lyα emission line, especially in the very broad wings. In addition, line photons emitted near 1200 Å (e.g., N V λ1240) that stream toward the neutral portion of …

Computer Intensive Physics, Robert Fuller

Robert G. Fuller Publications

In the abstract packet for the conference is an article of references about ideas from cognitive studies that help us teach physics (Fuller, 1998). There is also a pamphlet of references to innovative physics teaching programs in the United States and many of those programs have world-wide web sites so you can access information about those programs from Portugal (O'Kuma, 1998).

I want to talk about my research project last year, which I now call "Computer Intensive Physics", but it really started out as paper-less physics.

Event Shape Analysis Of Deep Inelastic Scattering Events With A Large Rapidity Gap At Hera, J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R. L. Talaga, R. Yoshida, H. Zhang, Margarita C. K. Mattingly, F. Anselmo, P. Antonioli, G. Bari, M. Basile, L. Bellagamba, D. Boscherini, A. Bruni, G. Bruni, G. Cara Romeo, G. Castellini, L. Cifarelli, F. Cindolo, A. Contin, M. Corradi, S. De Pasquale, I. Gialas, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

A global event shape analysis of the multihadronic final states observed in neutral current deep inelastic scattering events with a large rapidity gap with respect to the proton direction is presented. The analysis is performed in the range 5 ≤ Q2 ≤ 185 GeV2 and 160 ≤ W ≤ 250 GeV, where Q2 is the virtuality of the photon and W is the virtual-photon proton centre of mass energy. Particular emphasis is placed on the dependence of the shape variables, measured in the γ * -pomeron rest frame, on the mass of the hadronic final state, MX. With increasing MX …

The Texture Of Clouds, A. R. Jameson, Alexander Kostinski, R A. Black

Department of Physics Publications

Using a precise definition of clustering, it is shown that in two tropical cumulus clouds, droplets appear to be bunched over distances ranging from at least a kilometer or more down to several centimeters. A statistical framework is proposed for quantifying clustering in terms of a Poisson probability mixture. While these observations require further substantiation in many different clouds, droplet clustering may play a role in diverse phenomena from the coalescence growth of raindrops to the scattering of radiation by clouds.

Temporal Contrast In Ti:Sapphire Lasers: Characterization And Control, Marc Nantel, Jiro Itatani, An-Chun Tien, Jerome Faure, Daniel Kaplan, Marcel Bouvier, Takashi Buma, Paul Van Rompay, John Nees, Peter P. Pronko, Donald P. Umstadter, Gerald A. Mourou

Donald Umstadter Publications

As ultrafast lasers achieve ever higher focused intensities on target, the problem of ensuring a clean laser-solid interaction becomes more pressing. In this paper, we give concrete examples of the deleterious effects of low-contrast interactions, and address the problem of subpicosecond laser intensity contrast ratio on both characterization and control fronts. We present the new technique of high-dynamic-range plasma-shuttered streak camera contrast measurement, as well as two efficient and relatively inexpensive ways of improving the contrast of short pulse lasers without sacrificing on the output energy: a double-pass Pockels cell (PC), and clean high-energy-pulse seeding of the regenerative amplifier.

Full-Wave Modeling Of Small-Scale Gravity Waves Using Airborne Lidar And Observations Of The Hawaiian Airglow (Aloha-93) O(1s) Images & Coincident Na Wind/Temperature Lidar Measurements, M. P. Hickey, Michael J. Taylor, C. S. Gardner, C. R. Gibbons

All Physics Faculty Publications

Measurements were made of mesospheric gravity waves in the OI (5577 Å) nightglow observed from Maui, Hawaii, during the Airborne Lidar and Observations of Hawaiian Airglow (ALOHA-93) campaign. Clear, monochromatic gravity waves were observed on several nights. By using a full-wave model that realistically includes the major physical processes in this region, we have simulated the propagation of four waves through the mesopause region and calculated the O(1 S) nightglow response to the waves. Mean winds derived from Na wind/temperature lidar observations were employed in the computations. Wave amplitudes were calculated based on the requirement that the observed and simulated …

Observational Limits For Lidar, Radar And Airglow Imager Measurements Of Gravity Wave Parameters, C. S. Gardner, Michael J. Taylor

All Physics Faculty Publications

By examining the observational limits and biases for lidar, radar, and airglow imager measurements of middle atmosphere gravity waves, we provide plausible explanations for the characteristics of the monochromatic wave parameters that have been reported during the past decade. The systematic dependencies of vertical and horizontal wavelength on wave period, reported in many lidar and some radar studies, are associated with diffusive damping. The prominent waves with the largest amplitudes, most often observed by lidars and radars, are those with vertical phase speeds near the diffusive damping limit. The narrow range of horizontal phase velocities of the waves seen by …

Joint Wavelet Transform Correlation With Separated Target And Reference Planes, Boon Yi Soon, Mohammad A. Karim, Russell C. Hardie, Mohammad S. Alam

Electrical and Computer Engineering Faculty Publications

In recent years, we realize the usefulness of feature extraction for optical correlator and hereby, we investigate the capability of Laplace operator in feature extraction of multiple targets. The first-order terms and the false alarm terms in the correlation output would be removed using electronic power spectrum subtraction technique. Most importantly, the entire magneto-optic SLM is completely utilized for displaying only targets in the input scene. A new cost efficient hardware implementation is proposed and aforementioned result of the proposed system is evaluated through computer simulation.

Optical Physics Of Microcavity Surface Emitting Lasers, Michael J. Noble

Theses and Dissertations

This dissertation consists of an in-depth theoretical analysis of the optical impact of transverse index confinement on the lasing modes of microcavity surface emitting lasers. Two different variational techniques were employed to calculate the relevant optical laser parameters: (1) modal resonance, field profile, (2) confinement factor, and (3) threshold gain. Through a semianalytic field analysis, two new confinement related effects were discovered: (1) a polarization dependent change in mirror reflectance with aperture radius, and (2) a mode dependent blueshift. Through a numerical field analysis, the physical mechanisms governing diffraction were ascertained. These are: (1) the transverse confinement of the optical …