Physics Commons^™

Photon And Neutral Pion Production In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We report inclusive photon measurements about midrapidity (∣y∣<0.5) from ¹⁹⁷Au+¹⁹⁷Au collisions at √s_NN=130 GeV at RHIC. Photon pair conversions were reconstructed from electron and positron tracks measured with the Time Projection Chamber (TPC) of the STAR experiment. With this method, an energy resolution of ΔE ∕ E≈2% at 0.5GeV has been achieved. Reconstructed photons have also been used to measure the transverse momentum (p_t) spectra of π0mesons about midrapidity (∣y∣<1) via the π⁰→γγ decay channel. The fractional contribution of the π⁰→γγ decay to the inclusive photon spectrum decreases by 20%±5% between p_{t …}

Angular Dependence Of The Dipole-Dipole Interaction In A Nearly One-Dimensional Sample Of Rydberg Atoms, Thomas J. Carroll, Katharine Claringbould, Anne Goodsell, M. J. Lim, Michael Noel

Physics Faculty Research and Scholarship

Atoms in an ultracold highly excited sample are strongly coupled through the dipole-dipole interaction. In an effort to understand and manipulate the complicated interactions in this system we are investigating their dependence on the relative orientation of the dipoles. By focusing a 480 nm beam from a tunable dye laser into a magneto-optical trap, we produce a nearly one-dimensional sample of Rydberg atoms. The trap lies at the center of four conducting rods with which we can vary the magnitude and direction of the electric field at the trap, thus controlling the orientation of the dipoles with respect to the …

Mohanty And Webb Reply, P. Mohanty, Richard A. Webb

Faculty Publications

A Reply to the Comment by V. I. Fal'ko et al.

Rapidity And Centrality Dependence Of Proton And Antiproton Production From 197Au + 197Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We report on the rapidity and centrality dependence of proton and antiproton transverse mass distributions from ¹⁹⁷Au+¹⁹⁷Au collisions at √s_NN=130 GeV as measured by the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). Our results are from the rapidity and transverse momentum range of ∣y∣<0.5 and 0.35 < p_t < 1.00 GeV ∕ c. For both protons and antiprotons, transverse mass distributions become more convex from peripheral to central collisions demonstrating characteristics of collective expansion. The measured rapidity distributions and the mean transverse momenta versus rapidity are flat within ∣y∣<0.5. Comparisons of our data with results from model calculations indicate that in order to obtain a consistent picture of the proton (antiproton) yields and transverse mass distributions the possibility of prehadronic collective expansion may have to be taken into account.

Centrality And Pseudorapidity Dependence Of Charged Hadron Production At Intermediate PT In Au+Au Collisions At √SNn=130 Gev, Star Collaboration, T.D. Gutierrez

Physics

We present STAR measurements of charged hadron production as a function of centrality in Au+Au collisions at √s_NN=130 GeV. The measurements cover a phase space region of 0.2T<6.0GeV∕c in transverse momentum and −1<η<1 in pseudorapidity. Inclusive transverse momentum distributions of charged hadrons in the pseudorapidity region 0.5<∣η∣<1 are reported and compared to our previously published results for ∣η∣<0.5. No significant difference is seen for inclusive p_T distributions of charged hadrons in these two pseudorapidity bins. We measured dN∕dη distributions and truncated mean p_T in a region of p_T>p_T^cut, and studied the results in the framework of participant and binary scaling. No clear evidence is observed for participant scaling of charged hadron yield in the measured p_T region. The relative importance of hard scattering processes is investigated through binary …

Hohenberg-Kohn Theory Including Spin Magnetism And Magnetic Fields, Walter Kohn, Andreas Savin, Carsten A. Ullrich

Physics Faculty Research & Creative Works

Beginning with work by U. von Earth and L. Hedin in 1972 and continuing with recent papers in 2001 by K. Capelle and G. Vignale and by H. Eschrig and W. E. Pickett, questions have been raised about the meaning and validity of Hohenberg-Kohn theory when spin magnetism and/or magnetic fields are present. This article offers clarifications of some of these questions. in particular, it also concludes that these questions do not affect spin-density functional theory for nondegenerate ground states as currently practiced. © 2004 Wiley Periodicals, Inc.

Angular Dependence Of The Dipole-Dipole Interaction In A Nearly One-Dimensional Sample Of Rydberg Atoms, Thomas J. Carroll, Katharine Claringbould, Anne Goodsell, M. J. Lim, Michael W. Noel

Physics and Astronomy Faculty Publications

Atoms in an ultracold highly excited sample are strongly coupled through the dipole-dipole interaction. In an effort to understand and manipulate the complicated interactions in this system we are investigating their dependence on the relative orientation of the dipoles. By focusing a 480 nm beam from a tunable dye laser into a magneto-optical trap, we produce a nearly one-dimensional sample of Rydberg atoms. The trap lies at the center of four conducting rods with which we can vary the magnitude and direction of the electric field at the trap, thus controlling the orientation of the dipoles with respect to the …

Analysis And Comparison Of Three Acoustic Energy Density Probes, Lance Lester Locey

Theses and Dissertations

Traditional methods for the investigation of sound fields generally rely on a microphone to convert sound pressure into an electrical signal which can be recorded, displayed, and so forth. The squared sound pressure is directly related to potential energy density. Consequently, the measurement of sound pressure alone does not inherently provide insight into the total energy density of the sound field. Specifically, no information about the kinetic energy density of the sound field is available from this measurement alone. However, it is possible to use two microphones to estimate particle velocity. The squared particle velocity magnitude is directly related to …

Stabilizing Moduli With String Cosmology, Scott Watson

Physics - All Scholarship

In this talk I will discuss the role of finite temperature quantum corrections in string cosmology and show that they can lead to a stabilization mechanism for the volume moduli. I will show that from the higher dimensional perspective this results from the effect of states of enhanced symmetry on the one-loop free energy. These states lead not only to stabilization, but also suggest an alternative model for cold dark matter. At late times, when the low energy effective field theory gives the appropriate description of the dynamics, the moduli will begin to slow-roll and stabilization will generically fail. However, …

Wide Angle Decentered Lens Beam Steering For Infrared Countermeasures Applications, Jennifer L. Gibson, Bradley D. Duncan, Edward A. Watson, John S. Loomis

Electro-Optics and Photonics Faculty Publications

A beam-steering system consisting of three cemented achromatic doublets is presented. Intended for use in IR countermeasure applications, our system is designed to operate over the 2- to 5-μm spectrum with minimum angular dispersion. We show that dispersion can be minimized by using doublet lenses fashioned from AMTIR-1 and germanium. Our system is designed to be compact and lightweight, with no internal foci, while allowing steering to ±22.5 deg. We also maintain a minimum 2-in. clear aperture for all steering angles, and a nominal divergence of 1 mrad. Plane wave and Gaussian beam analyses of our system are presented.

Event Rate Estimates For Lisa Extreme Mass Ratio Capture Sources, J. Gair, L. Barack, T. Creighton, C. Cutler, Shane L. Larson, E. S. Phinney, M. Vallisneri

All Physics Faculty Publications

One of the most exciting prospects for the LISA gravitational wave observatory is the detection of gravitational radiation from the inspiral of a compact object into a supermassive black hole. The large inspiral parameter space and low amplitude of the signal make detection of these sources computationally challenging. We outline here a first-cut data analysis scheme that assumes realistic computational resources. In the context of this scheme, we estimate the signal-to-noise ratio that a source requires to pass our thresholds and be detected. Combining this with an estimate of the population of sources in the universe, we estimate the number …

On The Polarization Of Closed Strings By Ramond-Ramond Fluxes, Vatche Sahakian

All HMC Faculty Publications and Research

In the Green-Schwarz formalism, the closed string worldsheet of the IIB theory couples to Ramond-Ramond (RR) fluxes through spinor bilinears. We study the effect of such fluxes by analyzing the supersymmetry transformation of the worldsheet in general backgrounds. We show that, in the presence RR fields, the closed string can get `polarized', as the spinors acquire non-zero vevs in directions correlating with the orientation of close-by D-branes. Reversing the argument, this may allow for worldsheet configurations—with non-trivial spinor structure—that source RR moments.

Search For Doubly Charged Higgs Boson Pair Production In The Decay To Μ+Μ+Μ-Μ- In Pp̅ Collisions At √S = 1.96 Tev, V. M. Abazov, Gregory R. Snow, D0 Collaboration

Gregory Snow Publications

A search for pair production of doubly charged Higgs bosons in the process pp̅ → H⁺⁺H^-- → μ⁺μ⁺μ^-μ^- is performed with the D0 run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive dimuon data collected at an energy of √s = 1.96 TeV, corresponding to an integrated luminosity of 113 pb^-1. In the absence of a signal, 95% confidence level mass limits of M(H_L^±±) > 118.4 GeV/c² and M(H_R^±±) …

Radical, Getting To The Root: A Review Of Curriculum Dynamics: Recreating Heart, Dewey I. Dykstra

Physics Faculty Publications and Presentations

No abstract provided.

Asymptotic Accuracy Of Geoacoustic Inversions, Michele Zanolin, Ian Ingram, Aaron Thode, Nicholas C. Makris

Publications

Criteria necessary to accurately estimate a set of unknown geoacoustic parameters from remote acoustic measurements are developed in order to aid the design of geoacoustic experiments. The approach is to have estimation error fall within a specified design threshold by adjusting controllable quantities such as experimental sample size or signal-to-noise ratio (SNR). This is done by computing conditions on sample size and SNR necessary for any estimate to have a variance that (1) asymptotically attains the Cramer–Rao lower bound (CRLB) and (2) has a CRLB that falls within the specified design error threshold. Applications to narrow band deterministic signals received …

Nonrelativistic Qed Approach To The Bound-Electron G Factor, Krzysztof Pachucki, Ulrich D. Jentschura, Vladimir A. Yerokhin

Physics Faculty Research & Creative Works

Within a systematic approach based on nonrelativistic quantum electrodynamics, we derive the one-loop self-energy correction of order α ( Z α )⁴ to the bound-electron g factor. In combination with numerical data, this analytic result improves theoretical predictions for the self-energy correction for carbon and oxygen by an order of magnitude. Basing on one-loop calculations, we obtain the logarithmic two-loop contribution of order α² ( Z α )⁴ ln [ ( Z α )^{- 2} ] and the dominant part of the corresponding constant term. The results obtained improve the accuracy of the theoretical predictions for …

Fully Differential Three-Dimensional Angular Distributions Of Electrons Ionized In Ion-Atom Collisions, Michael Schulz, R. Moshammer, Daniel Fischer, Ahmad Hasan, N. V. Maydanyuk, J. D. Ullrich

Physics Faculty Research & Creative Works

We compare experimental fully differential three-dimensional angular distributions of electrons ionized from He in collision with ionic projectiles covering a broad range of perturbations (0.065 to 4.4). Even at very small perturbations clear signatures of higher-order contributions are observable. At large perturbations, such contributions become even dominant, especially those involving the post-collision interaction between the outgoing projectile and the ionized electron. Our results show that single ionization is not nearly as well understood as was assumed previously.

Nucleation Near The Spinodal: Limitations Of Mean Field Density Functional Theory, Gerald Wilemski, Jin-Song Li

Physics Faculty Research & Creative Works

We investigate the diverging size of the critical nucleus near the spinodal using the gradient theory ~GT! of van der Waals and Cahn and Hilliard and mean field density functional theory ~MFDFT!. As is well known, GT predicts that at the spinodal the free energy barrier to nucleation vanishes while the radius of the critical fluctuation diverges. We show numerically that the scaling behavior found by Cahn and Hilliard for these quantities holds quantitatively for both GT and MFDFT. We also show that the excess number of molecules Dg satisfies Cahn-Hilliard scaling near the spinodal and is consistent with the …

Measurement Of The Tt̅ Production Cross Section In Pp̅ Collisions At √S =1.96 Tev Using Dilepton Events, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report a measurement of the tt̅ production cross section using dilepton events with jets and missing transverse energy in pp̅ collisions at a center-of-mass energy of 1.96 TeV. Using a 197±12 pb^-1 data sample recorded by the upgraded Collider Detector at Fermilab, we use two complementary techniques to select candidate events. We compare the number of observed events and selected kinematical distributions with the predictions of the standard model and find good agreement. The combined result of the two techniques yields a tt̅ production cross section of 7.0_-2.1^+2.4 (stat) _-1.1^+1.6 (syst)±0.4(lum) pb.

Inclusive Double-Pomeron Exchange At The Fermilab Tevatron P̅P Collider, Darin Acosta, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We report results from a study of events with a double-Pomeron exchange topology produced in p̅p collisions at √s =1800 GeV. The events are characterized by a leading antiproton and a large rapidity gap on the outgoing proton side. We find that the differential production cross section agrees in shape with predictions based on Regge theory and factorization, and that the ratio of double-Pomeron exchange to single diffractive production rates is relatively unsuppressed as compared to the θ(10) suppression factor previously measured in single diffractive production.

Photometry Of Type Ii Cepheids. I. The Long-Period Stars, Edward G. Schmidt, Dale Johnston, Shawn Langan, Kevin M. Lee

Department of Physics and Astronomy: Faculty Publications

We present 1256 new photometric observations of 36 Cepheids with periods longer than 8 days. The majority are likely type II Cepheids, but we have included about a dozen classical Cepheids for comparison purposes, a few stars of uncertain type, and one putative RV Tauri star. We discuss the appearance of the light curves, the Fourier parameters, and the light-curve stability in terms of differentiation between type I and type II Cepheids. Although we encounter the same difficulties as previous investigators in using these parameters for this purpose, we are able to identify some stars of particular interest, including several …

Response Of The Martian Thermosphere/Ionosphere To Enhanced Fluxes Of Solar Soft X Rays, Jane L. Fox

Physics Faculty Publications

We have investigated the response of the thermosphere and ionosphere of Mars to enhanced fluxes of solar soft X rays, such as those that have been detected by the SNOE satellite (e.g., Bailey et al., 2000 ). We have constructed standard models by adopting the SC#21REFW and F79050N solar fluxes from H. E. Hinteregger (private communication) (see also Torr et al., 1979 ) for the low and high solar activity models, respectively. We then constructed enhanced soft X-ray models by multiplying the solar photon fluxes for wavelengths below 200 Å by a factor of 3 at low solar …

From Guts To God: Credulity, Postmodernism, And Contemporary Physics, Michael Hardin

Reconstruction: Studies in Contemporary Culture

[Editors' Introduction]

In an attempt to remove one of the major misunderstandings made by individuals in the humanities about contemporary physics, the issue of incredulity, this essay examines Lyotard's The Postmodern Condition: A Report on Knowledge against contemporary and twentieth-century theories and discoveries in physics. One of the best arguments against incredulity is the frequent use of god as metaphor within physics. In Fashionable Nonsense: Postmodern Intellectuals' Abuse of Science, Alan Sokal and Jean Bricmont, two physicists, argue that the use of metaphor is one of the characteristics of postmodern science; this essay concludes with a discussion of those elements …

Sequential Interferometric Techniques For Measuring Independent Values Of The Refractive Index And Material Thickness Of Semiconductor Wafers, Glen D. Gillen, Shekhar Guha

Physics

A technique is presented using both Michelson and Fabry-Perot interferometry to independently measure the refractive index and the material thickness of semiconductor wafers. The method does not require accurate prior knowledge of either quantity.

Vector Operations In Superscalar Architectures, Nathan Daniel Flinn

Electrical & Computer Engineering Theses & Dissertations

Vector calculations are very prevalent today. Though the vector-processing computer is quite an old concept, superscalar processors lack hardware support for vector operations. This thesis investigates whether an ordinary superscalar computer architecture can be designed to include hardware support for improved vector operations without drastically changing the existing superscalar design and behavior. A computer architecture design was created and implemented that included the vector multiply (dot product) operation. The design includes a Vector Operations Unit that captures incoming vector operations and generates the necessary set of machine instructions to complete the vector operation internally. It then delivers these instructions to …

Modeling And Simulation Of Photonic Crystal Fibers Using Finite Difference Frequency Domain Method, Md. Khalid Ikram

Electrical & Computer Engineering Theses & Dissertations

Photonic crystal fibers (PCFs) allow guiding light in low-index core. These fibers exhibit properties such as single-mode operation in broad wavelength region. The mode shape and group velocity dispersion can be controlled by designing the microstructures of the cladding. In order to study these properties, a fast, efficient, and highly accurate numerical modeling method is required.

A full-vectorial finite-difference frequency-domain (FDFD) method is implemented. The modal properties of conventional step index fiber and index-guiding PCF are analyzed using this modeling technique. Compared to plane wave expansion and biorthogonal basis methods, FDFD is found to be simple, reliable, and efficient. PCFs …

Lorentz-Violating Electrostatics And Magnetostatics, Quentin G. Bailey, V. Alan Kostelecký

Publications

Electromagnetostatics experiments show promise for improving existing sensitivities to parity-odd coefficients for Lorentz violation in the photon sector.

Achromatic Angle-Insensitive Infrared Quarter-Wave Retarder Based On Total Internal Reflection At The Si–Sio2 Interface, R. M.A. Azzam, Cristina L. Spinu

Electrical Engineering Faculty Publications

An achromatic infrared (λ = 1.2–4 μm), Si-prism quarter-wave retarder (QWR) is described that uses total internal reflection at a buried Si–SiO₂ interface at an angle of incidence φ near 33°, where ∂Δ/∂φ = 0. The retardance Δ deviates from 90° by <±2° within a field of view of ±10° (in air) over the entire bandwidth. Because the SiO₂ layer at the base of the prism is optically thick, this QWR is unaffected by environmental contamination.

Dissolution, Reactor, And Environmental Behavior Of Zro2-Mgo Inert Fuel Matrix: Neutronic Evaluation Of Zro2-Mgo Inert Fuels, E. Fridman, A. Galperin, E. Shwageraus

Fuels Campaign (TRP)

Second task of the BGU part of “Dissolution, Reactor, and Environmental Behavior of ZrO₂-MgO Inert Fuel Matrix” project aims at evaluation of the fertile free fuel matrix composition effect on the fuel reactivity and corresponding reactivity limited burnup. Fertile free fuel with different MgO to ZrO₂ ratio in the matrix will require different PuO₂ loading in order to assure certain fuel cycle length. This is due to the fact that absorption cross section of Zr is slightly higher than that of Mg, although absorption in both of these elements is small compared to Pu. Therefore, the …

Spatiotemporal Distribution Of Marine Magnetotactic Bacteria In A Seasonally Stratified Coastal Salt Pond, S. L. Simmons, S. M. Sievert, Richard B. Frankel, Dennis A. Bazylinski, K. J. Edwards

Physics

The occurrence and distribution of magnetotactic bacteria (MB) were studied as a function of the physical and chemical conditions in meromictic Salt Pond, Falmouth, Mass., throughout summer 2002. Three dominant MB morphotypes were observed to occur within the chemocline. Small microaerophilic magnetite-producing cocci were present at the top of the chemocline, while a greigite-producing packet-forming bacterium occurred at the base of the chemocline. The distributions of these groups displayed sharp changes in abundance over small length scales within the water column as well as strong seasonal fluctuations in population abundance. We identified a novel, greigite-producing rod in the sulfidic hypolimnion …