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Infrasonic observation of earthquakes

Description: Infrasound signals generated by earthquakes have been detected at arrays operated by the Los Alamos National Laboratory. Three modes of propagation are possible and all have been observed by the authors. The observations suggest that regions remote from the epicenters are excited and may serve as secondary source regions. A relation is found between the normalized peak amplitudes and the seismic magnitudes.
Date: December 31, 1998
Creator: Mutschlecner, J.P. & Whitaker, R.W.
Partner: UNT Libraries Government Documents Department

Nucleon-nucleon interactions

Description: Nucleon-nucleon interactions are at the heart of nuclear physics, bridging the gap between QCD and the effective interactions appropriate for the shell model. We discuss the current status of {ital NN} data sets, partial-wave analyses, and some of the issues that go into the construction of potential models. Our remarks are illustrated by reference to the Argonne {ital v}{sub 18} potential, one of a number of new potentials that fit elastic nucleon-nucleon data up to 350 MeV with a {Chi}{sup 2} per datum near 1. We also discuss the related issues of three-nucleon potentials, two-nucleon charge and current operators, and relativistic effects. We give some examples of calculations that can be made using these realistic descriptions of {ital NN} interactions. We conclude with some remarks on how our empirical knowledge of {ital NN} interactions may help constrain models at the quark level, and hence models of nucleon structure.
Date: December 31, 1996
Creator: Wiringa, R.B.
Partner: UNT Libraries Government Documents Department

Vibration modal analysis using all-optical photorefractive processing

Description: A new experimental method for vibration modal analysis based on all- optical photorefractive processing is presented. The method utilizes an optical lock-in approach to measure phase variations in light scattered from optically rough, continuously vibrating surfaces. In this four-wave mixing technique, all-optical processing refers to mixing the object beam containing the frequency modulation due to vibration with a single frequency modulated pump beam in the photorefractive medium that processes the modulated signals. This allows for simple detection of the conjugate wavefront image at a CCD. The conjugate intensity is shown to be a function of the first-order ordinary Bessel function and linearly dependent on the vibration displacement induced phase. Furthermore, the results demonstrate the unique capabilities of the optical lock-in vibration detection technique to measure vibration signals with very narrow bandwidth (< 1 Hz) and high displacement sensitivity (sub-Angstrom). This narrow bandwidth detection can be achieved over a wide frequency range from the photorefractive response limit to the reciprocal of the photoinduced carrier recombination time. The technique is applied to determine the modal characteristics of a rigidly clamped circular disc from 10 kHz to 100 kHz.
Date: December 31, 1996
Creator: Hale, T. & Telschow, K.
Partner: UNT Libraries Government Documents Department

Amplitude and phase modulation with waveguide optics

Description: We have developed amplitude and phase modulation systems for glass lasers using integrated electro-optic modulators and solid state high- speed electronics. The present and future generation of lasers for Inertial Confinement Fusion require laser beams with complex temporal and phase shaping to compensate for laser gain saturation, mitigate parametric processes such as transverse stimulated Brillouin scattering in optics, and to provide specialized drive to the fusion targets. These functions can be performed using bulk optoelectronic modulators, however using high-speed electronics to drive low voltage integrated optical modulators has many practical advantages. In particular, we utilize microwave GaAs transistors to perform precision, 250 ps resolution temporal shaping. Optical bandwidth is generated using a microwave oscillator at 3 GHz amplified by a solid state amplifier. This drives an integrated electrooptic modulator to achieve laser bandwidths exceeding 30 GHz.
Date: December 17, 1996
Creator: Burkhart, S.C.; Wilcox, R.B.; Browning, D. & Penko, F.A.
Partner: UNT Libraries Government Documents Department

Prospects of a baryon instability search in neutron-antineutron oscillations

Description: The purpose of this article is to review the current status and the future prospects for an experimental neutron-antineutron transition search. Traditional and new experimental techniques are discussed here. In the n {r_arrow} {anti n} search in experiments at existing reactors, it would be possible to increase the discovery potential up to four orders of magnitude for vacuum n {r_arrow} {anti n} transitions relative to the existing experimental level or to achieve the limit of {tau}{sub n-{anti n}{sup {approximately}}} 10{sup 10}s.. With dedicated future reactors and an ultimate experimental layout, it might be possible to reach the limit of 10{sup 11}s. Significant progress in an intranuclear n {r_arrow} {anti n} transition search expected to be made during the next decade by the SuperKamiokande and Icarus detectors. It can be matched, or even exceeded, in a new alternative approach, where unstable long-lived isotopes of technetium are searched in non radioactive deep-mined ores.
Date: December 31, 1996
Creator: Efremenko, Yu. & Kamyshkov, Yu.
Partner: UNT Libraries Government Documents Department

Phase synchronization of multiple klystrons in RF system

Description: The Low Energy Demonstration Accelerator (LEDA) being constructed at Los Alamos National Laboratory will serve as the prototype for the low energy section of the Acceleration Production of Tritium (APT) accelerator. The first LEDA RF system includes three, 1.2 MW, 350 MHz, continuous wave, klystrons driving a radio frequency quadrupole (RFQ). A phase control loop is necessary for each individual klystron in order to guarantee the phase matching of these klystrons. To meet this objective, they propose adaptive PI controllers which are based on simple adaptive control. These controllers guarantee not only phase matching but also amplitude matching.
Date: December 31, 1998
Creator: Kwon, S.; Regan, A.; Wang, Y.M. & Rohlev, T.
Partner: UNT Libraries Government Documents Department

Infrasound from the El Paso super-bolide of October 9, 1997

Description: During the noon hour on October 9, 1997 an extremely bright fireball ({approx}-21.5 in stellar magnitude putting it into the class of a super-bolide) was observed over western Texas with visual sightings from as far away as Arizona to northern Mexico and even in northern New Mexico over 300 miles away. This event produced tremendously loud sonic boom reports in the El Paso area. It was also detected locally by 4 seismometers which are part of a network of 5 seismic stations operated by the University of Texas at El Paso (UTEP). Subsequent investigations of the data from the six infrasound arrays used by LANL (Los Alamos National Laboratory) and operated for the DOE (Department of Energy) as a part of the CTB (Comprehensive Test Ban) Research and Development program for the IMS (International Monitoring System) showed the presence of an infrasonic signal from the proper direction at the correct time for this super-bolide from two of the six arrays. Both the seismic and infrasound recordings indicated that an explosion occurred in the atmosphere at source heights from 28--30 km, having its epicenter slightly to the northeast of Horizon City, Texas. The signal characteristics, analyzed from {approx}0.1 to 5.0 Hz, include a total duration of {approx}4 min (at Los Alamos, LA) to &gt;{approx}5 min at Lajitas, Texas, TXAR, another CTB IMS array operated by E. Herrin at Southern Methodist University (SMU) for a source directed from LA toward {approx}171--180 deg and from TXAR of {approx}321-4 deg respectively from true north. The observed signal trace velocities (for the part of the recording with the highest cross-correlation) at LA ranged from 300--360 m/sec with a signal velocity of 0.30 {+-} 0.03 km/sec, implying a Stratospheric (S Type) ducted path. The dominant signal frequency at LA was from 0.20 to 0.80 Hz, with ...
Date: December 31, 1998
Creator: ReVelle, D.O.; Whitaker, R.W. & Armstrong, W.T.
Partner: UNT Libraries Government Documents Department

Nonlinear Pulsation Modeling of Luminous Blue Variables

Description: Using an updated version of the Ostlie and Cox (1993) nonlinear hydrodynamics code, we show the results of Luminous Blue Variable (LBV) envelope models based on evolution models of initial mass 50-80 M solar. including mass loss. The models use OPAL opacities, contain 60-120 Lagrangian zones, include time dependent convection, and are given an initial photospheric radial velocity amplitude of 1 km/sec. Our goal is to explain the reason for the LBV instability strip and suggest a cause for LBV outbursts observed in massive stars in our Galaxy as well as the LMC and SMC.
Date: December 31, 1997
Creator: Despain, Kate M.; Guzik, Joyce A. & Cox, Arthur N.
Partner: UNT Libraries Government Documents Department

Amplitude path corrections for regional phases in China

Description: The authors investigate the effectiveness of amplitude path corrections for regional phases on seismic event discrimination and magnitude estimation. Waveform data from digital stations in China for regional, shallow (< 50 km) events were obtained from the IRIS Data Management Center (DMC) for years 1986 to 1996 using the USGS Preliminary Determination of Epicenters (PDE) and the Chinese State Seismological Bureau (SSB) catalogs. For each event, the amplitudes for each regional phase (P{sub n}, P{sub g}, S{sub n}, L{sub g}) were measured, as well as the P{sub g} and L{sub g} coda. Measured amplitudes were corrected for source scaling using estimates of m{sub b} and for distance using a power law that accounts for attenuation and spreading. The amplitude residuals were interpolated and mapped as 2-D amplitude correction surfaces. The authors employ several methods to create the amplitude correction surfaces: a waveguide method, and two interpolation methods (Baysian kriging and a circular moving window mean smoother). They explore the sensitivities of the surfaces to the method and to regional propagation, and apply these surfaces to correct amplitude data to reduce scatter in discrimination ratios and magnitude estimates.
Date: December 31, 1998
Creator: Phillips, W.S.; Velasco, A.A.; Taylor, S.R. & Randall, G.E.
Partner: UNT Libraries Government Documents Department

Reaction theories for N* excitations in {pi}N and {gamma}N reactions

Description: The importance of developing reaction theories for investigating N* physics is illustrated in an analysis of pion photoproduction on the nucleon. It is shown that the {gamma}N {leftrightarrow} {Delta} transition amplitudes predicted by the constituent quark model are in agreement with the values extracted from the {gamma}N {r_arrow} {pi}N data only when the contributions from the reaction mechanisms calculated using a dynamical approach are taken into account in the analysis.
Date: December 31, 1996
Creator: Lee, T. S. H.
Partner: UNT Libraries Government Documents Department

The Feynman-Schwinger (World Line) Representation in Perturbative QCD

Description: The proper time path integral representation is derived explicitly for an arbitrary $n$-point amplitude in QCD. In the standard perturbation theory the formalism allows to sum up the leading subseries, e.g. yielding double-logarithm Sudakov asymptotics for form factors. Correspondence with the standard perturbation theory is established and connection to the Bern-Kosower-Strassler method is illustrated.
Date: December 1, 2001
Creator: Simonov, Yu A. & Tjon, J.A.
Partner: UNT Libraries Government Documents Department

KN scattering in the nonrelativistic quark model

Description: KN scattering is of interest as a probe of nuclear structure and, more fundamentally, as a laboratory for the study of nonresonant hadron-hadron interactions. KN is a I theoretically attractive channel because of its simplicity, having only S = 1/2, no one pion exchange contributions and no valence q{anti q} annihilation. It may therefore be useful for the study of short-ranged quark forces analogous to the NN repulsive core. Since there are two isospin states, comparison of two closely related amplitudes is possible. This contribution reviews the experimental status of S-wave KN scattering and related theoretical studies based on quark-gluon dynamics. The experimental low-energy S-wave phase shift is well established for I = 1, but is not yet well determined for I = 0. The ratio of I = 0 to I = 1 scattering lengths is an interesting number theoretically, and may discriminate between different scattering mechanisms. A measurement of these scattering lengths at DAPHNE would be a useful contribution to low energy hadron physics.
Date: December 31, 1995
Creator: Barnes, F.E.
Partner: UNT Libraries Government Documents Department

Theoretical aspects of light meson spectroscopy

Description: In this pedagogical review the authors discuss the theoretical understanding of light hadron spectroscopy in terms of QCD and the quark model. They begin with a summary of the known and surmised properties of QCD and confinement. Following this they review the nonrelativistic quark potential model for q{anti q} mesons and discuss the quarkonium spectrum and methods for identifying q{anti q} states. Finally, they review theoretical expectations for non-q{anti q} states (glueballs, hybrids and multiquark systems) and the status of experimental candidates for these states.
Date: December 31, 1995
Creator: Barnes, T.
Partner: UNT Libraries Government Documents Department

The high energy behavior of the forward scattering parameters - an amplitude analysis update

Description: Utilizing the most recent experimental data, we reanalyze high energy pp and pp data, using the asymptotic amplitude analysis, under the assumption that we have reached {open_quotes}asymptopia{close_quotes}. This analysis gives strong evidence for a log (s/s{sub 0}) dependence at current energies and not log{sup 2} (s/s{sub 0}), and also demonstrates that odderons are not necessary to explain the experimental data.
Date: December 1995
Creator: Block, M. M.; Margolis, B. & White, A. R.
Partner: UNT Libraries Government Documents Department

Experiment to measure total cross sections, differential cross sections and polarization effects in pp elastic scattering at RHIC

Description: The author is describing an experiment to study proton-proton (pp) elastic scattering experiment at the Relativistic Heavy Ion Collider (RHIC). Using both polarized and unpolarized beams, the experiment will study pp elastic scattering from {radical}s = 60 GeV to {radical}s = 500 GeV in two kinematical regions .In the Coulomb Nuclear Interference (CNI) region, 0.0005 < {vert_bar}t{vert_bar} < 0.12 (GeV/c){sup 2}, we will measure and study the s dependence of the total and elastic cross sections, {sigma}{sub tot} and {sigma}{sub el}; the ratio of the real to the imaginary part of the forward elastic scattering amplitude, {rho}; and the nuclear slope parameter of the pp elastic scattering, b. In the medium {vert_bar}t{vert_bar}, {vert_bar}t{vert_bar} {le} 1.5 (GeV/c){sup 2}, we plan to study the evolution of the dip structure with s, as observed at ISR in the differential elastic cross section, d{sigma}{sub el}/dt, and the s and {vert_bar}t{vert_bar} dependence of b. With the polarized beams the following can be measured: the difference in the total cross sections as function of initial transverse spin stated {Delta}{sigma}{sub T}, the analyzing power, A{sub N}, and the transverse spin correlation parameter A{sub NN}. The behavior of the analyzing power A{sub N} at RHIC energies in the dip region of d{sigma}{sub el}/dt, where a pronounced structure was found at fixed-target experiments will be studied.
Date: December 31, 1995
Creator: Guryn, W.
Partner: UNT Libraries Government Documents Department

Applications of magnetized plasma to particle acceleration

Description: Magnetized plasma can be used as an accelerating structure capable of supporting large amplitude longitudinal fields which are externally driven by a high-frequency microwave source. Such structures can be used at very high frequencies (hundreds of gigahertz), placing them in the intermediate region between conventional (metallic) accelerators, and laser-driven plasma accelerators. They review two magnetic field configurations with respect to the direction of the particle beam propagation: (1) parallel magnetic field plus a helical undulator, and (2) perpendicular magnetic field. In the first configuration, plasma exhibits electromagnetically induced transparency (EIT) at the cyclotron frequency if the plasma frequency is equal to the electron cyclotron frequency. The second configuration corresponds to the inverse Cherenkov effect in magnetized plasma. In both cases, the group velocity of the accelerating plasma wave can be made very small, so that the incident electromagnetic wave is strongly compressed, resulting in the high accelerating gradient.
Date: December 12, 2002
Creator: Shvets, Gennady; Wurtele, Jonathan S. & Hur, Min-Sup
Partner: UNT Libraries Government Documents Department

Resonance Contributions to {eta} Photoproduction on Protons Found Using Dispersion Relations and an Isobar Model

Description: The contributions of the resonances D{sub 13}(1520), S{sub 11}(1535), S{sub 11}(1650), D{sub 15}(1675), F{sub 15}(1680), D{sub 13}(1700), P{sub 11}(1710), P{sub 13}(1720) to {gamma}p {yields} {eta}p are found from the data on cross sections, beam and target asymmetries using two approaches: fixed-t dispersion relations and an isobar model. Utilization of the two approaches and comparison of the results obtained with different parametrizations of the resonance contributions allowed us to make conclusions about the model-dependence of these contributions. We conclude that the results for the contributions of the resonances D{sub 13}(1520), S{sub 11}(1535), F{sub 15}(1680) to corresponding multipole amplitudes are stable. With this the results for D{sub 13}(1520) and F{sub 15}(1680), combined with their PDG photoexcitation helicity amplitudes, allowed us to find the branching ratios Br (D{sub 13}(1520) {yields} {eta}N) = 0.05 {+-} 0.02%, Br (F{sub 15}(1680) {yields} {eta} N) = 0.16 {+-} 0.04% which have significantly better accuracy than the PDG data. The total Breit-Wigner width of the S{sub 11}(1535) is model-dependent, we have obtained {Gamma} (S{sub 11}(1520)) = 142 MeV and 195 MeV using dispersion relations and the isobar model, respectively. The results for the S{sub 11}(1650), D{sub 15}(1675), P{sub 11}(1710), P{sub 13}(1720) are model dependent, only the signs and orders of magnitude of their contributions to multipole amplitudes are determined. The results for the D{sub 13}(1700) are strongly model-dependent.
Date: December 1, 2003
Creator: Aznauryan, Inna
Partner: UNT Libraries Government Documents Department

The photon polarization in b -&gt; X gamma in the standard model

Description: The standard model prediction for the {bar B}{sup 0} {yields} X{sub s,d}{gamma} decay amplitude with a right-handed photon is believed to be tiny, suppressed by m{sub s,d}/m{sub b}, compared to the amplitude with a left-handed photon. We show that this suppression is fictitious: in inclusive decays, the ratio of these two amplitudes is only suppressed by g{sub s}/(4{pi}), and in exclusive decays by {Lambda}{sub QCD}/m{sub b}. The suppression is not stronger in {bar B}{sup 0} {yields} X{sub d}{gamma} decays than it is in {bar B}{sup 0} {yields} X{sub s}{gamma}. We estimate that the time dependent CP asymmetries in B {yields} K*{gamma}, {rho}{gamma}, K{sub S}{pi}{sup 0}{gamma}, and {pi}{sup +}{pi}{sup -} {gamma} are of order 0.1 and that they have significant uncertainties.
Date: December 8, 2004
Creator: Grinstein, Benjamin; Grossman, Yuval; Ligeti, Zoltan & Pirjol, Dan
Partner: UNT Libraries Government Documents Department

Observation of Secondary Plasma Waves in Laser-Plasma Interaction Experiments

Description: An experiment is described where the two products of the Langmuir Decay Instability (LDI) of a primary electron plasma wave have been observed and identified without any ambiguity. Primary Langmuir waves are driven by Stimulated Raman Scattering (SRS) of an incident laser which provides well-defined electron plasma waves. Thomson scattering of a short wavelength probe beam yields measurements of the amplitude of the waves resolved in time, space, wavelength and wavevector, that allow identification of the probed waves.
Date: December 8, 1999
Creator: Depierreux, S.; Labaune, C.; Baldis, H.A.; Fuchs, J. & Michard, A.
Partner: UNT Libraries Government Documents Department

Upper limits on the strength of periodic gravitational waves from PSR J1939+2134

Description: The first science run of the LIGO and GEO gravitational wave detectors presented the opportunity to test methods of searching for gravitational waves from known pulsars. Here we present new direct upper limits on the strength of waves from the pulsar PSR J1939+2134 using two independent analysis methods, one in the frequency domain using frequentist statistics and one in the time domain using Bayesian inference. Both methods show that the strain amplitude at Earth from this pulsar is less than a few times 10{sup -22}.
Date: December 11, 2003
Creator: al., B. Allen et
Partner: UNT Libraries Government Documents Department

Synchrotron radiation from electron beams in plasma focusing channels

Description: Spontaneous radiation emitted from relativistic electrons undergoing betatron motion in a plasma focusing channel is analyzed and application to plasma wakefield accelerator experiments and to the ion channel laser (ICL) are discussed. Important similarities and differences between a free electron laser (FEL) and an ICL are delineated. It is shown that the frequency of spontaneous radiation is a strong function of the betatron strength parameter alpha-beta, which plays a similar role to that of the wiggler strength parameter in a conventional FEL. For alpha-beta > 1, radiation is emitted in numerous harmonics. Furthermore, alpha-beta is proportional to the amplitude of the betatron orbit, which varies for every electron in the beam. The radiation spectrum emitted from an electron beam is calculated by averaging the single electron spectrum over the electron distribution. This leads to a frequency broadening of the radiation spectrum, which places serious limits on the possibility of realizing an ICL.
Date: December 6, 2001
Creator: Esarey, E.; Shadwick, B.A.; Catravas, P. & Leemans, W.P.
Partner: UNT Libraries Government Documents Department

Measurement of Beam-Spin Asymmetries for Deep Inelastic pi{sup +} Electroproduction

Description: We report the first evidence for a non-zero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic region. Data have been obtained using a polarized electron beam of 4.3 GeV and with the CLAS detector at the Thomas Jefferson National Accelerator Facility (JLab). The amplitude of the sin phi modulation increases with the momentum of the pion relative to the virtual photon, z, with an average amplitude of 0.038+/-0.005+/-0.003 for 0.5&lt;z&lt;0.8 range.
Date: December 1, 2002
Creator: Avakian, H.; Burkert, Volker D.; Elouadrhiri, Latifa & al., et.
Partner: UNT Libraries Government Documents Department

Higher twist contributions to lepton-pair production and other QCD processes

Description: A general discussion of the calculations and phenomenological consequences of power-law suppressed QCD processes is given with emphasis on tests in massive lepton pair production. Absolutely normalized predictions are given for the leading twist (transverse current) and higher twist (longitudinal current) contributions to the meson structure function in the region of large x.
Date: December 1, 1982
Creator: Brodsky, S.J.; Berger, E.L. & Lepage, G.P.
Partner: UNT Libraries Government Documents Department

Introduction to conformal field theory and string theory

Description: These lectures are meant to provide a brief introduction to conformal field theory (CFT) and string theory for those with no prior exposure to the subjects. There are many excellent reviews already available, and most of these go in to much more detail than I will be able to here. 52 refs., 11 figs.
Date: December 1, 1989
Creator: Dixon, L.J.
Partner: UNT Libraries Government Documents Department