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A Dynamical Solution To The Problem Of A Small Cosmological Constant And Late-Time Cosmic Acceleration, Christian Armendariz-Picon, V. Mukhanov, Paul J. Steinhardt Apr 2000

A Dynamical Solution To The Problem Of A Small Cosmological Constant And Late-Time Cosmic Acceleration, Christian Armendariz-Picon, V. Mukhanov, Paul J. Steinhardt

Physics - All Scholarship

Increasing evidence suggests that most of the energy density of the universe consists of a dark energy component with negative pressure, a ``cosmological constant" that causes the cosmic expansion to accelerate. In this paper, we address the puzzle of why this component comes to dominate the universe only recently rather than at some much earlier epoch. We present a class of theories based on an evolving scalar field where the explanation is based entirely on internal dynamical properties of the solutions. In the theories we consider, the dynamics causes the scalar field to lock automatically into a negative pressure state …

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Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell Apr 2000

Reducing The Complexity Of Linear Optics Quantum Circuits, John C. Howell, John A. Yeazell

Mathematics, Physics, and Computer Science Faculty Articles and Research

Integrated optical elements can simplify the linear optics used to simulate quantum circuits. These linear optical simulations of quantum circuits have been developed primarily in terms of the free space optics associated with single-photon interferometry. For an L-bit simulation the number of required free-space optical elements is ∝2L if 50/50 beam splitters are used. The implementation (construction and alignment) of these circuits with these free-space elements is nontrivial. On the other hand, for the cases presented in this paper in which linear integrated optics (e.g., 2L×2L fiber couplers) are used, the number of optical devices does …

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Dense And Relativistic Plasmas Produced By Compact High-Intensity Lasers, Donald Umstadter, Shouyuan Chen, G. Ma, Anatoly Maksimchuk, G. Mourou, M. Nantel, S. Pikuz, G. Sarkisov, R. Wagner Apr 2000

Dense And Relativistic Plasmas Produced By Compact High-Intensity Lasers, Donald Umstadter, Shouyuan Chen, G. Ma, Anatoly Maksimchuk, G. Mourou, M. Nantel, S. Pikuz, G. Sarkisov, R. Wagner

Donald Umstadter Publications

High-intensity lasers interacting with plasmas are used to study processes in the laboratory that would otherwise only occur in astrophysics. These include relativistic plasmas, electron acceleration in ultrahigh Ðeld-gradient wake Ðelds, pressure ionization and continuum lowering in strongly coupled plasmas, and X-ray line emission via Raman scattering.

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Reply To ‘‘Comment On ‘Dynamically Maintained Steady-State Pressure Gradients’ ’’, D. P. Sheehan Apr 2000

Reply To ‘‘Comment On ‘Dynamically Maintained Steady-State Pressure Gradients’ ’’, D. P. Sheehan

Physics and Biophysics: Faculty Scholarship

A reply is made to Duncan’s Comment [T. L. Duncan, Phys. Rev. E 61, 4661 (2000)] on my earlier paper [D. P. Sheehan, Phys. Rev. E 57, 6660 (1998)] in which he raises an apparent second-law paradox arising from dynamically maintained, steady-state pressure gradients. Resolutions to this paradox are considered in light of current theoretical and experimental understanding.

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On The Main Irradiation-Induced Defect In Gan, L. Polenta, Z-Q. Fang, David C. Look Apr 2000

On The Main Irradiation-Induced Defect In Gan, L. Polenta, Z-Q. Fang, David C. Look

Physics Faculty Publications

We show that the usual Arrhenius analysis of the main electron-irradiation-induced defect trap in n-type GaN, observed by deep-level transient spectroscopy (DLTS), is not sufficiently accurate. Instead, an exact fitting of the DLTS spectrum for this trap reveals two components, each of which has a thermal energy near 60 meV, not the apparent 140–200 meV, as given in other DLTS studies. This result resolves the discrepancy between Hall-effect and DLTS determinations of the thermal energy of this defect center.

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Precision Measurement Of The Spin Structure Of The Proton And The Deuteron, Frank R. Wesselmann Apr 2000

Precision Measurement Of The Spin Structure Of The Proton And The Deuteron, Frank R. Wesselmann

Physics Theses & Dissertations

Experiment E155 at the Stanford Linear Accelerator Center measured the spin structure functions g1 and g2 of the proton and deuteron using deep inelastic scattering of 50 GeV polarized electrons from dynamically polarized, solid 15NH3 and 6LiD targets. Three independent spectrometers, covering a large kinematic region, 0.014 < xBjorken < 0.9 and 1 < Q2 < 40 (GeV /c)2, detected 200 million events. A fully self-consistent and statistically sound approach to calculating radiative corrections was developed, providing well-defined statistical errors for the E155 data set. Also, a comprehensive fit to the global data set was created which simultaneously …

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Divalent Metal Binding Properties Of The Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Brian Bennett, Alicja J. Copik, Richard C. Holz Apr 2000

Divalent Metal Binding Properties Of The Methionyl Aminopeptidase From Escherichia Coli, Ventris M. D'Souza, Brian Bennett, Alicja J. Copik, Richard C. Holz

Physics Faculty Research and Publications

The metal-binding properties of the methionyl aminopeptidase from Escherichia coli (MetAP) were investigated. Measurements of catalytic activity as a function of added Co(II) and Fe(II) revealed that maximal enzymatic activity is observed after the addition of only 1 equiv of divalent metal ion. Based on these studies, metal binding constants for the first metal binding event were found to be 0.3 ± 0.2 μM and 0.2 ± 0.2 μM for Co(II)- and Fe(II)-substituted MetAP, respectively. Binding of excess metal ions (>50 equiv) resulted in the loss of ∼50% of the catalytic activity. Electronic absorption spectral titration of a 1 …

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Holographic Optical Tweezers: Development And Analysis Of The First Holodeck Prototype, Matthew T. Dearing '00 Apr 2000

Holographic Optical Tweezers: Development And Analysis Of The First Holodeck Prototype, Matthew T. Dearing '00

Honors Projects

Tightly focused light can be used to non-invasively trap and manipulate micro-objects, a technique called "optical tweezing." By utilizing the large field gradients present in a focused laser beam, micro-particles-including biological specimens and many other materials-can become confined in all three dimensions. While optical tweezing has existed for over a decade, it has generally been limited to trapping one or two particles at a time. We have developed a technique that uses laser light to assemble large numbers of micro-particles in a highly controllable way. Here we describe, for the first time, the complete implementation of holographic optical tweezer arrays …

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Wavelength Modulation Spectroscopy Of Water Vapor And Line Center Stabilization At 1.462 Μm For Lidar Applications, Colleen Marie Fitzgerald Apr 2000

Wavelength Modulation Spectroscopy Of Water Vapor And Line Center Stabilization At 1.462 Μm For Lidar Applications, Colleen Marie Fitzgerald

Electrical & Computer Engineering Theses & Dissertations

Wavelength modulation spectroscopy was employed to investigate water vapor absorption lines in the 1.462 µm wavelength region using an external-cavity diode laser. These measurements were necessary in the development of a lidar (light detection and ranging) instrument for differential absorption measurement of the concentration and movement of water vapor in the Earth's atmosphere. Differential absorption measurements require that the laser frequency remain stable throughout the duration of the measurement. To ensure this stability, the laser output wavelength is monitored and a feedback control loop set up to minimize laser line drift. Three lines were investigated in the 1.462 µm region. …

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Measurement Of Sin 2Β From B→J/ΨKS0 With The Cdf Detector, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Apr 2000

Measurement Of Sin 2Β From B→J/ΨKS0 With The Cdf Detector, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

This paper reports an updated measurement of the standard model CP violation parameter sin 2β using the CDF Detector at Fermilab. The entire run I data sample of 110 pb-1 of proton-antiproton collisions at √s =1.8 TeV is used to identify a signal sample of ≈400 B→J/ ψKs0 events, where J/ψ→ μ+μ- and Ks0→ π+ π-. The flavor of the neutral B meson is identified at the time of production by combining information from three tagging algorithms: a same-side tag, a jet-charge tag, …

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Generalized Compton Amplitudes In Quantum Chromodynamics, Ignati Grigentch Apr 2000

Generalized Compton Amplitudes In Quantum Chromodynamics, Ignati Grigentch

Physics Theses & Dissertations

In this dissertation we describe results of our studies of generalized Compton amplitudes. We have calculated the one-loop corrections to the amplitude in the coordinate representation in terms of nonlocal string light-ray operators. We have also developed a consistent approach to the problem of constructing the gauge invariant Compton amplitude and obtained an expression for the explicitly gauge invariant amplitude which includes all the generalized target-mass corrections.

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Properties Of Dust Grains In Planetary Nebulae. I. The Ionized Region Of Ngc 6445, Peter A. M. Van Hoof, Griet C. Van De Steene, Douwe A. Beintema, P. G. Martin, Stuart R. Pottasch, Gary J. Ferland Mar 2000

Properties Of Dust Grains In Planetary Nebulae. I. The Ionized Region Of Ngc 6445, Peter A. M. Van Hoof, Griet C. Van De Steene, Douwe A. Beintema, P. G. Martin, Stuart R. Pottasch, Gary J. Ferland

Physics and Astronomy Faculty Publications

One of the factors influencing the spectral evolution of a planetary nebula is the fate of the dust grains that are emitting the infrared continuum. Several processes have been proposed that either destroy the grains or remove them from the ionized region. To test whether these processes are effective, we study new infrared spectra of the evolved nebula NGC 6445. These data show that the thermal emission from the grains is very cool and has a low flux compared to Hβ. A model of the ionized region is constructed, using the photoionization code CLOUDY 90.05. Based on this model, we …

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Gravitational Particle Production And The Moduli Problem, Gary Felder, Lev Kofman, Andrei Linde Mar 2000

Gravitational Particle Production And The Moduli Problem, Gary Felder, Lev Kofman, Andrei Linde

Physics: Faculty Publications

A theory of gravitational production of light scalar particles during and after inflation is investigated. We show that in the most interesting cases where long-wavelength fluctuations of light scalar fields can be generated during inflation, these fluctuations rather than quantum fluctuations produced after inflation give the dominant contribution to particle production. In such cases a simple analytical theory of particle production can be developed. Application of our results to the theory of quantum creation of moduli fields demonstrates that if the moduli mass is smaller than the Hubble constant then these fields are copiously produced during inflation. This gives rise …

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Production Of ϒ(1s) Mesons From ΧB Decays In Pp̅ Collisions At √S = 1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration Mar 2000

Production Of ϒ(1s) Mesons From ΧB Decays In Pp̅ Collisions At √S = 1.8 Tev, T. Affolder, Kenneth A. Bloom, Collider Detector At Fermilab Collaboration

Kenneth Bloom Publications

We have reconstructed the radiative decays χ b(1P) → Υ (1S) γ and χb(2P) → Υ (1S) γ in pp̅ collisions at √s = 1.8 TeV, and measured the fraction of Υ(1S) mesons that originate from these decays. For Υ(1S) mesons with pTY > 8.0 GeV/c, the fractions that come from χ b(1P) and χb(2P) decays are [27.1 ± 6.9(stat) ± 4.4(syst)]% and [10.5 ± 4.4(stat) ± 1.4(syst)]%, respectively. We have derived the fraction of directly produced Υ(1S) mesons to be [50.9 ± 8.2(stat) ± 9.0(syst)]%.

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Energetic Magnetosheath Ions Connected To The Earth's Bow Shock: Possible Source Of Cusp Energetic Ions, S. W. Chang, J. D. Scudder, J. F. Fennell, R. Friedel, R. P. Lepping, C. T. Russell, K. J. Trattner, S. A. Fuselier, W. K. Peterson, Harlan E. Spence Mar 2000

Energetic Magnetosheath Ions Connected To The Earth's Bow Shock: Possible Source Of Cusp Energetic Ions, S. W. Chang, J. D. Scudder, J. F. Fennell, R. Friedel, R. P. Lepping, C. T. Russell, K. J. Trattner, S. A. Fuselier, W. K. Peterson, Harlan E. Spence

Physics & Astronomy

No abstract provided.

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Parity Violation In Neutron Resonances In 115in, Sharon L. Stephenson, J D. Bowman, J Corvi, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, H M. Shimizu, Y-F Yen, V W. Yuan, L Zanini Mar 2000

Parity Violation In Neutron Resonances In 115in, Sharon L. Stephenson, J D. Bowman, J Corvi, Bret E. Crawford, P P J. Delheij, C M. Frankle, M Iinuma, J N. Knudsen, L Y. Lowie, A Masaike, Y Matsuda, G E. Mitchell, S I. Penttila, H Postma, N R. Roberson, S J. Seestrom, E I. Sharapov, H M. Shimizu, Y-F Yen, V W. Yuan, L Zanini

Physics and Astronomy Faculty Publications

Parity nonconservation (PNC) was studied in p-wave resonances in indium by measuring the helicity dependence of the neutron total cross section in the neutron energy range 6.0–316 eV with the time-of-flight method at LANSCE. A total of 36 p-wave neutron resonances were studied in 115In, and statistically significant asymmetries were observed for nine cases. An analysis treating the PNC matrix elements as random variables yields a weak matrix element of M=(0.67-0.12+0.16) meV and a weak spreading width of Γw=(1.30-0.43+0.76)×10-7 eV.

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Structural And Electronic Properties Of Cobalt/Alumina Tunnel Junctions From First Principles, Ivan I. Oleinik, Evgeny Y. Tsymbal, David G. Pettifor Mar 2000

Structural And Electronic Properties Of Cobalt/Alumina Tunnel Junctions From First Principles, Ivan I. Oleinik, Evgeny Y. Tsymbal, David G. Pettifor

Evgeny Tsymbal Publications

A detailed first-principles study of the atomic and electronic structure of the Co/Al2O3/Co magnetic tunnel junction has been performed in order to elucidate the key features determining the spin-dependent tunneling. The atomic structure of the multilayer with the O- and Al-terminated interfaces between fcc Co(111) and crystalline α-Al2O3(0001) has been optimized using self-consistent spin-polarized calculations within densityfunctional theory and the generalized gradient approximation. We found that the relaxed atomic structure of the O-terminated interface is characterized by a rippling of the Co interfacial plane, the average Co-O bond length being 2.04 Å …

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Electric-Octupole And Pure-Electric-Quadrupole Effects In Soft X-Ray Photoemission, Andrei Derevianko, Oliver Hemmers, S. Oblad, P. Glans, H. Wang, S. B. Whitfield, R. Wehlitz, I. A. Sellin, W. R. Johnson, Dennis W. Lindle Mar 2000

Electric-Octupole And Pure-Electric-Quadrupole Effects In Soft X-Ray Photoemission, Andrei Derevianko, Oliver Hemmers, S. Oblad, P. Glans, H. Wang, S. B. Whitfield, R. Wehlitz, I. A. Sellin, W. R. Johnson, Dennis W. Lindle

Environmental Studies Faculty Publications

Second-order [O(k2), k = ω/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100–1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms. Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.

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Classical Versus Quantum Dynamics For A Driven Relativistic Oscillator, Rainer Grobe, Qichang Su, P J. Peverly, R E. Wagner Mar 2000

Classical Versus Quantum Dynamics For A Driven Relativistic Oscillator, Rainer Grobe, Qichang Su, P J. Peverly, R E. Wagner

Faculty publications – Physics

We compare the time evolution of the quantum-mechanical spatial probability density obtained by solving the time-dependent Dirac equation with its classical counterpart obtained from the relativistic Liouville equation for the phase-space density in a regime in which the dynamics is essentially relativistic. For a resonantly driven one-dimensional harmonic oscillator, the simplest nontrivial model system to perform this comparison, we find that, despite the nonlinearity induced by relativity, the classical ensemble description matches the quantum evolution remarkably well.

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A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day Mar 2000

A High Energy X-Ray And Neutron Scattering Study Of Iron Phosphate Glasses Containing Uranium, Mevlüt Karabulut, G. K. Marasinghe, C. S. Ray, Y. S. Badyal, M.-L. Saboungi, S. Shastri, D. Haeffner, George Daniel Waddill, D. E. Day

Materials Science and Engineering Faculty Research & Creative Works

The atomic structure of iron phosphate glasses containing uranium has been studied by complementary neutron and x-ray scattering techniques. by combining x-ray and neutron structure factors, detailed information about different pair interactions has been obtained. Most of the basic structural features such as coordination numbers and O-O and P-O distances in uranium containing glasses are the same as those in the base glass of batch composition 40Fe2O3-60P2O5 (mol %). However, the Fe-O distances change slightly with the addition of uranium. The observed structural parameters support a structural model in which the waste elements occupy voids in the Fe-O-P network, hence, …

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Testing Of The New Usgs K Index Algorithm At Bear Lake Observatory, Ariel O. Acebal Mar 2000

Testing Of The New Usgs K Index Algorithm At Bear Lake Observatory, Ariel O. Acebal

Theses and Dissertations

The K index was developed by Bartels in 1939 as an estimate of the level of geomagnetic activity caused by the Sun. This index was computed manually every three hours at geomagnetic observatories using the magnetic traces of the surface planetary magnetic field. In 1991, the International Association of Geomagnetism and Aeronomy approved four additional methods to compute the K index; all of them were computer algorithms. One of the approved methods, the Wilson code, recently underwent some modifications. The new algorithm is now part of a Windows-based computer program being developed by the United States Geological Survey (USGS). After …

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Multi-Conjugate Adaptive Optics For The Compensation Of Amplitude And Phase Distortions, Peter N. Crabtree Mar 2000

Multi-Conjugate Adaptive Optics For The Compensation Of Amplitude And Phase Distortions, Peter N. Crabtree

Theses and Dissertations

Two deformable mirrors (DMs) with finite conjugate ranges are investigated for compensating amplitude and phase distortions due to laser propagation through turbulent atmospheres. Simulations are performed based on Adaptive Optics (AO) for an Airborne Laser-type scenario. The Strehl ratio, the number of branch points in DM controls, and the number of iterations to convergence are used as figures of merit to evaluate performance of the Sequential Generalized Projection Algorithm that generates mirror commands. The results are ensemble averages over 32 realizations of the scintillated test fields for each value of the Rytov parameter within the test scenario. The Gaussian beam …

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Optical Investigation Of Molecular Beam Epitaxy AlXGa1-XN To Determine Material Quality, Judith L. Mcfall Mar 2000

Optical Investigation Of Molecular Beam Epitaxy AlXGa1-XN To Determine Material Quality, Judith L. Mcfall

Theses and Dissertations

The purpose of this research was to determine the quality of AIGaN samples with various mole fractions of aluminum doped with silicon. The samples utilized for this study were composed of an AIN buffer layer sandwiched between the sapphire substrate and AIGaN epilayer grown by molecular beam epitaxy (MBE). Cathodoluminescence (CL) and photoluminescence (PL) were employed to determine the mole fraction of aluminum in each sample. These techniques also gave insight into the material's nonuniformity, defects, and impurities. CL was run at 4 different beam energies (2,5,10, & 15 keV) with four different currents (1,10,50, & 90 µA) for the …

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Temperature Determination In An I2 Gas Using Dopper-Limited Saturation Spectroscopy, James W. Myers Jr. Mar 2000

Temperature Determination In An I2 Gas Using Dopper-Limited Saturation Spectroscopy, James W. Myers Jr.

Theses and Dissertations

Saturation spectroscopy techniques were used to demonstrate the ability to make spatially resolved temperature measurements by exploiting the B3 ∏(O+u) - X1 Σ ;(O+g) electronic transition in molecular iodine (I2). Doppler-free saturation spectroscopy measurements resulted in hyperfine spectral profiles for the P(7O) 17-1 and P(53) 19-2 ro-vibrational transitions between the electronic levels. Doppler-limited saturation spectroscopy, an adaptation of the Doppler-free technique in which beams propagate in the same direction and cross within the gas sample, allowed for the measurement of spatially resolved Doppler profiles for the same transitions. The profiles were measured …

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Collection Of Detonation Signatures And Characterization Of Spectral Features, Jay A. Orson Mar 2000

Collection Of Detonation Signatures And Characterization Of Spectral Features, Jay A. Orson

Theses and Dissertations

The remote observations of the temporal and spectral characteristics of the infrared (IR) emissions from exploding ordnance have been correlated with explosion conditions. A Bomem MR-154 Fourier Transform Interferometer with two detectors, InSb and HgCdTe, and a 75 mrad telescope was used to record spectra in the 1.3 - 20 µm range. Data was collected at spectral resolutions of 16 cm-1 and 4 cm-1 and temporal resolutions of 0.045 s and 0.123 s respectively. Two field tests were conducted: (1) a set of dynamic drop explosions and (2) a series of static detonations. In most events, the temporal …

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Active Multispectral Bidirectional Reflectance Distribution Function Measurement System, Mark J. Proctor Mar 2000

Active Multispectral Bidirectional Reflectance Distribution Function Measurement System, Mark J. Proctor

Theses and Dissertations

Today's highly technical battlefield environment dictates the need for a method of standoff target identification, which reduces risk to personnel and equipment. It is widely known that a given material will react differently to incident radiation than a dissimilar material. Certain materials may respond specularly while others tend to be diffuse. By measuring these responses, materials can be identified by comparison with a known database. One method of building such a database for target recognition is by employing an active multi spectral bidirectional reflectance distribution function (BRDF) measurement system. In the following text, such a system is developed and tested …

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Atmospheric Temperature Profiles By Ground-Based Infrared Spectrometer Measurements, Jon M. Saul Mar 2000

Atmospheric Temperature Profiles By Ground-Based Infrared Spectrometer Measurements, Jon M. Saul

Theses and Dissertations

A method to recover atmospheric temperature profiles using a ground-based Fourier Transform Infrared spectrometer was investigated. The method used a difference form of the radiative transfer equation, a Bomem MR series Fourier Transform Infrared Spectrometer to collect atmospheric radiance values, and the Phillips Laboratory Expert- assisted User Software (PLEXUS) atmospheric radiance model, to recover an atmospheric temperature profile. The method researched uses radiance values from both the spectrometer measurements and the atmospheric model, along with kernel functions calculated by the atmospheric model as input to a difference form of the radiation transfer equation. From this the change in brightness temperatures …

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Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner Mar 2000

Optical Metrology Of Adaptive Membrane Mirrors, John W. Wagner

Theses and Dissertations

Current space-based imaging platforms are significantly constrained in both size and weight by the launch vehicle. Increased payload size and weight results in increased cost and a decrease in launch responsiveness. The USAF Scientific Advisory Board (SAB) identified "Large lightweight structures for optics and antennas" as a revolutionary primary technology to be developed for the Air Force of the 21st Century. A membrane primary mirror in a space-based imaging system has the ability to overcome current payload constraints and meet evolutionary needs of the future. The challenge of membrane optics in space is the process of implementing adaptive optics technology …

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Topologically Ordered Phases Of Smectics Confined In Anisotropic Random Media: Smectic Bragg Glasses, Karl Saunders, Brad Jacobsen, Leo Radzihovsky, John Toner Feb 2000

Topologically Ordered Phases Of Smectics Confined In Anisotropic Random Media: Smectic Bragg Glasses, Karl Saunders, Brad Jacobsen, Leo Radzihovsky, John Toner

Physics

We report the existence of two new topologically ordered glass phases of smectics in strained aerogel. In contrast to the case of unstrained aerogel, we find compelling theoretical arguments that a smectic in uniaxially stretched aerogel exhibits, for homeotropic nematic-aerogel alignment, a `smectic Bragg glass' in the universality class of the `XY Bragg glass'. On the other hand, a uniaxial compression, with homeotropic alignment, leads to an entirely novel type of anisotropic smectic elastic glass phase that we call the `m = 1 Bragg glass'. This latter phase exhibits anomalous elasticity, characterized by exponents that we calculate to high precision. …

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Measurement Of The E(T,Jet)/ 2 /Q 2 Dependence Of Forward-Jet Production At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti Feb 2000

Measurement Of The E(T,Jet)/ 2 /Q 2 Dependence Of Forward-Jet Production At Hera, J. Breitweg, S. Chekanov, M. Derrick, D. Krakauer, S. Magill, B. Musgrave, A. Pellegrino, J. Repond, R. Stanek, R. Yoshida, Margarita C. K. Mattingly, G. Abbiendi, 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, N. Coppola, M. Corradi, S. De Pasquale, P. Giusti, G. Iacobucci, G. Laurenti

Faculty Publications

The forward-jet cross section in deep inelastic e + p scattering has been measured using the ZEUS detector at HERA with an integrated luminosity of 6.36 pb -1 . The jet cross section is presented as a function of jet transverse energy squared, E(T,jet)/ 2 , and Q 2 in the kinematic ranges 10 -2 < E(T,jet)/ 2 /Q 2 < 10 2 and 2.5 · 10 -4 < x < 8.0 · 10 -2 . Since the perturbative QCD predictions for this cross section are sensitive to the treatment of the log(E(T,jet)/ 2 /Q2) terms, this measurement provides an important test. The measured cross section is compared to the predictions of a next-to-leading order pQCD calculation as well as to various leading-order Monte Carlo models. Whereas the predictions of all models agree with the measured cross section in the region of small E(T,jet/ 2 /Q 2 only one model, which includes a resolved photon component, describes the data over the whole kinematic range. (C) 2000 Elsevier Science B.V.

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