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Full-Text Articles in Physics
Measurement Of The Beam Asymmetry Sigma For Pi(0) And Eta Photoproduction On The Proton At E-Gamma=9 Gev, H. Al Ghoul, (...), Justin R. Stevens, Et Al.
Measurement Of The Beam Asymmetry Sigma For Pi(0) And Eta Photoproduction On The Proton At E-Gamma=9 Gev, H. Al Ghoul, (...), Justin R. Stevens, Et Al.
Arts & Sciences Articles
We report measurements of the photon beam asymmetry Sigma for the reactions (gamma) over right arrowp -> p pi(0) and gamma p -> p eta from the GLUEX experiment using a 9 GeV linearly polarized, tagged photon beam incident on a liquid hydrogen target in Jefferson Lab's Hall D. The asymmetries, measured as a function of the proton momentum transfer, possess greater precision than previous pi(0) measurements and are the first. measurements in this energy regime. The results are compared with theoretical predictions based on t-channel, quasiparticle exchange and constrain the axial-vector component of the neutral meson production mechanism in …
Isoscalar Pi Pi Scattering And The Sigma Meson Resonance From Qcd, Raul A. Briceño, Jozef J. Dudek, Robert G. Edwards, David J. Wilson
Isoscalar Pi Pi Scattering And The Sigma Meson Resonance From Qcd, Raul A. Briceño, Jozef J. Dudek, Robert G. Edwards, David J. Wilson
Arts & Sciences Articles
We present for the first time a determination of the energy dependence of the isoscalar pi pi elastic scattering phase shift within a first-principles numerical lattice approach to QCD. Hadronic correlation functions are computed including all required quark propagation diagrams, and from these the discrete spectrum of states in the finite volume defined by the lattice boundary is extracted. From the volume dependence of the spectrum, we obtain the S-wave phase shift up to the K (K) over bar threshold. Calculations are performed at two values of the u, d quark mass corresponding to m(pi) = 236; 391 MeV, and …
Q(Weak): First Direct Measurement Of The Proton's Weak Charge, J. F. Dowd
Q(Weak): First Direct Measurement Of The Proton's Weak Charge, J. F. Dowd
Arts & Sciences Articles
The Q(weak) experiment, which took data at Jefferson Lab in the period 2010 - 2012, will precisely determine the weak charge of the proton by measuring the parity-violating asymmetry in elastic e-p scattering at 1.1 GeV using a longitudinally polarized electron beam and a liquid hydrogen target at a low momentum transfer of Q(2) = 0.025 ( GeV/c)(2). The weak charge of the proton is predicted by the Standard Model and any significant deviation would indicate physics beyond the Standard Model. The technical challenges and experimental apparatus for measuring the weak charge of the proton will be discussed, as well …
Multispectrum Analysis Of The Oxygen A-Band, Brian J. Drouin, D. Chris Benner, Linda R. Brown, (...), V. Malathy Devi, Et Al.
Multispectrum Analysis Of The Oxygen A-Band, Brian J. Drouin, D. Chris Benner, Linda R. Brown, (...), V. Malathy Devi, Et Al.
Arts & Sciences Articles
Retrievals of atmospheric composition from near-infrared measurements require measurements of airmass to better than the desired precision of the composition. The oxygen bands are obvious choices to quantify airmass since the mixing ratio of oxygen is fixed over the full range of atmospheric conditions. The OCO-2 mission is currently retrieving carbon dioxide concentration using the oxygen A-band for airmass normalization. The 0.25% accuracy desired for the carbon dioxide concentration has pushed the required state-of-the-art for oxygen spectroscopy. To measure 02 A-band cross-sections with such accuracy through the full range of atmospheric pressure requires a sophisticated line shape model (Rautian or …
Analysis Of Drift Effects On The Tokamak Power Scrape-Off Width Using Solps-Iter, E. T. Meier, R. J. Goldston, E. G. Kaveeva, M. A. Makowski, Saskia Mordijck, V. A. Rozhansky, I. Yu Senichenkov, S. P. Voskoboynikov
Analysis Of Drift Effects On The Tokamak Power Scrape-Off Width Using Solps-Iter, E. T. Meier, R. J. Goldston, E. G. Kaveeva, M. A. Makowski, Saskia Mordijck, V. A. Rozhansky, I. Yu Senichenkov, S. P. Voskoboynikov
Arts & Sciences Articles
SOLPS-ITER, a comprehensive 2D scrape-off layer modeling package, is used to examine the physical mechanisms that set the scrape-off width (lambda(q)) for inter-ELM power exhaust. Guided by Goldston's heuristic drift (HD) model, which shows remarkable quantitative agreement with experimental data, this research examines drift effects on lambda(q) in a DIII-D H-mode magnetic equilibrium. As a numerical expedient, a low target recycling coefficient of 0.9 is used in the simulations, resulting in outer target plasma that is sheath limited instead of conduction limited as in the experiment. Scrape-off layer (SOL) particle diffusivity (D-SOL) is scanned from 1 to 0.1 m(2) s(-1). …
Enhanced Superconductivity In Aluminum-Based Hyperbolic Metamaterials, Vera N. Smolyaninova, Christopher Jensen, William Zimmerman, (...), M. M. Qazilbash, Et Al.
Enhanced Superconductivity In Aluminum-Based Hyperbolic Metamaterials, Vera N. Smolyaninova, Christopher Jensen, William Zimmerman, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
One of the most important goals of condensed matter physics is materials by design, i.e. the ability to reliably predict and design materials with a set of desired properties. A striking example is the deterministic enhancement of the superconducting properties of materials. Recent experiments have demonstrated that the metamaterial approach is capable of achieving this goal, such as tripling the critical temperature T-C in Al-Al2O3 epsilon near zero (ENZ) core-shell metamaterial superconductors. Here, we demonstrate that an Al/Al2O3 hyperbolic metamaterial geometry is capable of a similar T-C enhancement, while having superior transport and magnetic properties compared to the core-shell metamaterial …
Role Of Electron-Electron Interactions In The Charge Dynamics Of Rare-Earth-Doped Cafe2as2, Zhen Xing, T. J. Huffman, Peng Xu, (...), M. M. Qazilbash, Et Al.
Role Of Electron-Electron Interactions In The Charge Dynamics Of Rare-Earth-Doped Cafe2as2, Zhen Xing, T. J. Huffman, Peng Xu, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We have investigated the charge dynamics and the nature of many-body interactions in La- and Pr-doped CaFe2As2. From the infrared part of the optical conductivity, we discover that the scattering rate of mobile carriers above 200 K exhibits saturation at the Mott-Ioffe-Regel limit of metallic transport. However, the dc resistivity continues to increase with temperature above 200 K due to the loss of Drude spectral weight. The loss of Drude spectral weight with increasing temperature is seen in a wide temperature range in the uncollapsed tetragonal phase, and this spectral weight is recovered at energy scales about one order of …
Line Parameters Including Temperature Dependences Of Air- And Self-Broadened Line Shapes Of (Co2)-C-12-O-16: 2.06-Mu M Region, D. Chris Benner, V. Malathy Devi, Keeyoon Sung, Linda R. Brown, Et Al.
Line Parameters Including Temperature Dependences Of Air- And Self-Broadened Line Shapes Of (Co2)-C-12-O-16: 2.06-Mu M Region, D. Chris Benner, V. Malathy Devi, Keeyoon Sung, Linda R. Brown, Et Al.
Arts & Sciences Articles
This study reports the results from analyzing a number of high resolution, high signal-to-noise ratio (S/N) spectra in the 2.06-μm spectral region for pure CO2 and mixtures of CO2 in dry air. A multispectrum nonlinear least squares curve fitting technique has been used to retrieve the various spectral line parameters. The dataset includes 27 spectra: ten pure CO2, two 99% 13C-enriched CO2 and fifteen spectra of mixtures of 12C-enriched CO2 in dry air. The spectra were recorded at various gas sample temperatures between 170 and 297 K. The absorption path lengths range from 0.347 to 49 m. The sample pressures …
Controlling Excited-State Contamination In Nucleon Matrix Elements, Boram Yoon, Rajan Gupta, (...), Kostas Orginos, Et Al.
Controlling Excited-State Contamination In Nucleon Matrix Elements, Boram Yoon, Rajan Gupta, (...), Kostas Orginos, Et Al.
Arts & Sciences Articles
We present a detailed analysis of methods to reduce statistical errors and excited-state contamination in the calculation of matrix elements of quark bilinear operators in nucleon states. All the calculations were done on a 2 + 1-flavor ensemble with lattices of size 32(3) x 64 generated using the rational hybrid Monte Carlo algorithm at a = 0.081 fm and with M-pi = 312 MeV. The statistical precision of the data is improved using the all-mode-averaging method. We compare two methods for reducing excited-state contamination: a variational analysis and a 2-state fit to data at multiple values of the source-sink separation …
Turbulent Particle Transport As A Function Of Toroidal Rotation In Diii-D H-Mode Plasmas, X. Wang, Saskia Mordijck, L. Zeng, L. Schmitz, Et Al.
Turbulent Particle Transport As A Function Of Toroidal Rotation In Diii-D H-Mode Plasmas, X. Wang, Saskia Mordijck, L. Zeng, L. Schmitz, Et Al.
Arts & Sciences Articles
In this paper we show how changes in toroidal rotation, by controlling the injected torque, affect particle transport and confinement. The toroidal rotation is altered using the co- and counter neutral beam injection (NBI) in low collisionality H-mode plasmas on DIII-D (Luxon 2002 Nucl. Fusion 42 614) with dominant electron cyclotron heating (ECH). We find that there is no correlation between the toroidal rotation shear and the inverse density gradient, which is observed on AUG when T-e/T-i is varied using ECH (Angioni et al 2011 Phys. Rev. Lett. 107 215003). In DIII-D, we find that in a discharge with balanced …
A Sonic Net Excludes Birds From An Airfield: Implications For Reducing Bird Strike And Crop Losses, John P. Swaddle, Dana L. Moseley, Mark H. Hinders, Elizabeth P. Smith
A Sonic Net Excludes Birds From An Airfield: Implications For Reducing Bird Strike And Crop Losses, John P. Swaddle, Dana L. Moseley, Mark H. Hinders, Elizabeth P. Smith
Arts & Sciences Articles
Collisions between birds and aircraft cause billions of dollars of damages annually to civil, commercial, and military aviation. Yet technology to reduce bird strike is not generally effective, especially over longer time periods. Previous information from our lab indicated that filling an area with acoustic noise, which masks important communication channels for birds, can displace European Starlings (Sturnus vulgaris) from food sources. Here we deployed a spatially controlled noise (termed a “sonic net”), designed to overlap with the frequency range of bird vocalizations, at an airfield. By conducting point counts, we monitored the presence of birds for four …
Unitary Limit Of Two-Nucleon Interactions In Strong Magnetic Fields, William Detmold, Kostas Orginos, Assumpta Parreño, Martin J. Savage, Et Al.
Unitary Limit Of Two-Nucleon Interactions In Strong Magnetic Fields, William Detmold, Kostas Orginos, Assumpta Parreño, Martin J. Savage, Et Al.
Arts & Sciences Articles
Two-nucleon systems are shown to exhibit large scattering lengths in strong magnetic fields at unphysical quark masses, and the trends toward the physical values indicate that such features may exist in nature. Lattice QCD calculations of the energies of one and two nucleons systems are performed at pion masses of mπ∼450 and 806 MeV in uniform, time-independent magnetic fields of strength |B|∼1019–1020 G to determine the response of these hadronic systems to large magnetic fields. Fields of this strength may exist inside magnetars and in peripheral relativistic heavy ion collisions, and the unitary behavior at large scattering lengths may have …
Effects Of Resonant Magnetic Perturbations On Turbulence And Transport In Diii-D L-Mode Plasmas, Saskia Mordijck, T. L. Rhodes, L. Zeng, E. J. Doyle, Et Al.
Effects Of Resonant Magnetic Perturbations On Turbulence And Transport In Diii-D L-Mode Plasmas, Saskia Mordijck, T. L. Rhodes, L. Zeng, E. J. Doyle, Et Al.
Arts & Sciences Articles
In this paper we show that resonant magnetic perturbations (RMPs) affect the L- to H-mode power threshold. We find that during the L-mode phase, RMPs cause the particle pinch to reverse from traditionally inward to outward. As a result, the density at the plasma edge increases, while the density in the plasma core is reduced. Linear stability calculations indicate that the plasma transitions from an ion temperature gradient (ITG) to trapped electron mode (TEM) regime at the plasma edge. If the applied RMP current is below the threshold for penetration and island formation, we find that the changes in the …
Local, Global, And Nonlinear Screening In Twisted Double-Layer Graphene, Chih-Pin Lu, Martin Rodriguez-Vega, (...), Enrico Rossi, Et Al.
Local, Global, And Nonlinear Screening In Twisted Double-Layer Graphene, Chih-Pin Lu, Martin Rodriguez-Vega, (...), Enrico Rossi, Et Al.
Arts & Sciences Articles
One-atom-thick crystalline layers and their vertical heterostructures carry the promise of designer electronic materials that are unattainable by standard growth techniques. To realize their potential it is necessary to isolate them from environmental disturbances, in particular those introduced by the substrate. However, finding and characterizing suitable substrates, and minimizing the random potential fluctuations they introduce, has been a persistent challenge in this emerging field. Here we show that Landau-level (LL) spectroscopy offers the unique capability to quantify both the reduction of the quasiparticles' lifetime and the long-range inhomogeneity due to random potential fluctuations. Harnessing this technique together with direct scanning …
Two Nucleon Systems At M(Pi) Similar To 450 Mev From Lattice Qcd, Kostas Orginos, Assumpta Parreño, Martin J. Savage, Silas R. Beane, Et Al.
Two Nucleon Systems At M(Pi) Similar To 450 Mev From Lattice Qcd, Kostas Orginos, Assumpta Parreño, Martin J. Savage, Silas R. Beane, Et Al.
Arts & Sciences Articles
Nucleon-nucleon systems are studied with lattice quantum chromodynamics at a pion mass of m(pi) similar to 450 MeV in three spatial volumes using n(f) = 2 + 1 flavors of light quarks. At the quark masses employed in this work, the deuteron binding energy is calculated to be B-d = 14.4(-2.6)(+3.2) MeV, while the dineutron is bound by B-nn = 12.5(-5.0)(+3.0) MeV. Over the range of energies that are studied, the S-wave scattering phase shifts calculated in the S-1(0) and S-3(1)-D-3(1) channels are found to be similar to those in nature, and indicate repulsive short-range components of the interactions, consistent …
Particle Transport In Low-Collisionality H-Mode Plasmas On Diii-D, Saskia Mordijck, X. Wang, E. J. Doyle, T. L. Rhodes, Et Al.
Particle Transport In Low-Collisionality H-Mode Plasmas On Diii-D, Saskia Mordijck, X. Wang, E. J. Doyle, T. L. Rhodes, Et Al.
Arts & Sciences Articles
In this paper we show that changing from an ion temperature gradient (ITG) to a trapped electron mode (TEM) dominant turbulence regime (based on linear gyrokinetic simulations) results experimentally in a strong density pump-out (defined as a reduction in line-averaged density) in low collisionality, low power H-mode plasmas. We vary the turbulence drive by changing the heating from predominantly ion heated using neutral beam injection to electron heated using electron cyclotron heating, which changes the T-e/T-i ratio and the temperature gradients. Perturbed gas puff experiments show an increase in transport outside rho = 0.6, through a strong increase in the …
Phase Transition In Bulk Single Crystals And Thin Films Of Vo2 By Nanoscale Infrared Spectroscopy And Imaging, Mengkun Liu, Aaron J. Sternbach, (...), M. M. Qazilbash, Et Al.
Phase Transition In Bulk Single Crystals And Thin Films Of Vo2 By Nanoscale Infrared Spectroscopy And Imaging, Mengkun Liu, Aaron J. Sternbach, (...), M. M. Qazilbash, Et Al.
Arts & Sciences Articles
We have systematically studied a variety of vanadium dioxide (VO2) crystalline forms, including bulk single crystals and oriented thin films, using infrared (IR) near-field spectroscopic imaging techniques. By measuring the IR spectroscopic responses of electrons and phonons in VO2 with sub-grain-size spatial resolution (similar to 20 nm), we show that epitaxial strain in VO2 thin films not only triggers spontaneous local phase separations, but also leads to intermediate electronic and lattice states that are intrinsically different from those found in bulk. Generalized rules of strain-and symmetry-dependent mesoscopic phase inhomogeneity are also discussed. These results set the stage for a comprehensive …
Modification Of Electronic Structure In Compressively Strained Vanadium Dioxide Films, T. J. Huffman, Peng Xu, A. J. Hollingshad, M. M. Qazilbash, Et Al.
Modification Of Electronic Structure In Compressively Strained Vanadium Dioxide Films, T. J. Huffman, Peng Xu, A. J. Hollingshad, M. M. Qazilbash, Et Al.
Arts & Sciences Articles
Vanadium dioxide (VO2) undergoes a phase transition between an insulating monoclinic phase and a conducting rutile phase. Like other correlated electron systems, the properties of VO2 can be extremely sensitive to small changes in external parameters such as strain. In this paper, we investigate a compressively strained VO2 film grown on (001) quartz substrate in which the phase transition temperature (T-c) has been depressed to 325 K from the bulk value of 340 K. Infrared and optical spectroscopy reveals that the lattice dynamics of this strained film are similar to unstrained VO2. However, some of the electronic interband transitions of …
Precision Measurement Of The P(E,E ' P)Pi(0) Reaction At Threshold, K. Chirapatpimol, (...), David S. Armstrong, Et Al.
Precision Measurement Of The P(E,E ' P)Pi(0) Reaction At Threshold, K. Chirapatpimol, (...), David S. Armstrong, Et Al.
Arts & Sciences Articles
New results are reported from a measurement of pi(0) electroproduction near threshold using the p(e , e'p)pi(0) reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the. phi*(pi) and. theta*(pi) angles in the p pi(0) center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. …
Precision Measurements Of A^N1 In The Deep Inelastic Regime, Jefferson Lab Hall A Collaboration, Todd Averett
Precision Measurements Of A^N1 In The Deep Inelastic Regime, Jefferson Lab Hall A Collaboration, Todd Averett
Arts & Sciences Articles
We have performed precision measurements of the double-spin virtual-photon asymmetry A1 on the neutron in the deep inelastic scattering regime, using an open-geometry, large-acceptance spectrometer and a longitudinally and transversely polarized 3He target. Our data cover a wide kinematic range 0.277 ≤ x ≤ 0.548 at an average Q 2 value of 3.078 (GeV/c)2, doubling the available high-precision neutron data in this x range. We have combined our results with world data on proton targets to make a leading-order extraction of the ratio of polarized-to-unpolarized parton distribution functions for up quarks and for down quarks in the same kinematic range. …
The Q(Weak) Experimental Apparatus, T. Allison, (...), David S. Armstrong, Et Al.
The Q(Weak) Experimental Apparatus, T. Allison, (...), David S. Armstrong, Et Al.
Arts & Sciences Articles
The Jefferson Lab experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise (e) over right arrowp asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 mu A of 89% longitudinally polarized electrons whose helicity was reversed 960 …
Locally Smeared Operator Product Expansions In Scalar Field Theory, Christopher J. Monahan, Kostas Orginos
Locally Smeared Operator Product Expansions In Scalar Field Theory, Christopher J. Monahan, Kostas Orginos
Arts & Sciences Articles
We propose a new locally smeared operator product expansion to decompose nonlocal operators in terms of a basis of smeared operators. The smeared operator product expansion formally connects nonperturbative matrix elements determined numerically using lattice field theory to matrix elements of nonlocal operators in the continuum. These nonperturbative matrix elements do not suffer from power-divergent mixing on the lattice, which significantly complicates calculations of quantities such as the moments of parton distribution functions, provided the smearing scale is kept fixed in the continuum limit. The presence of this smearing scale complicates the connection to the Wilson coefficients of the standard …
Measurement Of Parity-Violating Asymmetry In Electron-Deuteron Inelastic Scattering, D. Wang, (...), D. S. Armstrong, Et Al.
Measurement Of Parity-Violating Asymmetry In Electron-Deuteron Inelastic Scattering, D. Wang, (...), D. S. Armstrong, Et Al.
Arts & Sciences Articles
The parity-violating asymmetries between a longitudinally polarized electron beam and an unpolarized deuterium target have been measured recently. The measurement covered two kinematic points in the deep-inelastic scattering region and five in the nucleon resonance region. We provide here details of the experimental setup, data analysis, and results on all asymmetry measurements including parity-violating electron asymmetries and those of inclusive pion production and beam-normal asymmetries. The parity-violating deep-inelastic asymmetries were used to extract the electron-quark weak effective couplings, and the resonance asymmetries provided the first evidence for quark-hadron duality in electroweak observables. These electron asymmetries and their interpretation were published …
Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin
Isotope Shifts In Francium Isotopes Fr206-213 And Fr-221, R. Collister, G. Gwinner, M. Tandecki, Seth Aubin
Arts & Sciences Articles
We present the isotope shifts of the 7s(1/2) to 7p(1/2) transition for francium isotopes Fr206-213 with reference to Fr-221 collected from two experimental periods. The shifts are measured on a sample of atoms prepared within a magneto-optical trap by a fast sweep of radio-frequency sidebands applied to a carrier laser. King plot analysis, which includes literature values for 7s(1/2) to 7p(3/2) isotope shifts, provides a field shift constant ratio of 1.0520(10) and a difference between the specific mass shift constants of 170(100) GHz amu between the D-1 and D-2 transitions, of sufficient precision to differentiate between ab initio calculations.
Matter, Energy, And Heat Transfer In A Classical Ballistic Atom Pump, Tommy A. Byrd, Kunal K. Das, Kevin Mitchell, Seth Aubin, John B. Delos
Matter, Energy, And Heat Transfer In A Classical Ballistic Atom Pump, Tommy A. Byrd, Kunal K. Das, Kevin Mitchell, Seth Aubin, John B. Delos
Arts & Sciences Articles
A ballistic atom pump is a system containing two reservoirs of neutral atoms or molecules and a junction connecting them containing a localized time-varying potential. Atoms move through the pump as independent particles. Under certain conditions, these pumps can create net transport of atoms from one reservoir to the other. While such systems are sometimes called “quantum pumps,” they are also models of classical chaotic transport, and their quantum behavior cannot be understood without study of the corresponding classical behavior. Here we examine classically such a pump's effect on energy and temperature in the reservoirs, in addition to net particle …
Ballistic Atom Pumps, Megan K. Ivory, Tommy A. Byrd, Andrew J. Pyle, Et Al., John B. Delos
Ballistic Atom Pumps, Megan K. Ivory, Tommy A. Byrd, Andrew J. Pyle, Et Al., John B. Delos
Arts & Sciences Articles
We examine a classically chaotic system consisting of two reservoirs of particles connected by a channel containing oscillating potential-energy barriers. We investigate whether such a system can preferentially pump particles from one reservoir to the other, a process often called “quantum pumping.” We show how to make a “particle diode” which under specified conditions permits net particle pumping in only one direction. Then we examine systems having symmetric barriers. We find that if all initial particle energies are considered, a system with symmetric barriers cannot preferentially pump particles. However, if only finite initial energy bands are considered, the system can …
Early Results From The Qweak Experiment, D. Androic, David S. Armstrong, A. Asaturyan, Todd Averett
Early Results From The Qweak Experiment, D. Androic, David S. Armstrong, A. Asaturyan, Todd Averett
Arts & Sciences Articles
A subset of results from the recently completed Jefferson Lab Qweak experiment are reported. This experiment, sensitive to physics beyond the Standard Model, exploits the small parity-violating asymmetry in elastic ~ep scattering to provide the first determination of the proton’s weak charge Q p w. The experiment employed a 180 µA longitudinally polarized 1.16 GeV electron beam on a 35 cm long liquid hydrogen target. Scattered electrons in the angular range 6◦ < θ < 12◦ corresponding to Q2 = 0.025 GeV2 were detected in eight Cerenkov detectors arrayed symmetrically around the beam axis. The goals of the experiment were to provide a measure of Q p w to 4.2% (combined statistical and systematic error), which implies a measure of sin2 (θw) at the level of 0.3%, and to help constrain the vector weak quark charges C1u and C1d. The experimental method is described, with particular focus on the challenges associated with the world’s highest power LH2 target. The new constraints on C1u and C1d provided by the subset of the experiment’s data analyzed to date will also be shown, together with the extracted weak charge of the neutron.
Topological Analysis Of Chaotic Transport Through A Ballistic Atom Pump, Tommy A. Byrd, John B. Delos
Topological Analysis Of Chaotic Transport Through A Ballistic Atom Pump, Tommy A. Byrd, John B. Delos
Arts & Sciences Articles
We examine a system consisting of two reservoirs of particles connected by a channel. In the channel are two oscillating repulsive potential-energy barriers. It is known that such a system can transport particles from one reservoir to the other, even when the chemical potentials in the reservoirs are equal. We use computations and the theory of chaotic transport to study this system. Chaotic transport is described by passage around or through a heteroclinic tangle. Topological properties of the tangle are described using a generalization of homotopic lobe dynamics, which is a theory that gives some properties of intermediate-time behavior from …
Photodetachment Near A Repulsive Center: Closed-Orbit Theory For The Total Cross Section, B. C. Yang, John B. Delos, M. L. Du
Photodetachment Near A Repulsive Center: Closed-Orbit Theory For The Total Cross Section, B. C. Yang, John B. Delos, M. L. Du
Arts & Sciences Articles
The total photodetachment cross section of a negative ion near a repulsive center is studied based on the closed-orbit theory. An analytical expression, written as a product of the zero-field photodetachment cross section and a modulation function, is obtained for energy above and below threshold. The expression also incorporates the different wave sources produced by different negative ions. The present results are shown to be accurate by comparing with quantum calculations based on the exact Coulomb Green's function. We also compared the photodetachment cross section near a repulsive center with that in a homogeneous electric field and found interesting connections …
Dynamical Monodromy, C. Chen, Megan K. Ivory, Seth Aubin, John B. Delos
Dynamical Monodromy, C. Chen, Megan K. Ivory, Seth Aubin, John B. Delos
Arts & Sciences Articles
Integrable Hamiltonian systems are said to display nontrivial monodromy if fundamental action-angle loops defined on phase-space tori change their topological structure when the system is carried around a circuit. In an earlier paper it was shown that this topological change can occur as a result of time evolution under certain rather abstract flows in phase space. In the present paper, we show that the same topological change can occur as a result of application of ordinary forces. We also show how this dynamical phenomenon could be observed experimentally in classical or in quantum systems.