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Nucleon-nucleon data

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). This work completes the determination of the nucleon-nucleon (NN) scattering amplitudes from 485 to 800 MeV. The data set is completed by the publication of two papers. These new data have a precision better than 1% and an absolute accuracy about 1%, which is generally an order of magnitude better than previous data. The NN data set is now complete and consistent. The set of spin-dependent NN-scattering amplitudes is now well determined up to 800 MeV.
Date: October 1, 1997
Creator: McNaughton, M.W.; Gulmez, E. & Whitten, C.A.
Partner: UNT Libraries Government Documents Department

Poroelastic modeling of seismic boundary conditions across afracture

Description: A fracture within a porous background is modeled as a thin porous layer with increased compliance and finite permeability. For small layer thickness, a set of boundary conditions can be derived that relate particle velocity and stress across a fracture, induced by incident poroelastic waves. These boundary conditions are given via phenomenological parameters that can be used to examine and characterize the seismic response of a fracture. One of these parameters, here it is called membrane permeability, is shown through several examples to control the scattering amplitude of the slow P waves for very low-permeability fractures, which in turn controls the intrinsic attenuation of the waves.
Date: June 29, 2006
Creator: Schoenberg, M.A. & Nakagawa, S.
Partner: UNT Libraries Government Documents Department

High-Precision Computation and Mathematical Physics

Description: At the present time, IEEE 64-bit floating-point arithmetic is sufficiently accurate for most scientific applications. However, for a rapidly growing body of important scientific computing applications, a higher level of numeric precision is required. Such calculations are facilitated by high-precision software packages that include high-level language translation modules to minimize the conversion effort. This paper presents a survey of recent applications of these techniques and provides some analysis of their numerical requirements. These applications include supernova simulations, climate modeling, planetary orbit calculations, Coulomb n-body atomic systems, scattering amplitudes of quarks, gluons and bosons, nonlinear oscillator theory, Ising theory, quantum field theory and experimental mathematics. We conclude that high-precision arithmetic facilities are now an indispensable component of a modern large-scale scientific computing environment.
Date: November 3, 2008
Creator: Bailey, David H. & Borwein, Jonathan M.
Partner: UNT Libraries Government Documents Department


Description: In this report the authors present a model that can produce a mass shift in a resonance due to interference between a scattering amplitude and that amplitude having rescattering through the resonance.
Date: March 31, 2003
Creator: LONGACRE,R.S.
Partner: UNT Libraries Government Documents Department

Electron-atom collision studies using optically state-selected beams. Final report, May 15, 1991--May 14, 1994

Description: As stated in the original proposal, the goal of the project has been to perform electron-scattering experiments on a few model systems with emphasis on resolving all the quantum-state variables possible. The purpose of these experimental studies has been to provide a set of measurements of unprecedented accuracy and completeness that can be used as benchmarks for comparison with theoretical calculations. During the period covered by this report, the work has concentrated on measuring low-energy electron scattering from sodium and chromium. Sodium provides an ideal one-electron test case, since it has a single loosely bound valence electron, making it approachable by even the most complex electron scattering calculations. In addition, the atom has a strong optical transition from the 3{sup 2}S{sub 1/2} ground state to the 3{sup 2}P{sub 3/2} excited state whose wavelength (589 nm) matches the peak output of the laser dye rhodamine 6G. Thus optical pumping techniques can be readily applied in the laboratory, leading to either a population of ground state atoms in which the spin of the valence electron is oriented either up or down in the laboratory, or a spin polarized pure angular momentum state of the excited 3{sup 2}P{sub 3/2} state. Such an excited state makes possible superelastic scattering, where the internal energy of the atom is transferred to the electron during the collision. This turns out to be a very efficient way to study the inelastic scattering process. Unlike sodium, chromium provides an extremely exacting test for theoretical methods because of its very complex electronic structure, not because it is simple. With a valence configuration consisting of five electrons in a half-filled 3d shell, plus another electron in a 4s shell, this atom provides a test case that can challenge even the simplest approximations.
Date: March 15, 1998
Creator: Kelley, M.H. & McClelland, J.J.
Partner: UNT Libraries Government Documents Department

Two-pion exchange potential and the {pi}N amplitude

Description: The authors discuss the two-pion exchange potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant {pi}N scattering amplitude which includes {Delta}, Roper, and D{sub 13} isobars, as well as contact terms and off-shell (non-pole) dressed nucleon terms. The {pi}N amplitude satisfies chiral symmetry constraints and fits {pi}N data below {approximately} 700 MeV pion energy. They find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit NN data below the pion production threshold.
Date: May 1, 1996
Creator: Pena, M. T.; Gross, Franz & Surya, Yohanes
Partner: UNT Libraries Government Documents Department

Factorization for high-energy scattering

Description: The author demonstrates that the amplitude of the high-energy scattering can be factorized in a product of two independent functional integrals over ''fast'' and ''slow'' fields which interact by means of Wilson-line operators -- gauge factors ordered along the straight lines.
Date: July 1, 1998
Creator: Balitsky, Ian
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

Calculating scattering amplitudes efficiently

Description: We review techniques for more efficient computation of perturbative scattering amplitudes in gauge theory, in particular tree and one- loop multi-parton amplitudes in QCD. We emphasize the advantages of (1) using color and helicity information to decompose amplitudes into smaller gauge-invariant pieces, and (2) exploiting the analytic properties of these pieces, namely their cuts and poles. Other useful tools include recursion relations, special gauges and supersymmetric rearrangements. 46 refs., 11 figs.
Date: January 1996
Creator: Dixon, L.
Partner: UNT Libraries Government Documents Department

Low frequency elastic wave scattering by an inclusion: Limits of applications

Description: The present investigation considers various approximations for the problem of low frequency elastic waves scattered by a single, small inclusion of constant elastic parameters. For the Rayleigh approximation containing both near and far field terms, the scattered amplitudes are investigated as a function of distance from the scatterer. Near field terms are found to be dominant for distances up to two wavelengths, after which far field solutions correctly describe the scattered field. At a distance of two wavelengths the relative error between the total and the far field solution is about 15% and decreases with increasing, distance. Deriving solutions for the linear and quadratic Rayleigh-Born approximation, the relative error between the nonlinear Rayleigh approximation and the linear and quadratic Rayleigh-Born approximation as a function of the scattering angle and the parameter perturbation is investigated. The relative error reveals a strong dependence on the scattering angle, while the addition of the quadratic term significantly improves the approximation for all scattering angles and parameter perturbations. An approximation for the error caused by linearization of the problem, based entirely on the perturbations of the parameters from the background medium, and its validity range given. We also investigate the limit of the wave parameter for Rayleigh scattering and find higher values than previously assumed. By choosing relative errors of 5%, 10% and 20% between the exact solution and the Rayleigh approximation, we find the upper limits for the parameter k{sub p}R to be 0.55, 0.7 and 0.9, respectively.
Date: May 1, 1995
Creator: Gritto, R.; Korneev, V.A. & Johnson, L.R.
Partner: UNT Libraries Government Documents Department

Seiberg duality and e+e- experiments

Description: Seiberg duality in supersymmetric gauge theories is the claim that two different theories describe the same physics in the infrared limit. However, one cannot easily work out physical quantities in strongly coupled theories and hence it has been difficult to compare the physics of the electric and magnetic theories. In order to gain more insight into the equivalence of two theories, we study the ''e{sup +}e{sup -}'' cross sections into ''hadrons'' for both theories in the superconformal window. We describe a technique which allows us to compute the cross sections exactly in the infrared limit. They are indeed equal in the low-energy limit and the equality is guaranteed because of the anomaly matching condition. The ultraviolet behavior of the total ''e{sup +}e{sup -}'' cross section is different for the two theories. We comment on proposed nonsupersymmetric dualities. We also analyze the agreement of the ''{gamma}{gamma}'' and ''WW'' scattering amplitudes in both theories, and in particular try to understand if their equivalence can be explained by the anomaly matching condition.
Date: October 2, 1998
Creator: De Gouvea, Andre; Friedland, Alexander & Murayama, Hitoshi
Partner: UNT Libraries Government Documents Department

Scattering of color dipoles: from low to high energies

Description: A dipole-dipole scattering amplitude is calculated exactly in the first two orders of perturbation theory. This amplitude is an analytic function of the relative energy and the dipoles' sizes. The cross section of the dipole-dipole scattering approached the high-energy BFKL asymptotics starting from relatively large rapidity {approx}4.
Date: November 1, 2002
Creator: Babansky, Alexander & Balitsky, Ian
Partner: UNT Libraries Government Documents Department

Toward improved photon-atom scattering predictions

Description: Photon-atom scattering is important in a variety of applications, but scattering from a composite system depends on the accurate characterization of the scattering from an isolated atom or ion. We have been examining the validity of simpler approximations of elastic scattering in the light of second-order S-matrix theory. Partitioning the many-body amplitude into Rayleigh and Delbrueck components, processes beyond photoionization contribute. Subtracted cross sections for bound-bound atomic transitions, bound pair annihilation, and bound pair production are required in anomalous scattering factors for: (1) convergence of the dispersion integral; (2) agreement with predictions of the more sophisticated S-matrix approach; (3) satisfying the Thomas-Reiche-Kuhn sum rule. New accurate tabulations of anomalous scattering factors have been prepared for all Z, for energies 0--10,000 keV, within the independent particle approximation (IPA) using a Dirac-Slater model of the atom. Separately, experimental atomic photoabsorption threshold information has been used to modify these IPA predictions for improved comparison with experiment.
Date: October 21, 1994
Creator: Kissel, L.
Partner: UNT Libraries Government Documents Department

NN Core Interactions and Differential Cross Sections from One Gluon Exchange

Description: We derive nonstrange baryon-baryon scattering amplitudes in the nonrelativistic quark model using the "quark Born diagram" formalism. This approach describes the scattering as a single interaction, here the one-gluon-exchange (OGE) spin-spin term followed by constituent interchange, with external nonrelativistic baryon wavefunctions attached to the scattering diagrams to incorporate higher-twist wavefunction effects. The short-range repulsive core in the NN interaction has previously been attributed to this spin-spin interaction in the literature; we find that these perturbative constituent-interchange diagrams do indeed predict repulsive interactions in all I,S channels of the nucleon-nucleon sytem, and we compare our results for the equivalent short-range potentials to the core potentials found by other authors using nonperturbative methods. We also apply our perturbative techniques to the NDelta and Delta Delta systems: Some Delta Delta channels are found to have attractive core
Date: January 1, 1993
Creator: Swanson, Eric; Kovarik, M.D.; Capstick, Simon & Barnes, Ted
Partner: UNT Libraries Government Documents Department

Semi-numerical evaluation of one-loop corrections

Description: We present a semi-numerical algorithm to calculate one-loop virtual corrections to scattering amplitudes. The divergences of the loop amplitudes are regulated using dimensional regularization. We treat in detail the case of amplitudes with up to five external legs and massless internal lines, although the method is more generally applicable. Tensor integrals are reduced to generalized scalar integrals, which in turn are reduced to a set of known basis integrals using recursion relations. The reduction algorithm is modified near exceptional configurations to ensure numerical stability. To test the procedure we apply these techniques to one-loop corrections to the Higgs to four quark process for which analytic results have recently become available.
Date: August 1, 2005
Creator: Ellis, R.K.; Giele, W.T.; Zanderighi, G. & /Fermilab
Partner: UNT Libraries Government Documents Department

Full one-loop amplitudes from tree amplitudes

Description: We establish an efficient polynomial-complexity algorithm for one-loop calculations, based on generalized D-dimensional unitarity. It allows automated computations of both cut-constructible and rational parts of one-loop scattering amplitudes from on-shell tree amplitudes. We illustrate the method by (re)-computing all four-, five- and six-gluon scattering amplitudes in QCD at one-loop.
Date: January 1, 2008
Creator: Giele, Walter T.; Kunszt, Zoltan & Melnikov, Kirill
Partner: UNT Libraries Government Documents Department

N >= 4 Supergravity Amplitudes from Gauge Theory at Two Loops

Description: We present the full two-loop four-graviton amplitudes in N = 4, 5, 6 supergravity. These results were obtained using the double-copy structure of gravity, which follows from the recently conjectured color-kinematics duality in gauge theory. The two-loop four-gluon scattering amplitudes in N = 0, 1, 2 supersymmetric gauge theory are a second essential ingredient. The gravity amplitudes have the expected infrared behavior: the two-loop divergences are given in terms of the squares of the corresponding one-loop amplitudes. The finite remainders are presented in a compact form. The finite remainder for N = 8 supergravity is also presented, in a form that utilizes a pure function with a very simple symbol.
Date: February 15, 2012
Creator: Boucher-Veronneau, C. & Dixon, L. J.
Partner: UNT Libraries Government Documents Department