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Sample records for multi-parton scattering amplitudes

  1. Bootstrapping Multi-Parton Loop Amplitudes in QCD

    SciTech Connect

    Bern, Zvi; Dixon, Lance J.; Kosower, David A.; /Saclay, SPhT

    2005-07-06

    The authors present a new method for computing complete one-loop amplitudes, including their rational parts, in non-supersymmetric gauge theory. This method merges the unitarity method with on-shell recursion relations. It systematizes a unitarity-factorization bootstrap approach previously applied by the authors to the one-loop amplitudes required for next-to-leading order QCD corrections to the processes e{sup +}e{sup -} {yields} Z, {gamma}* {yields} 4 jets and pp {yields} W + 2 jets. We illustrate the method by reproducing the one-loop color-ordered five-gluon helicity amplitudes in QCD that interfere with the tree amplitude, namely A{sub 5;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}) and A{sub 5;1}(1{sup -}, 2{sup +}, 3{sup -}, 4{sup +}, 5{sup +}). Then we describe the construction of the six- and seven-gluon amplitudes with two adjacent negative-helicity gluons, A{sub 6;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}) and A{sub 7;1}(1{sup -}, 2{sup -}, 3{sup +}, 4{sup +}, 5{sup +}, 6{sup +}, 7{sup +}), which uses the previously-computed logarithmic parts of the amplitudes as input. They present a compact expression for the six-gluon amplitude. No loop integrals are required to obtain the rational parts.

  2. One-Loop Multi-Parton Amplitudes with a Vector Boson for the LHC

    SciTech Connect

    Berger, C.F.; Bern, Z.; Dixon, L.J.; Cordero, F.Febres; Forde, D.; Ita, H.; Kosower, D.A.; Maitre, D.; /SLAC

    2008-08-11

    In this talk, we present the first, numerically stable, results for the one-loop amplitudes needed for computing W; Z + 3 jet cross sections at the LHC to next-to-leading order in the QCD coupling. We implemented these processes in BlackHat, an automated program based on on-shell methods. These methods scale very well with increasing numbers of external partons, and are applicable to a wide variety of problems of phenomenological interest at the LHC.

  3. Protostring scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Thorn, Charles B.

    2016-11-01

    We calculate some tree-level scattering amplitudes for a generalization of the protostring, which is a novel string model implied by the simplest string bit models. These bit models produce a light-cone world sheet which supports s integer moded Grassmann fields. In the generalization we supplement this Grassmann world-sheet system with d =24 -s transverse coordinate world-sheet fields. The protostring corresponds to s =24 and the bosonic string to s =0 . The interaction vertex is a simple overlap with no operator insertions at the break/join point. Assuming that s is even we calculate the multistring scattering amplitudes by bosonizing the Grassmann fields, each pair equivalent to one compactified bosonic field, and applying Mandelstam's interacting string formalism to a system of s /2 compactified and d uncompactified bosonic world-sheet fields. We obtain all amplitudes for open strings with no oscillator excitations and for closed strings with no oscillator excitations and zero winding number. We then study in detail some simple special cases. Multistring processes with maximal helicity violation have much simpler amplitudes. We also specialize to general four-string amplitudes and discuss their high energy behavior. Most of these models are not covariant under the full Lorentz group O (d +1 ,1 ). The exceptions are the bosonic string whose Lorentz group is O (25 ,1 ) and the protostring whose Lorentz group is O (1 ,1 ). The models in between only enjoy an O (1 ,1 )×O (d ) spacetime symmetry.

  4. Grassmannian origin of scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Trnka, Jaroslav

    Quantum field theory (QFT) is our central theoretical framework to describe the microscopic world, arising from the union of quantum mechanics and special relativity. Since QFTs play such a central role in our understanding of Nature, a deeper study of their physical properties is one of the most exciting directions of research in theoretical physics. This has led to the discovery of many important theoretical concepts, such as supersymmetry and string theory. One of the most prominent physical observable in any QFT is the scattering amplitude, which describes scattering processes of elementary particles. Theoretical progress in understanding and computing scattering amplitudes has accelerated in last few years with the discovery of amazing new mathematical structures in a close cousin of QCD, known as N=4 Super-Yang-Mills theory (SYM). In the first chapter we study integrands of loop amplitudes in planar N=4 SYM and show their astonishing simplicity when written in terms of special set of chiral integrals. In chapter two we show how to reconstruct the multi-loop integrand recursively starting from tree-level amplitudes. This approach makes the long-hidden Yangian symmetry of the theory completely manifest and provides a Lagrangian-independent approach for determining the integrand at any loop order. In chapter three we demonstrate that the problem of calculating of scattering amplitudes in planar N=4 SYM can be completely reformulated in a new framework in terms of on-shell diagrams and integrals over the positive Grassmannian G(k,n). Remarkably, the building blocks for amplitudes play a fundamental role in an active area of research in mathematics spanning algebraic geometry to combinatorics. In chapter four we sketch the argument that the amplitude itself is represented by a single geometrical object defined purely using a new striking property -- positivity -- and all physical concepts like unitarity and locality emerge as derived concepts, each having a sharp

  5. Computing Maximally Supersymmetric Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Stankowicz, James Michael, Jr.

    This dissertation reviews work in computing N = 4 super-Yang--Mills (sYM) and N = 8 maximally supersymmetric gravity (mSUGRA) scattering amplitudes in D = 4 spacetime dimensions in novel ways. After a brief introduction and overview in Ch. 1, the various techniques used to construct amplitudes in the remainder of the dissertation are discussed in Ch. 2. This includes several new concepts such as d log and pure integrand bases, as well as how to construct the amplitude using exactly one kinematic point where it vanishes. Also included in this chapter is an outline of the Mathematica package on shell diagrams and numerics.m (osdn) that was developed for the computations herein. The rest of the dissertation is devoted to explicit examples. In Ch. 3, the starting point is tree-level sYM amplitudes that have integral representations with residues that obey amplitude relations. These residues are shown to have corresponding residue numerators that allow a double copy prescription that results in mSUGRA residues. In Ch. 4, the two-loop four-point sYM amplitude is constructed in several ways, showcasing many of the techniques of Ch. 2; this includes an example of how to use osdn. The two-loop five-point amplitude is also presented in a pure integrand representation with comments on how it was constructed from one homogeneous cut of the amplitude. On-going work on the two-loop n-point amplitude is presented at the end of Ch. 4. In Ch. 5, the three-loop four-point amplitude is presented in the d log representation and in the pure integrand representation. In Ch. 6, there are several examples of four- through seven-loop planar diagrams that illustrate how considerations of the singularity structure of the amplitude underpin dual-conformal invariance. Taken with the previous examples, this is additional evidence that the structure known to exist in the planar sector extends to the full theory. At the end of this chapter is a proof that all mSUGRA amplitudes have a pole at

  6. Multi-parton interactions and rapidity gap survival probability in jet-gap-jet processes

    NASA Astrophysics Data System (ADS)

    Babiarz, Izabela; Staszewski, Rafał; Szczurek, Antoni

    2017-08-01

    We discuss an application of dynamical multi-parton interaction model, tuned to measurements of underlying event topology, for a description of destroying rapidity gaps in the jet-gap-jet processes at the LHC. We concentrate on the dynamical origin of the mechanism of destroying the rapidity gap. The cross section for jet-gap-jet is calculated within LL BFKL approximation. We discuss the topology of final states without and with the MPI effects. We discuss some examples of selected kinematical situations (fixed jet rapidities and transverse momenta) as distributions averaged over the dynamics of the jet-gap-jet scattering. The colour-singlet ladder exchange amplitude for the partonic subprocess is implemented into the PYTHIA 8 generator, which is then used for hadronisation and for the simulation of the MPI effects. Several differential distributions are shown and discussed. We present the ratio of cross section calculated with and without MPI effects as a function of rapidity gap in between the jets.

  7. Scattering amplitudes for dark and bright excitons

    NASA Astrophysics Data System (ADS)

    Shiau, Shiue-Yuan; Combescot, Monique; Combescot, Roland; Dubin, François; Chang, Yia-Chung

    2017-05-01

    Using the composite boson many-body formalism that takes single-exciton states rather than free carrier states as a basis, we derive the integral equation fulfilled by the exciton-exciton effective scattering from which the role of fermion exchanges can be unraveled. For excitons made of (+/-1/2) -spin electrons and (+/-3/2) -spin holes, as in GaAs heterostructures, one major result is that most spin configurations lead to brightness-conserving scatterings with equal amplitude Δ, despite differences in the carrier exchanges involved. A brightness-changing channel also exists when two opposite-spin excitons scatter: dark excitons (2,-2) can end either in the same dark states with an amplitude Δe , or in opposite-spin bright states (1,-1) , with a different amplitude Δo , the number of carrier exchanges involved in these scatterings being even or odd, respectively. Another major result is that these amplitudes are linked by a striking relation, Δ_e+Δ_o=Δ , which has decisive consequence on exciton Bose-Einstein condensation. By using Born values, we show that the exciton condensate can be optically observed through a bright part when excitons have large dipole only, that is, when the electrons and holes are in two well-separated layers, as in current experiments.

  8. Amplitude for N-Gluon Superstring Scattering

    SciTech Connect

    Stieberger, Stephan; Taylor, Tomasz R.

    2006-11-24

    We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope {alpha}{sup '}. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in {alpha}{sup '}, for the so-called maximally helicity violating configurations, with N=4, 5 and N=6. We also obtain the leading O({alpha}{sup '2}) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.

  9. Amplitude for N-gluon superstring scattering.

    PubMed

    Stieberger, Stephan; Taylor, Tomasz R

    2006-11-24

    We consider scattering processes involving N gluonic massless states of open superstrings with a certain Regge slope alpha'. At the semiclassical level, the string world-sheet sweeps a disk and N gluons are created or annihilated at the boundary. We present exact expressions for the corresponding amplitudes, valid to all orders in alpha', for the so-called maximally helicity violating configurations, with N = 4, 5 and N = 6. We also obtain the leading O(alpha '2) string corrections to the zero-slope N-gluon Yang-Mills amplitudes.

  10. Einstein-Yang-Mills scattering amplitudes from scattering equations

    NASA Astrophysics Data System (ADS)

    Cachazo, Freddy; He, Song; Yuan, Ellis Ye

    2015-01-01

    We present the building blocks that can be combined to produce tree-level S-matrix elements of a variety of theories with various spins mixed in arbitrary dimensions. The new formulas for the scattering of n massless particles are given by integrals over the positions of n points on a sphere restricted to satisfy the scattering equations. As applications, we obtain all single-trace amplitudes in Einstein-Yang-Mills (EYM) theory, and generalizations to include scalars. Also in EYM but extended by a B-field and a dilaton, we present all double-trace gluon amplitudes. The building blocks are made of Pfaffians and Parke-Taylor-like factors of subsets of particle labels.

  11. Direct Calculation of the Scattering Amplitude Without Partial Wave Analysis

    NASA Technical Reports Server (NTRS)

    Shertzer, J.; Temkin, A.; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Two new developments in scattering theory are reported. We show, in a practical way, how one can calculate the full scattering amplitude without invoking a partial wave expansion. First, the integral expression for the scattering amplitude f(theta) is simplified by an analytic integration over the azimuthal angle. Second, the full scattering wavefunction which appears in the integral expression for f(theta) is obtained by solving the Schrodinger equation with the finite element method (FEM). As an example, we calculate electron scattering from the Hartree potential. With minimal computational effort, we obtain accurate and stable results for the scattering amplitude.

  12. Properties of scattering amplitudes at very high energies

    NASA Technical Reports Server (NTRS)

    Mickens, R. E.

    1975-01-01

    The research is reported concerning the (1) total cross sections as the energy becomes infinite, (2) elastic scattering amplitude for nonforward directions, and (3) upper bound of neutrino scattering cross sections.

  13. Miracles in Scattering Amplitudes: from QCD to Gravity

    SciTech Connect

    Volovich, Anastasia

    2016-10-09

    The goal of my research project "Miracles in Scattering Amplitudes: from QCD to Gravity" involves deepening our understanding of gauge and gravity theories by exploring hidden structures in scattering amplitudes and using these rich structures as much as possible to aid practical calculations.

  14. Renormalization Scale-Fixing for Complex Scattering Amplitudes

    SciTech Connect

    Brodsky, Stanley J.; Llanes-Estrada, Felipe J.; /Madrid U.

    2005-12-21

    We show how to fix the renormalization scale for hard-scattering exclusive processes such as deeply virtual meson electroproduction by applying the BLM prescription to the imaginary part of the scattering amplitude and employing a fixed-t dispersion relation to obtain the scale-fixed real part. In this way we resolve the ambiguity in BLM renormalization scale-setting for complex scattering amplitudes. We illustrate this by computing the H generalized parton distribution at leading twist in an analytic quark-diquark model for the parton-proton scattering amplitude which can incorporate Regge exchange contributions characteristic of the deep inelastic structure functions.

  15. Chiral closed strings: four massless states scattering amplitude

    NASA Astrophysics Data System (ADS)

    Leite, Marcelo M.; Siegel, Warren

    2017-01-01

    We compute the scattering amplitudes of four massless states for chiral (closed) bosonic and type II superstrings using the Kawai-Lewellen-Tye ( KLT ) factorization method. The amplitude in the chiral bosonic case is identical to a field theory amplitude corresponding to the spin-2 tachyon, massless gravitational sector and massive spin-2 tardyon states of the spectrum. Chiral type II superstrings amplitude only possess poles associated with the massless gravitational sector. We briefly discuss the extension of the calculation to heterotic superstrings.

  16. Cluster functions and scattering amplitudes for six and seven points

    NASA Astrophysics Data System (ADS)

    Harrington, Thomas; Spradlin, Marcus

    2017-07-01

    Scattering amplitudes in planar super-Yang-Mills theory satisfy several basic physical and mathematical constraints, including physical constraints on their branch cut structure and various empirically discovered connections to the mathematics of cluster algebras. The power of the bootstrap program for amplitudes is inversely proportional to the size of the intersection between these physical and mathematical constraints: ideally we would like a list of constraints which determine scattering amplitudes uniquely. We explore this intersection quantitatively for two-loop six- and seven-point amplitudes by providing a complete taxonomy of the Gr(4, 6) and Gr(4, 7) cluster polylogarithm functions of [15] at weight 4.

  17. Cluster functions and scattering amplitudes for six and seven points

    DOE PAGES

    Harrington, Thomas; Spradlin, Marcus

    2017-07-05

    Scattering amplitudes in planar super-Yang-Mills theory satisfy several basic physical and mathematical constraints, including physical constraints on their branch cut structure and various empirically discovered connections to the mathematics of cluster algebras. The power of the bootstrap program for amplitudes is inversely proportional to the size of the intersection between these physical and mathematical constraints: ideally we would like a list of constraints which determine scattering amplitudes uniquely. Here, we explore this intersection quantitatively for two-loop six- and seven-point amplitudes by providing a complete taxonomy of the Gr(4, 6) and Gr(4, 7) cluster polylogarithm functions of [15] at weight 4.

  18. Writing CFT correlation functions as AdS scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Penedones, Joao

    2011-03-01

    We explore the Mellin representation of conformal correlation functions recently proposed by Mack. Examples in the AdS/CFT context reinforce the analogy between Mellin amplitudes and scattering amplitudes. We conjecture a simple formula relating the bulk scattering amplitudes to the asymptotic behavior of Mellin amplitudes and show that previous results on the flat space limit of AdS follow from our new formula. We find that the Mellin amplitudes are particularly useful in the case of conformal gauge theories in the planar limit. In this case, the four point Mellin amplitudes are meromorphic functions whose poles and their residues are entirely determined by two and three point functions of single-trace operators. This makes the Mellin amplitudes the ideal objects to attempt the conformal bootstrap program in higher dimensions.

  19. Scattering amplitudes in gauge theories: progress and outlook Scattering amplitudes in gauge theories: progress and outlook

    NASA Astrophysics Data System (ADS)

    Roiban, Radu; Spradlin, Marcus; Volovich, Anastasia

    2011-11-01

    This issue aims to serve as an introduction to our current understanding of the structure of scattering amplitudes in gauge theory, an area which has seen particularly rapid advances in recent years following decades of steady progress. The articles contained herein provide a snapshot of the latest developments which we hope will serve as a valuable resource for graduate students and other scientists wishing to learn about the current state of the field, even if our continually evolving understanding of the subject might soon render this compilation incomplete. Why the fascination with scattering amplitudes, which have attracted the imagination and dedicated effort of so many physicists? Part of it stems from the belief, supported now by numerous examples, that unexpected simplifications of otherwise apparently complicated calculations do not happen by accident. Instead they provide a strong motivation to seek out an underlying explanation. The insight thereby gained can subsequently be used to make the next class of seemingly impossible calculations not only possible, but in some cases even trivial. This two-pronged strategy of exploring and exploiting the structure of gauge theory amplitudes appeals to a wide audience from formal theorists interested in mathematical structure for the sake of its own beauty to more phenomenologically-minded physicists eager to speed up the next generation of analysis software. Understandably it is the maximally supersymmetric 𝒩 = 4 Yang-Mills theory (SYM) which has the simplest structure and has correspondingly received the most attention. Rarely in theoretical physics are we fortunate enough to encounter a toy model which is simple enough to be solved completely yet rich enough to possess interesting non-trivial structure while simultaneously, and most importantly, being applicable (even if only as a good approximation) to a wide range of 'real' systems. The canonical example in quantum mechanics is of course the harmonic

  20. Singularity structure of maximally supersymmetric scattering amplitudes.

    PubMed

    Arkani-Hamed, Nima; Bourjaily, Jacob L; Cachazo, Freddy; Trnka, Jaroslav

    2014-12-31

    We present evidence that loop amplitudes in maximally supersymmetric (N=4) Yang-Mills theory (SYM) beyond the planar limit share some of the remarkable structures of the planar theory. In particular, we show that through two loops, the four-particle amplitude in full N=4 SYM has only logarithmic singularities and is free of any poles at infinity--properties closely related to uniform transcendentality and the UV finiteness of the theory. We also briefly comment on implications for maximal (N=8) supergravity theory (SUGRA).

  1. Calculation of the Scattering Amplitude Without Partial Wave Expansion

    NASA Technical Reports Server (NTRS)

    Shertzer, J.; Temkin, Aaron; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    Two developments in the direct calculation of the angular differential scattering amplitude have been implemented: (a) The integral expansion of the scattering amplitude is simplified by analytically integration over the azimuthal angle. (b) The resulting integral as a function of scattering angle is calculated by using the numerically generated wave function from a finite element method calculation. Results for electron-hydrogen scattering in the static approximation will be shown to be as accurate as a partial wave expansion with as many l's as is necessary for convergence at the incident energy being calculated.

  2. Scattering amplitudes and BCFW recursion in twistor space

    NASA Astrophysics Data System (ADS)

    Mason, Lionel; Skinner, David

    2010-01-01

    Twistor ideas have led to a number of recent advances in our understanding of scattering amplitudes. Much of this work has been indirect, determining the twistor space support of scattering amplitudes by examining the amplitudes in momentum space. In this paper, we construct the actual twistor scattering amplitudes themselves. We show that the recursion relations of Britto, Cachazo, Feng and Witten have a natural twistor formulation that, together with the three-point seed amplitudes, allows us to recursively construct general tree amplitudes in twistor space. We obtain explicit formulae for n-particle MHV and NMHV super-amplitudes, their CPT conjugates (whose representations are distinct in our chiral framework), and the eight particle N2MHV super-amplitude. We also give simple closed form formulae for the mathcal{N} = 8 supergravity recursion and the MHV and overline {text{MHV}} amplitudes. This gives a formulation of scattering amplitudes in maximally supersymmetric theories in which superconformal symmetry and its breaking is manifest. For N k MHV, the amplitudes are given by 2 n - 4 integrals in the form of Hilbert transforms of a product of n - k - 2 purely geometric, superconformally invariant twistor delta functions, dressed by certain sign operators. These sign operators subtly violate conformal invariance, even for tree-level amplitudes in mathcal{N} = 4 super Yang-Mills, and we trace their origin to a topological property of split signature space-time. We develop the twistor transform to relate our work to the ambidextrous twistor diagram approach of Hodges and of Arkani-Hamed, Cachazo, Cheung and Kaplan.

  3. Scattering Amplitudes: The Most Perfect Microscopic Structures in the Universe

    SciTech Connect

    Dixon, Lance J.; /CERN /SLAC

    2011-11-04

    This article gives an overview of many of the recent developments in understanding the structure of relativistic scattering amplitudes in gauge theories ranging from QCD to N = 4 super-Yang-Mills theory, as well as (super)gravity. I also provide a pedagogical introduction to some of the basic tools used to organize and illuminate the color and kinematic structure of amplitudes. This article is an invited review introducing a special issue of Journal of Physics A devoted to 'Scattering Amplitudes in Gauge Theories'.

  4. Operator form of the three-nucleon scattering amplitude

    NASA Astrophysics Data System (ADS)

    Topolnicki, Kacper; Golak, Jacek; Skibiński, Roman; Witała, Henryk

    2017-07-01

    To extend the applications of the so-called "three-dimensional" formalism to the description of three-nucleon scattering within the Faddeev formalism, we develop a general form of the three-nucleon scattering amplitude. This form significantly decreases the numerical complexity of the "three-dimensional" calculations by reducing the scattering amplitude to a linear combination of momentum-dependent spin operators and scalar functions of momenta. The number and structure of the spin operators is fixed and the scalar functions can be represented numerically using standard methods such as multidimensional arrays. In this paper, we show that all orders of the iterated Faddeev equation can be written in this general form. We argue that calculations utilizing the three-nucleon force will also conform to the same general form. Additionally, we show how the general form of the scattering amplitude can be used to transform the Faddeev equation to make it suitable for numerical calculations using iterative methods.

  5. Loop Integrands for Scattering Amplitudes from the Riemann Sphere

    NASA Astrophysics Data System (ADS)

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2015-09-01

    The scattering equations on the Riemann sphere give rise to remarkable formulas for tree-level gauge theory and gravity amplitudes. Adamo, Casali, and Skinner conjectured a one-loop formula for supergravity amplitudes based on scattering equations on a torus. We use a residue theorem to transform this into a formula on the Riemann sphere. What emerges is a framework for loop integrands on the Riemann sphere that promises to have a wide application, based on off-shell scattering equations that depend on the loop momentum. We present new formulas, checked explicitly at low points, for supergravity and super-Yang-Mills amplitudes and for n -gon integrands at one loop. Finally, we show that the off-shell scattering equations naturally extend to arbitrary loop order, and we give a proposal for the all-loop integrands for supergravity and planar super-Yang-Mills theory.

  6. Wilson loops and QCD/string scattering amplitudes

    SciTech Connect

    Makeenko, Yuri; Olesen, Poul

    2009-07-15

    We generalize modern ideas about the duality between Wilson loops and scattering amplitudes in N=4 super Yang-Mills theory to large N QCD by deriving a general relation between QCD meson scattering amplitudes and Wilson loops. We then investigate properties of the open-string disk amplitude integrated over reparametrizations. When the Wilson-loop is approximated by the area behavior, we find that the QCD scattering amplitude is a convolution of the standard Koba-Nielsen integrand and a kernel. As usual poles originate from the first factor, whereas no (momentum-dependent) poles can arise from the kernel. We show that the kernel becomes a constant when the number of external particles becomes large. The usual Veneziano amplitude then emerges in the kinematical regime, where the Wilson loop can be reliably approximated by the area behavior. In this case, we obtain a direct duality between Wilson loops and scattering amplitudes when spatial variables and momenta are interchanged, in analogy with the N=4 super Yang-Mills theory case.

  7. Scattering amplitude without an explicit enforcement of boundary conditions

    SciTech Connect

    Kruppa, A. T.; Suzuki, R.; Kato, K.

    2007-04-15

    It has been known for some time that for short range potentials scattering observables can be calculated using complex coordinates. We will show that the standard uniform complex scaling can be applied to calculate the scattering amplitude even in the presence of a long range interaction. The main advantage of the application of the complex scaling to the scattering problem is that the direct imposition of the complicated scattering boundary condition can be avoided. As a result, the scattering problem can be solved using only square integrable functions. The method will be applied not only for potential scattering but for the coupled-channel reaction model. As an application we calculate the phase shifts of the charge exchange reaction {sup 3}H(p,n){sup 3}He.

  8. Gauge and Gravity Scattering Amplitudes from CHY Formalism

    NASA Astrophysics Data System (ADS)

    Teng, Fei

    In this dissertation, we first review some recent progress on exploring the nature of scattering amplitudes. Then we present our recent work on direct evaluation of tree level maximally helicity violating (MHV) amplitudes by Cachazo-He-Yuan (CHY) formula, which naturally reproduce the Parke-Taylor and Hodges formula, respectively, for gauge and gravity. We also verify that they are supported only by one single solution to the scattering equation. In addition, we derive a new compact formula for tree level single trace MHV amplitudes for Einstein-Yang-Mills theory, which is equivalent to, but much simpler than the known Selivanov-Bern-De Freitas-Wong (SBDW) formula. It can be shown that other solutions do not contribute to the MHV amplitudes of Yang-Mills, gravity and Einstein-Yang-Mills theory. We further propose a method to characterize the solutions to the scattering equations using the rank of two discriminant matrices. In four dimensions, such a characterization can be used to understand the correspondence between the helicity configurations of external scattering particles and the solutions to the scattering equation.

  9. Recent progress in one-loop multi-parton calculations

    SciTech Connect

    Bern, Z.; Dixon, L.; Dunbar, D.C.; Kosower, D.A.

    1994-09-01

    The authors describe techniques that simplify the calculation of one-loop QCD amplitudes with many external legs, which are needed for next-to-leading-order (NLO) corrections to multi-jet processes. The constraints imposed by perturbative unitarity, collinear singularities and a supersymmetry-inspired organization of helicity amplitudes are particularly useful. Certain sequences of one-loop helicity amplitudes may be obtained for an arbitrary number of external gluons using these techniques. They also report on progress in completing the set of one-loop helicity amplitudes required for NLO three-jet production at hadron colliders, namely the amplitudes with two external quarks and three gluons.

  10. Effective Field Theories from Soft Limits of Scattering Amplitudes.

    PubMed

    Cheung, Clifford; Kampf, Karol; Novotny, Jiri; Trnka, Jaroslav

    2015-06-05

    We derive scalar effective field theories-Lagrangians, symmetries, and all-from on-shell scattering amplitudes constructed purely from Lorentz invariance, factorization, a fixed power counting order in derivatives, and a fixed order at which amplitudes vanish in the soft limit. These constraints leave free parameters in the amplitude which are the coupling constants of well-known theories: Nambu-Goldstone bosons, Dirac-Born-Infeld scalars, and Galilean internal shift symmetries. Moreover, soft limits imply conditions on the Noether current which can then be inverted to derive Lagrangians for each theory. We propose a natural classification of all scalar effective field theories according to two numbers which encode the derivative power counting and soft behavior of the corresponding amplitudes. In those cases where there is no consistent amplitude, the corresponding theory does not exist.

  11. Limits of applicability of the concept of scattering amplitude in small-angle scattering problems

    NASA Astrophysics Data System (ADS)

    Dzheparov, F. S.; Lvov, D. V.

    2014-01-01

    The applicability of the concept of scattering amplitude to the description of small-angle scattering experiments has been considered. An expression has been obtained for a scattered radiation flux on a detector under much milder conditions than the condition of Fraunhofer diffraction. The influence of incoherence of the source on the results has been evaluated.

  12. Born amplitudes and seagull term in meson-soliton scattering

    NASA Astrophysics Data System (ADS)

    Liang, Y. G.; Li, B. A.; Liu, K. F.; Su, R. K.

    1990-06-01

    The meson-soliton scattering for the ⊘ 4 theory in 1 + 1 dimensions is calculated. We show that when the seagull term from the equal time commutator is included in addition to the Born amplitudes, the t-matrix from the reduction formula approach is identical to that of the potential scattering with small quantum fluctuations to leading order in weak coupling. The seagull term is equal to the Born term in the potential scattering. This confirms the speculation that the leading order Yukawa coupling is derivable from the classical soliton.

  13. Effects produced by multi-parton interactions and color reconnection in small systems

    NASA Astrophysics Data System (ADS)

    Cuautle, Eleazar; Ortiz, Antonio; Paić, Guy

    2016-12-01

    Multi-parton interactions and color reconnection can produce QGP-like effects in small systems, specifically, radial flow-like patterns. For pp collisions simulated with Pythia 8.212, in this work we investigate their effects on different observables like event multiplicity, event shapes and transverse momentum distributions.

  14. Ward identities and high energy scattering amplitudes in string theory

    NASA Astrophysics Data System (ADS)

    Chan, Chuan-Tsung; Ho, Pei-Ming; Lee, Jen-Chi

    2005-02-01

    High-energy limit α→∞ of stringy Ward identities derived from the decoupling of two types of zero-norm states in the old covariant first quantized (OCFQ) spectrum of open bosonic string are used to check the consistency of saddle point calculations of high energy scattering amplitudes of Gross and Mende and Gross and Manes. Some inconsistencies of their saddle point calculations are found even for the string-tree scattering amplitudes of the excited string states. We discuss and calculate the missing terms of the calculation by those authors to recover the stringy Ward identities. In addition, based on the tree-level stringy Ward identities, we give the proof of a general formula, which was proposed previously, of all high energy four-point string-tree amplitudes of arbitrary particles in the string spectrum. In this formula all such scattering amplitudes are expressed in terms of those of tachyons as conjectured by Gross. The formula is extremely simple which manifestly demonstrates the universal high energy behavior of the interactions among all string states.

  15. The Lauricella functions and exact string scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Lai, Sheng-Hong; Lee, Jen-Chi; Yang, Yi

    2016-11-01

    We discover that the 26 D open bosonic string scattering amplitudes (SSA) of three tachyons and one arbitrary string state can be expressed in terms of the D-type Lauricella functions with associated SL(K+3,C) symmetry. As a result, SSA and symmetries or relations among SSA of different string states at various limits calculated previously can be rederived. These include the linear relations first conjectured by Gross [1-5] and later corrected and proved in [6-12] in the hard scattering limit, the recurrence relations in the Regge scattering limit with associated SL(5,C) symmetry [24-26] and the extended recurrence relations in the nonrelativistic scattering limit with associated SL(4,C) symmetry [29] discovered recently. Finally, as an application, we calculate a new recurrence relation of SSA which is valid for all energies.

  16. Unambiguous ionization amplitudes for electron-hydrogen scattering

    SciTech Connect

    Bartlett, P. L.; Bray, I.; Jones, S.; Stelbovics, A. T.; Kadyrov, A. S.; Bartschat, K.; Ver Steeg, G. L.; Scott, M. P.; Burke, P. G.

    2003-08-01

    According to quantum collision theory, scattering amplitudes are complex numbers, which are completely defined by their magnitude and phase. Although the phase information is generally not determined entirely in collision experiments, the phases are well defined and can be used to check computational models. We use four state-of-the-art approaches to calculate the magnitude and phase of the electron-hydrogen ionization amplitude in the Temkin-Poet S-wave model. We demonstrate that the correct phase can be extracted for each method by using the appropriate final-state continuum functions.

  17. Harmonic R matrices for scattering amplitudes and spectral regularization.

    PubMed

    Ferro, Livia; Łukowski, Tomasz; Meneghelli, Carlo; Plefka, Jan; Staudacher, Matthias

    2013-03-22

    Planar N = 4 supersymmetric Yang-Mills theory appears to be integrable. While this allows one to find this theory's exact spectrum, integrability has hitherto been of no direct use for scattering amplitudes. To remedy this, we deform all scattering amplitudes by a spectral parameter. The deformed tree-level four-point function turns out to be essentially the one-loop R matrix of the integrable N = 4 spin chain satisfying the Yang-Baxter equation. Deformed on-shell three-point functions yield novel three-leg R matrices satisfying bootstrap equations. Finally, we supply initial evidence that the spectral parameter might find its use as a novel symmetry-respecting regulator replacing dimensional regularization. Its physical meaning is a local deformation of particle helicity, a fact which might be useful for a much larger class of nonintegrable four-dimensional field theories.

  18. Infrared singularities of scattering amplitudes in perturbative QCD

    SciTech Connect

    Becher, Thomas; Neubert, Matthias

    2013-11-01

    An exact formula is derived for the infrared singularities of dimensionally regularized scattering amplitudes in massless QCD with an arbitrary number of legs, valid at any number of loops. It is based on the conjecture that the anomalous-dimension matrix of n-jet operators in soft-collinear effective theory contains only a single non-trivial color structure, whose coefficient is the cusp anomalous dimension of Wilson loops with light-like segments. Its color-diagonal part is characterized by two anomalous dimensions, which are extracted to three-loop order from known perturbative results for the quark and gluon form factors. This allows us to predict the three-loop coefficients of all 1/epsilon^k poles for an arbitrary n-parton scattering amplitudes, generalizing existing two-loop results.

  19. Scattering amplitudes and Wilson loops in twistor space

    NASA Astrophysics Data System (ADS)

    Adamo, Tim; Bullimore, Mathew; Mason, Lionel; Skinner, David

    2011-11-01

    This paper reviews the recent progress in twistor approaches to Wilson loops, amplitudes and their duality for {N}=4 super-Yang-Mills. Wilson loops and amplitudes are derived from first principles using the twistor action for maximally supersymmetric Yang-Mills theory. We start by deriving the MHV rules for gauge theory amplitudes from the twistor action in an axial gauge in twistor space, and show that this gives rise to the original momentum space version given by Cachazo, Svrček and Witten. We then go on to obtain from these the construction of the momentum twistor space loop integrand using (planar) MHV rules and show how it arises as the expectation value of a holomorphic Wilson loop in twistor space. We explain the connection between the holomorphic Wilson loop and certain light-cone limits of correlation functions. We give a brief review of other ideas in connection with amplitudes in twistor space: twistor-strings, recursion in twistor space, the Grassmannian residue formula for leading singularities and amplitudes as polytopes. This paper is an invited review for a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Scattering amplitudes in gauge theories’.

  20. Constraints on scattering amplitudes in multistate Landau-Zener theory

    DOE PAGES

    Sinitsyn, Nikolai A.; Lin, Jeffmin; Chernyak, Vladimir Y.

    2017-01-30

    Here, we derive a set of constraints, which we will call hierarchy constraints, on scattering amplitudes of an arbitrary multistate Landau-Zener model (MLZM). The presence of additional symmetries can transform such constraints into nontrivial relations between elements of the transition probability matrix. This observation can be used to derive complete solutions of some MLZMs or, for models that cannot be solved completely, to reduce the number of independent elements of the transition probability matrix.

  1. Massive quark-gluon scattering amplitudes at tree level

    NASA Astrophysics Data System (ADS)

    Hall, Anthony

    2008-01-01

    Results for four-, five-, and six-parton tree amplitudes for massive quark-antiquark scattering with gluons are calculated using the recursion relations of Britto, Cachazo, Feng, and Witten. The required diagrams are generated using shifts of the momenta of a pair of massless legs to complex values. Checks verifying the calculations are described, and a simple formula for the shifted spinors of an internal gluon is presented.

  2. Constraints on scattering amplitudes in multistate Landau-Zener theory

    NASA Astrophysics Data System (ADS)

    Sinitsyn, Nikolai A.; Lin, Jeffmin; Chernyak, Vladimir Y.

    2017-01-01

    We derive a set of constraints, which we will call hierarchy constraints, on scattering amplitudes of an arbitrary multistate Landau-Zener model (MLZM). The presence of additional symmetries can transform such constraints into nontrivial relations between elements of the transition probability matrix. This observation can be used to derive complete solutions of some MLZMs or, for models that cannot be solved completely, to reduce the number of independent elements of the transition probability matrix.

  3. Two-loop scattering amplitudes from the Riemann sphere

    NASA Astrophysics Data System (ADS)

    Geyer, Yvonne; Mason, Lionel; Monteiro, Ricardo; Tourkine, Piotr

    2016-12-01

    The scattering equations give striking formulas for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor-string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the genus of the world sheet is equivalent to an expansion in terms of nodes of a Riemann sphere, with the nodes carrying the loop momenta. In this paper, we show how to obtain two-loop scattering equations with the correct factorization properties. We adapt genus-two integrands from the ambitwistor string to the nodal Riemann sphere and show that these yield correct answers, by matching standard results for the four-point two-loop amplitudes of maximal supergravity and super-Yang-Mills theory. In the Yang-Mills case, this requires the loop analogue of the Parke-Taylor factor carrying the color dependence, which includes nonplanar contributions.

  4. Scattering amplitudes over finite fields and multivariate functional reconstruction

    NASA Astrophysics Data System (ADS)

    Peraro, Tiziano

    2016-12-01

    Several problems in computer algebra can be efficiently solved by reducing them to calculations over finite fields. In this paper, we describe an algorithm for the reconstruction of multivariate polynomials and rational functions from their evaluation over finite fields. Calculations over finite fields can in turn be efficiently performed using machine-size integers in statically-typed languages. We then discuss the application of the algorithm to several techniques related to the computation of scattering amplitudes, such as the four- and six-dimensional spinor-helicity formalism, tree-level recursion relations, and multi-loop integrand reduction via generalized unitarity. The method has good efficiency and scales well with the number of variables and the complexity of the problem. As an example combining these techniques, we present the calculation of full analytic expressions for the two-loop five-point on-shell integrands of the maximal cuts of the planar penta-box and the non-planar double-pentagon topologies in Yang-Mills theory, for a complete set of independent helicity configurations.

  5. Propagating light through a scattering medium with specific amplitude and phase (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tseng, Snow H.; Kung, Te-Jen; Yu, Min-Lun

    2016-03-01

    By means of numerical solutions of Maxwell's equations, we model the complex light scattering phenomenon. Light propagation through scattering medium is a deterministic process; with specific amplitude and phase, light can propagate to the target position via multiple scattering. By means of numerical solutions of Maxwell's equations, the complex light scattering phenomenon can be accurately analyzed. The reported simulation enables qualitative and quantitative analyses of the effectiveness of directing light through turbid media to a targeted position

  6. Scattering amplitudes for the rationally extended PT symmetric complex potentials

    NASA Astrophysics Data System (ADS)

    Kumari, Nisha; Yadav, Rajesh Kumar; Khare, Avinash; Bagchi, Bijan; Mandal, Bhabani Prasad

    2016-10-01

    In this paper, we consider the rational extensions of two different classes of PT symmetric complex potentials namely the asymptotically vanishing Scarf II and asymptotically non-vanishing Rosen-Morse II [ RM-II] and obtain the accompanying bound state eigenfunctions in terms of the exceptional Xm Jacobi polynomials and a certain class of orthogonal polynomials. By considering the asymptotic behavior of the exceptional polynomials, we also derive the reflection and transmission amplitudes for them and discuss the various novel properties of the corresponding amplitudes.

  7. Implementation of Recursion Relations in Gluon Scattering Amplitude Calculations in AdS4 /CFT3

    NASA Astrophysics Data System (ADS)

    Dokmetzoglou, Nikolaos; Kharel, Savan

    2017-01-01

    The Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence is a duality between a theory of gravity in curved-space (AdS) and a conformally-invariant quantum field theory in flat-space (CFT). Scattering amplitudes are observables associated with the probability of the interaction of a given assembly of particles. Gluons, being the exchange particles associated with the strong nuclear force, which holds quarks together to form protons, are abundant byproducts of fundamental particle collisions. Thus, studying gluon scattering amplitudes is an effective way of deepening our understanding of these observables in AdS/CFT. Traditionally, Feynman diagrams have been used to calculate such scattering amplitudes. In this project, we use factorization properties and recursion relations to simplify these calculations. More specifically, we calculate multiple (different helicity combinations) four-point gluon scattering amplitudes in AdS4 /CFT3 (4-D AdS and 3-D CFT) as sums of products of three-point amplitudes. And then we calculate a five-point gluon scattering amplitude in AdS4 /CFT3 by decomposing it into a sum of products of these four-point and three-point amplitudes. Finally we comment on useful identities for checking these amplitudes. This work was supported by a Weinstein Davidson College Research Initiative Summer Research grant.

  8. Multipole scattering amplitudes in the color glass condensate formalism

    NASA Astrophysics Data System (ADS)

    Shi, Yu; Zhang, Cheng; Wang, Enke

    2017-06-01

    We evaluate the octupole in the large-Nc limit in the McLerran-Venugopalan model and derive a general expression of the 2n-point correlator, which can be applied in analytical studies of the multiparticle production in the scatterings between hard probes and dense targets.

  9. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition. 2; Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, Aaron

    2004-01-01

    The development of a practical method of accurately calculating the full scattering amplitude, without making a partial wave decomposition is continued. The method is developed in the context of electron-hydrogen scattering, and here exchange is dealt with by considering e-H scattering in the static exchange approximation. The Schroedinger equation in this approximation can be simplified to a set of coupled integro-differential equations. The equations are solved numerically for the full scattering wave function. The scattering amplitude can most accurately be calculated from an integral expression for the amplitude; that integral can be formally simplified, and then evaluated using the numerically determined wave function. The results are essentially identical to converged partial wave results.

  10. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition. 2; Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, Aaron

    2004-01-01

    The development of a practical method of accurately calculating the full scattering amplitude, without making a partial wave decomposition is continued. The method is developed in the context of electron-hydrogen scattering, and here exchange is dealt with by considering e-H scattering in the static exchange approximation. The Schroedinger equation in this approximation can be simplified to a set of coupled integro-differential equations. The equations are solved numerically for the full scattering wave function. The scattering amplitude can most accurately be calculated from an integral expression for the amplitude; that integral can be formally simplified, and then evaluated using the numerically determined wave function. The results are essentially identical to converged partial wave results.

  11. Symmetries of tree-level scattering amplitudes in N=6 superconformal Chern-Simons theory

    SciTech Connect

    Bargheer, Till; Loebbert, Florian; Meneghelli, Carlo

    2010-08-15

    Constraints of the osp(6|4) symmetry on tree-level scattering amplitudes in N=6 superconformal Chern-Simons theory are derived. Supplemented by Feynman diagram calculations, solutions to these constraints, namely, the four- and six-point superamplitudes, are presented and shown to be invariant under Yangian symmetry. This introduces integrability into the amplitude sector of the theory.

  12. Topics in Nonsupersymmetric Scattering Amplitudes in Gauge and Gravity Theories

    NASA Astrophysics Data System (ADS)

    Nohle, Joshua David

    In Chapters 1 and 2, we introduce and review the duality between color and kinematics in Yang-Mills theory uncovered by Bern, Carrasco and Johansson (BCJ). In Chapter 3, we provide evidence in favor of the conjectured duality between color and kinematics for the case of nonsupersymmetric pure Yang-Mills amplitudes by constructing a form of the one-loop four-point amplitude of this theory that makes the duality manifest. Our construction is valid in any dimension. We also describe a duality-satisfying representation for the two-loop four-point amplitude with identical four-dimensional external helicities. We use these results to obtain corresponding gravity integrands for a theory containing a graviton, dilaton, and antisymmetric tensor, simply by replacing color factors with specified diagram numerators. Using this, we give explicit forms of ultraviolet divergences at one loop in four, six, and eight dimensions, and at two loops in four dimensions. In Chapter 4, we extend the four-point one-loop nonsupersymmetric pure Yang-Mills discussion of Chapter 3 to include fermions and scalars circulating in the loop with all external gluons. This gives another nontrivial loop-level example showing that the duality between color and kinematics holds in nonsupersymmetric gauge theory. The construction is valid in any spacetime dimension and written in terms of formal polarization vectors. We also convert these expressions into a four-dimensional form with explicit external helicity states. Using this, we compare our results to one-loop duality-satisfying amplitudes that are already present in literature. In Chapter 5, we switch from the topic of color-kinematics duality to discuss the recently renewed interest in the soft behavior of gravitons and gluons. Specifically, we discuss the subleading low-energy behavior. Cachazo and Strominger recently proposed an extension of the soft-graviton theorem found by Weinberg. In addition, they proved the validity of their extension at

  13. Implementation of the Duality between Wilson Loops and Scattering Amplitudes in QCD

    SciTech Connect

    Makeenko, Yuri; Olesen, Poul

    2009-02-20

    We generalize modern ideas about the duality between Wilson loops and scattering amplitudes in N=4 super Yang-Mills theory to large-N (or quenched) QCD. We show that the area-law behavior of asymptotically large Wilson loops is dual to the Regge-Veneziano behavior of scattering amplitudes at high energies and fixed momentum transfer, when the quark mass is small and/or the number of particles is large. We elaborate on this duality for string theory in flat space, identifying the asymptotes of the disk amplitude and the Wilson loop of large-N QCD.

  14. Born term of the {pi}N scattering amplitude in the Skyrme model

    SciTech Connect

    Itoh, Tomoaki; Arima, Masaki

    2011-04-15

    The Skyrme model is applied to the study of the {pi}N scattering amplitude. The useful expression of amplitude given by the chiral reduction formula is employed. The calculation is performed in the lowest order of 1/N{sub c}: a source of interaction is a classical soliton taking a hedgehog configuration. It is important to consider the zero modes both for the translation invariance and for the isospin symmetry simultaneously. Despite the former negative impression, the Skyrme model correctly produces the Born term in the scattering amplitude.

  15. Scattering amplitudes to all orders in meson exchange

    SciTech Connect

    Silbar, R.R.; Mattis, M.P.

    1990-01-01

    As the number of colors in QCD, N{sub C}, becomes large, it is possible to sum up all meson-exchange contributions, however arbitrarily complicated, to meson-baryon and baryon-baryon scattering. A semi-classical structure for the two-flavor theory emerges, in close correspondence to vector-meson-augmented Skyrme models. In this limit, baryons act as extended static sources for the classical meson fields. This leads to non-linear differential equations for the classical meson fields which can be solved numerically for static radial (hedgehog-like) solutions. The non-linear terms in the equations of motion for the quantized meson fields can then be simplified, to leading order in 1/N{sub C}, by replacing all factors of the meson field but one by the previously-found classical field. This results in linear, Schroedinger-like equations, which are easily solved. For the meson-baryon case the solution can be subsequently analyzed to obtain the phase shifts for the scattering and, from these, the baryon resonance spectrum of the model. As the warm-up, we have carried out this calculation for the simple case of {sigma} mesons only, finding sensible results. 8 refs., 3 figs.

  16. Direct Calculation of the Scattering Amplitude Without Partial Wave Decomposition. III; Inclusion of Correlation Effects

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, Aaron

    2007-01-01

    In the first two papers in this series, we developed a method for studying electron-hydrogen scattering that does not use partial wave analysis. We constructed an ansatz for the wave function in both the static and static exchange approximations and calculated the full scattering amplitude. Here we go beyond the static exchange approximation, and include correlation in the wave function via a modified polarized orbital. This correlation function provides a significant improvement over the static exchange approximation: the resultant elastic scattering amplitudes are in very good agreement with fully converged partial wave calculations for electron-hydrogen scattering. A fully variational modification of this approach is discussed in the conclusion of the article Popular summary of Direct calculation of the scattering amplitude without partial wave expansion. III ....." by J. Shertzer and A. Temkin. In this paper we continue the development of In this paper we continue the development of a new approach to the way in which researchers have traditionally used to calculate the scattering cross section of (low-energy) electrons from atoms. The basic mathematical problem is to solve the Schroedinger Equation (SE) corresponding the above physical process. Traditionally it was always the case that the SE was reduced to a sequence of one-dimensional (ordinary) differential equations - called partial waves which were solved and from the solutions "phase shifts" were extracted, from which the scattering cross section was calculated.

  17. Scattering amplitude of ultracold atoms near the p-wave magnetic Feshbach resonance

    SciTech Connect

    Zhang Peng; Naidon, Pascal; Ueda, Masahito

    2010-12-15

    Most of the current theories on the p-wave superfluid in cold atomic gases are based on the effective-range theory for the two-body scattering, where the low-energy p-wave scattering amplitude f{sub 1}(k) is given by f{sub 1}(k)=-1/[ik+1/(Vk{sup 2})+1/R]. Here k is the incident momentum, V and R are the k-independent scattering volume and effective range, respectively. However, due to the long-range nature of the van der Waals interaction between two colliding ultracold atoms, the p-wave scattering amplitude of the two atoms is not described by the effective-range theory [J. Math. Phys. 4, 54 (1963); Phys. Rev. A 58, 4222 (1998)]. In this paper we provide an explicit calculation for the p-wave scattering of two ultracold atoms near the p-wave magnetic Feshbach resonance. We show that in this case the low-energy p-wave scattering amplitude f{sub 1}(k)=-1/[ik+1/(V{sup eff}k{sup 2})+1/(S{sup eff}k)+1/R{sup eff}] where V{sup eff}, S{sup eff}, and R{sup eff} are k-dependent parameters. Based on this result, we identify sufficient conditions for the effective-range theory to be a good approximation of the exact scattering amplitude. Using these conditions we show that the effective-range theory is a good approximation for the p-wave scattering in the ultracold gases of {sup 6}Li and {sup 40}K when the scattering volume is enhanced by the resonance.

  18. Analyticity properties and asymptotic behavior of scattering amplitude in higher dimensional theories

    NASA Astrophysics Data System (ADS)

    Maharana, Jnanadeva

    2017-01-01

    The properties of the high energy behavior of the scattering amplitude of massive, neutral, and spinless particles in higher dimensional field theories are investigated. The axiomatic formulation of Lehmann, Symanzik, and Zimmermann (LSZ) is adopted. The analyticity properties of the causal, the retarded, and the advanced functions associated with the four point elastic amplitudes are studied. The analog of the Lehmann-Jost-Dyson representation is obtained in higher dimensional field theories. The generalized J-L-D representation is utilized to derive the t-plane analyticity property of the amplitude. The existence of an ellipse analogous to the Lehmann ellipse is demonstrated. Thus a fixed-t dispersion relation can be written down with a finite number of subtractions due to the temperedness of the amplitudes. The domain of analyticity of scattering amplitude in s and t variables is extended by imposing unitarity constraints. A generalized version of Martin's theorem is derived to prove the existence of such a domain in D-dimensional field theories. It is shown that the amplitude can be expanded in a power series in t which converges for |" separators=" t | < R , R being s-independent. The positivity properties of absorptive amplitudes are derived to prove the t-plane analyticity of amplitude. In the extended analyticity domain dispersion relations are written with two subtractions. The bound on the total cross section is derived from LSZ axioms without any extra ad hoc assumptions.

  19. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II

    NASA Technical Reports Server (NTRS)

    Shertzer, J.; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE) can be reduced to a 2d partial differential equation (pde), and was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation. The resultant equation can be reduced to a pair of coupled pde's, to which the finite element method can still be applied. The resultant scattering amplitudes, both singlet and triplet, as a function of angle can be calculated for various energies. The results are in excellent agreement with converged partial wave results.

  20. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II: Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE), which can be reduced to a 2d partial differential equation (pde), was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation, which is reducible to a pair of coupled pde's. The resultant scattering amplitudes, both singlet and triplet, calculated as a function of energy are in excellent agreement with converged partial wave results.

  1. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II: Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Shertzer, Janine; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE), which can be reduced to a 2d partial differential equation (pde), was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation, which is reducible to a pair of coupled pde's. The resultant scattering amplitudes, both singlet and triplet, calculated as a function of energy are in excellent agreement with converged partial wave results.

  2. Calculation of the Full Scattering Amplitude without Partial Wave Decomposition II

    NASA Technical Reports Server (NTRS)

    Shertzer, J.; Temkin, A.

    2003-01-01

    As is well known, the full scattering amplitude can be expressed as an integral involving the complete scattering wave function. We have shown that the integral can be simplified and used in a practical way. Initial application to electron-hydrogen scattering without exchange was highly successful. The Schrodinger equation (SE) can be reduced to a 2d partial differential equation (pde), and was solved using the finite element method. We have now included exchange by solving the resultant SE, in the static exchange approximation. The resultant equation can be reduced to a pair of coupled pde's, to which the finite element method can still be applied. The resultant scattering amplitudes, both singlet and triplet, as a function of angle can be calculated for various energies. The results are in excellent agreement with converged partial wave results.

  3. Non-relativistic scattering amplitude for a new multi-parameter exponential-type potential

    NASA Astrophysics Data System (ADS)

    Yazarloo, B. H.; Mehraban, H.; Hassanabadi, H.

    2016-08-01

    In this paper, we study the scattering properties of s-wave Schrödinger equation for the multi-parameter potential, which can be reduced into four special cases for different values of potential parameters, i.e., Hulthén, Manning-Rosen, and Eckart potentials. We also obtain and investigate the scattering amplitudes of these special cases. Some numerical results are also obtained and reported.

  4. A novel sampling method for multiple multiscale targets from scattering amplitudes at a fixed frequency

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodong

    2017-08-01

    A sampling method by using scattering amplitude is proposed for shape and location reconstruction in inverse acoustic scattering problems. Only matrix multiplication is involved in the computation, thus the novel sampling method is very easy and simple to implement. With the help of the factorization of the far field operator, we establish an inf-criterion for characterization of underlying scatterers. This result is then used to give a lower bound of the proposed indicator functional for sampling points inside the scatterers. While for the sampling points outside the scatterers, we show that the indicator functional decays like the bessel functions as the sampling point goes away from the boundary of the scatterers. We also show that the proposed indicator functional continuously depends on the scattering amplitude, this further implies that the novel sampling method is extremely stable with respect to errors in the data. Different to the classical sampling method such as the linear sampling method or the factorization method, from the numerical point of view, the novel indicator takes its maximum near the boundary of the underlying target and decays like the bessel functions as the sampling points go away from the boundary. The numerical simulations also show that the proposed sampling method can deal with multiple multiscale case, even the different components are close to each other.

  5. Stimulated scattering of a large amplitude electromagnetic wave by the eigenmodes of a plasma slab

    NASA Astrophysics Data System (ADS)

    Gradov, O. M.; Stenflo, L.

    1983-08-01

    New results are presented from a theoretical investigation of the scattering of an electromagnetic pump wave that is normally incident on a plasma slab. In the case considered here, the leaking surface wave eigenmode represents the scattered radiation. The generation of harmonics in the scattered wave will thus be responsible for the saturation of the wave intensities. It is shown that a large-amplitude electromagnetic pump wave can be scattered in a nonlinear process where both the low-frequency and high-frequency oscillations are eigenmodes of the plasma slab. The second harmonic generation that occurs in this case leads to efficient saturation of the scattering instability. It is pointed out that other mechanisms, for example, the screening of the pump wave by the surface mode current, may also contribute significantly to the establishment of the stationary wave.

  6. The string BCJ relations revisited and extended recurrence relations of nonrelativistic string scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Lai, Sheng-Hong; Lee, Jen-Chi; Yang, Yi

    2016-05-01

    We review and extend high energy four point string BCJ relations in both the fixed angle and Regge regimes. We then give an explicit proof of four point string BCJ relations for all energy. This calculation provides an alternative proof of the one based on monodromy of integration in string amplitude calculation. In addition, we calculate both s- t and t- u channel nonrelativistic low energy string scattering amplitudes of three tachyons and one higher spin string state at arbitrary mass levels. We discover that the mass and spin dependent nonrelativistic string BCJ relations can be expressed in terms of Gauss hypergeometry functions. As an application, for each fixed mass level N, we derive extended recurrence relations among nonrelativistic low energy string scattering amplitudes of string states with different spins and different channels.

  7. Scattering amplitudes from unitarity-based reduction algorithm at the integrand-level

    NASA Astrophysics Data System (ADS)

    Mastrolia, P.; Ossola, G.; Reiter, T.; Tramontano, F.

    2010-08-01

    samurai is a tool for the automated numerical evaluation of one-loop corrections to any scattering amplitudes within the dimensional-regularization scheme. It is based on the decomposition of the integrand according to the OPP -approach, extended to accommodate an implementation of the generalized d-dimensional unitarity-cuts technique, and uses a polynomial interpolation exploiting the Discrete Fourier Transform. samurai can process integrands written either as numerator of Feynman diagrams or as product of tree-level amplitudes. We discuss some applications, among which the 6-and 8-photon scattering in QED, and the 6-quark scattering in QCD. samurai has been implemented as a Fortran90 library, publicly available, and it could be a useful module for the systematic evaluation of the virtual corrections oriented towards automating next-to-leading order calculations relevant for the LHC phenomenology.

  8. Scattering amplitudes of massive N =2 gauge theories in three dimensions

    NASA Astrophysics Data System (ADS)

    Agarwal, Abhishek; Lipstein, Arthur E.; Young, Donovan

    2014-02-01

    We study the scattering amplitudes of mass-deformed Chern-Simons theories and Yang-Mills-Chern-Simons theories with N =2 supersymmetry in three dimensions. In particular, we derive the on-shell supersymmetry algebras which underlie the scattering matrices of these theories. We then compute various 3 and 4-point on-shell tree-level amplitudes in these theories. For the mass-deformed Chern-Simons theory, odd-point amplitudes vanish and we find that all of the 4-point amplitudes can be encoded elegantly in superamplitudes. For the Yang-Mills-Chern-Simons theory, we obtain all of the 4-point tree-level amplitudes using a combination of perturbative techniques and algebraic constraints and we comment on difficulties related to computing amplitudes with external gauge fields using Feynman diagrams. Finally, we propose a Britto-Cachazo-Feng-Witten recursion relation for mass-deformed theories in three dimensions and discuss the applicability of this proposal to mass-deformed N =2 theories.

  9. Statistical density model for composite system scattering: Modified ensemble densities and bounded amplitudes

    NASA Astrophysics Data System (ADS)

    Hahn, Y. K.

    2016-09-01

    A statistical density model for composite system scattering is formulated, by incorporating the ensemble density functional approach in describing the correlation dynamics during the collision. The principal difficulty of non-integrable propagating waves is first resolved by treating the open and closed channels separately; only the closed channel part does allow a density description. The unique open/closed channel separation adopted here allows not only the closed channel Hamiltonian MQ to support integrable densities, but also to establish the important bounds on the scattering amplitude. A modified ensemble energy functional for the MQ is constructed, and the statistical densities ρmtQ for the closed channels are generated. The scattering amplitude is then formulated in terms of the ρmtQ and the coefficients of variation that connect the closed channels to the asymptotic source. Evaluation of the amplitude integrals requires the determinantal functions deduced from the ρmtQ, which also leads to a coupled channel approach. The bound property of the amplitude allows variational optimization of the coefficients. Approximate procedures for securing the orthogonality of the MQ and for evaluation of the source term itself are discussed, including a judicious choice of configurations with zero and one inner-shell holes. Validity of the several critical modifications introduced is assessed.

  10. J. J. Sakurai Prize: Scattering Amplitudes - the Story of Loops and Legs

    NASA Astrophysics Data System (ADS)

    Dixon, Lance

    2014-03-01

    Scattering amplitudes are at the interface between quantum field theory and particle experiment. Precise predictions for reactions at energy frontier machines such as the Large Hadron Collider (LHC) rely on quantum corrections to scattering amplitudes involving multiple quarks and gluons, as well as other particles. For decades, theorists used Feynman diagrams for this job. However, Feynman diagrams are just too slow, even on fast computers, to allow adequate precision for complicated events with many jets of hadrons in the final state. Such events are produced copiously at the LHC, and constitute formidable backgrounds to many searches for new physics. Over the past two decades, alternative methods to Feynman diagrams have come to fruition. The new ``on-shell'' methods are based on the old principle of unitarity. They can be much more efficient because they exploit the underlying simplicity of scattering amplitudes, and recycle lower-loop information. The same methods have also enabled new insight into the structure of gauge theory and gravity at the quantum level, especially in highly supersymmetric theories where they maintain all of the symmetries. I'll give a brief motivation for and introduction to the new methods, which will be followed by descriptions of their phenomenological and formal applications by David Kosower and Zvi Bern.

  11. Scattering of glue by glue on the light-cone worldsheet: Helicity nonconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C.B.

    2005-09-15

    We give the light-cone gauge calculation of the one-loop on-shell scattering amplitudes for gluon-gluon scattering which violate helicity conservation. We regulate infrared divergences by discretizing the p{sup +} integrations, omitting the terms with p{sup +}=0. Collinear divergences are absent diagram by diagram for the helicity nonconserving amplitudes. We also employ a novel ultraviolet regulator that is natural for the light-cone worldsheet description of planar Feynman diagrams. We show that these regulators give the known answers for the helicity nonconserving one-loop amplitudes, which do not suffer from the usual infrared vagaries of massless particle scattering. For the maximal helicity violating process we elucidate the physics of the remarkable fact that the loop momentum integrand for the on-shell Green function associated with this process, with a suitable momentum routing of the different contributing topologies, is identically zero. We enumerate the counterterms that must be included to give Lorentz covariant results to this order, and we show that they can be described locally in the light-cone worldsheet formulation of the sum of planar diagrams.

  12. Scattering Amplitudes Interpolating Between Instant Form and Front Form of Relativistic Dynamics

    NASA Astrophysics Data System (ADS)

    Ji, Chueng-Ryong; Bakker, Bernard L. G.; Li, Ziyue; Suzuki, Alfredo T.

    2014-06-01

    Among the three forms of relativistic Hamiltonian dynamics proposed by Dirac in 1949, the front form has the largest number of kinematic generators. This distinction provides useful consequences in the analysis of physical observables in hadron physics. Using the method of interpolation between the instant form and the front form, we introduce the interpolating scattering amplitude that links the corresponding time-ordered amplitudes between the two forms of dynamics and provide the physical meaning of the kinematic transformations as they allow the invariance of each individual time-ordered amplitude for an arbitrary interpolation angle. We discuss the rationale for using front form dynamics, nowadays known as light-front dynamics (LFD), and present a few explicit examples of hadron phenomenology that LFD uniquely can offer from first-principles quantum chromodynamics. In particular, model-independent constraints are provided for the analyses of deuteron form factors and the N Δ transition form factors at large momentum transfer squared Q 2. The swap of helicity amplitudes between the collinear and non-collinear kinematics is also discussed in deeply virtual Compton scattering.

  13. J. J. Sakurai Prize: Harmony of Scattering Amplitudes: From Gauge Theory to Supergravity

    NASA Astrophysics Data System (ADS)

    Bern, Zvi

    2014-03-01

    As explained in the two previous talks by Lance Dixon and David Kosower, on-shell methods have had an important impact on our understanding of scattering amplitudes and their application to collider physics. In this talk I will describe examples where these ideas have also had impacts in more theoretical areas. The first example shows how these methods have led to the construction of all quantum corrections to specific scattering amplitudes in maximally supersymmetric gauge theory with a large number of color charges. An active area of current research is to do the same for more intricate generic amplitudes of the theory. A second example shows how on-shell methods have uncovered new algebraic structures in gauge-theory amplitudes that have applications to quantum gravity. The advances make it possible to carry out computations in quantum gravity that would have been hopeless with more traditional Feynman diagram methods and to elucidate a remarkable connection between gauge and gravity theories. The results from these investigations have renewed hope that highly supersymmetric gravity theories may be ultraviolet finite, contrary to the prevailing wisdom.

  14. Broadband flat-amplitude multiwavelength Brillouin-Raman fiber laser with spectral reshaping by Rayleigh scattering.

    PubMed

    Wang, Zinan; Wu, Han; Fan, Mengqiu; Li, Yi; Gong, Yuan; Rao, Yunjiang

    2013-12-02

    In this letter, we propose a novel configuration for generating multiwavelength Brillouin-Raman fiber laser (MBRFL). The spectral reshaping effect introduced by Rayleigh scattering in a 50 km single mode fiber unifies the generated Brillouin comb in terms of both power level and linewidth. As a consequence, we are able to obtain a 40 nm flat-amplitude MBRFL with wide bandwidth from 1557 nm to 1597 nm covering >500 Stokes lines. This is, to the best of our knowledge, the widest flat-amplitude bandwidth of MBRFL with uniform Stokes combs using just a single Raman pump laser. The channel-spacing is 0.08 nm and the measured OSNR is higher than 12.5 dB. We also demonstrate that the output spectrum of the MBRFL is nearly unaffected over 14 dB range of Brillouin pumping power.

  15. Scattering of glue by glue on the light-cone worldsheet. II. Helicityconserving amplitudes

    SciTech Connect

    Chakrabarti, D.; Qiu, J.; Thorn, C. B.

    2006-08-15

    This is the second of a pair of articles on scattering of glue by glue,in which we give the light-cone gauge calculation of the one-loop on-shellhelicity conserving scattering amplitudes for gluon-gluon scattering (neglectingquark loops). The 1/p{sup +} factors in the gluon propagatorare regulated by replacing p{sup +} integrals with discretized sums omitting the p{sup +}=0 terms in each sum. We alsoemploy a novel ultraviolet regulator that is convenient for the light-coneworldsheet description of planar Feynman diagrams. The helicity conservingscattering amplitudes are divergent in the infrared. The infrared divergencesin the elastic one-loop amplitude are shown to cancel, in their contributionto cross sections, against ones in the cross section for unseen bremsstrahlunggluons. We include here the explicit calculation of the latter, because itassumes an unfamiliar form due to the peculiar way discretization of p{sup +} regulates infrared divergences. In resolving the infrareddivergences we employ a covariant definition of jets, which allows a transparentdemonstration of the Lorentz invariance of our final results. Because we usean explicit cutoff of the ultraviolet divergences in exactly four spacetimedimensions, we must introduce explicit counterterms to achieve this finalcovariant result. These counterterms are polynomials in the external momentaof the precise order dictated by power counting. We discuss the modificationsthey entail for the light-cone worldsheet action that reproduces the bareplanar diagrams of the gluonic sector of QCD. The simplest way to do thisis to interpret the QCD string as moving in six spacetime dimensions.

  16. Retarded thermal Green's functions and forward scattering amplitudes at two loops

    NASA Astrophysics Data System (ADS)

    Brandt, F. T.; Das, Ashok; Frenkel, J.

    1999-11-01

    In this paper, we extend our earlier one loop analysis to two loops and give a simple diagrammatic description for the retarded Green's functions at finite temperature in terms of forward scattering amplitudes of on-shell thermal particles. We present a simple discussion, which can be easily generalized to any field theory, of the temperature dependent parts of the retarded two and three point functions in scalar field theory and QED. As an application of our result at two loops, we show how the infrared singularities in the thermal part of the retarded photon self-energy cancel in QED2 in the limit of vanishing electron mass.

  17. Nonplanar on-shell diagrams and leading singularities of scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Chen, Baoyi; Chen, Gang; Cheung, Yeuk-Kwan E.; Li, Yunxuan; Xie, Ruofei; Xin, Yuan

    2017-02-01

    Bipartite on-shell diagrams are the latest tool in constructing scattering amplitudes. In this paper we prove that a Britto-Cachazo-Feng-Witten (BCFW) decomposable on-shell diagram process a rational top form if and only if the algebraic ideal comprised the geometrical constraints are shifted linearly during successive BCFW integrations. With a proper geometric interpretation of the constraints in the Grassmannian manifold, the rational top form integration contours can thus be obtained, and understood, in a straightforward way. All rational top form integrands of arbitrary higher loops leading singularities can therefore be derived recursively, as long as the corresponding on-shell diagram is BCFW decomposable.

  18. Scattering Amplitudes, the AdS/CFT Correspondence, Minimal Surfaces, and Integrability

    DOE PAGES

    Alday, Luis F.

    2010-01-01

    We focus on the computation of scattering amplitudes of planar maximally supersymmetric Yang-Mill in four dimensions at strong coupling by means of the AdS/CFT correspondence and explain how the problem boils down to the computation of minimal surfaces in AdS in the first part of this paper. In the second part of this review we explain how integrability allows to give a solution to the problem in terms of a set of integral equations. The intention of the review is to give a pedagogical, rather than very detailed, exposition.

  19. Calculation of Scattering Amplitude Without Partial Analysis. II; Inclusion of Exchange

    NASA Technical Reports Server (NTRS)

    Temkin, Aaron; Shertzer, J.; Fisher, Richard R. (Technical Monitor)

    2002-01-01

    There was a method for calculating the whole scattering amplitude, f(Omega(sub k)), directly. The idea was to calculate the complete wave function Psi numerically, and use it in an integral expression for f, which can be reduced to a 2 dimensional quadrature. The original application was for e-H scattering without exchange. There the Schrodinger reduces a 2-d partial differential equation (pde), which was solved using the finite element method (FEM). Here we extend the method to the exchange approximation. The S.E. can be reduced to a pair of coupled pde's, which are again solved by the FEM. The formal expression for f(Omega(sub k)) consists two integrals, f+/- = f(sub d) +/- f(sub e); f(sub d) is formally the same integral as the no-exchange f. We have also succeeded in reducing f(sub e) to a 2-d integral. Results will be presented at the meeting.

  20. Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

    NASA Astrophysics Data System (ADS)

    Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

    2001-02-01

    Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions.

  1. Scattering amplitude and bosonization duality in general Chern-Simons vector models

    NASA Astrophysics Data System (ADS)

    Yokoyama, Shuichi

    2016-09-01

    We present the exact large N calculus of four point functions in general Chern-Simons bosonic and fermionic vector models. Applying the LSZ formula to the four point function we determine the two body scattering amplitudes in these theories taking a special care for a non-analytic term to achieve unitarity in the singlet channel. We show that the S-matrix enjoys the bosonization duality, an unusual crossing relation and a non-relativistic reduction to Aharonov-Bohm scattering. We also argue that the S-matrix develops a pole in a certain range of coupling constants, which disappears in the range where the theory reduces to the Chern-Simons theory interacting with free fermions.

  2. Proton-Nucleus Elastic Cross Sections Using Two-Body In-Medium Scattering Amplitudes

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Wilson, John W.; Cucinotta, Francis A.

    2001-01-01

    Recently, a method was developed of extracting nucleon-nucleon (NN) cross sections in the medium directly from experiment. The in-medium NN cross sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the Langley Research Center. The ratio of the real to the imaginary part of the two-body scattering amplitude in the medium was investigated. These ratios are used in combination with the in-medium NN cross sections to calculate elastic proton-nucleus cross sections. The agreement is excellent with the available experimental data. These cross sections are needed for the radiation risk assessment of space missions.

  3. Decomposition of the scattering amplitude into shadow and surface components with inclusion of spin-orbit coupling

    SciTech Connect

    Melo, German; David, Jorge; Restrepo, Albeiro

    2008-09-15

    We propose a decomposition of the scattering amplitude into shadow and surface components for proton scattering against calcium isotopes as targets at 21 MeV. We account for spin-orbit coupling effects for the optical potential in the nonrelativistic limit. Our calculations show very good agreement with experimental trends.

  4. Improved Persistent Scatterer analysis using Amplitude Dispersion Index optimization of dual polarimetry data

    NASA Astrophysics Data System (ADS)

    Esmaeili, Mostafa; Motagh, Mahdi

    2016-07-01

    Time-series analysis of Synthetic Aperture Radar (SAR) data using the two techniques of Small BAseline Subset (SBAS) and Persistent Scatterer Interferometric SAR (PSInSAR) extends the capability of conventional interferometry technique for deformation monitoring and mitigating many of its limitations. Using dual/quad polarized data provides us with an additional source of information to improve further the capability of InSAR time-series analysis. In this paper we use dual-polarized data and combine the Amplitude Dispersion Index (ADI) optimization of pixels with phase stability criterion for PSInSAR analysis. ADI optimization is performed by using Simulated Annealing algorithm to increase the number of Persistent Scatterer Candidate (PSC). The phase stability of PSCs is then measured using their temporal coherence to select the final sets of pixels for deformation analysis. We evaluate the method for a dataset comprising of 17 dual polarization SAR data (HH/VV) acquired by TerraSAR-X data from July 2013 to January 2014 over a subsidence area in Iran and compare the effectiveness of the method for both agricultural and urban regions. The results reveal that using optimum scattering mechanism decreases the ADI values in urban and non-urban regions. As compared to single-pol data the use of optimized polarization increases initially the number of PSCs by about three times and improves the final PS density by about 50%, in particular in regions with high rate of deformation which suffer from losing phase stability over the time. The classification of PS pixels based on their optimum scattering mechanism revealed that the dominant scattering mechanism of the PS pixels in the urban area is double-bounce while for the non-urban regions (ground surfaces and farmlands) it is mostly single-bounce mechanism.

  5. Determination of the Amplitudes and Phases of the Scattering Matrix upon Photodissociation of Molecules

    SciTech Connect

    Korovin, K.O.; Veselov, A.A.; Mikheev, E.M.; Vasyutinskii, O.S.; Zimmermann, D.

    2005-12-15

    The photodissociation of RbI molecules via the second excited state under the action of circularly polarized radiation with a wavelength of 266 nm is studied. By using sub-Doppler Faraday spectroscopy, the angular distributions of the orientation of spins of Rb(5{sup 2}S{sub 1/2}) atoms formed are studied and the anisotropy parameters describing these angular distributions are determined. Based on the anisotropy parameters, the ratio between the amplitudes of the inelastic scattering matrix elements corresponding to the two possible photodissociation channels is determined to be r{sub {omega}}{sub =1}/r{sub {omega}}{sub =0} = 0.71 {+-} 0.15, while the phase difference for these matrix elements is found to amount to {delta}{phi} = 173 deg.n {+-} 29 deg.

  6. 4D scattering amplitudes and asymptotic symmetries from 2D CFT

    NASA Astrophysics Data System (ADS)

    Cheung, Clifford; de la Fuente, Anton; Sundrum, Raman

    2017-01-01

    We reformulate the scattering amplitudes of 4D flat space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D flat space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlators via the (A)dS/CFT dictionary. The Ward identities for the 2D conserved currents are dual to 4D soft theorems, while the bulk-boundary propagators of massless (A)dS modes are superpositions of the leading and subleading Weinberg soft factors of gauge theory and gravity. In general, the massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft, single helicity sectors of 4D gauge theory and gravity. Consistent with the topological nature of Chern-Simons theory, Aharonov-Bohm effects record the "tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. Soft particle exchanges between hard processes define the Kac-Moody level and Virasoro central charge, which are thereby related to the 4D gauge coupling and gravitational strength in units of an infrared cutoff. Finally, we discuss a toy model for black hole horizons via a restriction to the Rindler region.

  7. 4D scattering amplitudes and asymptotic symmetries from 2D CFT

    DOE PAGES

    Cheung, Clifford; de la Fuente, Anton; Sundrum, Raman

    2017-01-25

    We reformulate the scattering amplitudes of 4D at space gauge theory and gravity in the language of a 2D CFT on the celestial sphere. The resulting CFT structure exhibits an OPE constructed from 4D collinear singularities, as well as infinite-dimensional Kac-Moody and Virasoro algebras encoding the asymptotic symmetries of 4D at space. We derive these results by recasting 4D dynamics in terms of a convenient foliation of flat space into 3D Euclidean AdS and Lorentzian dS geometries. Tree-level scattering amplitudes take the form of Witten diagrams for a continuum of (A)dS modes, which are in turn equivalent to CFT correlatorsmore » via the (A)dS/CFT dictionary. The Ward identities for the 2D conserved currents are dual to 4D soft theorems, while the bulk-boundary propagators of massless (A)dS modes are superpositions of the leading and subleading Weinberg soft factors of gauge theory and gravity. In general, the massless (A)dS modes are 3D Chern-Simons gauge fields describing the soft, single helicity sectors of 4D gauge theory and gravity. Consistent with the topological nature of Chern-Simons theory, Aharonov-Bohm effects record the \\tracks" of hard particles in the soft radiation, leading to a simple characterization of gauge and gravitational memories. Soft particle exchanges between hard processes define the Kac-Moody level and Virasoro central charge, which are thereby related to the 4D gauge coupling and gravitational strength in units of an infrared cutoff. Lastly, we discuss a toy model for black hole horizons via a restriction to the Rindler region.« less

  8. Subharmonic scattering of phospholipid-shell microbubbles at low acoustic pressure amplitudes.

    PubMed

    Frinking, Peter J A; Brochot, Jean; Arditi, Marcel

    2010-08-01

    Subharmonic scattering of phospholipid-shell microbubbles excited at relatively low acoustic pressure amplitudes (<30 kPa) has been associated with echo responses from compression-only bubbles having initial surface tension values close to zero. In this work, the relation between sbharmonics and compression-only behavior of phospholipid-shell microbubbles was investigated, experimentally and by simulation, as a function of the initial surface tension by applying ambient overpressures of 0 and 180 mmHg. The microbubbles were excited using a 64-cycle transmit burst with a center frequency of 4 MHz and peak-negative pressure amplitudes ranging from 20 of 150 kPa. In these conditions, an increase in subharmonic response of 28.9 dB (P < 0.05) was measured at 50 kPa after applying an overpressure of 180 mmHg. Simulations using the Marmottant model, taking into account the effect of ambient overpressure on bubble size and initial surface tension, confirmed the relation between subharmonics observed in the pressure-time curves and compression-only behavior observed in the radius-time curves. The trend of an increase in subharmonic response as a function of ambient overpressure, i.e., as a function of the initial surface tension, was predicted by the model. Subharmonics present in the echo responses of phospholipid-shell microbubbles excited at low acoustic pressure amplitudes are indeed related to the echo responses from compression-only bubbles. The increase in subharmonics as a function of ambient overpressure may be exploited for improving methods for noninvasive pressure measurement in heart cavities or big vessels in the human body.

  9. Calculation of scattering amplitude without partial wave analysis: Inclusion of exchange

    NASA Astrophysics Data System (ADS)

    Temkin, Aaron; Shertzer, Janine

    2002-05-01

    In Ref. [1], a method is given for calculating the scattering amplitude f(Ω) directly. The idea is to calculate the complete wave function Ψ_k( r) numerically and use it in an integral expression for f(Ω). The original application was for electron scattering from static hydrogen without exchange. The Schrödinger equation (SE) reduces to a 2D partial differential equation (PDE), which is solved using the finite element method (FEM) [2]. The integral over dφr is done analytically, reducing the integral expression for f(Ω_k) to a 2D integral. Here we extend the method to include the effects of exchange. The SE can be reduced to a pair of 2D coupled PDE's which are again solved by the FEM. The formal expression for f(Ω) consists of two integrals, f^=fd f_e; fd is formally the same integral as the no-exchange f. We have also succeeded in reducing fe to a 2D integral. Results will be presented at the meeting. [1] J. Shertzer and A. Temkin, Phys. Rev. A 63, 062714 (2001). [2] J. Shertzer and J. Botero, Phys. Rev. A 49, 3673 (1994).

  10. Medium modified two-body scattering amplitude from proton-nucleus total cross-sections

    NASA Technical Reports Server (NTRS)

    Tripathi, R. K.; Wilson, J. W.; Cucinotta, F. A.

    2001-01-01

    Recently (R.K. Tripathi, J.W. Wilson, F.A. Cucinotta, Nucl. Instr. and Meth. B 145 (1998) 277; R.K. Tripathi, F.A. Cucinotta, J.W. Wilson, NASA-TP-1998-208438), we have extracted nucleon-nucleon (N-N) cross-sections in the medium directly from experiment. The in-medium N-N cross-sections form the basic ingredients of several heavy-ion scattering approaches including the coupled-channel approach developed at the NASA Langley Research Center. Here, we investigate the ratio of real to imaginary part of the two-body scattering amplitude in the medium. These ratios are used in combination with the in-medium N-N cross-sections to calculate total proton-nucleus cross-sections. The agreement is excellent with the available experimental data. These cross-sections are needed for the radiation risk assessment of space missions. c2001 Elsevier Science B.V. All rights reserved.

  11. Relationship between the Amplitude and Phase of a Signal Scattered by a Point-Like Acoustic Inhomogeneity

    NASA Astrophysics Data System (ADS)

    Burov, V. A.; Morozov, S. A.

    2001-11-01

    Wave scattering by a point-like inhomogeneity, i.e., a strong inhomogeneity with infinitesimal dimensions, is described. This type of inhomogeneity model is used in investigating the point-spread functions of different algorithms and systems. Two approaches are used to derive the rigorous relationship between the amplitude and phase of a signal scattered by a point-like acoustic inhomogeneity. The first approach is based on a Marchenko-type equation. The second approach uses the scattering by a scatterer whose size decreases simultaneously with an increase in its contrast. It is shown that the retarded and advanced waves are scattered differently despite the relationship between the phases of the corresponding scattered waves.

  12. Amplitude of Biot's slow wave scattered by a spherical inclusion in a fluid-saturated poroelastic medium

    NASA Astrophysics Data System (ADS)

    Ciz, Radim; Gurevich, Boris

    2005-03-01

    Spatial heterogeneity of hydrocarbon reservoirs causes significant attenuation and dispersion of seismic waves due to wave-induced flow of the pore fluid between more compliant and less compliant areas. This paper investigates the interaction between a plane elastic wave in a poroelastic medium with a spherical inhomogeneity of another porous material. The behaviour of both the inclusion and the background medium is described by the low-frequency variant of Biot's equations of poroelasticity with the standard boundary conditions at the inclusion surface, and for the inclusion size much smaller than the wavelength of the fast compressional wave. The scattering problem is formulated as a series expansion of displacements expressed in the spherical harmonics. The resulting scattered wavefield consists of the scattered normal compressional and shear waves and Biot's slow wave, which attenuates rapidly with distance from the inclusion and represents the main difference from the elastic case. This study concentrates on the attenuation effects caused by the mode conversion into Biot's slow wave. The solution obtained for Biot's slow wave is well described by the two terms of order n= 0 and n= 2 of the scattering series. The scattering amplitude for the term of order n= 0 is given by a simple expression. The full expression for the term of order n= 2 is very complicated, but can be simplified assuming that the amplitude of the scattered fast (normal) compressional and shear waves are well approximated by the solution of the equivalent elastic problem. This assumption yields a simple approximation for the amplitude of the scattered slow wave, which is accurate for a wide range of material properties and is sufficient for the analysis of the scattering amplitude as a function of frequency. In the low-frequency limit the scattering amplitude of the slow wave scales with ω3/2, and reduces to the asymptotic long-wavelength solution of Berryman (1985), which is valid for

  13. Elastic Scattering of Low Energy Pions by Nuclei and the In-Medium Isovector πN Amplitude

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G.

    2006-07-01

    Measurements of elastic scattering of 21.5 MeV π± by Si, Ca, Ni and Zr were made using a single arm magnetic spectrometer and absolute calibration was made by parallel measurements of Coulomb scattering of muons. Optical model fits to the data reveal the `anomalous' s-wave repulsion known from pionic atoms. Introducing a chiral-motivated density dependence of the isovector scattering amplitude, and considering the energy dependence of the free πN interaction greatly improve fits to the data and remove the `anomaly'.

  14. Large-Amplitude, Scattered Tsunami Wave Mapping Enabled by Ocean Bottom Seismometer Array Recordings

    NASA Astrophysics Data System (ADS)

    Shi, J.; Kohler, M. D.; Ampuero, J. P.; Sutton, J.

    2015-12-01

    A deployment of ocean bottom seismometers off the coast of southern California recorded the March 2011 Tohoku tsunami on 22 differential pressure gauges (DPGs). The DPG tsunami records across the entire array show multiple large-amplitude, coherent phases arriving one hour to more than 36 hours after the initial tsunami phase. Analysis of the DPG recordings reveals possible locations of the geographical sources that contributed to secondary tsunami arrivals in southern California. A beamforming technique is applied to the DPG data to determine the azimuths and arrival times of scattered wave energy. In addition, a backward ray tracing procedure is applied to a wide range of back azimuth starting values from the DPG array to map possible source locations. The results show several possible candidates of secondary tsunami source structures. These include the Alaskan Peninsula island chain producing a tsunami arrival ~60 minutes after the first arrival, and the Hawaiian Islands producing an arrival ~170 minutes after the first arrival. The results are mapped into modified tsunami warning messages to show how a time-varying hazard could be communicated with more effective message format and content. The results are demonstrating the effects of including clearly described locations, time of impact, and hazard impact consequences on message perception among the public.

  15. Partial-differential-equation-constrained amplitude-based shape detection in inverse acoustic scattering

    NASA Astrophysics Data System (ADS)

    Na, Seong-Won; Kallivokas, Loukas F.

    2008-03-01

    In this article we discuss a formal framework for casting the inverse problem of detecting the location and shape of an insonified scatterer embedded within a two-dimensional homogeneous acoustic host, in terms of a partial-differential-equation-constrained optimization approach. We seek to satisfy the ensuing Karush-Kuhn-Tucker first-order optimality conditions using boundary integral equations. The treatment of evolving boundary shapes, which arise naturally during the search for the true shape, resides on the use of total derivatives, borrowing from recent work by Bonnet and Guzina [1-4] in elastodynamics. We consider incomplete information collected at stations sparsely spaced at the assumed obstacle’s backscattered region. To improve on the ability of the optimizer to arrive at the global optimum we: (a) favor an amplitude-based misfit functional; and (b) iterate over both the frequency- and wave-direction spaces through a sequence of problems. We report numerical results for sound-hard objects with shapes ranging from circles, to penny- and kite-shaped, including obstacles with arbitrarily shaped non-convex boundaries.

  16. Elastic scattering of low energy pions by nuclei and the in-medium isovector πN amplitude

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Kritchman, S.; Meier, R.; Wagner, G. J.; Yaari, G.

    2005-09-01

    Measurements of elastic scattering of 21.5 MeV π± by Si, Ca, Ni, and Zr were made by using a single-arm magnetic spectrometer. Absolute calibration was made by parallel measurements of Coulomb scattering of muons. Parameters of a pion-nucleus optical potential were obtained from fits to all eight angular distributions put together. The anomalous s-wave repulsion known from pionic atoms is clearly observed and could be removed by introducing a chiral-motivated density dependence of the isovector scattering amplitude, which also greatly improved the fits to the data. The empirical energy dependence of the isoscalar amplitude also improves the fits to the data but, contrary to what is found with pionic atoms, on its own is incapable of removing the anomaly.

  17. On the determination of Ω - Ω scattering amplitudes from finite volume spectra

    NASA Astrophysics Data System (ADS)

    Li, Ning; Wu, Ya-Jie

    2016-12-01

    The elastic scattering phase shifts to the two-particle energy levels in a finite cubic box is related by the Lüscher’s formula. In this paper, based on the nonrelativistic quantum mechanics model which is usually assumed to be the low energy scattering case in lattice simulations, we confirmed the generalized Lüscher’s formula for the case of two-particle scattering with arbitrary spin in Ref. 1. In particular, Lüscher’s formula is synthesized for two-spin-3/2-particle scattering, i.e. Ω - Ω scattering on lattice that may help us study the promising dibaryon states.

  18. Strong-field cyclotron scattering. I - Scattering amplitudes and natural line width. [in spectra of accretion-powered X-ray pulsars

    NASA Technical Reports Server (NTRS)

    Graziani, Carlo

    1993-01-01

    The introduction of resonance line width into the QED cyclotron scattering amplitudes is considered. It is shown that the width arises from loop corrections to the electron propagator, which also bring about shifts in the Landau energy levels. A formalism is developed that allows the dressed electron propagator to be derived. It is shown that the states of Herold et al. (1982) and of Sokolov and Ternov (1968), which diagonalize the component of the magnetic moment operator parallel to the external magnetic field, are appropriate for calculation of the scattering amplitudes, whereas the states of Johnson and Lippmann (1949) are not. In addition, it is shown that the Breit-Wigner broadening approximation E tends to E - i(Gamma)/2 is consistent with the perturbation-theoretic order of the calculation, if the former basis states are chosen, but not the latter.

  19. Characterizing the solutions to scattering equations that support tree-level N k MHV gauge/gravity amplitudes

    NASA Astrophysics Data System (ADS)

    Du, Yi-Jian; Teng, Fei; Wu, Yong-Shi

    2016-11-01

    In this paper we define, independent of theories, two discriminant matrices involving a solution to the scattering equations in four dimensions, the ranks of which are used to divide the solution set into a disjoint union of subsets. We further demonstrate, entirely within the Cachazo-He-Yuan formalism, that each subset of solutions gives nonzero contribution to tree-level N k MHV gauge/gravity amplitudes only for a specific value of k. Thus the solutions can be characterized by the rank of their discriminant matrices, which in turn determines the value of k of the N k MHV amplitudes a solution can support. As another application of the technique developed, we show analytically that in Einstein-Yang-Mills theory, if all gluons have the same helicity, the tree-level single-trace amplitudes must vanish.

  20. Amplitude-phase coupling and chirp in quantum-dot lasers: influence of charge carrier scattering dynamics.

    PubMed

    Lingnau, Benjamin; Chow, Weng W; Lüdge, Kathy

    2014-03-10

    We investigate the dependence of the amplitude-phase coupling in quantum-dot (QD) lasers on the charge-carrier scattering timescales. The carrier scattering processes influence the relaxation oscillation parameters, as well as the frequency chirp, which are both important parameters when determining the modulation performance of the laser device and its reaction to optical perturbations. We find that the FM/AM response exhibits a strong dependence on the modulation frequency, which leads to a modified optical response of QD lasers when compared to conventional laser devices. Furthermore, the frequency response curve changes with the scattering time scales, which can allow for an optimization of the laser stability towards optical perturbations.

  1. Detecting the Amplitude Mode of Strongly Interacting Lattice Bosons by Bragg Scattering

    SciTech Connect

    Bissbort, Ulf; Hofstetter, Walter; Li Yongqiang

    2011-05-20

    We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.

  2. Detecting the amplitude mode of strongly interacting lattice bosons by Bragg scattering.

    PubMed

    Bissbort, Ulf; Götze, Sören; Li, Yongqiang; Heinze, Jannes; Krauser, Jasper S; Weinberg, Malte; Becker, Christoph; Sengstock, Klaus; Hofstetter, Walter

    2011-05-20

    We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.

  3. The Analytic Structure of Scattering Amplitudes in N = 4 Super-Yang-Mills Theory

    NASA Astrophysics Data System (ADS)

    Litsey, Sean Christopher

    We begin the dissertation in Chapter 1 with a discussion of tree-level amplitudes in Yang-. Mills theories. The DDM and BCJ decompositions of the amplitudes are described and. related to one another by the introduction of a transformation matrix. This is related to the. Kleiss-Kuijf and BCJ amplitude identities, and we conjecture a connection to the existence. of a BCJ representation via a condition on the generalized inverse of that matrix. Under. two widely-believed assumptions, this relationship is proved. Switching gears somewhat, we introduce the RSVW formulation of the amplitude, and the extension of BCJ-like features to residues of the RSVW integrand is proposed. Using the previously proven connection of BCJ representations to the generalized inverse condition, this extension is validated, including a version of gravitational double copy. The remainder of the dissertation involves an analysis of the analytic properties of loop. amplitudes in N = 4 super-Yang-Mills theory. Chapter 2 contains a review of the planar case, including an exposition of dual variables and momentum twistors, dual conformal symmetry, and their implications for the amplitude. After defining the integrand and on-shell diagrams, we explain the crucial properties that the amplitude has no poles at infinite momentum and that its leading singularities are dual-conformally-invariant cross ratios, and can therefore be normalized to unity. We define the concept of a dlog form, and show that it is a feature of the planar integrand as well. This leads to the definition of a pure integrand basis. The proceeding setup is connected to the amplituhedron formulation, and we put forward the hypothesis that the amplitude is determined by zero conditions. Chapter 3 contains the primary computations of the dissertation. This chapter treats. amplitudes in fully nonplanar N = 4 super-Yang-Mills, analyzing the conjecture that they. follow the pattern of having no poles at infinity, can be written in dlog

  4. Application of scattering theory to P-wave amplitude fluctuations in the crust

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Kazuo; Takemura, Shunsuke; Kobayashi, Manabu

    2015-12-01

    The amplitudes of high-frequency seismic waves generated by local and/or regional earthquakes vary from site to site, even at similar hypocentral distances. It had been suggested that, in addition to local site effects (e.g., variable attenuation and amplification in surficial layers), complex wave propagation in inhomogeneous crustal media is responsible for this observation. To quantitatively investigate this effect, we performed observational, theoretical, and numerical studies on the characteristics of seismic amplitude fluctuations in inhomogeneous crust. Our observations of P-wave amplitude for small to moderately sized crustal earthquakes revealed that fluctuations in P-wave amplitude increase with increasing frequency and hypocentral distance, with large fluctuations showing up to ten-times difference between the largest and the smallest P-wave amplitudes. Based on our theoretical investigation, we developed an equation to evaluate the amplitude fluctuations of time-harmonic waves that radiated isotropically from a point source and propagated spherically in acoustic von Kármán-type random media. Our equation predicted relationships between amplitude fluctuations and observational parameters (e.g., wave frequency and hypocentral distance). Our numerical investigation, which was based on the finite difference method, enabled us to investigate the characteristics of wave propagation in both acoustic and elastic random inhomogeneous media using a variety of source time functions. The numerical simulations indicate that amplitude fluctuation characteristics differ a little between medium types (i.e., acoustic or elastic) or source time function durations. These results confirm the applicability of our analytical equation to practical seismic data analysis.

  5. Flat amplitude multiwavelength Brillouin-Raman comb fiber laser in Rayleigh-scattering-enhanced linear cavity.

    PubMed

    Zamzuri, A K; Mahdi, M A; Ahmad, A; Md Ali, M I; Al-Mansoori, M H

    2007-03-19

    We investigate the amplitude flatness of Rayleigh-assisted Brillouin-Raman comb laser in a linear cavity in which feedbacks are formed by high-reflectivity mirror. The optimization of Brillouin pump power and wavelength is very crucial in order to obtain a uniform power level between Stokes lines. The Brillouin pump must have a relatively large power and its wavelength must be located closer to the Raman peak gain region. The flat-amplitude bandwidth is also determined by the choice of Raman pump wavelengths. A flat-amplitude bandwidth of 30.7 nm from 1527.32 to 1558.02 nm is measured when Raman pump wavelengths are set to 1435 and 1450 nm. 357 uniform Brillouin Stokes lines with 0.086 nm spacing are generated across the wavelength range. The average signal-to-noise ratio of 17 dB is obtained for all the Brillouin Stokes lines.

  6. Recursion relations for graviton scattering amplitudes from Bose symmetry and bonus scaling laws

    NASA Astrophysics Data System (ADS)

    McGady, David A.; Rodina, Laurentiu

    2015-05-01

    Modern on-shell S -matrix methods may dramatically improve our understanding of perturbative quantum gravity, but current foundations of on-shell techniques for general relativity still rely on off-shell Feynman diagram analysis. Here, we complete the fully on-shell proof of Schuster and Toro J. High Energy Phys. 06 (2009) 079] that the recursion relations of Britto, Cachazo, Feng, and Witten (BCFW) apply to relativity tree amplitudes. We do so by showing that the surprising requirement of "bonus" z-2 scaling under a BCFW shift directly follows from Bose symmetry. Moreover, we show that amplitudes in generic theories subjected to BCFW deformations of identical particles necessarily scale as zeven. When applied to the color ordered expansions of Yang-Mills, this directly implies the improved behavior under nonadjacent gluon shifts. Using the same analysis, three-dimensional gravity amplitudes scale as z-4, compared to the z-1 behavior for conformal Chern-Simons matter theory.

  7. Phenomenological extraction of two-photon exchange amplitudes from elastic electron-proton scattering cross section data

    NASA Astrophysics Data System (ADS)

    Qattan, I. A.

    2017-05-01

    Background: The inconsistency in the results obtained from the Rosenbluth separation method and the high-Q2 recoil polarization results on the ratio μpGEp/GMp implies a systematic difference between the two techniques. Several studies suggest that missing higher-order radiative corrections to elastic electron-proton scattering cross section σR(ɛ ,Q2) and in particular hard two-photon-exchange (TPE) contributions could account for the discrepancy. Purpose: In this work, I improve on and extend to low and high Q2 values the extractions of the ɛ dependence of the real parts of the TPE amplitudes relative to the magnetic form factor, as well as the ratio Pl/PlBorn(ɛ ,Q2) by using world data on σR(ɛ ,Q2) with an emphasis on precise new data covering the low-momentum region which is sensitive to the large-scale structure of the nucleon. Method: I combine cross section and polarization measurements of elastic electron-proton scattering to extract the TPE amplitudes. Because the recoil polarization data were confirmed "experimentally" to be essentially independent of ɛ , I constrain the ratio Pt/Pl(ɛ ,Q2) to its ɛ -independent term (Born value) by setting the TPE contributions to zero. This allows for the amplitude YM(ɛ ,Q2) and σR(ɛ ,Q2) to be expressed in terms of the remaining two amplitudes YE(ɛ ,Q2) and Y3(ɛ ,Q2) which in turn are parametrized as second-order polynomials in ɛ and Q2 to reserve as possible the linearity of σR(ɛ ,Q2) as well as to account for possible nonlinearities in the TPE amplitudes. Furthermore, I impose the Regge limit which ensures the vanishing of the TPE contributions to σR(ɛ ,Q2) and the TPE amplitudes in the limit ɛ →1 . Results: I provide simple parametrizations of the TPE amplitudes, along with an estimate of the fit uncertainties. The extracted TPE amplitudes are compared with previous phenomenological extractions and TPE calculations. The Pl/PlBorn ratio is extracted by using the new parametrizations of the TPE

  8. Surface plasmon transmission through discontinuous conducting surfaces: Plasmon amplitude modulation by grazing scattered fields

    SciTech Connect

    Mayoral-Astorga, L. A.; Gaspar-Armenta, J. A.; Ramos-Mendieta, F.

    2016-04-15

    We have studied numerically the diffraction of a surface plasmon polariton (SPP) when it encounters a wide multi-wavelength slit in conducting films. As a jump process a SPP is excited beyond the slit by wave scattering at the second slit edge. The exciting radiation is produced when the incident SPP collapses at the first slit edge. We have found that the transmitted SPP supports inherent and unavoidable interference with grazing scattered radiation; the spatial modulation extends to the fields in the diffraction region where a series of low intensity spots arises. We demonstrate that the SPP generated on the second slab depends on the frequency but not on the wave vector of the collapsed SPP; a SPP is transmitted even when the two metals forming the slit are different. The numerical results were obtained using the Finite Difference Time Domain (FDTD) method with a grid size λ/100.

  9. Decay instability of finite-amplitude circularly polarized Alfven waves - A numerical simulation of stimulated Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Terasawa, T.; Hoshino, M.; Sakai, J.-I.; Hada, T.

    1986-04-01

    By means of a numerical simulation, the nonlinear evolution of large amplitude dispersive Alfven waves is studied. An energy transfer from the parent wave to two daughter Alfven-like waves and a soundlike wave is observed (a stimulated Brillouin scattering process). The observed growth rates and propagation characteristics of these daughter waves agree with the analytical results, which are obtained by extending the previous treatments by Goldstein (1978), Sakai (1978), and Sonnerup (1983). Ions are first trapped by the electrostatic potential of the daughter soundlike waves. Along with the eventual decay (ion Landau damping) of the soundlike waves, ions are phase-mixed and left heated in the parallel direction. The increased parallel energy of ions is transferred to the perpendicular thermal energy through the nonresonant scattering process in the colliding Alfven waves (parent and daughter waves). It is observed that the daughter Alfven waves, which still have a large amplitude, are also unstable for further decay, and that the wave energy is continuously transferred to the longer wavelength regime (inverse cascading process).

  10. In-Medium Isovector πN Amplitude from Low-Energy Pion Scattering

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Bauer, M.; Breitschopf, J.; Clement, H.; Denz, H.; Doroshkevich, E.; Erhardt, A.; Hofman, G. J.; Meier, R.; Wagner, G. J.; Yaari, G.

    2004-09-01

    Differential cross sections for elastic scattering of 21.5MeV positive and negative pions by Si, Ca, Ni, and Zr have been measured as part of a study of the pion-nucleus potential across the threshold. The “anomalous” repulsion in the s-wave term was observed, as is the case with pionic atoms. The extra repulsion can be accounted for by a chiral-motivated model where the pion decay constant is modified in the medium. Unlike in pionic atoms, the anomaly cannot be removed by merely introducing an empirical on-shell energy dependence.

  11. From finite geometry exact quantities to (elliptic) scattering amplitudes for spin chains: the 1/2-XYZ

    NASA Astrophysics Data System (ADS)

    Fioravanti, Davide; Rossi, Marco

    2005-08-01

    Initially, we derive a nonlinear integral equation for the vacuum counting function of the spin 1/2-XYZ chain in the disordered regime, thus paralleling similar results by Klümper [1], achieved through a different technique in the antiferroelectric regime. In terms of the counting function we obtain the usual physical quantities, like the energy and the transfer matrix (eigenvalues). Then, we introduce a double scaling limit which appears to describe the sine-Gordon theory on cylindrical geometry, so generalising famous results in the plane by Luther [2] and Johnson et al. [3]. Furthermore, after extending the nonlinear integral equation to excitations, we derive scattering amplitudes involving solitons/antisolitons first, and bound states later. The latter case comes out as manifestly related to the Deformed Virasoro Algebra of Shiraishi et al. [4]. Although this nonlinear integral equations framework was contrived to deal with finite geometries, we prove it to be effective for discovering or rediscovering S-matrices. As a particular example, we prove that this unique model furnishes explicitly two S-matrices, proposed respectively by Zamolodchikov [5] and Lukyanov-Mussardo-Penati [6,7] as plausible scattering description of unknown integrable field theories.

  12. Accessing the real part of the forward J /ψ -p scattering amplitude from J /ψ photoproduction on protons around threshold

    NASA Astrophysics Data System (ADS)

    Gryniuk, Oleksii; Vanderhaeghen, Marc

    2016-10-01

    We provide an updated analysis of the forward J /ψ -p scattering amplitude, relating its imaginary part to γ p →J /ψ p and γ p →c c ¯X cross section data, and calculating its real part through a once-subtracted dispersion relation. From a global fit to both differential and total cross section data, we extract a value for the spin-averaged J /ψ -p s-wave scattering length aψ p=0.046 ±0.005 fm , which can be translated into a J /ψ binding energy in nuclear matter of Bψ=2.7 ±0.3 MeV . We estimate the forward-backward asymmetry to the γ p →e-e+p process around the J /ψ resonance, which results from interchanging the leptons in the interference between the J /ψ production and the Bethe-Heitler mechanisms. We show that to good approximation this asymmetry depends linearly on aψ p, and can reach values around -25 % for forthcoming J /ψ threshold production experiments at Jefferson Lab. Its measurement can thus provide a very sensitive observable for a refined extraction of aψ p.

  13. Application of a folding-model optical potential to analyzing inelastic pion–nucleus scattering and the in-medium effect on a pion–nucleon amplitude

    SciTech Connect

    Lukyanov, V. K. Zemlyanaya, E. V.; Lukyanov, K. V.; Abdul-Magead, I. A. M.

    2016-11-15

    The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π{sup ±}-mesons on {sup 28}Si, {sup 40}Ca, {sup 58}Ni, and {sup 208}Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2{sup +} and 3{sup −} collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion–nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole (β{sub 2}) and octupole (β{sub 3}) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion–nucleon amplitude is emphasized.

  14. Application of a folding-model optical potential to analyzing inelastic pion-nucleus scattering and the in-medium effect on a pion-nucleon amplitude

    NASA Astrophysics Data System (ADS)

    Lukyanov, V. K.; Zemlyanaya, E. V.; Lukyanov, K. V.; Abdul-Magead, I. A. M.

    2016-11-01

    The folding-model optical potential is generalized in such a way as to apply it to calculating the cross sections for inelastic scattering of π ±-mesons on 28Si, 40Ca, 58Ni, and 208Pb nuclei at the energies of 162, 180, 226, and 291 MeV leading to the excitation of the 2+ and 3- collective states. In doing this, use is made of known nucleon-density distributions in nuclei and the pion-nucleon scattering amplitude whose parameters were obtained previously by fitting the elastic scattering cross sections for the same nuclei. Thus, the values of quadrupole ( β 2) and octupole ( β 3) deformations of nuclei appear here as the only adjustable parameters. The scattering cross section is calculated by solving the relativistic wave equation, whereby effects of relativization and distortion in the entrance and exit scattering channels are taken exactly into account. The cross sections calculated in this way for inelastic scattering are in good agreement with respective experimental data. The importance of the inclusion of in-medium effects in choosing parameters of the pion-nucleon amplitude is emphasized.

  15. Connected formulas for amplitudes in standard model

    NASA Astrophysics Data System (ADS)

    He, Song; Zhang, Yong

    2017-03-01

    Witten's twistor string theory has led to new representations of S-matrix in massless QFT as a single object, including Cachazo-He-Yuan formulas in general and connected formulas in four dimensions. As a first step towards more realistic processes of the standard model, we extend the construction to QCD tree amplitudes with massless quarks and those with a Higgs boson. For both cases, we find connected formulas in four dimensions for all multiplicities which are very similar to the one for Yang-Mills amplitudes. The formula for quark-gluon color-ordered amplitudes differs from the pure-gluon case only by a Jacobian factor that depends on flavors and orderings of the quarks. In the formula for Higgs plus multi-parton amplitudes, the massive Higgs boson is effectively described by two additional massless legs which do not appear in the Parke-Taylor factor. The latter also represents the first twistor-string/connected formula for form factors.

  16. Broad-band linear polarization in cool stars. II - Amplitude and wavelength dependence for magnetic and scattering regions

    NASA Technical Reports Server (NTRS)

    Saar, Steven H.; Huovelin, Juhani

    1993-01-01

    We have developed a model to estimate the amplitude and wavelength dependence of broad-band linear polarization (BLP) from magnetic regions on cool stars. The model includes corrections both for line blends and for the partial cancellation of polarization in the vector sum over the stellar disk. Our results agree with recent calculations of BLP in the red, but show larger amplitudes and a different wavelength dependence in the blue. We find that the detailed wavelength dependence of the polarization is complex and varies with effective temperature and gravity due to changes in line blanketing. The BLP amplitudes depend strongly on field strength, blanketing, and magnetic region filling factor and geometry. We make rough estimates of the maximum BLP for stars of various spectral types and demonstrate a method for deriving a lower limit to the filling factor from the maximum observed BLP. This lower limit is related to the fractional area covered by the spatially asymmetric component of magnetic regions.

  17. Resonance of the exchange amplitude of a photon by an electron scattering in a pulsed laser field

    NASA Astrophysics Data System (ADS)

    Nedoreshta, V. N.; Roshchupkin, S. P.; Voroshilo, A. I.

    2015-06-01

    Resonant scattering of a photon by an electron in the presence of the field of the low intensity circularly polarized pulsed laser wave is studied theoretically. The approximation used the case in which a laser-pulse duration is significantly greater than the characteristic oscillation time. The resonance conditions of the exchange diagrams by electron and positron intermediate states were determined. The probability of such a process is calculated. It is demonstrated that the resonant probability may be six to ten orders of magnitude higher than the probability of the Compton effect in the absence of the external field. Obtained results can be verified experimentally in the framework of modern research projects (SLAC, FAIR, XFEL, and ELI).

  18. Singularity structure of the πN scattering amplitude in a meson-exchange model up to energies W⩽2.0 GeV

    NASA Astrophysics Data System (ADS)

    Tiator, L.; Kamalov, S. S.; Ceci, S.; Chen, Guan Yeu; Drechsel, D.; Svarc, A.; Yang, Shin Nan

    2010-11-01

    Within the previously developed Dubna-Mainz-Taipei meson-exchange model, the singularity structure of the πN scattering amplitudes has been investigated. For all partial waves up to F waves and c.m. energies up to W~2 GeV, the T-matrix poles have been calculated by three different techniques: analytic continuation into the complex energy plane and speed-plot and regularization method. For all four-star resonances except the S11(1535), we find very good agreement between the analytic continuation and the regularization method. We also find resonance poles for resonances that are not so well established, but in these cases the pole positions and residues obtained by analytic continuation can substantially differ from the results predicted by the speed-plot and regularization methods.

  19. Lorentzian amplitude and phase pulse shaping for nonresonant background suppression and enhanced spectral resolution in coherent anti-Stokes Raman scattering spectroscopy and microscopy.

    PubMed

    Konorov, Stanislav O; Blades, Michael W; Turner, Robin F B

    2010-07-01

    Femtosecond coherent anti-Stokes Raman scattering (CARS) spectroscopy offers several advantages over spontaneous Raman spectroscopy due to the inherently high sensitivity and low average power deposition in the sample. Femtosecond CARS can be implemented in a collinear pump/probe beam configuration for microspectroscopy applications and has emerged as a powerful technique for chemical imaging of biological specimens. However, one serious limitation of this approach is the presence of a high nonresonant background component that often obscures the resonant signals of interest. We report here an innovative pulse-shaping method based on Lorentzian amplitude and phase spectral modulation of a broadband femtosecond probe pulse that yields spectra with both high spectral resolution and no nonresonant background. No further mathematical analysis is needed to extract Raman spectra. The utility of the proposed method for CARS microscopy is demonstrated using a mixture of polystyrene and latex beads, as well as dry-fixed embryonic stem cells.

  20. Mathematical Aspects of Scattering Amplitudes

    NASA Astrophysics Data System (ADS)

    Duhr, Claude

    In these lectures we discuss some of the mathematical structures that appear when computing multi-loop Feynman integrals. We focus on a specific class of special functions, the so-called multiple polylogarithms, and introduce their Hopf algebra structure. We show how these mathematical concepts are useful in physics by illustrating on several examples how these algebraic structures are useful to perform analytic computations of loop integrals, in particular to derive functional equations among polylogarithms.

  1. Scattering amplitudes and static atomic correction factors for the composition-sensitive 002 reflection in sphalerite ternary III-V and II-VI semiconductors.

    PubMed

    Schowalter, M; Müller, K; Rosenauer, A

    2012-01-01

    Modified atomic scattering amplitudes (MASAs), taking into account the redistribution of charge due to bonds, and the respective correction factors considering the effect of static atomic displacements were computed for the chemically sensitive 002 reflection for ternary III-V and II-VI semiconductors. MASAs were derived from computations within the density functional theory formalism. Binary eight-atom unit cells were strained according to each strain state s (thin, intermediate, thick and fully relaxed electron microscopic specimen) and each concentration (x = 0, …, 1 in 0.01 steps), where the lattice parameters for composition x in strain state s were calculated using continuum elasticity theory. The concentration dependence was derived by computing MASAs for each of these binary cells. Correction factors for static atomic displacements were computed from relaxed atom positions by generating 50 × 50 × 50 supercells using the lattice parameter of the eight-atom unit cells. Atoms were randomly distributed according to the required composition. Polynomials were fitted to the composition dependence of the MASAs and the correction factors for the different strain states. Fit parameters are given in the paper.

  2. Amplitudes of Field Theories

    SciTech Connect

    Feng Bo

    2007-11-20

    In this talk, we will present recent progresses in perturbative calculations of scattering amplitudes at tree and one-loop levels. At tree level, we will discuss MHV-diagram method and on-shell recursion relation. At one-loop level, we will establish the framework of Unitarity cut method.

  3. A course in amplitudes

    NASA Astrophysics Data System (ADS)

    Taylor, Tomasz R.

    2017-05-01

    This a pedagogical introduction to scattering amplitudes in gauge theories. It proceeds from Dirac equation and Weyl fermions to the two pivot points of current developments: the recursion relations of Britto, Cachazo, Feng and Witten, and the unitarity cut method pioneered by Bern, Dixon, Dunbar and Kosower. In ten lectures, it covers the basic elements of on-shell methods.

  4. Off-shell extrapolation of Regge-model NN scattering amplitudes describing final state interactions in 2H(e,e'p)

    SciTech Connect

    Ford, William Paul; van Orden, Wally

    2013-11-25

    In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.

  5. Off-shell extrapolation of Regge-model NN scattering amplitudes describing final state interactions in 2H(e,e'p)

    DOE PAGES

    Ford, William Paul; van Orden, Wally

    2013-11-25

    In this work, an off-shell extrapolation is proposed for the Regge-model NN amplitudes presented in a paper by Ford and Van Orden [ Phys. Rev. C 87 014004 (2013)] and in an eprint by Ford (arXiv:1310.0871 [nucl-th]). The prescriptions for extrapolating these amplitudes for one nucleon off-shell in the initial state are presented. Application of these amplitudes to calculations of deuteron electrodisintegration are presented and compared to the limited available precision data in the kinematical region covered by the Regge model.

  6. A recursion relation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    Bedford, James; Brandhuber, Andreas; Spence, Bill; Travaglini, Gabriele

    2005-08-01

    Britto, Cachazo and Feng have recently derived a recursion relation for tree-level scattering amplitudes in Yang-Mills. This relation has a bilinear structure inherited from factorisation on multi-particle poles of the scattering amplitudes—a rather generic feature of field theory. Motivated by this, we propose a new recursion relation for scattering amplitudes of gravitons at tree level. Using this, we derive a new general formula for the MHV tree-level scattering amplitude for n gravitons. Finally, we comment on the existence of recursion relations in general field theories.

  7. On-Shell Methods in Perturbative QCD

    SciTech Connect

    Bern, Zvi; Dixon, Lance J.; Kosower, David A.

    2007-04-25

    We review on-shell methods for computing multi-parton scattering amplitudes in perturbative QCD, utilizing their unitarity and factorization properties. We focus on aspects which are useful for the construction of one-loop amplitudes needed for phenomenological studies at the Large Hadron Collider.

  8. Microstructure and rheology of a thermoreversible gel under large amplitude oscillatory shear (LAOS) deformation using time-resolved oscillatory rheo-small-angle neutron scattering (tOr-SANS)

    NASA Astrophysics Data System (ADS)

    Kim, Jung Min; Gurnon, A. Kate; Wagner, Norman; Eberle, Aaron

    2013-03-01

    Large amplitude oscillatory shear (LAOS) rheology is an effective way of studying the nonlinear dynamics of complex fluids. Here, we present a new method for a direct, quantitative study of the microstructure under LAOS deformation in the framework of the alignment factor, Af. We use a model thermoreversible adhesive hard-sphere system composed of octadecyl-coated silica particles suspended in n-tetradecane. With temperature the particle potential is controlled and the system is shifted from behaving as a near hard-sphere to an adhesive hard-sphere system leading to aggregation and ultimately a dynamical arrest transition to macroscopic gelation. Time-resolved oscillatory rheo-small-angle neutron scattering (tOr-SANS) measurements in the 1-3 plane are performed by stroboscopically probing the structural evolution as a function of time during LAOS. Under strong shear, the 2D scattering pattern of the system in the gelled state exhibits a strong anisotropy commonly known as a ``butterfly'' pattern, which corresponds to the stretching of the microstructure along the flow direction. The first structure-Lissajous plots of this model system are presented in terms of an order parameter and Af as a function of instantaneous strain and strain rate. This new analysis demonstrates a novel method for simultaneously measuring the rheology and microstructure during a time-dependent deformation (LAOS).

  9. Toward complete pion nucleon amplitudes

    DOE PAGES

    Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; ...

    2015-10-05

    We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.

  10. Toward complete pion nucleon amplitudes

    SciTech Connect

    Mathieu, Vincent; Danilkin, Igor V.; Fernández-Ramírez, Cesar; Pennington, Michael R.; Schott, Diane M.; Szczepaniak, Adam P.; Fox, G.

    2015-10-05

    We compare the low-energy partial wave analyses πN scattering with a high-energy data via finite energy sum rules. We also construct a new set of amplitudes by matching the imaginary part from the low-energy analysis with the high-energy, Regge parametrization and then reconstruct the real parts using dispersion relations.

  11. Constraining higher derivative supergravity with scattering amplitudes

    DOE PAGES

    Wang, Yifan; Yin, Xi

    2015-08-31

    We study supersymmetry constraints on higher derivative deformations of type IIB supergravity by consideration of superamplitudes. Thus, combining constraints of on-shell supervertices and basic results from string perturbation theory, we give a simple argument for the non-renormalization theorem of Green and Sethi, and some of its generalizations.

  12. Recent Developments in Perturbative QCD

    SciTech Connect

    Dixon, Lance J.; /SLAC

    2005-07-11

    I review recent progress in perturbative QCD on two fronts: extending next-to-next-to-leading order QCD corrections to a broader range of collider processes, and applying twistor-space methods (and related spinoffs) to computations of multi-parton scattering amplitudes.

  13. DVCS amplitude with kinematical twist-3 terms

    SciTech Connect

    Radyushkin, A.V.; Weiss, C.

    2000-08-01

    The authors compute the amplitude of deeply virtual Compton scattering (DVCS) using the calculus of QCD string operators in coordinate representation. To restore the electromagnetic gauge invariance (transversality) of the twist-2 amplitude they include the operators of twist-3 which appear as total derivatives of twist-2 operators. The results are equivalent to a Wandzura-Wilczek approximation for twist-3 skewed parton distributions. They find that this approximation gives a finite result for the amplitude of a longitudinally polarized virtual photon, while the amplitude for transverse polarization is divergent, i.e., factorization breaks down in this term.

  14. Scattering of fermions by gravitons

    NASA Astrophysics Data System (ADS)

    Ulhoa, S. C.; Santos, A. F.; Khanna, Faqir C.

    2017-04-01

    The interaction between gravitons and fermions is investigated in the teleparallel gravity. The scattering of fermions and gravitons in the weak field approximation is analyzed. The transition amplitudes of M\\varnothing ller, Compton and new gravitational scattering are calculated.

  15. Gravitational Bhabha scattering

    NASA Astrophysics Data System (ADS)

    Santos, A. F.; Khanna, Faqir C.

    2017-10-01

    Gravitoelectromagnetism (GEM) as a theory for gravity has been developed similar to the electromagnetic field theory. A weak field approximation of Einstein theory of relativity is similar to GEM. This theory has been quantized. Traditional Bhabha scattering, electron–positron scattering, is based on quantized electrodynamics theory. Usually the amplitude is written in terms of one photon exchange process. With the development of quantized GEM theory, the scattering amplitude will have an additional component based on an exchange of one graviton at the lowest order of perturbation theory. An analysis will provide the relative importance of the two amplitudes for Bhabha scattering. This will allow an analysis of the relative importance of the two amplitudes as the energy of the exchanged particles increases.

  16. Analytic representations of Yang-Mills amplitudes

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Bourjaily, Jacob L.; Damgaard, Poul H.; Feng, Bo

    2016-12-01

    Scattering amplitudes in Yang-Mills theory can be represented in the formalism of Cachazo, He and Yuan (CHY) as integrals over an auxiliary projective space-fully localized on the support of the scattering equations. Because solving the scattering equations is difficult and summing over the solutions algebraically complex, a method of directly integrating the terms that appear in this representation has long been sought. We solve this important open problem by first rewriting the terms in a manifestly Möbius-invariant form and then using monodromy relations (inspired by analogy to string theory) to decompose terms into those for which combinatorial rules of integration are known. The result is the foundations of a systematic procedure to obtain analytic, covariant forms of Yang-Mills tree-amplitudes for any number of external legs and in any number of dimensions. As examples, we provide compact analytic expressions for amplitudes involving up to six gluons of arbitrary helicities.

  17. Hidden simplicity of gauge theory amplitudes

    NASA Astrophysics Data System (ADS)

    Drummond, J. M.

    2010-11-01

    These notes were given as lectures at the CERN Winter School on Supergravity, Strings and Gauge Theory 2010. We describe the structure of scattering amplitudes in gauge theories, focussing on the maximally supersymmetric theory to highlight the hidden symmetries which appear. Using the Britto, Cachzo, Feng and Witten (BCFW) recursion relations we solve the tree-level S-matrix in \\ {N}=4 super Yang-Mills theory and describe how it produces a sum of invariants of a large symmetry algebra. We review amplitudes in the planar theory beyond tree level, describing the connection between amplitudes and Wilson loops, and discuss the implications of the hidden symmetries.

  18. Perturbative QCD correlations in multi-parton collisions

    NASA Astrophysics Data System (ADS)

    Blok, B.; Dokshitzer, Yu.; Frankfurt, L.; Strikman, M.

    2014-06-01

    We examine the role played in double-parton interactions (DPI) by the parton-parton correlations originating from perturbative QCD parton splittings. Also presented are the results of the numerical analysis of the integrated DPI cross sections at Tevatron and LHC energies. To obtain the numerical results the knowledge of the single-parton GPDs gained by the HERA experiments was used to construct the non-perturbative input for generalized double-parton distributions. The perturbative two-parton correlations induced by three-parton interactions contribute significantly to a resolution of the longstanding puzzle of an excess of multi-jet production events in the back-to-back kinematics observed at the Tevatron.

  19. Compton scattering by nuclei

    NASA Astrophysics Data System (ADS)

    Hütt, M.-Th.; L'vov, A. I.; Milstein, A. I.; Schumacher, M.

    2000-01-01

    The concept of Compton scattering by even-even nuclei from giant-resonance to nucleon-resonance energies and the status of experimental and theoretical researches in this field are outlined. The description of Compton scattering by nuclei starts from different complementary approaches, namely from second-order S-matrix and from dispersion theories. Making use of these, it is possible to incorporate into the predicted nuclear scattering amplitudes all the information available from other channels, viz. photon-nucleon and photon-meson channels, and to efficiently make use of models of the nucleon, the nucleus and the nucleon-nucleon interaction. The total photoabsorption cross section constrains the nuclear scattering amplitude in the forward direction. The specific information obtained from Compton scattering therefore stems from the angular dependence of the nuclear scattering amplitude, providing detailed insight into the dynamics of the nuclear and nucleon degrees of freedom and into the interplay between them. Nuclear Compton scattering in the giant-resonance energy-region provides information on the dynamical properties of the in-medium mass of the nucleon. Most prominently, the electromagnetic polarizabilities of the nucleon in the nuclear medium can be extracted from nuclear Compton scattering data obtained in the quasi-deuteron energy-region. In our description of this latter process special emphasis is laid upon the exploration of many-body and two-body effects entering into the nuclear dynamics. Recent results are presented for two-body effects due to the mesonic seagull amplitude and due to the excitation of nucleon internal degrees of freedom accompanied by meson exchanges. Due to these studies the in-medium electromagnetic polarizabilities are by now well understood, whereas the understanding of nuclear Compton scattering in the Δ-resonance range is only at the beginning. Furthermore, phenomenological methods how to include retardation effects in the

  20. Holographic corrections to the Veneziano amplitude

    NASA Astrophysics Data System (ADS)

    Armoni, Adi; Ireson, Edwin

    2017-08-01

    We propose a holographic computation of the 2 → 2 meson scattering in a curved string background, dual to a QCD-like theory. We recover the Veneziano amplitude and compute a perturbative correction due to the background curvature. The result implies a small deviation from a linear trajectory, which is a requirement of the UV regime of QCD.

  1. Phase variation of hadronic amplitudes

    SciTech Connect

    Dedonder, J.-P.; Gibbs, W. R.; Nuseirat, Mutazz

    2008-04-15

    The phase variation with angle of hadronic amplitudes is studied with a view to understanding the underlying physical quantities that control it and how well it can be determined in free space. We find that unitarity forces a moderately accurate determination of the phase in standard amplitude analyses but that the nucleon-nucleon analyses done to date do not give the phase variation needed to achieve a good representation of the data in multiple scattering calculations. Models are examined that suggest its behavior near forward angles is related to the radii of the real and absorptive parts of the interaction. The dependence of this phase on model parameters is such that if these radii are modified in the nuclear medium (in combination with the change due to the shift in energy of the effective amplitude in the medium) then the larger magnitudes of the phase needed to fit the data might be attainable but only for negative values of the phase variation parameter.

  2. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Maung, Khin Maung; Wilson, John W.; Buck, Warren W.

    1989-01-01

    The derivations of the Lippmann-Schwinger equation and Watson multiple scattering are given. A simple optical potential is found to be the first term of that series. The number density distribution models of the nucleus, harmonic well, and Woods-Saxon are used without t-matrix taken from the scattering experiments. The parameterized two-body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to the imaginary part of the forward elastic scattering amplitude, are presented. The eikonal approximation was chosen as our solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  3. PULSE AMPLITUDE ANALYSERS

    DOEpatents

    Lewis, I.A.D.

    1956-05-15

    This patent pentains to an electrical pulse amplitude analyzer, capable of accepting input pulses having a separation between adjacent pulses in the order of one microsecond while providing a large number of channels of classification. In its broad aspect the described pulse amplitude analyzer utilizes a storage cathode ray tube und control circuitry whereby the amplitude of the analyzed pulses controls both the intensity and vertical defiection of the beam to charge particular spots in horizontal sectors of the tube face as the beam is moved horizontally across the tube face. As soon as the beam has swept the length of the tube the information stored therein is read out by scanning individually each horizontal sector corresponding to a certain range of pulse amplitudes and applying the output signal from each scan to separate indicating means.

  4. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Greenblatt, M.H.

    1958-03-25

    This patent pertains to pulse amplitude analyzers for sorting and counting a serles of pulses, and specifically discloses an analyzer which ls simple in construction and presents the puise height distribution visually on an oscilloscope screen. According to the invention, the pulses are applied to the vertical deflection plates of an oscilloscope and trigger the horizontal sweep. Each pulse starts at the same point on the screen and has a maximum amplitude substantially along the same vertical line. A mask is placed over the screen except for a slot running along the line where the maximum amplitudes of the pulses appear. After the slot has been scanned by a photocell in combination with a slotted rotating disk, the photocell signal is displayed on an auxiliary oscilloscope as vertical deflection along a horizontal time base to portray the pulse amplitude distribution.

  5. Real topological string amplitudes

    NASA Astrophysics Data System (ADS)

    Narain, K. S.; Piazzalunga, N.; Tanzini, A.

    2017-03-01

    We discuss the physical superstring correlation functions in type I theory (or equivalently type II with orientifold) that compute real topological string amplitudes. We consider the correlator corresponding to holomorphic derivative of the real topological amplitude G_{χ } , at fixed worldsheet Euler characteristic χ. This corresponds in the low-energy effective action to N=2 Weyl multiplet, appropriately reduced to the orientifold invariant part, and raised to the power g' = -χ + 1. We show that the physical string correlator gives precisely the holomorphic derivative of topological amplitude. Finally, we apply this method to the standard closed oriented case as well, and prove a similar statement for the topological amplitude F_g.

  6. Amplitudes in N = 4 Super-Yang-Mills Theory

    NASA Astrophysics Data System (ADS)

    Spradlin, Marcus

    These lecture notes provide a lightning introduction to some aspects of scattering amplitudes in maximally supersymmetric theory, aimed at the audience of students attending the 2014 TASI summer school "Journeys Through the Precision Frontier: Amplitudes for Colliders". Emphasis is placed on explaining modern terminology so that students needing to delve further may more easily access the available literature.

  7. Amplitude Models for Discrimination and Yield Estimation

    SciTech Connect

    Phillips, William Scott

    2016-09-01

    This seminar presentation describes amplitude models and yield estimations that look at the data in order to inform legislation. The following points were brought forth in the summary: global models that will predict three-component amplitudes (R-T-Z) were produced; Q models match regional geology; corrected source spectra can be used for discrimination and yield estimation; three-component data increase coverage and reduce scatter in source spectral estimates; three-component efforts must include distance-dependent effects; a community effort on instrument calibration is needed.

  8. Amplitudes and Ultraviolet Behavior of N = 8 Supergravity

    SciTech Connect

    Bern, Zvi; Carrasco, John Joseph; Dixon, Lance J.; Johansson, Henrik; Roiban, Radu; /Penn State U.

    2011-05-20

    In this contribution we describe computational tools that permit the evaluation of multi-loop scattering amplitudes in N = 8 supergravity, in terms of amplitudes in N = 4 super-Yang-Mills theory. We also discuss the remarkable ultraviolet behavior of N = 8 supergravity, which follows from these amplitudes, and is as good as that of N = 4 super-Yang-Mills theory through at least four loops.

  9. Compositions of bosonic string amplitudes with cylinder topology

    SciTech Connect

    Trisnadi, J.I.

    1989-01-01

    Many issues in string theory are conveniently addressed and handled in a quantum fleld theoretical framework, from which Feynman rules can then be derived. Although at present a generally acceptable quantum field theory of closed strings does not yet exist, the Feynman rules are known. This is due to another development in string theory, namely, the Polyakov path integral approach. In this approach, scattering amplitudes are calculated directly without appealing to the quantum fleld theoretical description. It is therefore important to examine if the scattering amplitude can be reconstructed by composing propagators and vertices. In general, the author is interested in knowing if Polyakov amplitudes can be consistently composed. Composition of amplitudes in general has been studied formally. Explicit composition, however, is limited to amplitudes that have been calculated explicitly. Among them is the amplitude with cylinder topology. In this dissertation, the author will rederive this cylinder amplitude. The author uses the action principle in the evaluation of the path integral. This way, the contributions of the ghost zero modes, which are usually introduced by hand, come out automatically. Then, the author studies three compositions of the cylinder amplitude: two cylinder amplitudes into one, a single cylinder amplitude into a torus amplitude, and a cylinder amplitude into a Klein-bottle amplitude. The author shows that the resulting amplitudes agree with known results. Using the cylinder amplitude, the author also demonstrates the derivation of the (imaginary time) Schrodinger equation for the free closed bosonic string. Finally, the author applies the techniques to derive the composable transition amplitude of gravity in a Friedmann-RobertsonWalker cosmology.

  10. ABJM amplitudes and the positive orthogonal Grassmannian

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Wen, CongKao

    2014-02-01

    A remarkable connection between perturbative scattering amplitudes of four dimensional planar SYM, and the stratification of the positive Grassmannian, was revealed in the seminal work of Arkani-Hamed et al. Similar extension for three-dimensional ABJM theory was proposed. Here we establish a direct connection between planar scattering amplitudes of ABJM theory, and singularities thereof, to the stratification of the positive orthogonal Grassmannian. In particular, scattering processes are constructed through on-shell diagrams, which are simply iterative gluing of the fundamental four-point amplitude. Each diagram is then equivalent to the merging of fundamental OG2 orthogonal Grassmannian to form a larger OG k , where 2 k is the number of external particles. The invariant information that is encoded in each diagram is precisely this stratification. This information can be easily read off via permutation paths of the on-shell diagram, which also can be used to derive a canonical representation of OG k that manifests the vanishing of consecutive minors as the singularity of all on-shell diagrams. Quite remarkably, for the BCFW recursion representation of the tree-level amplitudes, the on-shell diagram manifests the presence of all physical factorization poles, as well as the cancellation of the spurious poles. After analytically continuing the orthogonal Grassmannian to split signature, we reveal that each on-shell diagram in fact resides in the positive cell of the orthogonal Grassmannian, where all minors are positive. In this language, the amplitudes of ABJM theory is simply an integral of a product of d log forms, over the positive orthogonal Grassmannian.

  11. Reinforcing Saccadic Amplitude Variability

    ERIC Educational Resources Information Center

    Paeye, Celine; Madelain, Laurent

    2011-01-01

    Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we…

  12. Planar amplitude ammonia sensor

    NASA Astrophysics Data System (ADS)

    Karasinski, Pawel; Rogozinski, Roman

    2004-09-01

    The paper presents the results of investigation involving the influence of the change of launching conditions on the characteristics of amplitude ammonia sensors produced with the application of strip waveguides of different refractive profiles. Strip waveguides were produced using ion exchange technique, and the absorption sensitive films were produced using sol-gel technology.

  13. New formulas for amplitudes from higher-dimensional operators

    NASA Astrophysics Data System (ADS)

    He, Song; Zhang, Yong

    2017-02-01

    In this paper we study tree-level amplitudes from higher-dimensional operators, including F 3 operator of gauge theory, and R 2, R 3 operators of gravity, in the Cachazo-He-Yuan formulation. As a generalization of the reduced Pfaffian in Yang-Mills theory, we find a new, gauge-invariant object that leads to gluon amplitudes with a single insertion of F 3, and gravity amplitudes by Kawai-Lewellen-Tye relations. When reduced to four dimensions for given helicities, the new object vanishes for any solution of scattering equations on which the reduced Pfaffian is non-vanishing. This intriguing behavior in four dimensions explains the vanishing of graviton helicity amplitudes produced by the Gauss-Bonnet R 2 term, and provides a scattering-equation origin of the decomposition into self-dual and anti-self-dual parts for F 3 and R 3 amplitudes.

  14. Kaon-nucleus scattering

    NASA Technical Reports Server (NTRS)

    Hong, Byungsik; Buck, Warren W.; Maung, Khin M.

    1989-01-01

    Two kinds of number density distributions of the nucleus, harmonic well and Woods-Saxon models, are used with the t-matrix that is taken from the scattering experiments to find a simple optical potential. The parameterized two body inputs, which are kaon-nucleon total cross sections, elastic slope parameters, and the ratio of the real to imaginary part of the forward elastic scattering amplitude, are shown. The eikonal approximation was chosen as the solution method to estimate the total and absorptive cross sections for the kaon-nucleus scattering.

  15. An algebraic approach to the scattering equations

    NASA Astrophysics Data System (ADS)

    Huang, Rijun; Rao, Junjie; Feng, Bo; He, Yang-Hui

    2015-12-01

    We employ the so-called companion matrix method from computational algebraic geometry, tailored for zero-dimensional ideals, to study the scattering equations. The method renders the CHY-integrand of scattering amplitudes computable using simple linear algebra and is amenable to an algorithmic approach. Certain identities in the amplitudes as well as rationality of the final integrand become immediate in this formalism.

  16. Purely bianisotropic scatterers

    NASA Astrophysics Data System (ADS)

    Albooyeh, M.; Asadchy, V. S.; Alaee, R.; Hashemi, S. M.; Yazdi, M.; Mirmoosa, M. S.; Rockstuhl, C.; Simovski, C. R.; Tretyakov, S. A.

    2016-12-01

    The polarization response of molecules or meta-atoms to external electric and magnetic fields, which defines the electromagnetic properties of materials, can either be direct (electric field induces electric moment and magnetic field induces magnetic moment) or indirect (magnetoelectric coupling in bianisotropic scatterers). Earlier studies suggest that there is a fundamental bound on the indirect response of all passive scatterers: It is believed to be always weaker than the direct one. In this paper, we prove that there exist scatterers which overcome this bound substantially. Moreover, we show that the amplitudes of electric and magnetic polarizabilities can be negligibly small as compared to the magnetoelectric coupling coefficients. However, we prove that if at least one of the direct-excitation coefficients vanishes, magnetoelectric coupling effects in passive scatterers cannot exist. Our findings open a way to a new class of electromagnetic scatterers and composite materials.

  17. Weak boson production amplitude zeros; equalities of the helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Mamedov, Fizuli

    2002-08-01

    We investigate the radiation amplitude zeros exhibited by many standard model amplitudes for triple weak gauge boson production processes. We show that WZγ production amplitudes have an especially rich structure in terms of zeros; these amplitudes have zeros originating from several different sources. It is also shown that the type-I current null zone is the special case of the equality of the specific helicity amplitudes.

  18. Rutherford scattering of electron vortices

    NASA Astrophysics Data System (ADS)

    Van Boxem, Ruben; Partoens, Bart; Verbeeck, Johan

    2014-03-01

    By considering a cylindrically symmetric generalization of a plane wave, the first-order Born approximation of screened Coulomb scattering unfolds two new dimensions in the scattering problem: transverse momentum and orbital angular momentum of the incoming beam. In this paper, the elastic Coulomb scattering amplitude is calculated analytically for incoming Bessel beams. This reveals novel features occurring for wide-angle scattering and quantitative insights for small-angle vortex scattering. The result successfully generalizes the well-known Rutherford formula, incorporating transverse and orbital angular momentum into the formalism.

  19. Ramped-amplitude NOVEL

    NASA Astrophysics Data System (ADS)

    Can, T. V.; Weber, R. T.; Walish, J. J.; Swager, T. M.; Griffin, R. G.

    2017-04-01

    We present a pulsed dynamic nuclear polarization (DNP) study using a ramped-amplitude nuclear orientation via electron spin locking (RA-NOVEL) sequence that utilizes a fast arbitrary waveform generator (AWG) to modulate the microwave pulses together with samples doped with narrow-line radicals such as 1,3-bisdiphenylene-2-phenylallyl (BDPA), sulfonated-BDPA (SA-BDPA), and trityl-OX063. Similar to ramped-amplitude cross polarization in solid-state nuclear magnetic resonance, RA-NOVEL improves the DNP efficiency by a factor of up to 1.6 compared to constant-amplitude NOVEL (CA-NOVEL) but requires a longer mixing time. For example, at τmix = 8 μs, the DNP efficiency reaches a plateau at a ramp amplitude of ˜20 MHz for both SA-BDPA and trityl-OX063, regardless of the ramp profile (linear vs. tangent). At shorter mixing times (τmix = 0.8 μs), we found that the tangent ramp is superior to its linear counterpart and in both cases there exists an optimum ramp size and therefore ramp rate. Our results suggest that RA-NOVEL should be used instead of CA-NOVEL as long as the electronic spin lattice relaxation T1e is sufficiently long and/or the duty cycle of the microwave amplifier is not exceeded. To the best of our knowledge, this is the first example of a time domain DNP experiment that utilizes modulated microwave pulses. Our results also suggest that a precise modulation of the microwave pulses can play an important role in optimizing the efficiency of pulsed DNP experiments and an AWG is an elegant instrumental solution for this purpose.

  20. Amplitude Modulator Chassis

    SciTech Connect

    Erbert, G

    2009-09-01

    The Amplitude Modulator Chassis (AMC) is the final component in the MOR system and connects directly to the PAM input through a 100-meter fiber. The 48 AMCs temporally shape the 48 outputs of the MOR using an arbitrary waveform generator coupled to an amplitude modulator. The amplitude modulation element is a two stage, Lithium Niobate waveguide device, where the intensity of the light passing through the device is a function of the electrical drive applied. The first stage of the modulator is connected to a programmable high performance Arbitrary Waveform Generator (AWG) consisting of 140 impulse generators space 250 ps apart. An arbitrary waveform is generated by independently varying the amplitude of each impulse generator and then summing the impulses together. In addition to the AWG a short pulse generator is also connected to the first stage of the modulator to provide a sub 100-ps pulse used for timing experiments. The second stage of the modulator is connect to a square pulse generator used to further attenuate any pre or post pulse light passing through the first stage of the modulator. The fast rise and fall time of the square pulse generator is also used to produce fast rise and fall times of the AWG by clipping the AWG pulse. For maximum extinction, a pulse bias voltage is applied to each stage of the modulator. A pulse voltage is applied as opposed to a DC voltage to prevent charge buildup on the modulator. Each bias voltage is adjustable to provide a minimum of 50-dB extinction. The AMC is controlled through ICCS to generate the desired temporal pulse shape. This process involves a closed-loop control algorithm, which compares the desired temporal waveform to the produced optical pulse, and iterates the programming of the AWG until the two waveforms agree within an allowable tolerance.

  1. High amplitude propagated contractions.

    PubMed

    Bharucha, A E

    2012-11-01

    While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. High amplitude propagated contractions occur spontaneously, in response to pharmacological agents or colonic distention. A subset of patients with slow transit constipation have fewer HAPC. In this issue of Neurogastroenterology and Motility, Rodriguez et al. report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. High amplitude propagated contractions are also used to evaluate the motor response to a meal and pharmacological stimuli (e.g., bisacodyl, neostigmine) and to identify colonic inertia during colonic motility testing in chronic constipation. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. © 2012 Blackwell Publishing Ltd.

  2. Amplitudes of Spiral Perturbations

    NASA Astrophysics Data System (ADS)

    Grosbol, P.; Patsis, P. A.

    2014-03-01

    It has proven very difficult to estimate the amplitudes of spiral perturbations in disk galaxies from observations due to the variation of mass-to-light ratio and extinction across spiral arms. Deep, near-infrared images of grand-design spiral galaxies obtained with HAWK-I/VLT were used to analyze the azimuthal amplitude and shape of arms, which, even in the K-band may, be significantly biased by the presence of young stellar populations. Several techniques were applied to evaluate the relative importance of young stars across the arms, such as surface brightness of the disk with light from clusters subtracted, number density of clusters detected, and texture of the disk. The modulation of the texture measurement, which correlates with the number density of faint clusters, yields amplitudes of the spiral perturbation in the range 0.1-0.2. This estimate gives a better estimate of the mass perturbation in the spiral arms, since it is dominated by old clusters.

  3. PULSE AMPLITUDE ANALYZER

    DOEpatents

    Gray, G.W.; Jensen, A.S.

    1957-10-22

    A pulse-height analyzer system of improved design for sorting and counting a series of pulses, such as provided by a scintillation detector in nuclear radiation measurements, is described. The analyzer comprises a main transmission line, a cathode-ray tube for each section of the line with its deflection plates acting as the line capacitance; means to bias the respective cathode ray tubes so that the beam strikes a target only when a prearranged pulse amplitude is applied, with each tube progressively biased to respond to smaller amplitudes; pulse generating and counting means associated with each tube to respond when the beam is deflected; a control transmission line having the same time constant as the first line per section with pulse generating means for each tube for initiating a pulse on the second transmission line when a pulse triggers the tube of corresponding amplitude response, the former pulse acting to prevent successive tubes from responding to the pulse under test. This arrangement permits greater deflection sensitivity in the cathode ray tube and overcomes many of the disadvantages of prior art pulse-height analyzer circuits.

  4. Weak Deeply Virtual Compton Scattering

    SciTech Connect

    Ales Psaker; Wolodymyr Melnitchouk; Anatoly Radyushkin

    2007-03-01

    We extend the analysis of the deeply virtual Compton scattering process to the weak interaction sector in the generalized Bjorken limit. The virtual Compton scattering amplitudes for the weak neutral and charged currents are calculated at the leading twist within the framework of the nonlocal light-cone expansion via coordinate space QCD string operators. Using a simple model, we estimate cross sections for neutrino scattering off the nucleon, relevant for future high intensity neutrino beam facilities.

  5. Λ scattering equations

    NASA Astrophysics Data System (ADS)

    Gomez, Humberto

    2016-06-01

    The CHY representation of scattering amplitudes is based on integrals over the moduli space of a punctured sphere. We replace the punctured sphere by a double-cover version. The resulting scattering equations depend on a parameter Λ controlling the opening of a branch cut. The new representation of scattering amplitudes possesses an enhanced redundancy which can be used to fix, modulo branches, the location of four punctures while promoting Λ to a variable. Via residue theorems we show how CHY formulas break up into sums of products of smaller (off-shell) ones times a propagator. This leads to a powerful way of evaluating CHY integrals of generic rational functions, which we call the Λ algorithm.

  6. HIGH AMPLITUDE PROPAGATED CONTRACTIONS

    PubMed Central

    Bharucha, Adil E.

    2012-01-01

    While most colonic motor activity is segmental and non-propulsive, colonic high amplitude propagated contractions (HAPC) can transfer colonic contents over long distances and often precede defecation. HAPC occur spontaneously, in response to pharmacological agents or colonic distention. In this issue of Neurogastroenterology and Motility, Rodriguez and colleagues report that anal relaxation during spontaneous and bisacodyl-induced HAPC exceeds anal relaxation during rectal distention in constipated children undergoing colonic manometry. Moreover, and consistent with a neural mechanism, anal relaxation often precedes arrival of HAPC in the left colon. This editorial comprehensively reviews the characteristics, physiology and pharmacology of HAPC, their assessment by manometry, and relevance to constipation and diarrhea. PMID:23057554

  7. Eikonal Scattering at Strong Coupling

    NASA Astrophysics Data System (ADS)

    Irizarry-Gelpi, Melvin Eloy

    The scattering of subatomic particles is a source of important physical phenomena. Decades of work have yielded many techniques for the computation of scattering amplitudes. Most of these techniques involve perturbative quantum field theory and thus apply only at weak coupling. Complementary to scattering is the formation of bound states, which are intrinsically nonperturbative. Regge theory arose in the late 1950s as an attempt to describe, with a single framework, both scattering and the formation of bound states. In Regge theory one obtains an amplitude with bound state poles after analytic continuation of a nonperturbative scattering amplitude, corresponding to a sum of an infinite number of Feynman diagrams at large energy and fixed momentum transfer (but with crossed kinematics). Thus, in order to obtain bound states at fixed energy, one computes an amplitude at large momentum transfer. In this dissertation we calculate amplitudes with bound states in the regime of fixed energy and small momentum transfer. We formulate the elastic scattering problem in terms of many-body path integrals, familiar from quantum mechanics. Then we invoke the semiclassical JWKB approximation, where the path integral is dominated by classical paths. The dynamics in the semiclassical regime are strongly coupled, as found by Halpern and Siegel. When the momentum transfer is small, the classical paths are simple straight lines and the resulting semiclassical amplitudes display a spectrum of bound states that agrees with the spectrum found by solving wave equations with potentials. In this work we study the bound states of matter particles with various types of interactions, including electromagnetic and gravitational interactions. Our work has many analogies with the work started by Alday and Maldacena, who computed scattering amplitudes of gluons at strong coupling with semiclassical quantum mechanics of strings in anti de-Sitter spacetime. We hope that in the future we can apply our

  8. Pion distribution amplitude and quasidistributions

    DOE PAGES

    Radyushkin, Anatoly V.

    2017-03-27

    We extend our analysis of quasidistributions onto the pion distribution amplitude. Using the formalism of parton virtuality distribution amplitudes, we establish a connection between the pion transverse momentum dependent distribution amplitude Ψ(x,k2⊥) and the pion quasidistribution amplitude (QDA) Qπ(y,p3). We build models for the QDAs from the virtuality-distribution-amplitude-based models for soft transverse momentum dependent distribution amplitudes, and analyze the p3 dependence of the resulting QDAs. As there are many models claimed to describe the primordial shape of the pion distribution amplitude, we present the p3-evolution patterns for models producing some popular proposals: Chernyak-Zhitnitsky, flat, and asymptotic distribution amplitude. Finally, ourmore » results may be used as a guide for future studies of the pion distribution amplitude on the lattice using the quasidistribution approach.« less

  9. Bootstrapping a five-loop amplitude using Steinmann relations

    DOE PAGES

    Caron-Huot, Simon; Dixon, Lance J.; McLeod, Andrew; ...

    2016-12-05

    Here, the analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.

  10. Bootstrapping a Five-Loop Amplitude Using Steinmann Relations.

    PubMed

    Caron-Huot, Simon; Dixon, Lance J; McLeod, Andrew; von Hippel, Matt

    2016-12-09

    The analytic structure of scattering amplitudes is restricted by Steinmann relations, which enforce the vanishing of certain discontinuities of discontinuities. We show that these relations dramatically simplify the function space for the hexagon function bootstrap in planar maximally supersymmetric Yang-Mills theory. Armed with this simplification, along with the constraints of dual conformal symmetry and Regge exponentiation, we obtain the complete five-loop six-particle amplitude.

  11. Particle Distribution Modification by Low Amplitude Modes

    SciTech Connect

    White, R. B.; Gorelenkov, N.; Heidbrink, W. W.; Van Zeeland, M. A.

    2009-08-28

    Modification of a high energy particle distribution by a spectrum of low amplitude modes is investigated using a guiding center code. Only through resonance are modes effective in modifying the distribution. Diagnostics are used to illustrate the mode-particle interaction and to find which effects are relevant in producing significant resonance, including kinetic Poincare plots and plots showing those orbits with time averaged mode-particle energy transfer. Effects of pitch angle scattering and drag are studied, as well as plasma rotation and time dependence of the equilibrium and mode frequencies. A specific example of changes observed in a DIII-D deuterium beam distribution in the presence of low amplitude experimentally validated Toroidal Alfven (TAE) eigenmodes and Reversed Shear Alfven (RSAE) eigenmodes is examined in detail. Comparison with experimental data shows that multiple low amplitude modes can account for significant modification of high energy beam particle distributions. It is found that there is a stochastic threshold for beam profile modification, and that the experimental amplitudes are only slightly above this threshold.

  12. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  13. Rayleigh Scattering.

    ERIC Educational Resources Information Center

    Young, Andrew T.

    1982-01-01

    The correct usage of such terminology as "Rayleigh scattering,""Rayleigh lines,""Raman lines," and "Tyndall scattering" is resolved during an historical excursion through the physics of light-scattering by gas molecules. (Author/JN)

  14. Monte Carlo eikonal scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Dedonder, J. P.

    2012-08-01

    Background: The eikonal approximation is commonly used to calculate heavy-ion elastic scattering. However, the full evaluation has only been done (without the use of Monte Carlo techniques or additional approximations) for α-α scattering.Purpose: Develop, improve, and test the Monte Carlo eikonal method for elastic scattering over a wide range of nuclei, energies, and angles.Method: Monte Carlo evaluation is used to calculate heavy-ion elastic scattering for heavy nuclei including the center-of-mass correction introduced in this paper and the Coulomb interaction in terms of a partial-wave expansion. A technique for the efficient expansion of the Glauber amplitude in partial waves is developed.Results: Angular distributions are presented for a number of nuclear pairs over a wide energy range using nucleon-nucleon scattering parameters taken from phase-shift analyses and densities from independent sources. We present the first calculations of the Glauber amplitude, without further approximation, and with realistic densities for nuclei heavier than helium. These densities respect the center-of-mass constraints. The Coulomb interaction is included in these calculations.Conclusion: The center-of-mass and Coulomb corrections are essential. Angular distributions can be predicted only up to certain critical angles which vary with the nuclear pairs and the energy, but we point out that all critical angles correspond to a momentum transfer near 1 fm-1.

  15. Inelastic Light Scattering Processes

    NASA Technical Reports Server (NTRS)

    Fouche, Daniel G.; Chang, Richard K.

    1973-01-01

    Five different inelastic light scattering processes will be denoted by, ordinary Raman scattering (ORS), resonance Raman scattering (RRS), off-resonance fluorescence (ORF), resonance fluorescence (RF), and broad fluorescence (BF). A distinction between fluorescence (including ORF and RF) and Raman scattering (including ORS and RRS) will be made in terms of the number of intermediate molecular states which contribute significantly to the scattered amplitude, and not in terms of excited state lifetimes or virtual versus real processes. The theory of these processes will be reviewed, including the effects of pressure, laser wavelength, and laser spectral distribution on the scattered intensity. The application of these processes to the remote sensing of atmospheric pollutants will be discussed briefly. It will be pointed out that the poor sensitivity of the ORS technique cannot be increased by going toward resonance without also compromising the advantages it has over the RF technique. Experimental results on inelastic light scattering from I(sub 2) vapor will be presented. As a single longitudinal mode 5145 A argon-ion laser line was tuned away from an I(sub 2) absorption line, the scattering was observed to change from RF to ORF. The basis, of the distinction is the different pressure dependence of the scattered intensity. Nearly three orders of magnitude enhancement of the scattered intensity was measured in going from ORF to RF. Forty-seven overtones were observed and their relative intensities measured. The ORF cross section of I(sub 2) compared to the ORS cross section of N2 was found to be 3 x 10(exp 6), with I(sub 2) at its room temperature vapor pressure.

  16. PULSE AMPLITUDE DISTRIBUTION RECORDER

    DOEpatents

    Cowper, G.

    1958-08-12

    A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.

  17. Multiple scattering expansion with distortion

    NASA Astrophysics Data System (ADS)

    Tandy, P. C.; Thaler, R. M.

    1980-12-01

    A multiple scattering description of elastic scattering is formulated in terms of impulsive scatterings from single target nucleons and pairs of target nucleons. In this description, distortion effects on the projectile from the residual medium are also described by multiple scattering in terms of the same single and pair amplitudes. At the level of single scattering, this procedure yields the first order optical potential result of Kerman, McManus, and Thaler. When scattering from both single nucleons and pairs of nucleons is included, the method leads to a one-body integral equation which requires the physical projectile-nucleon and projectile-pair transition amplitudes as input. This input is similar, but not exactly equivalent to that required by the spectator expansion for the optical potential truncated at second order. A principal advantage of the present formulation is that there need be no explicit dependence upon the projection operator Q which projects off the target ground state. This feature introduces a scaling which appears to be a direct extension of the first order Kerman, McManus, and Thaler type of scaling. We follow up suggestions arising in the foregoing to show that the exact optical potential to second order in the spectator expansion can also be cast into a form having no explicit dependence upon Q, and requiring physical projectile-nucleon and projectile-pair transition amplitudes as input. NUCLEAR REACTIONS Multiple scattering from single nucleons, pairs of nucleons in nucleus. Distortion from residual medium. Optical potential. spectator expansion.

  18. Hadron scattering and resonances in QCD

    NASA Astrophysics Data System (ADS)

    Dudek, Jozef J.

    2016-05-01

    I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study ππ elastic scattering, including the ρ resonance, as well as coupled-channel π >K, ηK scattering. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.

  19. Hadron scattering and resonances in QCD

    SciTech Connect

    Dudek, Jozef J.

    2016-05-01

    I describe how hadron-hadron scattering amplitudes are related to the eigenstates of QCD in a finite cubic volume. The discrete spectrum of such eigenstates can be determined from correlation functions computed using lattice QCD, and the corresponding scattering amplitudes extracted. I review results from the Hadron Spectrum Collaboration who have used these finite volume methods to study pi pi elastic scattering, including the rho resonance, as well as coupled-channel pi K, eta K scattering. Ongoing calculations are advertised and the outlook for finite volume approaches is presented.

  20. Invariant amplitudes for pion electroproduction

    NASA Astrophysics Data System (ADS)

    Pasquini, B.; Drechsel, D.; Tiator, L.

    2007-12-01

    The invariant amplitudes for pion electroproduction on the nucleon are evaluated by dispersion relations at constant t with MAID as input for the imaginary parts of these amplitudes. In the threshold region these amplitudes are confronted with the predictions of several low-energy theorems derived in the soft-pion limit. In general agreement with chiral perturbation theory, the dispersive approach yields large corrections to these theorems because of the finite pion mass.

  1. Mellin amplitudes for dual conformal integrals

    NASA Astrophysics Data System (ADS)

    Paulos, Miguel F.; Spradlin, Marcus; Volovich, Anastasia

    2012-08-01

    Motivated by recent work on the utility of Mellin space for representing conformal correlators in AdS/CFT, we study its suitability for representing dual conformal integrals of the type which appear in perturbative scattering amplitudes in super-Yang-Mills theory. We discuss Feynman-like rules for writing Mellin amplitudes for a large class of integrals in any dimension, and find explicit representations for several familiar toy integrals. However we show that the power of Mellin space is that it provides simple representations even for fully massive integrals, which except for the single case of the 4-mass box have not yet been computed by any available technology. Mellin space is also useful for exhibiting differential relations between various multi-loop integrals, and we show that certain higher-loop integrals may be written as integral operators acting on the fully massive scalar n-gon in n dimensions, whose Mellin amplitude is exactly 1. Our chief example is a very simple formula expressing the 6-mass double box as a single integral of the 6-mass scalar hexagon in 6 dimensions.

  2. Amplitude variations in coarticulated vowels

    PubMed Central

    Jacewicz, Ewa; Fox, Robert Allen

    2008-01-01

    This paper seeks to characterize the nature, size, and range of acoustic amplitude variation in naturally produced coarticulated vowels in order to determine its potential contribution and relevance to vowel perception. The study is a partial replication and extension of the pioneering work by House and Fairbanks [J. Acoust. Soc. Am. 22, 105–113 (1953)], who reported large variation in vowel amplitude as a function of consonantal context. Eight American English vowels spoken by men and women were recorded in ten symmetrical CVC consonantal contexts. Acoustic amplitude measures included overall rms amplitude, amplitude of the rms peak along with its relative location in the CVC-word, and the amplitudes of individual formants F1–F4 along with their frequencies. House and Fairbanks’ amplitude results were not replicated: Neither the overall rms nor the rms peak varied appreciably as a function of consonantal context. However, consonantal context was shown to affect significantly and systematically the amplitudes of individual formants at the vowel nucleus. These effects persisted in the auditory representation of the vowel signal. Auditory spectra showed that the pattern of spectral amplitude variation as a function of contextual effects may still be encoded and represented at early stages of processing by the peripheral auditory system. PMID:18529192

  3. On the Period-Amplitude and Amplitude-Period Relationships

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.; Hathaway, David H.

    2008-01-01

    Examined are Period-Amplitude and Amplitude-Period relationships based on the cyclic behavior of the 12-month moving averages of monthly mean sunspot numbers for cycles 0.23, both in terms of Fisher's exact tests for 2x2 contingency tables and linear regression analyses. Concerning the Period-Amplitude relationship (same cycle), because cycle 23's maximum amplitude is known to be 120.8, the inferred regressions (90-percent prediction intervals) suggest that its period will be 131 +/- 24 months (using all cycles) or 131 +/- 18 months (ignoring cycles 2 and 4, which have the extremes of period, 108 and 164 months, respectively). Because cycle 23 has already persisted for 142 months (May 1996 through February 2008), based on the latter prediction, it should end before September 2008. Concerning the Amplitude-Period relationship (following cycle maximum amplitude versus preceding cycle period), because cycle 23's period is known to be at least 142 months, the inferred regressions (90-percent prediction intervals) suggest that cycle 24's maximum amplitude will be about less than or equal to 96.1 +/- 55.0 (using all cycle pairs) or less than or equal to 91.0 +/- 36.7 (ignoring statistical outlier cycle pairs). Hence, cycle 24's maximum amplitude is expected to be less than 151, perhaps even less than 128, unless cycle pair 23/24 proves to be a statistical outlier.

  4. Scattering Via Conformal Higher Spin Exchanges

    NASA Astrophysics Data System (ADS)

    Tseytlin, A. A.

    We consider a model of massless scalars interacting (via bilinear conserved currents) with conformal higher spin fields in flat space. We compute the tree-level four-scalar scattering amplitude using a natural prescription for summation over an infinite set of conformal higher spin exchanges and find that it vanishes. Independently, we show that the vanishing of the scalar scattering amplitude is, in fact, implied by the global conformal higher spin symmetry of this model.

  5. Formulation of spin 7/2 and 9/2 nucleon resonance amplitudes for kaon photoproduction off a proton

    SciTech Connect

    Clymton, S. Mart, T.

    2016-04-19

    We have constructed the formulation of scattering amplitude for kaon photoproduction off a proton that includes nucleon resonances with spins 7/2 and 9/2. To this end we start with the formalism of projection operator for higher spins and derive the spins 7/2 and 9/2 projection operators. The corresponding Feynman propagators are obtained from these projection operators. To calculate the scattering amplitude we use the vertex factor proposed by Pascalutsa. The scattering amplitudes are then decomposed into six Lorentz- and gauge-invariant amplitudes, from which the cross section and polarization observables can be calculated.

  6. Some tree-level string amplitudes in the NSR formalism

    NASA Astrophysics Data System (ADS)

    Becker, Katrin; Becker, Melanie; Melnikov, Ilarion V.; Robbins, Daniel; Royston, Andrew B.

    2015-12-01

    We calculate tree level scattering amplitudes for open strings using the NSR formalism. We present a streamlined symmetry-based and pedagogical approach to the computations, which we first develop by checking two-, three-, and four-point functions involving bosons and fermions. We calculate the five-point amplitude for massless gluons and find agreement with an earlier result by Brandt, Machado and Medina. We then compute the five-point amplitudes involving two and four fermions respectively, the general form of which has not been previously obtained in the NSR formalism. The results nicely confirm expectations from the supersymmetric F 4 effective action. Finally we use the prescription of Kawai, Lewellen and Tye (KLT) to compute the amplitudes for the closed string sector.

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

    SciTech Connect

    Boucher-Veronneau, C.; Dixon, L.J.; /SLAC

    2012-02-15

    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.

  8. The Last of the Finite Loop Amplitudes in QCD

    SciTech Connect

    Bern, Zvi; Dixon, Lance J.; Kosower, David A.

    2005-05-31

    We use on-shell recursion relations to determine the one-loop QCD scattering amplitudes with a massless external quark pair and an arbitrary number (n - 2) of positive-helicity gluons. These amplitudes are the last of the unknown infrared- and ultraviolet-finite loop amplitudes of QCD. The recursion relations are similar to ones applied at tree level, but contain new non-trivial features corresponding to poles present for complex momentum arguments but absent for real momenta. We present the relations and the compact solutions to them, valid for all n. We also present compact forms for the previously-computed one-loop n-gluon amplitudes with a single negative helicity and the rest positive helicity.

  9. Substorm statistics: Occurrences and amplitudes

    SciTech Connect

    Borovsky, J.E.; Nemzek, R.J.

    1994-05-01

    The occurrences and amplitudes of substorms are statistically investigated with the use of three data sets: the AL index, the Los Alamos 3-satellite geosynchronous energetic-electron measurements, and the GOES-5 and -6 geosynchronous magnetic-field measurements. The investigation utilizes {approximately} 13,800 substorms in AL, {approximately} 1400 substorms in the energetic-electron flux, and {approximately} 100 substorms in the magnetic field. The rate of occurrence of substorms is determined as a function of the time of day, the time of year, the amount of magnetotail bending, the orientation of the geomagnetic dipole, the toward/away configuration of the IMF, and the parameters of the solar wind. The relative roles of dayside reconnection and viscous coupling in the production of substorms are assessed. Three amplitudes are defined for a substorms: the jump in the AL index, the peak of the >30-keV integral electron flux at geosynchronous orbit near midnight, and the angle of rotation of the geosynchronous magnetic field near midnight. The substorm amplitudes are statistically analyzed, the amplitude measurements are cross correlated with each other, and the substorm amplitudes are determined as functions of the solar-wind parameters. Periodically occurring and randomly occurring substorms are analyzed separately. The energetic-particle-flux amplitudes are consistent with unloading and the AL amplitudes are consistent with direct driving plus unloading.

  10. A survey of the physical optics inverse scattering identity

    NASA Astrophysics Data System (ADS)

    Bojarski, N. N.

    1982-09-01

    An inverse scattering identity relating the characteristic function of a scatterer to the three-dimensional spatial Fourier transform of the augmented far field scattering amplitude is derived by applying the physical optics approximation to the acoustic and electromagnetic direct scattering integral representation. Because this identity requires full scattering data for all frequencies and aspect angles, an integral equation is developed for incomplete scattering data which solves for the unknown characteristic function of the scatterer in terms of the known incomplete scattering data. A regularized analytic closed form solution to this integral equation is obtained, and synthesized numerico-experimental results verifying the solution are presented.

  11. Amplitude path corrections for regional phases in China

    SciTech Connect

    Phillips, W.S.; Velasco, A.A.; Taylor, S.R.; Randall, G.E.

    1998-12-31

    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.

  12. Conformal basis for flat space amplitudes

    NASA Astrophysics Data System (ADS)

    Pasterski, Sabrina; Shao, Shu-Heng

    2017-09-01

    We study solutions of the Klein-Gordon, Maxwell, and linearized Einstein equations in R1 ,d +1 that transform as d -dimensional conformal primaries under the Lorentz group S O (1 ,d +1 ). Such solutions, called conformal primary wavefunctions, are labeled by a conformal dimension Δ and a point in Rd, rather than an on-shell (d +2 )-dimensional momentum. We show that the continuum of scalar conformal primary wavefunctions on the principal continuous series Δ ∈d/2 +i R of S O (1 ,d +1 ) spans a complete set of normalizable solutions to the wave equation. In the massless case, with or without spin, the transition from momentum space to conformal primary wavefunctions is implemented by a Mellin transform. As a consequence of this construction, scattering amplitudes in this basis transform covariantly under S O (1 ,d +1 ) as d -dimensional conformal correlators.

  13. Small amplitude quasibreathers and oscillons

    SciTech Connect

    Fodor, Gyula; Lukacs, Arpad; Forgacs, Peter; Horvath, Zalan

    2008-07-15

    Quasibreathers (QB) are time-periodic solutions with weak spatial localization introduced in G. Fodor et al. in [Phys. Rev. D 74, 124003 (2006)]. QB's provide a simple description of oscillons (very long-living spatially localized time dependent solutions). The small amplitude limit of QB's is worked out in a large class of scalar theories with a general self-interaction potential, in D spatial dimensions. It is shown that the problem of small amplitude QB's is reduced to a universal elliptic partial differential equation. It is also found that there is the critical dimension, D{sub crit}=4, above which no small amplitude QB's exist. The QB's obtained this way are shown to provide very good initial data for oscillons. Thus these QB's provide the solution of the complicated, nonlinear time dependent problem of small amplitude oscillons in scalar theories.

  14. Relativistic quantum scattering yielded by Lorentz symmetry breaking effects

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bakke, K.; Belich, H.

    2017-08-01

    We investigate the scattering of a relativistic scalar quantum particle induced by a scattering-like potential that arises from the effects of the violation of the Lorentz symmetry. We then obtain the scattering phase shift caused by the influence of such a potential and use it to calculate the exact expressions for the scattering amplitude as well as for the total scattering cross-section through the optical theorem. In addition, we estimate an upper bound for the Lorentz symmetry violation parameters.

  15. Large Amplitude Oscillations in Prominences

    NASA Astrophysics Data System (ADS)

    Tripathi, D.; Isobe, H.; Jain, R.

    2009-12-01

    Since the first reports of oscillations in prominences in the 1930s, there have been major theoretical and observational developments to understand the nature of these oscillatory phenomena, leading to the whole new field of the so-called “prominence seismology”. There are two types of oscillatory phenomena observed in prominences; “small-amplitude oscillations” (2-3 km s-1), which are quite common, and “large-amplitude oscillations” (>20 km s-1) for which observations are scarce. Large-amplitude oscillations have been found as “winking filament” in H α as well as motion in the plane-of-sky in H α, EUV, micro-wave and He 10830 observations. Historically, it has been suggested that the large-amplitude oscillations in prominences were triggered by disturbances such as fast-mode MHD waves (Moreton wave) produced by remote flares. Recent observations show, in addition, that near-by flares or jets can also create such large-amplitude oscillations in prominences. Large-amplitude oscillations, which are observed both in transverse as well as longitudinal direction, have a range of periods varying from tens of minutes to a few hours. Using the observed period of oscillation and simple theoretical models, the obtained magnetic field in prominences has shown quite a good agreement with directly measured one and, therefore, justifies prominence seismology as a powerful diagnostic tool. On rare occasions, when the large-amplitude oscillations have been observed before or during the eruption, the oscillations may be applied to diagnose the stability and the eruption mechanism. Here we review the recent developments and understanding in the observational properties of large-amplitude oscillations and their trigger mechanisms and stability in the context of prominence seismology.

  16. Tempo and amplitude in growth.

    PubMed

    Hermanussen, Michael

    2011-01-01

    Growth is defined as an increase of size over time with time usually defined as physical time. Yet, the rigid metric of physical time is not directly relevant to the internal dynamics of growth. Growth is linked to maturation. Children and adolescents differ in the tempo at which they mature. One calendar year differs in its meaning in a fast maturing, and in a slow maturing child. The slow child needs more calendar years for completing the same stage of maturity. Many characteristics in the human growth curve are tempo characteristics. Tempo - being fast or slow maturing - has to be carefully separated from amplitude - being tall or short. Several characteristic phenomena such as catch-up growth after periods of illness and starvation are largely tempo phenomena, and do usually not affect the amplitude component of growth. Applying Functional Data Analysis and Principal Component Analysis, the two main sources of height variance: tempo and amplitude can statistically be separate and quantified. Tempo appears to be more sensitive than amplitude to nutrition, health and environmental stress. An appropriate analysis of growth requires disentangling its two major components: amplitude and tempo. The assessment of the developmental tempo thus is an integral part of assessing child and adolescent growth. Though an Internet portal is currently available to process small amounts of height data (www.willi-will-wachsen.com) for separately determining amplitude and tempo in growth, there is urgent need of better and practical solutions for analyzing individual growth.

  17. Baryon-to-Meson Transition Distribution Amplitudes: Formalism and Models

    NASA Astrophysics Data System (ADS)

    Pire, B.; Semenov-Tian-Shansky, K.; Szymanowski, L.

    2017-03-01

    In specific kinematics, hard exclusive amplitudes may be factorized into a short distance dominated part computable in a perturbative way on the one hand, and universal, confinement related hadronic matrix elements on the other hand. The extension of this description to processes such as backward meson electroproduction and forward meson production in antiproton-nucleon scattering leads to define new hadronic matrix elements of three quark operators on the light cone, the nucleon-to-meson transition distribution amplitudes, which shed a new light on the nucleon structure.

  18. The scattering of the screened Coulomb potential

    NASA Astrophysics Data System (ADS)

    Cao, Xin-Wei; Chen, Wen-Li; Li, Yuan-Yuan; Wei, Gao-Feng

    2014-08-01

    We study the scattering states of the screened Coulomb potential in the nonrelativistic frame. The explicitly calculation formula of phase shift is derived and the normalized radial wave functions of scattering states on the ^{\\prime} k/2\\pi scale^{\\prime} are presented. By studying analytical properties of scattering amplitude the screening effects on bound states are discussed numerically. It is shown that the screening effects increase with increasing screened parameter, especially for large quantum states.

  19. Scattering calculations and confining interactions

    NASA Technical Reports Server (NTRS)

    Buck, Warren W.; Maung, Khin M.

    1993-01-01

    Most of the research work performed under this grant were concerned with strong interaction processes ranging from kaon-nucleon interaction to proton-nucleus scattering calculations. Research performed under this grant can be categorized into three groups: (1) parametrization of fundamental interactions, (2) development of formal theory, and (3) calculations based upon the first two. Parametrizations of certain fundamental interactions, such as kaon-nucleon interaction, for example, were necessary because kaon-nucleon scattering amplitude was needed to perform kaon-nucleus scattering calculations. It was possible to calculate kaon-nucleon amplitudes from the first principle, but it was unnecessary for the purpose of the project. Similar work was also done for example for anti-protons and anti-nuclei. Formal developments to some extent were also pursued so that consistent calculations can be done.

  20. Graviton and Gluon Scattering from First Principles.

    PubMed

    Boels, Rutger H; Medina, Ricardo

    2017-02-10

    Graviton and gluon scattering are studied from minimal physical assumptions such as Poincare and gauge symmetry as well as unitarity. The assumptions lead to an interesting and surprisingly restrictive set of linear equations. This shows gluon and graviton scattering to be related in many field and string theories, explaining and extending several known results. By systematic analysis exceptional graviton scattering amplitudes are derived, which in general dimensions cannot be related to gluon amplitudes. The simplicity of the formalism guarantees wide further applicability to gauge and gravity theories.

  1. Quantum scattering on a cone revisited

    NASA Astrophysics Data System (ADS)

    Barroso, V. S.; Pitelli, J. P. M.

    2017-07-01

    We revisit the scattering of quantum test particles on the conical (2 +1 )-dimensional spacetime and find the scattering amplitude as a function of the boundary conditions imposed at the apex of the cone. We show that the boundary condition is responsible for a purely analytical term in the scattering amplitude, in addition to those coming from purely topological effects. Since it is possible to have nonequivalent physical evolutions for the wave packet (each one corresponding to a different boundary condition), it seems crucial to have an observable quantity specifying which evolution has been prescribed.

  2. Phase coherence and pairing amplitude in photo-excited superconductors

    NASA Astrophysics Data System (ADS)

    Perfetti, Luca; Piovera, Christian; Zhang, Zailan

    2016-05-01

    New data on Bi2Sr2CaCu2O8+δ (Bi2212) reveal interesting aspects of photoexcited superconductors. The electrons dynamics show that inelastic scattering by nodal quasiparticles decreases when the temperature is lowered below the critical value of the superconducting phase transition. This drop of electronic dissipation is astonishingly robust and survives to photoexcitation densities much larger than the value sustained by long-range superconductivity. The unconventional behavior of quasiparticle scattering is ascribed to superconducting correlations extending on a length scale comparable to the inelastic mean-free path. Our measurements indicate that strongly driven superconductors enter in a regime without phase coherence but finite pairing amplitude.

  3. Massive superstring scatterings in the Regge regime

    SciTech Connect

    He Song; Lee, Jen-Chi; Takahashi, Keijiro; Yang Yi

    2011-03-15

    We calculate four classes of high-energy massive string scattering amplitudes of fermionic string theory at arbitrary mass levels in the Regge regime (RR). We show that all four leading order amplitudes in the RR can be expressed in terms of the Kummer function of the second kind. Based on the summation algorithm of a set of extended signed Stirling number identities, we show that all four ratios calculated previously by the method of decoupling of zero-norm states among scattering amplitudes in the Gross regime can be extracted from this Kummer function in the RR. Finally, we conjecture and give evidence that the existence of these four Gross regime ratios in the RR persists to subleading orders in the Regge expansion of all high-energy fermionic string scattering amplitudes.

  4. Diffraction phenomena in elastic scattering of heavy ions

    SciTech Connect

    Kotlyar, V.V.; Shebeko, A.V.

    1981-08-01

    Nuclear diffraction phenomena in elastic scattering of heavy ions are studied in the intermediate energy range. Examination is carried out using the strong absorption models for the S-matrix in the angular momentum representation. New asymptotic expressions for the diffraction scattering amplitudes are obtained. The main attention is paid to the study of the relation between the Fresnel and the Fraunhofer parts of the amplitudes obtained in different regions of scattering angles.

  5. Scattering problem in deformed space with minimal length

    SciTech Connect

    Stetsko, M. M.; Tkachuk, V. M.

    2007-07-15

    We investigated the elastic scattering problem with deformed Heisenberg algebra leading to the existence of a minimal length. The continuity equations for the moving particle in deformed space were constructed. We obtained the Green's function for a free particle, the scattering amplitude, and the cross section in deformed space. We also calculated the scattering amplitudes and differential cross sections for the Yukawa and the Coulomb potentials in the Born approximation.

  6. Zero energy scattering calculation in Euclidean space

    NASA Astrophysics Data System (ADS)

    Carbonell, J.; Karmanov, V. A.

    2016-03-01

    We show that the Bethe-Salpeter equation for the scattering amplitude in the limit of zero incident energy can be transformed into a purely Euclidean form, as it is the case for the bound states. The decoupling between Euclidean and Minkowski amplitudes is only possible for zero energy scattering observables and allows determining the scattering length from the Euclidean Bethe-Salpeter amplitude. Such a possibility strongly simplifies the numerical solution of the Bethe-Salpeter equation and suggests an alternative way to compute the scattering length in Lattice Euclidean calculations without using the Luscher formalism. The derivations contained in this work were performed for scalar particles and one-boson exchange kernel. They can be generalized to the fermion case and more involved interactions.

  7. Lorentzian proper vertex amplitude: Asymptotics

    NASA Astrophysics Data System (ADS)

    Engle, Jonathan; Vilensky, Ilya; Zipfel, Antonia

    2016-09-01

    In previous work, the Lorentzian proper vertex amplitude for a spin-foam model of quantum gravity was derived. In the present work, the asymptotics of this amplitude are studied in the semiclassical limit. The starting point of the analysis is an expression for the amplitude as an action integral with action differing from that in the Engle-Pereira-Rovelli-Livine (EPRL) case by an extra "projector" term. This extra term scales linearly with spins only in the asymptotic limit, and is discontinuous on a (lower dimensional) submanifold of the integration domain in the sense that its value at each such point depends on the direction of approach. New tools are introduced to generalize stationary phase methods to this case. For the case of boundary data which can be glued to a nondegenerate Lorentzian 4-simplex, the asymptotic limit of the amplitude is shown to equal the single Feynman term, showing that the extra term in the asymptotics of the EPRL amplitude has been eliminated.

  8. K- nuclear potentials based on chiral meson-baryon amplitudes

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Cieplý, A.; Gazda, D.; Friedman, E.; Gal, A.

    2012-09-01

    K- nuclear optical potentials are constructed from in-medium subthreshold K¯N scattering amplitudes within a chirally motivated coupled-channel model. We demonstrate how the strong energy and density dependence of the scattering amplitudes at and below threshold leads to a deep K- nuclear potential VK- for kaonic atoms and K- nuclear quasibound states. Selfconsistent evaluations yield K- potential depths -ReVK- (ρ0) of order 100 MeV. Allowing for K- NN absorption, better agreement with K- atoms data is achieved, leading to increased potential depths, -ReVK- (ρ0) ˜ 175 MeV, in accord with density dependent potentials obtained in purely phenomenological fits. Self consistent dynamical calculations of K- nuclear quasibound states are reported and discussed, as well.

  9. TASI 2014: Lectures on Gauge and Gravity Amplitude Relations

    NASA Astrophysics Data System (ADS)

    Carrasco, John Joseph M.

    In these lectures I talk about simplifications and universalities found in scattering amplitudes for gauge and gravity theories. In contrast to Ward identities, which are understood to arise from familiar symmetries of the classical action, these structures are currently only understood in terms of graphical organizational principles, such as the gauge-theoretic color-kinematics duality and the gravitational double-copy structure, for local representations of multi-loop S-matrix elements. These graphical principles make manifest new relationships in and between gauge and gravity scattering amplitudes. My lectures will focus on arriving at such graphical organizations for generic theories with examples presented from maximal supersymmetry, and their use in unitarity-based multiloop integrand construction.

  10. Timelike Compton Scattering

    SciTech Connect

    T. Horn, Y. Illieva, F. J. Klein, P. Nadel‐Turonski, R. Paremuzyan, S. Stepanyan

    2011-10-01

    Generalized Parton Distributions (GPDs) have become a key concept in our studies of hadron structure in QCD. The measurement of suitable experimental observables and the extraction of GPDs from these data is one of the high priority 12 GeV programs at Jefferson Lab. Deeply Virtual Compton Scattering (DVCS) is generally thought of as the most promising channel for probing GPDs in the valence quark region. However, the inverse process, Timelike Compton Scattering (TCS) can provide an important complementary measurement, in particular of the real part of the Compton amplitude and power corrections at intermediate values of Q2. The first studies of TCS using real tagged and quasi-real untagged photons were performed in Hall B at Jefferson Lab.

  11. Factorization of chiral string amplitudes

    NASA Astrophysics Data System (ADS)

    Huang, Yu-tin; Siegel, Warren; Yuan, Ellis Ye

    2016-09-01

    We re-examine a closed-string model defined by altering the boundary conditions for one handedness of two-dimensional propagators in otherwise-standard string theory. We evaluate the amplitudes using Kawai-Lewellen-Tye factorization into open-string amplitudes. The only modification to standard string theory is effectively that the spacetime Minkowski metric changes overall sign in one open-string factor. This cancels all but a finite number of states: as found in earlier approaches, with enough supersymmetry (e.g., type II) the tree amplitudes reproduce those of the massless truncation of ordinary string theory. However, we now find for the other cases that additional fields, formerly thought to be auxiliary, describe new spin-2 states at the two adjacent mass levels (tachyonic and tardyonic). The tachyon is always a ghost, but can be avoided in the heterotic case.

  12. Amplitude relations in non-linear sigma model

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Du, Yi-Jian

    2014-01-01

    In this paper, we investigate tree-level scattering amplitude relations in U( N) non-linear sigma model. We use Cayley parametrization. As was shown in the recent works [23,24], both on-shell amplitudes and off-shell currents with odd points have to vanish under Cayley parametrization. We prove the off-shell U(1) identity and fundamental BCJ relation for even-point currents. By taking the on-shell limits of the off-shell relations, we show that the color-ordered tree amplitudes with even points satisfy U(1)-decoupling identity and fundamental BCJ relation, which have the same formations within Yang-Mills theory. We further state that all the on-shell general KK, BCJ relations as well as the minimal-basis expansion are also satisfied by color-ordered tree amplitudes. As a consequence of the relations among color-ordered amplitudes, the total 2 m-point tree amplitudes satisfy DDM form of color decomposition as well as KLT relation.

  13. Einstein-Yang-Mills from pure Yang-Mills amplitudes

    NASA Astrophysics Data System (ADS)

    Nandan, Dhritiman; Plefka, Jan; Schlotterer, Oliver; Wen, Congkao

    2016-10-01

    We present new relations for scattering amplitudes of color ordered gluons and gravitons in Einstein-Yang-Mills theory. Tree-level amplitudes of arbitrary multiplicities and polarizations involving up to three gravitons and up to two color traces are reduced to partial amplitudes of pure Yang-Mills theory. In fact, the double-trace identities apply to Einstein-Yang-Mills extended by a dilaton and a B-field. Our results generalize recent work of Stieberger and Taylor for the single graviton case with a single color trace. As the derivation is made in the dimension-agnostic Cachazo-He-Yuan formalism, our results are valid for external bosons in any number of spacetime dimensions. Moreover, they generalize to the superamplitudes in theories with 16 supercharges.

  14. Amplitude and phase-shaping effects in beamwaveguides

    NASA Technical Reports Server (NTRS)

    Rengarajan, Sembiam R.; Galindo-Israel, Victor; Imbriale, William A.

    1991-01-01

    Results are presented of an investigation on improvements in a geometrical optics (GO) design of a beam-waveguide antenna for operation at multiple frequency bands. Improvements might be possible by changing the design of the lower-frequency input pattern to the beam waveguide. The effects of amplitude and phase shaping the input pattern have been studied with an aperture diffraction model. Accurate vector near-field computations were made rapidly with a spherical wave expansion of the input and scattered fields. Numerical results indicate that for aperture sizes of less than 30 wavelengths, there is insufficient control on defocusing due to amplitude and phase shaping. Design tradeoffs on spillover loss and defocusing are possible by changing the amplitude and phase distribution of the input wavefront for larger size apertures.

  15. Thermodynamic constraints on the amplitude of quantum oscillations

    NASA Astrophysics Data System (ADS)

    Shekhter, Arkady; Modic, K. A.; McDonald, R. D.; Ramshaw, B. J.

    2017-03-01

    Magneto-quantum oscillation experiments in high-temperature superconductors show a strong thermally induced suppression of the oscillation amplitude approaching the critical dopings [B. J. Ramshaw et al., Science 348, 317 (2014), 10.1126/science.aaa4990; H. Shishido et al., Phys. Rev. Lett. 104, 057008 (2010), 10.1103/PhysRevLett.104.057008; P. Walmsley et al., Phys. Rev. Lett. 110, 257002 (2013), 10.1103/PhysRevLett.110.257002]—in support of a quantum-critical origin of their phase diagrams. We suggest that, in addition to a thermodynamic mass enhancement, these experiments may directly indicate the increasing role of quantum fluctuations that suppress the quantum oscillation amplitude through inelastic scattering. We show that the traditional theoretical approaches beyond Lifshitz-Kosevich to calculate the oscillation amplitude in correlated metals result in a contradiction with the third law of thermodynamics and suggest a way to rectify this problem.

  16. Superstring disk amplitudes in a rolling tachyon background

    SciTech Connect

    Jokela, Niko; Majumder, Jaydeep; Keski-Vakkuri, Esko

    2006-02-15

    We study the tree level scattering or emission of n closed superstrings from a decaying non-BPS brane in Type II superstring theory. We attempt to calculate generic n-point superstring disk amplitudes in the rolling tachyon background. We show that these can be written as infinite power series of Toeplitz determinants, related to expectation values of a periodic function in Circular Unitary Ensembles. Further analytical progress is possible in the special case of bulk-boundary disk amplitudes. These are interpreted as probability amplitudes for emission of a closed string with initial conditions perturbed by the addition of an open string vertex operator. This calculation has been performed previously in bosonic string theory, here we extend the analysis for superstrings. We obtain a result for the average energy of closed superstrings produced in the perturbed background.

  17. Large amplitude drop shape oscillations

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Wang, T. G.

    1982-01-01

    An experimental study of large amplitude drop shape oscillation was conducted in immiscible liquids systems and with levitated free liquid drops in air. In liquid-liquid systems the results indicate the existence of familiar characteristics of nonlinear phenomena. The resonance frequency of the fundamental quadrupole mode of stationary, low viscosity Silicone oil drops acoustically levitated in water falls to noticeably low values as the amplitude of oscillation is increased. A typical, experimentally determined relative frequency decrease of a 0.5 cubic centimeters drop would be about 10% when the maximum deformed shape is characterized by a major to minor axial ratio of 1.9. On the other hand, no change in the fundamental mode frequency could be detected for 1 mm drops levitated in air. The experimental data for the decay constant of the quadrupole mode of drops immersed in a liquid host indicate a slight increase for larger oscillation amplitudes. A qualitative investigation of the internal fluid flows for such drops revealed the existence of steady internal circulation within drops oscillating in the fundamental and higher modes. The flow field configuration in the outer host liquid is also significantly altered when the drop oscillation amplitude becomes large.

  18. Structured light, transmission, and scattering

    NASA Astrophysics Data System (ADS)

    Andrews, David L.

    2011-03-01

    Numerous theoretical and experimental studies have established the principle that beams conveying orbital angular momentum offer a rich scope for information transfer. However, it is not clear how far it is practicable to operate such a concept at the single-photon level - especially when such a beam propagates through a system in which scattering can occur. In cases where scattering leads to photon deflection, it produces losses; however in terms of the retention of information content, there should be more concern over forward scattering. Based on a quantum electrodynamical formulation of theory, this paper aims to frame and resolve the key issues. A quantum amplitude is constructed for the representation of single and multiple scattering events in the propagation an individual photon, from a suitably structured beam. The analysis identifies potential limitations of principle, undermining complete fidelity of quantum information transmission.

  19. Quasi-steady, marginally unstable electron cyclotron harmonic wave amplitudes

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojia; Angelopoulos, Vassilis; Ni, Binbin; Thorne, Richard M.; Horne, Richard B.

    2013-06-01

    Electron cyclotron harmonic (ECH) waves have long been considered a potential driver of diffuse aurora in Earth's magnetotail. However, the scarcity of intense ECH emissions in the outer magnetotail suggests that our understanding of the amplification and the relative importance of these waves for electron scattering is lacking. We conduct a comprehensive study of wave growth and quasi-linear diffusion to estimate the amplitude of loss-cone-driven ECH waves once diffusion and growth balance but before convection or losses alter the background hot plasma sheet population. We expect this to be the most common state of the plasma sheet between episodes of fast convection. For any given wave amplitude, we model electron diffusion caused by interaction with ECH waves using a 2-D bounce-averaged Fokker-Planck equation. After fitting the resultant electron distributions as a superposition of multicomponent subtracted bi-Maxwellians, we estimate the maximum path-integrated gain using the HOTRAY ray-tracing code. We argue that the wave amplitude during quasi-steady state is the inflection point on a gain-amplitude curve. During quasi-steady state, ECH wave amplitudes can be significant (~1 mV/m) at L ~ 8 but drop to very low values (<~0.1 mV/m) in the outer magnetotail (L ~ 16) and likely fall below the sensitivity of typical instrumentation relatively close to Earth mainly because of the smallness of the loss cone. Our result reinforces the potentially important role of ECH waves in driving diffuse aurora and suggests that careful comparison of theoretical wave amplitude estimates and observations is required for resolving the equatorial scattering mechanism of diffuse auroral precipitation.

  20. Amplitude modulation technique for designing metalenses with apodized and enhanced resolution focal spots

    NASA Astrophysics Data System (ADS)

    Hashemi, Mahdieh; Moazami, Amin; Naserpour, Mahin; Zapata-Rodríguez, Carlos J.

    2017-06-01

    In this paper we show that engineering both phase and amplitude of the scattered light can be employed in designing metalenses with either higher resolution or apodized focal spots. C-shaped split-ring micro-resonators (CSRRs) with different geometrical parameters are selected to have a full control of amplitude and phase. While phase engineering is necessary for light focusing, amplitude modulation of the scattered wave can be applied to characterize the focal point properties such as resolution gain and sidelobe level. We show that both axial and transverse resolution improvement or apodization is possible in the far-field region by applying proper amplitude function. Amplitude modulation technique, which is introduced in this paper, paves a new way to design efficient lenses which can be utilized in imaging and lithography applications in all frequency ranges.

  1. Multiple scattering and charged-particle - hydrogen-atom collisions

    NASA Technical Reports Server (NTRS)

    Franco, V.; Thomas, B. K.

    1979-01-01

    Glauber-approximation scattering amplitudes for charged-particle - hydrogen-atom elastic and inelastic collisions are derived directly in terms of the known particle-electron and particle-proton Coulomb scattering amplitudes and the known hydrogen-atom form factors. It is shown that the particle-hydrogen amplitude contains no single-scattering term. The double-scattering term is obtained as a two-dimensional integral in momentum space. It is demonstrated how the result can be used as the starting point for an alternative and relatively simple derivation, in closed form, of the Glauber particle-hydrogen scattering amplitude for transitions from the ground state to an arbitrary (nlm) state.

  2. Helicity selection rules and noninterference for BSM amplitudes

    NASA Astrophysics Data System (ADS)

    Azatov, Aleksandr; Contino, Roberto; Machado, Camila S.; Riva, Francesco

    2017-03-01

    Precision studies of scattering processes at colliders provide powerful indirect constraints on new physics. We study the helicity structure of scattering amplitudes in the standard model (SM) and in the context of an effective Lagrangian description of beyond-the-SM (BSM) dynamics. Our analysis reveals a novel set of helicity selection rules according to which, in the majority of 2 →2 scattering processes at high energy, the SM and the leading BSM effects do not interfere. In such situations, the naive expectation that dimension-6 operators represent the leading BSM contribution is compromised, as corrections from dimension-8 operators can become equally (if not more) important well within the validity of the effective field theory approach.

  3. Proton-deuteron double scattering

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.

    1974-01-01

    A simple but accurate form for the proton-deuteron elastic double scattering amplitude, which includes both projectile and target recoil motion and is applicable at all momentum transfer, is derived by taking advantage of the restricted range of Fermi momentum allowed by the deuteron wave function. This amplitude can be directly compared to approximations which have neglected target recoil or are limited to small momentum transfer; the target recoil and large momentum transfer effects are evaluated explicitly within the context of a Gaussian model.

  4. Parity Violating Electron Scattering

    NASA Astrophysics Data System (ADS)

    Kumar, Krishna S.

    2003-07-01

    We report on a mature experimental program to measure the parity violating asymmetry in the elastic scattering of longitudinally polarized electrons from unpolarized 1H, 2H, 4He and 208Pb targets. One focus is the measurement of the nucleon neutral weak form factors at intermediate four-momentum transfer (0.1 < Q2 < 1) (GeV/c)2 which provide information about the impact of virtual strange quarks on the charge and current distributions inside nucleons. Another focus is the neutral current elastic amplitude at very low Q2, which can provide stringent tests of the standard model and possess unique sensitivity to new physics at the TeV scale. Finally, the elastic neutral weak amplitude from scattering off a heavy spinless nucleus is very sensitive to the presence of a neutron skin. We report on recent technical progress in the design and scope of the experimental techniques. The physics implications of the published measurements are discussed and the current status and anticipated results experiments under construction are summarized.

  5. Coupled-channel scattering on a torus

    SciTech Connect

    Guo, Peng; Dudek, Jozef Jon; Edwards, Robert G.; Szczepaniak, Adam Pawel

    2013-07-01

    Based on the Hamiltonian formalism approach, a generalized Luscher's formula for two particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice QCD computations.

  6. Coupled-channel scattering on a torus

    DOE PAGES

    Guo, Peng; Dudek, Jozef Jon; Edwards, Robert G.; ...

    2013-07-01

    Based on the Hamiltonian formalism approach, a generalized Luscher's formula for two particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice QCD computations.

  7. True amplitude prestack depth migration

    NASA Astrophysics Data System (ADS)

    Deng, Feng

    Reliable analysis of amplitude variation with offset (or with angle) requires accurate amplitudes from prestack migration. In routine seismic data processing, amplitude balancing and automatic gain control are often used to reduce amplitude lateral variations. However, these methods are empirical and lack a solid physical basis; thus, there are uncertainties that might produce erroneous conclusions, and hence cause economic loss. During wavefield propagation, geometrical spreading, intrinsic attenuation, transmission losses and the energy conversion significantly distort the wavefield amplitude. Most current true-amplitude migrations usually compensate only for geometrical spreading. A new prestack depth migration based on the framework of reverse-time migration in the time-space domain was developed in this dissertation with the aim of compensating all of the propagation effects in one integrated algorithm. Geometrical spreading is automatically included because of the use of full two-way wave extrapolation. Viscoelastic wave equations are solved to handle the intrinsic attenuation with a priori quality factor. Transmission losses for both up- and down-going waves are compensated using a two-pass, recursive procedure based on extracting the angle-dependent reflection/transmission coefficients from prestack migration. The losses caused by the conversion of energy from one elastic model to another are accounted for through elastic wave extrapolation; the influence of the S wave velocity contrast on the P wave reflection coefficient is implicitly included by using the Zoeppritz equations to describe the reflection and transmission at an elastic interface. Only smooth background models are assumed to be known. The contrasts/ratios of the model parameters can be estimated by fitting the compensated angle-dependent reflection coefficients obtained from data for multiple sources. This is one useful by-product of the algorithm. Numerical tests on both 2D and 3D scalar

  8. Scattering of sound waves by a compressible vortex

    NASA Technical Reports Server (NTRS)

    Colonius, Tim; Lele, Sanjiva K.; Moin, Parviz

    1991-01-01

    Scattering of plane sound waves by a compressible vortex is investigated by direct computation of the two-dimensional Navier-Stokes equations. Nonreflecting boundary conditions are utilized, and their accuracy is established by comparing results on different sized domains. Scattered waves are directly measured from the computations. The resulting amplitude and directivity pattern of the scattered waves is discussed, and compared to various theoretical predictions. For compact vortices (zero circulation), the scattered waves directly computed are in good agreement with predictions based on an acoustic analogy. Strong scattering at about + or - 30 degrees from the direction of incident wave propagation is observed. Back scattering is an order of magnitude smaller than forward scattering. For vortices with finite circulation refraction of the sound by the mean flow field outside the vortex core is found to be important in determining the amplitude and directivity of the scattered wave field.

  9. Bootstrapping an NMHV amplitude through three loops

    NASA Astrophysics Data System (ADS)

    Dixon, Lance J.; von Hippel, Matt

    2014-10-01

    We extend the hexagon function bootstrap to the next-to-maximally-helicity-violating (NMHV) configuration for six-point scattering in planar = 4 super-Yang-Mills theory at three loops. Constraints from the differential equation, from the operator product expansion (OPE) for Wilson loops with operator insertions, and from multi-Regge factorization, lead to a unique answer for the three-loop ratio function. The three-loop result also predicts additional terms in the OPE expansion, as well as the behavior of NMHV amplitudes in the multi-Regge limit at one higher logarithmic accuracy (NNLL) than was used as input. Both predictions are in agreement with recent results from the flux-tube approach. We also study the multi-particle factorization of multi-loop amplitudes for the first time. We find that the function controlling this factorization is purely logarithmic through three loops. We show that a function U , which is closely related to the parity-even part of the ratio function V , is remarkably simple; only five of the nine possible final entries in its symbol are non-vanishing. We study the analytic and numerical behavior of both the parity-even and parity-odd parts of the ratio function on simple lines traversing the space of cross ratios ( u, v, w), as well as on a few two-dimensional planes. Finally, we present an empirical formula for V in terms of elements of the coproduct of the six-gluon MHV remainder function R 6 at one higher loop, which works through three loops for V (four loops for R 6).

  10. Pulse amplitude modulated chlorophyll fluorometer

    DOEpatents

    Greenbaum, Elias; Wu, Jie

    2015-12-29

    Chlorophyll fluorometry may be used for detecting toxins in a sample because of changes in micro algae. A portable lab on a chip ("LOAC") based chlorophyll fluorometer may be used for toxin detection and environmental monitoring. In particular, the system may include a microfluidic pulse amplitude modulated ("PAM") chlorophyll fluorometer. The LOAC PAM chlorophyll fluorometer may analyze microalgae and cyanobacteria that grow naturally in source drinking water.

  11. Genus dependence of superstring amplitudes

    SciTech Connect

    Davis, Simon

    2006-11-15

    The problem of the consistency of the finiteness of the supermoduli space integral in the limit of vanishing super-fixed point distance and the genus-dependence of the integral over the super-Schottky coordinates in the fundamental region containing a neighborhood of |K{sub n}|=0 is resolved. Given a choice of the categories of isometric circles representing the integration region, the exponential form of bounds for superstring amplitudes is derived.

  12. Ultraviolet divergences and factorization for coordinate-space amplitudes

    NASA Astrophysics Data System (ADS)

    Erdoǧan, Ozan; Sterman, George

    2015-03-01

    We consider the coordinate-space matrix elements that correspond to fixed-angle scattering amplitudes involving partons and Wilson lines in coordinate space, working in Feynman gauge. In coordinate space, both collinear and short-distance limits produce ultraviolet divergences. We classify singularities in coordinate space, and identify neighborhoods associated unambiguously with individual subspaces (pinch surfaces) where the integrals are singular. The set of such regions is finite for any diagram. Within each of these regions, coordinate-space soft-collinear and hard-collinear approximations reproduce singular behavior. Based on this classification of regions and approximations, we develop a series of nested subtraction approximations by analogy to the formalism in momentum space. This enables us to rewrite each amplitude as a sum of terms to which gauge-theory Ward identities can be applied, factorizing them into hard, jet and soft factors, and to confirm the multiplicative renormalizability of products of lightlike Wilson lines. We study in some detail the simplest case, the color-singlet cusp linking two Wilson lines, and show that the logarithm of this amplitude, which is a sum of diagrams known as webs, is closely related to the corresponding subtracted amplitude order by order in perturbation theory. This enables us to confirm that the logarithm of the cusp can be written as the integral of an ultraviolet-finite function over a surface. We study to what extent this result generalizes to amplitudes involving multiple Wilson lines.

  13. Effect of Multiple Scattering in a Quantum Well

    NASA Astrophysics Data System (ADS)

    Sheng, Hanyu; Chua, Soo-Jin; Sinkkonen, Juha

    This paper gives a potentially useful application to quantum well of the theory of scattering in the Born approximation. The simple formulae for multiple scattering in a quantum well of double barrier structure are derived. The multiple scattering parameter is the complex mean free path. We show that the amplitude of the coherent wave will be exponentially attenuated and the phase of the wave will be delayed because of the scattering.

  14. Optical scattering methods applicable to drops and bubbles

    NASA Technical Reports Server (NTRS)

    Marston, Philip L.

    1990-01-01

    An overview of optical scattering properties of drops and bubbles is presented. The properties lead to unconventional methods for optically monitoring the size or shape of a scatterer and are applicable to acoustically levitated objects. Several of the methods are applicable to the detection and measurement of small amplitude oscillations. Relevant optical phenomena include: (1) rainbows; (2) diffraction catastrophes from spheroids; (3) critical angle scattering; (4) effects of coatings; (5) glory scattering; and (6) optical levitation.

  15. Crisis in Amplitude Control Hides in Multistability

    NASA Astrophysics Data System (ADS)

    Li, Chunbiao; Sprott, Julien Clinton; Xing, Hongyan

    2016-12-01

    A crisis of amplitude control can occur when a system is multistable. This paper proposes a new chaotic system with a line of equilibria to demonstrate the threat to amplitude control from multistability. The new symmetric system has two coefficients for amplitude control, one of which is a partial amplitude controller, while the other is a total amplitude controller that simultaneously controls the frequency. The amplitude parameter rescales the basins of attraction and triggers a state switch among different states resulting in a failure of amplitude control to the desired state.

  16. Calculation of multi-loop superstring amplitudes

    NASA Astrophysics Data System (ADS)

    Danilov, G. S.

    2016-12-01

    The multi-loop interaction amplitudes in the closed, oriented superstring theory are obtained by the integration of local amplitudes. The local amplitude is represented by a sum over the spinning string local amplitudes. The spinning string local amplitudes are given explicitly through super-Schottky group parameters and through interaction vertex coordinates on the (1| 1) complex, non-split supermanifold. The obtained amplitudes are free from divergences. They are consistent with the world-sheet spinning string symmetries. The vacuum amplitude vanishes along with 1-, 2- and 3-point amplitudes of massless states. The vanishing of the above-mentioned amplitude occurs after the integration of the corresponding local amplitude has been performed over the super-Schottky group limiting points and over interaction vertex coordinate, except for those (3| 2) variables which are fixed due to SL(2)-symmetry.

  17. Two-photon exchange in electron-trinucleon elastic scattering

    NASA Astrophysics Data System (ADS)

    Kobushkin, A. P.; Timoshenko, Ju. V.

    2013-10-01

    We discuss two-photon exchange (TPE) in elastic electron scattering off the trinucleon systems, 3He and 3H. The calculations are done in the semirelativistic approximation with the trinucleon wave functions obtained with the Paris and CD-Bonn nucleon-nucleon potentials. An applicability area of the model is wide enough and includes the main part of kinematical domain where experimental data exist. All three TPE amplitudes (generalized form factors) for electron 3He elastic scattering are calculated. We find that the TPE amplitudes are a few times more significant in the scattering of electrons off 3He then in the electron-proton scattering.

  18. Unitarization and low-energy scattering data

    NASA Astrophysics Data System (ADS)

    Magalhães, P. C.; Robilotta, M. R.

    2014-07-01

    A procedure based on the well-known K-matrix formalism is presented, which makes patterns in inelastic regions of low-energy scattering data considerably more transparent. It relies on the use of an empirical kernel, obtained by eliminating elastic loops from the experimental amplitude. This allows structures associated with resonances, such as locations, widths, and heights, to become visible with the naked eye. The method is illustrated with a study of the P-wave Kπ amplitude.

  19. An optical model for composite nuclear scattering

    NASA Technical Reports Server (NTRS)

    Wilson, J. W.; Townsend, L. W.

    1981-01-01

    The optical model of composite particle scattering is considered and compared to the accuracies of other models. A nonrelativistic Schroedinger equation with two-body potentials is used for the scattering of a single particle by an energy-dependent local potential. The potential for the elastic channel is composed of matrix elements of a single scattering operator taken between the ground states of the projectile and the target; the coherent amplitude is considered as dominating the scattering in the forward direction. A multiple scattering series is analytically explored and formally summed by the solution of an equivalent Schroedinger equation. Cross sections of nuclear scattering are then determined for He-4 and C-12 nuclei at 3.6 GeV/nucleus and O-16 projectiles at 2.1 GeV/nucleus, and the optical model approximations are found to be consistently lower and more accurate than approximations made by use of Glauber's theory.

  20. Nonlinear harmonic generation in finite amplitude black hole oscillations

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Philippos

    2002-04-01

    The nonlinear generation of harmonics in gravitational perturbations of black holes is explored using numerical relativity based on an ingoing light-cone framework. Localized, finite, perturbations of an isolated black hole are parametrized by amplitude and angular harmonic form. The response of the black hole spacetime is monitored and its harmonic content analyzed to identify the strength of the nonlinear generation of harmonics as a function of the initial data amplitude. It is found that overwhelmingly the black hole responds at the harmonic mode perturbed, even for spacetimes with 10% of the black hole mass radiated. The coefficients for down and up scattering in harmonic space are computed for a range of couplings. Down scattering, leading to smoothing out of angular structure, is found to be equally as or more efficient than the up scatterings that would lead to increased rippling. The details of this nonlinear balance may form the quantitative mechanism by which black holes avoid fission even for arbitrary strong distortions.

  1. Quasidistribution amplitude of heavy quarkonia

    NASA Astrophysics Data System (ADS)

    Jia, Yu; Xiong, Xiaonu

    2016-11-01

    The recently proposed quasidistributions point out a promising direction for lattice QCD to investigate the light-cone correlators, such as parton distribution functions and distribution amplitudes (DAs), directly in the x space. Owing to its excessive simplicity, heavy quarkonium can serve as an ideal theoretical laboratory to ascertain certain features of quasi-DAs. In the framework of nonrelativistic QCD factorization, we compute the order-αs correction to both light-cone distribution amplitudes (LCDAs) and quasi-DAs associated with the lowest-lying quarkonia, with the transverse-momentum UV cutoff interpreted as the renormalization scale. We confirm analytically that the quasi-DA of a quarkonium does reduce to the respective LCDA in the infinite-momentum limit. We also observe that, provided that the momentum of a charmonium reaches about 2-3 times its mass, the quasi-DAs already converge to the LCDAs to a decent level. These results might provide some useful guidance for the future lattice study of quasidistributions.

  2. Two-Loop Gluon to Gluon-Gluon Splitting Amplitudes in QCD

    SciTech Connect

    Bern, Z.

    2004-04-30

    Splitting amplitudes are universal functions governing the collinear behavior of scattering amplitudes for massless particles. We compute the two-loop g {yields} gg splitting amplitudes in QCD, N = 1, and N = 4 super-Yang-Mills theories, which describe the limits of two-loop n-point amplitudes where two gluon momenta become parallel. They also represent an ingredient in a direct x-space computation of DGLAP evolution kernels at next-to-next-to-leading order. To obtain the splitting amplitudes, we use the unitarity sewing method. In contrast to the usual light-cone gauge treatment, our calculation does not rely on the principal-value or Mandelstam-Leibbrandt prescriptions, even though the loop integrals contain some of the denominators typically encountered in light-cone gauge. We reduce the integrals to a set of 13 master integrals using integration-by-parts and Lorentz invariance identities. The master integrals are computed with the aid of differential equations in the splitting momentum fraction z. The {epsilon}-poles of the splitting amplitudes are consistent with a formula due to Catani for the infrared singularities of two-loop scattering amplitudes. This consistency essentially provides an inductive proof of Catani's formula, as well as an ansatz for previously-unknown 1/{epsilon} pole terms having non-trivial color structure. Finite terms in the splitting amplitudes determine the collinear behavior of finite remainders in this formula.

  3. Resonances in pi-K scattering

    SciTech Connect

    Wilson, David J.

    2014-06-23

    We have obtained clear signals of resonances in coupled-channel pi K - eta K scattering. Using distillation and a large basis of operators we are able to extract a precise spectrum of energy levels using the variational method. These energies are analysed using inelastic extensions of the Luescher method to obtain scattering amplitudes that clearly describe S, P and D wave resonances, corresponding to the physical K_0^*(1430), the K^*(892) and the K_2^*(1430).

  4. Neutron scattering by Dirac multipoles

    NASA Astrophysics Data System (ADS)

    Lovesey, S. W.; Khalyavin, D. D.

    2017-06-01

    Scattering by magnetic charge formed by Dirac multipoles that are magnetic and polar is examined in the context of materials with properties that challenge conventional concepts. An order parameter composed of Dirac quadrupoles has been revealed in the pseudo-gap phase of ceramic, high-T c superconductors on the basis of Kerr effect and magnetic neutron Bragg diffraction measurements. Construction of Dirac quadrupoles that emerge from centrosymmetric sites used by Cu ions in the ceramic superconductor Hg1201 is illustrated, together with selection rules for excitations that will feature in neutron inelastic scattering, and RIXS experiments. We report magnetic scattering amplitudes for diffraction by polar multipoles that have universal value, because they are not specific to ceramic superconductors. To illustrate this attribute, we consider neutron Bragg diffraction from a magnetically ordered iridate (Sr2IrO4) and discuss shortcomings in published interpretations of diffraction data.

  5. Hedgehog bases for A n cluster polylogarithms and an application to six-point amplitudes

    NASA Astrophysics Data System (ADS)

    Parker, Daniel E.; Scherlis, Adam; Spradlin, Marcus; Volovich, Anastasia

    2015-11-01

    Multi-loop scattering amplitudes in N=4 Yang-Mills theory possess cluster algebra structure. In order to develop a computational framework which exploits this connection, we show how to construct bases of Goncharov polylogarithm functions, at any weight, whose symbol alphabet consists of cluster coordinates on the A n cluster algebra. Using such a basis we present a new expression for the 2-loop 6-particle NMHV amplitude which makes some of its cluster structure manifest.

  6. Calculations of bar K-nuclear quasi-bound states using chiral bar KN amplitudes

    NASA Astrophysics Data System (ADS)

    Mareš, J.; Barnea, N.; Cieplý, A.; Friedman, E.; Gal, A.; Gazda, D.

    2014-03-01

    We review our recent calculations of K- quasi-bound states in nuclear systems using subthreshold energy dependent chiral bar KN amplitudes. Strong energy dependence of the scattering amplitudes requires self-consistent evaluation of the involved bar KN interactions. In view of sizable widths predicted by our calculations, an unambiguous identification of K--nuclear quasi-bound states in ongoing experimental searches would be difficult.

  7. Integrable amplitude deformations for N =4 super Yang-Mills and ABJM theory

    NASA Astrophysics Data System (ADS)

    Bargheer, Till; Huang, Yu-Tin; Loebbert, Florian; Yamazaki, Masahito

    2015-01-01

    We study Yangian-invariant deformations of scattering amplitudes in 4d N =4 super Yang-Mills theory and 3d N =6 Aharony-Bergman-Jafferis-Maldacena (ABJM) theory. In particular, we obtain the deformed Graßmannian integral for 4d N =4 supersymmetric Yang-Mills theory, both in momentum and momentum-twistor space. For 3d ABJM theory, we initiate the study of deformed scattering amplitudes. We investigate general deformations of on-shell diagrams, and find the deformed Graßmannian integral for this theory. We furthermore introduce the algebraic R-matrix construction of deformed Yangian invariants for ABJM theory.

  8. Modelling Broadband Scattering From Shelled Spheres in a Waveguide

    DTIC Science & Technology

    2007-10-01

    DRDC Atlantic TM 2007-270 17 0.12 0.14 0.16 0.18 Time(sec) Figure 11: The scattered Geld time series (amplitude) as a function of sphere depth. 0.5...discussed in Ref. 5. 20 DRDC Atlantic TM 2007-270 1.5 2 2.5 Frequency(kHz) Figure 15: The scattered Geld amplitude (scaled by 104j as function of

  9. Positroid stratification of orthogonal Grassmannian and ABJM amplitudes

    NASA Astrophysics Data System (ADS)

    Kim, Joonho; Lee, Sangmin

    2014-09-01

    A novel understanding of scattering amplitudes in terms of on-shell diagrams and positive Grassmannian has been recently established for four dimensional Yang-Mills theories and three dimensional Chern-Simons theories of ABJM type. We give a detailed construction of the positroid stratification of orthogonal Grassmannian relevant for ABJM amplitudes. On-shell diagrams are classified by pairing of external particles. We introduce a combinatorial aid called `OG tableaux' and map each equivalence class of on-shell diagrams to a unique tableau. The on-shell diagrams related to each other through BCFW bridging are naturally grouped by the OG tableaux. Introducing suitably ordered BCFW bridges and positive coordinates, we construct the complete coordinate charts to cover the entire positive orthogonal Grassmannian for arbitrary number of external particles. The graded counting of OG tableaux suggests that the positive orthogonal Grassmannian constitutes a combinatorial polytope.

  10. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude

    NASA Astrophysics Data System (ADS)

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-01

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed.

  11. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude.

    PubMed

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-05

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed.

  12. Tunable metasurfaces via subwavelength phase shifters with uniform amplitude

    PubMed Central

    Colburn, Shane; Zhan, Alan; Majumdar, Arka

    2017-01-01

    Metasurfaces with tunable spatial phase functions could benefit numerous applications. Currently, most approaches to tuning rely on mechanical stretching which cannot control phase locally, or by modulating the refractive index to exploit rapid phase changes with the drawback of also modulating amplitude. Here, we propose a method to realize phase modulation at subwavelength length scales while maintaining unity amplitude. Our device is inspired by an asymmetric Fabry-Perot resonator, with pixels comprising a scattering nanopost on top of a distributed Bragg reflector, capable of providing a nearly 2π nonlinear phase shift with less than 2% refractive index modulation. Using the designed pixels, we simulate a tunable metasurface composed of an array of moderately coupled nanopost resonators, realizing axicons, vortex beam generators, and aspherical lenses with both variable focal length and in-plane scanning capability, achieving nearly diffraction-limited performance. The experimental feasibility of the proposed method is also discussed. PMID:28054662

  13. The discovery of an extremely low amplitude Cepheid?

    NASA Technical Reports Server (NTRS)

    Butler, R. P.

    1992-01-01

    Extremely low amplitude periodic radial velocity variations are found for HR 7796 (F8 Ib), thought to be a non-Cepheid in (or near) the instability strip. Two and one-half complete cycles have been monitored over three observing runs. The period is found to be 11.874 +/- 0.02 days. Observations of the reference star HR 509 (G8 V) taken on the same nights show no periodicities and a scatter of just 20 m/s. A first-order approximation shows that HR 7796 does appear to follow the Cepheid period-luminosity relation. If HR 7796 is a Cepheid, it is the smallest amplitude Cepheid by more than an order of magnitude.

  14. BPS amplitudes, helicity supertraces and membranes in M-theory

    NASA Astrophysics Data System (ADS)

    Wit, B. d.; Lüst, D.

    2000-03-01

    We study BPS dominated loop amplitudes in M-theory on T2. For this purpose we generalize the concept of helicity supertraces to nine spacetime dimensions. These traces distinguish between various massive supermultiplets and appear as coefficients in their one-loop contributions to n-graviton scattering amplitudes. This can be used to show that only ultrashort BPS multiplets contribute to the R4 term in the effective action, which was first computed by Green, Gutperle and Vanhove. There are two inequivalent ultrashort BPS multiplets which describe the Kaluza-Klein states and the wrapped membranes that cover the torus a number of times. From the perspective of the type-II strings they correspond to momentum and winding states and D0 or D1 branes.

  15. Large amplitude relativistic plasma waves

    SciTech Connect

    Coffey, Timothy

    2010-05-15

    Relativistic, longitudinal plasma oscillations are studied for the case of a simple water bag distribution of electrons having cylindrical symmetry in momentum space with the axis of the cylinder parallel to the velocity of wave propagation. The plasma is required to obey the relativistic Vlasov-Poisson equations, and solutions are sought in the wave frame. An exact solution for the plasma density as a function of the electrostatic field is derived. The maximum electric field is presented in terms of an integral over the known density. It is shown that when the perpendicular momentum is neglected, the maximum electric field approaches infinity as the wave phase velocity approaches the speed of light. It is also shown that for any nonzero perpendicular momentum, the maximum electric field will remain finite as the wave phase velocity approaches the speed of light. The relationship to previously published solutions is discussed as is some recent controversy regarding the proper modeling of large amplitude relativistic plasma waves.

  16. Expansion of Einstein-Yang-Mills amplitude

    NASA Astrophysics Data System (ADS)

    Fu, Chih-Hao; Du, Yi-Jian; Huang, Rijun; Feng, Bo

    2017-09-01

    In this paper, we study from various perspectives the expansion of tree level single trace Einstein-Yang-Mills amplitudes into linear combination of color-ordered Yang-Mills amplitudes. By applying the gauge invariance principle, a programable recursive construction is devised to expand EYM amplitude with arbitrary number of gravitons into EYM amplitudes with fewer gravitons. Based on this recursive technique we write down the complete expansion of any single trace EYM amplitude in the basis of color-order Yang-Mills amplitude. As a byproduct, an algorithm for constructing a polynomial form of the BCJ numerator for Yang-Mills amplitudes is also outlined in this paper. In addition, by applying BCFW recursion relation we show how to arrive at the same EYM amplitude expansion from the on-shell perspective. And we examine the EYM expansion using KLT relations and show how to evaluate the expansion coefficients efficiently.

  17. Constructing amplitudes from their soft limits

    NASA Astrophysics Data System (ADS)

    Boucher-Veronneau, Camille; Larkoski, Andrew J.

    2011-09-01

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an ( n - 1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which "soft" particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  18. Constructing Amplitudes from Their Soft Limits

    SciTech Connect

    Boucher-Veronneau, Camille; Larkoski, Andrew J.; /SLAC

    2011-12-09

    The existence of universal soft limits for gauge-theory and gravity amplitudes has been known for a long time. The properties of the soft limits have been exploited in numerous ways; in particular for relating an n-point amplitude to an (n-1)-point amplitude by removing a soft particle. Recently, a procedure called inverse soft was developed by which 'soft' particles can be systematically added to an amplitude to construct a higher-point amplitude for generic kinematics. We review this procedure and relate it to Britto-Cachazo-Feng-Witten recursion. We show that all tree-level amplitudes in gauge theory and gravity up through seven points can be constructed in this way, as well as certain classes of NMHV gauge-theory amplitudes with any number of external legs. This provides us with a systematic procedure for constructing amplitudes solely from their soft limits.

  19. Elliptic scattering equations

    NASA Astrophysics Data System (ADS)

    Cardona, Carlos; Gomez, Humberto

    2016-06-01

    Recently the CHY approach has been extended to one loop level using elliptic functions and modular forms over a Jacobian variety. Due to the difficulty in manipulating these kind of functions, we propose an alternative prescription that is totally algebraic. This new proposal is based on an elliptic algebraic curve embedded in a mathbb{C}{P}^2 space. We show that for the simplest integrand, namely the n - gon, our proposal indeed reproduces the expected result. By using the recently formulated Λ-algorithm, we found a novel recurrence relation expansion in terms of tree level off-shell amplitudes. Our results connect nicely with recent results on the one-loop formulation of the scattering equations. In addition, this new proposal can be easily stretched out to hyperelliptic curves in order to compute higher genus.

  20. Coherent backscattering of light with nonlinear atomic scatterers

    SciTech Connect

    Wellens, T.; Gremaud, B.; Delande, D.; Miniatura, C.

    2006-01-15

    We study coherent backscattering of a monochromatic laser by a dilute gas of cold two-level atoms in the weakly nonlinear regime. The nonlinear response of the atoms results in a modification of both the average field propagation (nonlinear refractive index) and the scattering events. Using a perturbative approach, the nonlinear effects arise from inelastic two-photon scattering processes. We present a detailed diagrammatic derivation of the elastic and inelastic components of the backscattering signal for both scalar and vectorial photons. In particular, we show that the coherent backscattering phenomenon originates in some cases from the interference between three different scattering amplitudes. This is in marked contrast with the linear regime where it is due to the interference between two different scattering amplitudes. In particular we show that, if elastically scattered photons are filtered out from the photodetection signal, the nonlinear backscattering enhancement factor exceeds the linear barrier of 2, consistently with a three-amplitude interference effect.

  1. Transition Distribution Amplitudes for γ⋆γ collisions

    NASA Astrophysics Data System (ADS)

    Lansberg, J. P.; Pire, B.; Szymanowski, L.

    2008-11-01

    We study the exclusive production of ππ and ρπ in hard γ⋆γ scattering in the forward kinematical region where the virtuality of one photon provides us with a hard scale in the process. The newly introduced concept of Transition Distribution Amplitudes (TDA) is used to perform a QCD calculation of these reactions thanks to two simple models for TDAs. The sizable cross sections for ρπ and ππ production may be tested at intense electron-positron colliders such as CLEO and B factories (Belle and BABAR).

  2. Elliptic multiple zeta values and one-loop superstring amplitudes

    NASA Astrophysics Data System (ADS)

    Broedel, Johannes; Mafra, Carlos R.; Matthes, Nils; Schlotterer, Oliver

    2015-07-01

    We investigate iterated integrals on an elliptic curve, which are a natural genus-one generalization of multiple polylogarithms. These iterated integrals coincide with the multiple elliptic polylogarithms introduced by Brown and Levin when constrained to the real line. At unit argument they reduce to an elliptic analogue of multiple zeta values, whose network of relations we start to explore. A simple and natural application of this framework are one-loop scattering amplitudes in open superstring theory. In particular, elliptic multiple zeta values are a suitable language to express their low energy limit. Similar to the techniques available at tree-level, our formalism allows to completely automatize the calculation.

  3. Amplitude-masked photoacoustic wavefront shaping and application in flowmetry

    PubMed Central

    Tay, Jian Wei; Liang, Jinyang; Wang, Lihong V.

    2014-01-01

    Optical-resolution photoacoustic flowmetry allows non-invasive single-cell flow measurements. However, its operational depth is limited by optical diffusion, which prevents focusing beyond shallow depths in scattering media, as well as reducing the measurement signal-to-noise ratio (SNR). To overcome this limitation, we used binary-amplitude wavefront shaping to enhance light focusing in the presence of scattering. Here, the transmission modes that contributed constructively to the intensity at the optical focus were identified and selectively illuminated, resulting in a 14-fold intensity increase and a corresponding increase in SNR. This technique can potentially extend the operational depth of optical-resolution photoacoustic flowmetry beyond 1 mm in tissue. PMID:25360912

  4. Forward collisions and spin effects in evaluating amplitudes

    SciTech Connect

    Buttimore, N. H.

    2011-07-15

    Total cross sections and the phases of forward collision amplitudes form part of the early studies when a new energy window becomes available as is provided by the Large Hadron Collider. Enhancement of the forward elastic differential cross section above that expected from estimates of dispersion and optical theorem values may result from the presence of hadronic spin dependence in addition to effects induced by vacuum polarization contributions to the photon propagator. The elastic scattering of protons and ions at small angles is important in the evaluation of the luminosities of the corresponding incident beams and invites detailed examination. Polarization measurements taken at a number of high energies have yielded information on the extent of spin effects in hadronic scattering, particularly at the low momentum transfers related to diffraction.

  5. Tsunami Focusing and Leading Amplitude

    NASA Astrophysics Data System (ADS)

    Kanoglu, U.

    2016-12-01

    Tsunamis transform substantially through spatial and temporal spreading from their source region. This substantial spreading might result unique maximum tsunami wave heights which might be attributed to the source configuration, directivity, the waveguide structures of mid-ocean ridges and continental shelves, focusing and defocusing through submarine seamounts, random focusing due to small changes in bathymetry, dispersion, and, most likely, combination of some of these effects. In terms of the maximum tsunami wave height, after Okal and Synolakis (2016 Geophys. J. Int. 204, 719-735), it is clear that dispersion would be one of the reasons to drive the leading wave amplitude in a tsunami wave train. Okal and Synolakis (2016), referring to this phenomenon as sequencing -later waves in the train becoming higher than the leading one, considered Hammack's (1972, Ph.D. Dissertation, Calif. Inst. Tech., 261 pp) formalism, in addition to LeMéhauté and Wang's (1995 Water waves generated by underwater explosion, World Scientific, 367 pp), to evaluate linear dispersive tsunami propagation from a circular plug uplifted on an ocean of constant depth. They identified transition distance, as the second wave being larger, performing parametric study for the radius of the plug and the depth of the ocean. Here, we extend Okal and Synolakis' (2016) analysis to an initial wave field with a finite crest length and, in addition, to a most common tsunami initial wave form of N-wave (Tadepalli and Synolakis, 1994 Proc. R. Soc. A: Math. Phys. Eng. Sci. 445, 99-112). First, we investigate the focusing feature in the leading-depression side, which enhance tsunami wave height as presented by Kanoglu et al. (2013 Proc. R. Soc. A: Math. Phys. Eng. Sci. 469, 20130015). We then discuss the results in terms of leading wave amplitude presenting a parametric study and identify a simple relation for the transition distance. The solution presented here could be used to better analyze dispersive

  6. Generating all tree amplitudes in {N} = 4{{SYM}} by Inverse Soft Limit

    NASA Astrophysics Data System (ADS)

    Nandan, Dhritiman; Wen, Congkao

    2012-08-01

    The idea of adding particles to construct amplitudes has been utilized in various ways in exploring the structure of scattering amplitudes. This idea is often called Inverse Soft Limit, namely it is the reverse mechanism of taking particles to be soft. We apply the Inverse Soft Limit to the tree-level amplitudes in {N} = 4 super Yang-Mills theory, which allows us to generate full tree-level superamplitudes by adding "soft" particles in a certain way. With the help from Britto-Cachazo-Feng-Witten recursion relations, a systematic and concrete way of adding particles is determined recursively. The amplitudes constructed solely by adding particles not only have manifest Yangian symmetry, but also make the soft limit transparent. The method of generating amplitudes by Inverse Soft Limit can also be generalized for constructing form factors.

  7. The isomonodromy method for black hole scattering

    SciTech Connect

    Carneiro da Cunha, Bruno; Novaes, Fábio

    2015-12-17

    We summarize recent results by the authors [7, 8, 35] on the extraction of scattering amplitudes for scalar fields in Kerr/Kerr-de Sitter backgrounds. Analytical, closed forms are found in terms of the Painlevé V and VI transcendents for generic values of the physical parameters.

  8. Symmetry considerations in the scattering of identical composite bodies

    NASA Technical Reports Server (NTRS)

    Norbury, J. W.; Townsend, L. W.; Deutchman, P. A.

    1986-01-01

    Previous studies of the interactions between composite particles were extended to the case in which the composites are identical. The form of the total interaction potential matrix elements was obtained, and guidelines for their explicit evaluation were given. For the case of elastic scattering of identical composites, the matrix element approach was shown to be equivalent to the scattering amplitude method.

  9. Parity-Violating in e - e + Scattering at Finite Temperature

    NASA Astrophysics Data System (ADS)

    Chekerker, M.; Santos, A. F.; Khanna, Faqir C.; Ladrem, M.

    2017-09-01

    Parity violation implies that physics laws are not invariant under spatial coordinate reversal. Electron-positron scattering is a process that displays parity violation. Using the Thermo Field Dynamics formalism this scattering at finite temperature is analyzed. The transition amplitude is calculated as a function of temperature. The parity violation at very high temperatures tend to go to zero.

  10. The Scattering of Fast Nucleons from Nuclei

    NASA Astrophysics Data System (ADS)

    Kerman, A. K.; McManus, H.; Thaler, R. M.

    2000-04-01

    The formal theory of the scattering of high-energy nucleons by nuclei is developed in terms of the nucleon-nucleon scattering amplitude. The most important approximations necessary to make numerical calculation feasible are then examined. The optical model potential is derived on this basis and compared with the optical model parameters found from experiment. The elastic scattering and polarization of nucleons from light nuclei is predicted and compared with experiment. The effect of nuclear correlations is discussed. The polarization of inelastically scattered nucleons is discussed and predictions compared with experiments. To within the validity of the approximations the experimental data on the scattering of nucleons from nuclei at energies above ˜100 Mev appears to be consistent with the theory.

  11. Heterodyne x-ray diffuse scattering from coherent phonons

    DOE PAGES

    Kozina, M.; Trigo, M.; Chollet, M.; ...

    2017-08-10

    Here in this paper, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector. The nanoparticles break the discrete translational symmetry of the lattice, enabling the generation of large wavevector coherent phonons. Elastic scattering of x-ray photons frommore » the nanoparticles provides a reference for heterodyne mixing, yielding signals proportional to the phonon amplitude.« less

  12. Light scattering from a randomly occupied optical lattice. II. The multiple scattering problem.

    PubMed

    Guo, Wei; Prasad, Sudhakar

    2003-05-01

    In this paper, we study the problem of multiple scattering of light from a randomly occupied optical lattice, thereby extending the first-order Born analysis of the previous paper. A full multiple-scattering analysis is essential to a complete understanding of the nature of light propagation inside a medium. Our calculations show that the incident wave, when resonant with the atomic medium, is rapidly extinguished due to multiple scattering. The decay constant depends critically on the incident wavelength, the lattice constant, the average number density of atoms, and their polarizability. Both the Bragg scattering amplitudes and directions are modified as a result of multiple scattering. Because of the random site occupation of an otherwise regular lattice structure, a coherent enhancement of the scattering cross section is also predicted to occur along a discrete set of directions that are related to the strictly backward direction by reciprocal lattice vectors.

  13. Considerations concerning diffraction scattering in quantum chromodynamics

    NASA Astrophysics Data System (ADS)

    Nachtmann, O.

    1991-08-01

    A model for diffractive, especially elastic hadron-hadron scattering at high c.m. energies squared s and small momentum transfer squared | t| is developed, based on quantum chromodynamics (QCD). First the scattering of hadron constituents, partons, is considered. In this paper we study mainly the scattering of quarks and antiquarks. The s-dependence of the amplitudes is treated by analytical means using a functional integral approach and an eikonal approximation. The t-dependence of the amplitudes is then shown to be governed by a certain correlation function of gluon string operators. A calculation of this function by non-perturbative methods in the framework of lattice OCD or in the stochastic vacuum field model should be feasible. The transition from the parton to the hadron level is accomplished by constructing an effective S-operator in terms of local tensor operators. In this way we avoid dealing explicitly with hadronic wave functions. In our approach the bound state nature of the hadrons enters through matrix elements of the local operators, where information from deep inelastic lepton-hadron scattering exists. The resulting expression for the elastic hadron-hadron scattering amplitude is discussed and is shown to lead to an understanding of various phenomenological findings. The physical picture emerging is one where single partons of the hadrons interact at a time, i.e., the "Pomeron" couples to single partons. This was suggested previously by phenomenological analyses of experiments and by theoretical investigations of an abelian gluon model.

  14. O the Theory of Ultrasonic Wave Scattering from Rough Surfaces.

    NASA Astrophysics Data System (ADS)

    Ogilvy, Jill Audrey

    Available from UMI in association with The British Library. This thesis contains a theoretical study of wave scattering by randomly rough surfaces. The work was undertaken to help understand the extent to which ultrasonic testing procedures are affected by roughness on the faces of real defects. The work concentrates on Kirchhoff theory as an approximate method of solution of the scattering problem. A literature review shows this approximation to be prevalent, applied mostly to monochromatic, acoustic wave scattering. Here such theory is extended to monochromatic elastic wave scattering. A calculation of the loss of the coherent field as roughness increases shows a clear analogy with the results of earlier acoustic theories, although mode-conversion effects are now also seen. A computer simulation technique is then presented. Individual surface realizations are generated and the scattering determined for each realization, using acoustic Kirchhoff theory. This gives explicit calculations of both the coherent and diffuse field and also allows for a study of time-dependent wave scattering. Mean signal amplitudes are calculated, as well as the expected statistical spread in amplitudes arising from differences between surface realizations. The thesis also includes a study of the accuracy of Kirchhoff theory. A stationary expression is obtained for a rough surface scattering coefficient, involving trial fields on the rough surface. Kirchhoff theory provides these trial fields and the scattering amplitude is compared with the amplitude using Kirchhoff theory in the Helmholtz scattering theorem. Predictions of the theory are compared with previously published experimental results. The greater probability of detecting small rough defects compared with small smooth defects, as sometimes seen in practice, is predicted by the theory. Also, comparison with experimentally determined backscattered signal amplitudes shows very good agreement and highlights the importance of taking

  15. Compton scattering by mesons in nuclei: Experiment on 208Pb

    NASA Astrophysics Data System (ADS)

    Fuhrberg, K.; Martin, G.; Häger, D.; Ludwig, M.; Schumacher, M.; Andersson, B.-E.; Blomqvist, K. I.; Ruijter, H.; Sandell, A.; Schröder, B.; Hayward, E.; Nilsson, L.; Zorro, R.

    1992-10-01

    Using 58 and 73 MeV tagged photons and scattering angles from 60° to 150°, it is shown that it is possible to observe Compton scattering by "mesons in nuclei" through an incomplete cancellation of the mesonic (exchange-current) seagull amplitude by parts of the nuclear resonance amplitude related to the giant-dipole resonance of 208Pb. This phenomenon is a property of an extended nucleus and, therefore, cannot be studied on the deuteron. Predictions of the exchange from factor which determines the angular distribution of the exchange seagull amplitude are compared with experimental data.

  16. The relationship between sensory latency and amplitude.

    PubMed

    Bodofsky, Elliot B; Cohen, Stephen J; Kumar, Rohini J; Schindelheim, Adam; Gaughan, John

    2016-12-01

    To prove that the relationship between sensory latencies and amplitudes is useful in determining the severity of neuropathies. This is achieved by deriving a mathematical relationship between sensory distal latency and amplitude. Determine whether sensory amplitudes below predicted correlate with a worse pathology. Patients seen for Nerve Conduction Studies by the Department of Physical Medicine and Rehabilitation at Cooper University Hospital between 12/1/12 and 12/31/14 were invited to participate in a prospective database. The median, ulnar and sural sensory latencies and amplitudes were analyzed with both linear and power regression. Patients with amplitudes above and below the regression curve were compared for latency, amplitude and velocity of other nerves. Carpal Tunnel Patients were analyzed to determine whether Median sensory amplitude below predicted correlated with more severe disease. For the Median nerve, Power Regression Analysis showed a stronger correlation (R(2)=0.54) than linear regression (R(2)=0.34). Patients with Median sensory amplitude below the power correlation curve showed significantly longer ulnar sensory latency, and lower sensory amplitude than those above. Carpal Tunnel Syndrome patients with Median sensory amplitude well below predicted by the power relationship showed more advanced disease. For the ulnar and sural sensory nerve, the difference between power and linear regression was not significant. A power regression curve correlates sensory latency and amplitude better than linear regression. The latency amplitude relationship correlates with other parameters of nerve function and severity of Carpal Tunnel Syndrome. This implies that below predicted sensory amplitude may indicate worse disease, and could be a useful diagnostic tool. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Coherent scatter implementation for SimSET

    NASA Astrophysics Data System (ADS)

    Kaplan, M. S.; Harrison, R. L.; Vannoy, S. D.

    1998-12-01

    At 140 keV, 3% of photon scatter interactions in human tissues are coherent scatter; at Tl-201 emission energies, this fraction increases to approximately 7%. However, since coherent scatter at these energies is sharply forward-peaked, it is often the dominant scatter interaction at small angles. SimSET (Simulation System for Emission Tomography), which previously modeled only photoelectric absorption and Compton scatter, has been extended to include coherent scatter. The current implementation uses form factor and anomalous scattering amplitude data from the Livermore Evaluated Photon Data Library. Interaction probability and angular distribution tables for several human tissues and common detector materials were calculated using the independent atoms approximation and human-tissue composition data from the ICRP Reference Man. These data were also used to generate new tables for photoelectric absorption and Compton scatter, significantly improving the accuracy of SimSET and extending its photon tracking capability to lower photon energy (from 50 keV to 1 keV). The form, content, and structure of the tables were carefully designed for efficient data storage, access, and use by the software. The derived data tables and implementation of coherent scatter were validated by comparing simulation results to published differential cross-section data.

  18. Light-like scattering in quantum gravity

    NASA Astrophysics Data System (ADS)

    Bjerrum-Bohr, N. E. J.; Donoghue, John F.; Holstein, Barry R.; Planté, Ludovic; Vanhove, Pierre

    2016-11-01

    We consider scattering in quantum gravity and derive long-range classical and quantum contributions to the scattering of light-like bosons and fermions (spin-0, spin- 1/2 , spin-1) from an external massive scalar field, such as the Sun or a black hole. This is achieved by treating general relativity as an effective field theory and identifying the non-analytic pieces of the one-loop gravitational scattering amplitude. It is emphasized throughout the paper how modern amplitude techniques, involving spinor-helicity variables, unitarity, and squaring relations in gravity enable much simplified computations. We directly verify, as predicted by general relativity, that all classical effects in our computation are universal (in the context of matter type and statistics). Using an eikonal procedure we confirm the post-Newtonian general relativity correction for light-like bending around large stellar objects. We also comment on treating effects from quantum ℏ dependent terms using the same eikonal method.

  19. Spin-rotation functions for 500-MeV protons scattered by UCa nuclei

    SciTech Connect

    Berezhnoi, Y.A.; Molev, A.S.; Pilipenko, V.V.; Soznik, A.P.

    1985-06-01

    The polarization characteristics in the elastic and inelastic scattering of 500-MeV protons by UCa nuclei are analyzed, using the theory of multiple diffraction scattering. The investigated proton-spin-rotation functions are very sensitive to the NN-amplitude parameters. A set of NN-amplitude parameters is found that correctly describes the set of measured observables. The analysis yields valuable information on the NN amplitude, especially on its spin-orbit part.

  20. Virasoro amplitude from theS N R24-orbifold sigma model

    NASA Astrophysics Data System (ADS)

    Arutyunov, G. E.; Frolov, S. A.

    1998-01-01

    Four tachyon scattering amplitude is derived from the $S^N\\R^{24}$ orbifold sigma model in the large $N$ limit. The closed string interaction is described by a vertex which is a bosonic analog of the supersymmetric one, recently proposed by Dijkgraaf, Verlinde and Verlinde.

  1. Amplitude-dependent station magnitude

    NASA Astrophysics Data System (ADS)

    Radzyner, Yael; Ben Horin, Yochai; Steinberg, David M.

    2016-04-01

    Magnitude, a concept first presented by Gutenberg and Richter, adjusts measurements of ground motion for epicentral distance and source depth. Following this principle, the IDC defines the j'th station body wave magnitude for event i as mb(stai,j) = log 10(Aj,i/Tj,i) + V C(Δj,i,hi) , where VC is the Veith-Clawson (VC) correction to compensate for the epicentral distance of the station and the depth of the source. The network magnitude is calculated as the average of station magnitudes. The IDC magnitude estimation is used for event characterization and discrimination and it should be as accurate as possible. Ideally, the network magnitude should be close in value to the station magnitudes. In reality, it is observed that the residuals range between -1 and 1 mu or ±25% of a given mb(neti) value. We show that the residual, mb(neti) -mb(staj,i), depends linearly on log 10(Aj,i/Tj,i), and we correct for this dependence using the following procedure: Calculate a "jackknifed" network magnitude, mbj,n(neti), i.e. an average over all participating stations except station n. Using all measurements at station n, calculate the parameters an, bn of the linear fit of the residual mbj,n(neti) - mb(stan,i to log 10(An,i/Tn,i). For each event i at station n calculate the new station magnitude mbnew(stan,i) = (an + 1)log(An,i/Tn,i) + V C(Δn,i,hi) + bn Calculate the new network magnitude: mbnew(neti) = 1N- ∑ n=1nmbnew(stan,i) The procedure was used on more than two million station-event pairs. Correcting for the station-specific dependence on log amplitude reduces the residuals by roughly a third. We have calculated the spread of the distributions, and compared the original values and those for the corrected magnitudes. The spread is the ratio between the variance of the network magnitudes, and the variance of the residual. Calculations show an increase in the ratio of the variance, meaning that the correction process presented in this document did not lead to loss of variance

  2. Gravity and Yang-Mills amplitude relations

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas; FengBo

    2010-11-15

    Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.

  3. Minimal Basis for Gauge Theory Amplitudes

    SciTech Connect

    Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Vanhove, Pierre

    2009-10-16

    Identities based on monodromy for integrations in string theory are used to derive relations between different color-ordered tree-level amplitudes in both bosonic and supersymmetric string theory. These relations imply that the color-ordered tree-level n-point gauge theory amplitudes can be expanded in a minimal basis of (n-3)exclamation amplitudes. This result holds for any choice of polarizations of the external states and in any number of dimensions.

  4. Discontinuities of multi-Regge amplitudes

    NASA Astrophysics Data System (ADS)

    Fadin, V. S.

    2015-04-01

    In the BFKL approach, discontinuities of multiple production amplitudes in invariant masses of produced particles are discussed. It turns out that they are in evident contradiction with the BDS ansatz for n-gluon amplitudes in the planar N = 4 SYM at n ≥ 6. An explicit expression for the NLO discontinuity of the two-to-four amplitude in the invariant mass of two produced gluons is is presented.

  5. Three applications of a bonus relation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    Spradlin, Marcus; Volovich, Anastasia; Wen, Congkao

    2009-04-01

    Arkani-Hamed et al. have recently shown that all tree-level scattering amplitudes in maximal supergravity exhibit exceptionally soft behavior when two supermomenta are taken to infinity in a particular complex direction, and that this behavior implies new non-trivial relations amongst amplitudes in addition to the well-known on-shell recursion relations. We consider the application of these new 'bonus relations' to MHV amplitudes, showing that they can be used quite generally to relate (n - 2) !-term formulas typically obtained from recursion relations to (n - 3) !-term formulas related to the original BGK conjecture. Specifically we provide (1) a direct proof of a formula presented by Elvang and Freedman, (2) a new formula based on one due to Bedford et al., and (3) an alternate proof of a formula recently obtained by Mason and Skinner. Our results also provide the first direct proof that the conjectured BGK formula, only very recently proven via completely different methods, satisfies the on-shell recursion.

  6. Type I/heterotic duality and M-theory amplitudes

    NASA Astrophysics Data System (ADS)

    Green, Michael B.; Rudra, Arnab

    2016-12-01

    This paper investigates relationships between low-energy four-particle scattering amplitudes with external gauge particles and gravitons in the E 8 × E 8 and SO(32) heterotic string theories and the type I and type IA superstring theories by considering a variety of tree level and one-loop Feynman diagrams describing such amplitudes in eleven-dimensional supergravity in a Horava-Witten background compactified on a circle. This accounts for a number of perturbative and non-perturbative aspects of low order higher derivative terms in the low-energy expansion of string theory amplitudes, which are expected to be protected by half maximal supersymmetry from receiving corrections beyond one or two loops. It also suggests the manner in which type I/heterotic duality may be realised for certain higher derivative interactions that are not so obviously protected. For example, our considerations suggest that R 4 interactions (where R is the Riemann curvature) might receive no perturbative corrections beyond one loop by virtue of a conspiracy involving contributions from (non-BPS) {Z}_2 D-instantons in the type I and heterotic SO(32) theories.

  7. Landau retardation on the occurrence scattering time in quantum electron-hole plasmas

    NASA Astrophysics Data System (ADS)

    Hong, Woo-Pyo; Jung, Young-Dae

    2016-03-01

    The Landau damping effects on the occurrence scattering time in electron collisions are investigated in a quantum plasma composed of electrons and holes. The Shukla-Stenflo-Bingham effective potential model is employed to obtain the occurrence scattering time in a quantum electron-hole plasma. The result shows that the influence of Landau damping produces the imaginary term in the scattering amplitude. It is then found that the Landau damping generates the retardation effect on the occurrence scattering time. It is found that the occurrence scattering time increases in forward scattering domains and decreases in backward scattering domains with an increase of the Landau parameter. It is also found that the occurrence scattering time decreases with increasing collision energy. In addition, it is found that the quantum shielding effect enhances the occurrence scattering time in the forward scattering and, however, suppresses the occurrence scattering time in the backward scattering.

  8. Chiral splitting and N=4 Einstein-Yang-Mills tree amplitudes in 4d

    NASA Astrophysics Data System (ADS)

    Roehrig, Kai A.

    2017-08-01

    We present a world-sheet formula for all tree level scattering amplitudes, in all trace sectors, of four dimensional N\\le 4 supersymmetric Einstein-Yang-Mills theory, based on the refined scattering equations. This generalizes previously known formulas for all-trace purely bosonic, or supersymmetric single-trace amplitudes. We find this formula by applying a new chiral splitting formula for all CHY Pfaffians in 4d, into two determinants, of positive and negative helicity respectively. The splitting of CHY Pfaffians is shown to be a special case of the splitting of TM valued fermion correlators on the sphere, which does not require the scattering equations to hold, and is a consequence of the isomorphism TM˜eq S+⊗ S- between the tangent bundle of Minkowski space and the left- and right-handed spin bundles. We present and prove this general splitting formula.

  9. Hadron scattering, resonances, and QCD

    SciTech Connect

    Briceno, Raul

    2016-12-01

    The non-perturbative nature of quantum chromodynamics (QCD) has historically left a gap in our understanding of the connection between the fundamental theory of the strong interactions and the rich structure of experimentally observed phenomena. For the simplest properties of stable hadrons, this is now circumvented with the use of lattice QCD (LQCD). In this talk I discuss a path towards a rigorous determination of few-hadron observables from LQCD. I illustrate the power of the methodology by presenting recently determined scattering amplitudes in the light-meson sector and their resonance content.

  10. Secondary threshold amplitudes for sinuous streak breakdown

    NASA Astrophysics Data System (ADS)

    Cossu, Carlo; Brandt, Luca; Bagheri, Shervin; Henningson, Dan S.

    2011-07-01

    The nonlinear stability of laminar sinuously bent streaks is studied for the plane Couette flow at Re = 500 in a nearly minimal box and for the Blasius boundary layer at Reδ*=700. The initial perturbations are nonlinearly saturated streamwise streaks of amplitude AU perturbed with sinuous perturbations of amplitude AW. The local boundary of the basin of attraction of the linearly stable laminar flow is computed by bisection and projected in the AU - AW plane providing a well defined critical curve. Different streak transition scenarios are seen to correspond to different regions of the critical curve. The modal instability of the streaks is responsible for transition for AU = 25%-27% for the considered flows, where sinuous perturbations of amplitude below AW ≈ 1%-2% are sufficient to counteract the streak viscous dissipation and induce breakdown. The critical amplitude of the sinuous perturbations increases when the streamwise streak amplitude is decreased. With secondary perturbations amplitude AW ≈ 4%, breakdown is induced on stable streamwise streaks with AU ≈ 13%, following the secondary transient growth scenario first examined by Schoppa and Hussain [J. Fluid Mech. 453, 57 (2002)]. A cross-over, where the critical amplitude of the sinuous perturbation becomes larger than the amplitude of streamwise streaks, is observed for streaks of small amplitude AU < 5%-6%. In this case, the transition is induced by an initial transient amplification of streamwise vortices, forced by the decaying sinuous mode. This is followed by the growth of the streaks and final breakdown. The shape of the critical AU - AW curve is very similar for Couette and boundary layer flows and seems to be relatively insensitive to the nature of the edge states on the basin boundary. The shape of this critical curve indicates that the stability of streamwise streaks should always be assessed in terms of both the streak amplitude and the amplitude of spanwise velocity perturbations.

  11. A Simple Discrete Model of Scattering in a Fluctuating Inhomogeneous Medium.

    ERIC Educational Resources Information Center

    West, Bruce J.

    1978-01-01

    Discusses scattering problems in continuous media, and presents a simple discrete model for scalar wave scattering from inhomogeneities on a lattice. Illustrates the relationships between the amplitude of the scattered wave and the characteristic function of the fluctuating motion of a point reflector in one dimension. (Author/GA)

  12. Off-shell amplitudes and Grassmannians

    NASA Astrophysics Data System (ADS)

    Bork, L. V.; Onishchenko, A. I.

    2017-09-01

    The Grassmannian representation for gauge-invariant amplitudes for arbitrary number of legs with one of them being off-shell is derived for the case of N = 4 SYM. The obtained formula are successfully checked against known BCFW results for MHV n , NMHV4 and NMHV5 amplitudes.

  13. BCFW construction of the Veneziano amplitude

    NASA Astrophysics Data System (ADS)

    Fotopoulos, Angelos

    2011-06-01

    In this paper we demonstrate how one can compute the Veneziano amplitude for bosonic string theory using the Britto-Cachazo-Feng-Witten method. We use an educated ansatz for the cubic amplitude of two tachyons and an arbitrary level string state.

  14. Formant Amplitude of Children with Down's Syndrome.

    ERIC Educational Resources Information Center

    Pentz, Arthur L., Jr.

    1987-01-01

    The sustained vowel sounds of 14 noninstitutionalized 7- to 10-year-old children with Down's syndrome were analyzed acoustically for vowel formant amplitude levels. The subjects with Down's syndrome had formant amplitude intensity levels significantly lower than those of a similar group of speakers without Down's syndrome. (Author/DB)

  15. Deterministic forward scatter from surface gravity waves.

    PubMed

    Deane, Grant B; Preisig, James C; Tindle, Chris T; Lavery, Andone; Stokes, M Dale

    2012-12-01

    Deterministic structures in sound reflected by gravity waves, such as focused arrivals and Doppler shifts, have implications for underwater acoustics and sonar, and the performance of underwater acoustic communications systems. A stationary phase analysis of the Helmholtz-Kirchhoff scattering integral yields the trajectory of focused arrivals and their relationship to the curvature of the surface wave field. Deterministic effects along paths up to 70 water depths long are observed in shallow water measurements of surface-scattered sound at the Martha's Vineyard Coastal Observatory. The arrival time and amplitude of surface-scattered pulses are reconciled with model calculations using measurements of surface waves made with an upward-looking sonar mounted mid-way along the propagation path. The root mean square difference between the modeled and observed pulse arrival amplitude and delay, respectively, normalized by the maximum range of amplitudes and delays, is found to be 0.2 or less for the observation periods analyzed. Cross-correlation coefficients for modeled and observed pulse arrival delays varied from 0.83 to 0.16 depending on surface conditions. Cross-correlation coefficients for normalized pulse energy for the same conditions were small and varied from 0.16 to 0.06. In contrast, the modeled and observed pulse arrival delay and amplitude statistics were in good agreement.

  16. Amplitude image processing by diffractive optics.

    PubMed

    Cagigal, Manuel P; Valle, Pedro J; Canales, V F

    2016-02-22

    In contrast to the standard digital image processing, which operates over the detected image intensity, we propose to perform amplitude image processing. Amplitude processing, like low pass or high pass filtering, is carried out using diffractive optics elements (DOE) since it allows to operate over the field complex amplitude before it has been detected. We show the procedure for designing the DOE that corresponds to each operation. Furthermore, we accomplish an analysis of amplitude image processing performances. In particular, a DOE Laplacian filter is applied to simulated astronomical images for detecting two stars one Airy ring apart. We also check by numerical simulations that the use of a Laplacian amplitude filter produces less noisy images than the standard digital image processing.

  17. Magnetospheric chorus - Amplitude and growth rate

    NASA Technical Reports Server (NTRS)

    Burtis, W. J.; Helliwell, R. A.

    1975-01-01

    A new study of the amplitude of magnetospheric chorus with 1966-1967 data from the Stanford University/Stanford Research Institute VLF receivers on Ogo 1 and Ogo 3 has confirmed the band-limited character of magnetospheric chorus in general and the double-banding of near-equatorial chorus. Chorus amplitude tended to be inversely correlated with frequency, implying lower intensities at lower L values. Individual chorus emissions often showed a characteristic amplitude variation, with rise times of 10 to 300 ms, a short duration at peak amplitude, and decay times of 100 to 3000 msec. Growth was often approximately exponential, with rates from 200 to nearly 2000 dB/sec. Rate of change of frequency was found in many cases to be independent of emission amplitude, in agreement with the cyclotron feedback theory of chorus (Helliwell, 1967, 1970).

  18. Thermal cracking and amplitude dependent attenuation

    SciTech Connect

    Johnston, D.H.; Toksoez, M.N.

    1980-02-10

    The role of crack and grain boundary contacts in determining seismic wave attenuation in rock is investigated by examining Q as a function of thermal cycling (cracking) and wave strain amplitude. Q values are obtained using a longitudinal resonant bar technique in the 10- to 20-kHz range for maximum strain amplitudes varying from roughly 10/sup -8/ to 10/sup -5/. The samples studied include the Berea and Navajo sandstones, Plexiglas, Westerly granite, Solenhofen limestone, and Frederick diabase, the latter two relatively crack free in their virgin state. Measurements were made at room temperature and pressure in air. Q values for both sandstones are constant at low strains (<10/sup -6/) but decrease rapidly with amplitude at higher strains. There is no hysteresis of Q with amplitude. Q values for Plexiglas show no indication of amplitude dependent behavior. The granite, limestone, and diabase are thermally cycled at both fast and slow heating rates in order to induce cracking. Samples slowly cycled at 400/sup 0/C show a marked increase in Q that cannot be entirely explained by outgassing of volatiles. Cycling may also widen thin cracks and grain boundaries, reducing contact areas. Samples heated beyond 400/sup 0/C, or rapidly heated, result in generally decreasing Q values. The amplitude dependence of Q is found to be coupled to the effects of thermal cycling. For rock slowly cycled 400)C or less, the transition from low-amplitude contant Q to high-amplitude variable Q behavior decreases to lower amplitudes as a function of maximum temperature. Above 400/sup 0/C, and possibly in th rapidly heated samples also, the transition moves to higher amplitudes.

  19. Nonlinear Aharonov-Bohm Scattering by Optical Vortices

    SciTech Connect

    Neshev, Dragomir; Nepomnyashchy, Alexander; Kivshar, Yuri S.

    2001-07-23

    We study linear and nonlinear wave scattering by an optical vortex in a self-defocusing nonlinear Kerr medium. In the linear case, we find a splitting of a plane-wave front at the vortex proportional to its circulation, similar to what occurs in the scattered wave of electrons for the Aharonov-Bohm effect. For larger wave amplitudes, we study analytically and numerically the scattering of a dark-soliton stripe (a nonlinear analog of a small-amplitude wave packet) by a vortex and observe a significant asymmetry of the scattered wave. Subsequently, a wave-front splitting of the scattered wave develops into transverse modulational instability, ''unzipping'' the stripe into trains of vortices with opposite charges.

  20. Conformal bootstrap, universality and gravitational scattering

    NASA Astrophysics Data System (ADS)

    Jackson, Steven; McGough, Lauren; Verlinde, Herman

    2015-12-01

    We use the conformal bootstrap equations to study the non-perturbative gravitational scattering between infalling and outgoing particles in the vicinity of a black hole horizon in AdS. We focus on irrational 2D CFTs with large c and only Virasoro symmetry. The scattering process is described by the matrix element of two light operators (particles) between two heavy states (BTZ black holes). We find that the operator algebra in this regime is (i) universal and identical to that of Liouville CFT, and (ii) takes the form of an exchange algebra, specified by an R-matrix that exactly matches the scattering amplitude of 2 + 1 gravity. The R-matrix is given by a quantum 6j-symbol and the scattering phase by the volume of a hyperbolic tetrahedron. We comment on the relevance of our results to scrambling and the holographic reconstruction of the bulk physics near black hole horizons.

  1. Rayleigh scattering. [molecular scattering terminology redefined

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1981-01-01

    The physical phenomena of molecular scattering are examined with the objective of redefining the confusing terminology currently used. The following definitions are proposed: molecular scattering consists of Rayleigh and vibrational Raman scattering; the Rayleigh scattering consists of rotational Raman lines and the central Cabannes line; the Cabannes line is composed of the Brillouin doublet and the central Gross or Landau-Placzek line. The term 'Rayleigh line' should never be used.

  2. Discriminator amplitude walk correction in gamma-ray coincidence experiments using list-mode time-stamping data acquisition

    NASA Astrophysics Data System (ADS)

    Khamzin, Murat K.; Valentine, John D.

    2003-06-01

    When pulse amplitude and time stamp are recorded in list-mode time-stamping data acquisition, it is possible to correct for the system amplitude walk, typically observed as the time pickoff dependence on pulse amplitude. In this study, a method of correcting for amplitude walk during post-acquisition analysis of such list mode data is developed and demonstrated. The method is demonstrated using a simple two-channel system and a photon source capable of producing coincidence events ( 22Na). Two leading-edge discriminators, vulnerable to the amplitude walk, were used to produce the time pickoffs. The resulting corrected data show an amplitude walk less than the detector timing resolution. The method developed can be used in list-mode data acquisition systems such as medical imaging scanners or Compton scatter cameras.

  3. Color-kinematics duality for QCD amplitudes

    NASA Astrophysics Data System (ADS)

    Johansson, Henrik; Ochirov, Alexander

    2016-01-01

    We show that color-kinematics duality is present in tree-level amplitudes of quantum chromodynamics with massive flavored quarks. Starting with the color structure of QCD, we work out a new color decomposition for n-point tree amplitudes in a reduced basis of primitive amplitudes. These primitives, with k quark-antiquark pairs and ( n - 2 k) gluons, are taken in the ( n - 2)! /k! Melia basis, and are independent under the color-algebra Kleiss-Kuijf relations. This generalizes the color decomposition of Del Duca, Dixon, and Maltoni to an arbitrary number of quarks. The color coefficients in the new decomposition are given by compact expressions valid for arbitrary gauge group and representation. Considering the kinematic structure, we show through explicit calculations that color-kinematics duality holds for amplitudes with general configurations of gluons and massive quarks. The new (massive) amplitude relations that follow from the duality can be mapped to a well-defined subset of the familiar BCJ relations for gluons. They restrict the amplitude basis further down to ( n - 3)!(2 k - 2) /k! primitives, for two or more quark lines. We give a decomposition of the full amplitude in that basis. The presented results provide strong evidence that QCD obeys the color-kinematics duality, at least at tree level. The results are also applicable to supersymmetric and D-dimensional extensions of QCD.

  4. Classical ultra-relativistic scattering in ADD

    NASA Astrophysics Data System (ADS)

    Gal'tsov, Dmitry V.; Kofinas, Georgios; Spirin, Pavel; Tomaras, Theodore N.

    2009-05-01

    The classical differential cross-section is calculated for high-energy small-angle gravitational scattering in the factorizable model with toroidal extra dimensions. The three main features of the classical computation are: (a) It involves summation over the infinite Kaluza-Klein towers but, contrary to the Born amplitude, it is finite with no need of an ultraviolet cutoff. (b) It is shown to correspond to the non-perturbative saddle-point approximation of the eikonal amplitude, obtained by the summation of an infinite number of ladder graphs of the quantum theory. (c) In the absence of extra dimensions it reproduces all previously known results.

  5. Amplitude- and rise-time-compensated filters

    DOEpatents

    Nowlin, Charles H.

    1984-01-01

    An amplitude-compensated rise-time-compensated filter for a pulse time-of-occurrence (TOOC) measurement system is disclosed. The filter converts an input pulse, having the characteristics of random amplitudes and random, non-zero rise times, to a bipolar output pulse wherein the output pulse has a zero-crossing time that is independent of the rise time and amplitude of the input pulse. The filter differentiates the input pulse, along the linear leading edge of the input pulse, and subtracts therefrom a pulse fractionally proportional to the input pulse. The filter of the present invention can use discrete circuit components and avoids the use of delay lines.

  6. Phase and amplitude errors in FM radars

    NASA Astrophysics Data System (ADS)

    Griffiths, Hugh D.

    The constraints on phase and amplitude errors are determined for various types of FM radar by calculating the range sidelobe levels on the point target response due to the phase and amplitude modulation of the target echo. It is shown that under certain circumstances the constraints on phase linearity appropriate for conventional pulse compression radars are unnecessarily stringent, and quite large phase errors can be tolerated provided the relative delay of the local oscillator with respect to the target echo is small compared with the periodicity of the phase error characteristic. The constraints on amplitude flatness, however, are severe under almost all circumstances.

  7. A link representation for gravity amplitudes

    NASA Astrophysics Data System (ADS)

    He, Song

    2013-10-01

    We derive a link representation for all tree amplitudes in supergravity, from a recent conjecture by Cachazo and Skinner. The new formula explicitly writes amplitudes as contour integrals over constrained link variables, with an integrand naturally expressed in terms of determinants, or equivalently tree diagrams. Important symmetries of the amplitude, such as supersymmetry, parity and (partial) permutation invariance, are kept manifest in the formulation. We also comment on rewriting the formula in a GL( k)-invariant manner, which may serve as a starting point for the generalization to possible Grassmannian contour integrals.

  8. Coupled-channel scattering in 1 + 1 dimensional lattice model

    SciTech Connect

    Guo, Peng

    2013-07-01

    Based on the Lippmann-Schwinger equation approach, a generalized Lüscher’s formula in 1+1 dimensions for two particles scattering in both the elastic and coupled-channel cases in moving frames is derived. A two-dimensional coupled-channel scattering lattice model is presented, which represents a two-coupled-channel resonant scattering scalars system. The Monte Carlo simulation is performed on finite lattices and in various moving frames. The two-dimensional generalized Lüscher’s formula is used to extract the scattering amplitudes for the coupled-channel system from the discrete finite-volume spectrum.

  9. The integrated extinction for broadband scattering of acoustic waves.

    PubMed

    Sohl, Christian; Gustafsson, Mats; Kristensson, Gerhard

    2007-12-01

    In this paper, physical bounds on scattering of acoustic waves over a frequency interval are discussed based on the holomorphic properties of the scattering amplitude in the forward direction. The result is given by a dispersion relation for the extinction cross section which yields an upper bound on the product of the extinction cross section and the associated bandwidth of any frequency interval. The upper bound is shown to depend only on the geometry and the material properties of the scatterer in the static or low-frequency limit. The results are exemplified by permeable and impermeable scatterers with homogeneous and isotropic material properties.

  10. Timelike Compton Scattering - A First Look (CLAS)

    SciTech Connect

    Pawel Nadel-Turonski

    2009-12-01

    A major goal of the 12 GeV upgrade at Jefferson Lab is to map out the Generalized Parton Distributions (GPDs) in the valence region. This is primarily done through Deeply Virtual Compton Scattering (DVCS), which provides the simplest and cleanest way of accessing the GPDs. However, the “inverse” process, Timelike Compton Scattering (TCS), can provide an important complement, in particular formeasuring the real part of the amplitude and understanding corrections at finite Q2. The first measurements of TCS have recently been carried out in Hall B at Jefferson Lab, using both tagged and untagged photon beams.

  11. Noninertial effects on nonrelativistic topological quantum scattering

    NASA Astrophysics Data System (ADS)

    Mota, H. F.; Bakke, K.

    2017-08-01

    We investigate noninertial effects on the scattering problem of a nonrelativistic particle in the cosmic string spacetime. By considering the nonrelativistic limit of the Dirac equation we are able to show, in the regime of small rotational frequencies, that the phase shift has two contribution: one related to the noninertial reference frame, and the other, due to the cosmic string conical topology. We also show that both the incident wave and the scattering amplitude are altered as a consequence of the noninertial reference frame and depend on the rotational frequency.

  12. Scattering States in AdS/CFT

    SciTech Connect

    Fitzpatrick, A.Liam; Kaplan, Jared; /SLAC

    2012-02-14

    We show that suitably regulated multi-trace primary states in large N CFTs behave like 'in' and 'out' scattering states in the flat-space limit of AdS. Their transition matrix elements approach the exact scattering amplitudes for the bulk theory, providing a natural CFT definition of the flat space S-Matrix. We study corrections resulting from the AdS curvature and particle propagation far from the center of AdS, and show that AdS simply provides an IR regulator that disappears in the flat space limit.

  13. Texture In Amplitude Modulated (AM) And Phase Derivative (PD) Echograms

    NASA Astrophysics Data System (ADS)

    Thijssen, Johan M.; Oosterveld, Bernard J.; Romijn, R. L.

    1987-09-01

    The information about the condition of parenchymal tissues is obscured by the performance characteristics of echographic equipment. The authors investigated by realistic 3-D simulations the so-called beam diffraction effects on two echographic imaging modalities: amplitude modulated (AM) and phase derivative (PD) echograms. Furthermore the modification of the image texture by attenuation was quantified. In order to assess the potentials of statistical analysis of texture for medical diagnostics the effects caused by varying the density of scattering particles in a homogeneous medium were studied. It is concluded, that unless beam diffraction effects are either prevented, or adequately corrected for, quantitative texture analysis is not meaningful. In addition, the data have to be corrected for the non-linear and time dependent amplifier characteristics. Data-acquisition and preprocessing equipment performing these tasks has been developed at the authors' laboratory.

  14. Ultrasound transmission attenuation tomography using energy-scaled amplitude ratios

    NASA Astrophysics Data System (ADS)

    Chen, Ting; Shin, Junseob; Huang, Lianjie

    2016-04-01

    Ultrasound attenuation of breast tumors is related to their types and pathological states, and can be used to detect and characterize breast cancer. Particularly, ultrasound scattering attenuation can infer the margin properties of breast tumors. Ultrasound attenuation tomography quantitatively reconstructs the attenuation properties of the breast. Our synthetic-aperture breast ultrasound tomography system with two parallel transducer arrays records both ultrasound reflection and transmission signals. We develop an ultrasound attenuation tomography method using ultrasound energy-scaled amplitude decays of ultrasound transmission signals and conduct ultrasound attenuation tomography using a known sound-speed model. We apply our ultrasound transmission attenuation tomography method to a breast phantom dataset, and compare the ultrasound attenuation tomography results with conventional beamforming ultrasound images obtained using reflection signals. We show that ultrasound transmission attenuation tomography complements beamforming images in identifying breast lesions.

  15. Amplitude dynamics favors synchronization in complex networks

    PubMed Central

    Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia

    2016-01-01

    In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics. PMID:27108847

  16. Stable ac phase and amplitude comparator

    NASA Technical Reports Server (NTRS)

    Bruce, H. P.

    1967-01-01

    Stable ac phase and amplitude comparator detects excessive vehicle maneuvering or vibration. It has phase demodulation, low-pass filter, and multiple threshold-setting capability designed specifically for low drifts over a wide range of temperatures.

  17. Pion distribution amplitude from lattice QCD

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Hui; Chen, Jiunn-Wei; Ji, Xiangdong; Jin, Luchang; Lin, Huey-Wen

    2017-05-01

    We present the first lattice-QCD calculation of the pion distribution amplitude using the large-momentum effective field theory (LaMET) approach, which allows us to extract light cone parton observables from a Euclidean lattice. The mass corrections needed to extract the pion distribution amplitude from this approach are calculated to all orders in mπ2/Pz2 . We also implement the Wilson-line renormalization which is crucial to remove the power divergences in this approach, and find that it reduces the oscillation at the end points of the distribution amplitude. Our exploratory result at 310-MeV pion mass favors a single-hump form broader than the asymptotic form of the pion distribution amplitude.

  18. The periods and amplitudes of TU Cas

    NASA Technical Reports Server (NTRS)

    Hodson, S. W.; Cox, A. N.

    1980-01-01

    Light curve observations of the double-mode Cepheid TU Cas obtained by 10 different sets of observers on several photometric systems over a time span of 67 years were carefully studied to determine the fundamental and first overtone periods and their amplitudes on the V magnitude scale. The presence of a second overtone radial pulsation is discussed, and it is concluded that a previous detection of this mode was spurious due to the lack of a proper zero point correction for two groups of observations. The amplitudes of the two modes are shown to possibly vary during the entire observing period with the fundamental mode amplitude of 0.69 + or - 0.03 and the overtone amplitude decreasing about 0.2 or 0.3 magnitude. If this Cepheid displays the two pulsation modes because it is mode switching, this switching time scale might be less than a hundred years.

  19. Amplitude dynamics favors synchronization in complex networks

    NASA Astrophysics Data System (ADS)

    Gambuzza, Lucia Valentina; Gómez-Gardeñes, Jesus; Frasca, Mattia

    2016-04-01

    In this paper we study phase synchronization in random complex networks of coupled periodic oscillators. In particular, we show that, when amplitude dynamics is not negligible, phase synchronization may be enhanced. To illustrate this, we compare the behavior of heterogeneous units with both amplitude and phase dynamics and pure (Kuramoto) phase oscillators. We find that in small network motifs the behavior crucially depends on the topology and on the node frequency distribution. Surprisingly, the microscopic structures for which the amplitude dynamics improves synchronization are those that are statistically more abundant in random complex networks. Thus, amplitude dynamics leads to a general lowering of the synchronization threshold in arbitrary random topologies. Finally, we show that this synchronization enhancement is generic of oscillators close to Hopf bifurcations. To this aim we consider coupled FitzHugh-Nagumo units modeling neuron dynamics.

  20. Large Amplitude Oscillations of a Double Pendulum

    NASA Astrophysics Data System (ADS)

    Gerres, Jeffrey M.; Jacobs, Robert M.; Kasun, Sara F.; Bacon, Margaret E.; Nagolu, Chakravarthi M.; Owens, Erin L.; Siehl, Kevin F.; Thomsen, Marshall; Troyer, Jon S.

    2008-03-01

    The nature of the normal modes of oscillation in the small angle regime of a double pendulum is well established. However, for large amplitude oscillations, a closed form solution of the differential equations of motion does not exist. Using Lagrange formalism, we explore both the in-phase and out-of-phase normal modes of oscillation of a double pendulum as a function of the mass ratio of the two bobs and their initial angular positions. We conduct the analysis using MatLab, where we initially verify our code in the known small amplitude limit. Among our results we find that certain symmetries between the in-phase and out-of-phase normal modes that exist in the small amplitude limit are no longer present at large amplitudes.

  1. Quartic Amplitudes for Minkowski Higher Spin

    NASA Astrophysics Data System (ADS)

    Bengtsson, Anders K. H.

    The old problem of finding general quartic interaction terms between fields of higher helicities on the light-front is discussed from the point of view of calculating the corresponding amplitudes directly from the cubic vertices using BCFW recursion. Amplitude based no-go results that has appeared in the literature are reviewed and discussed and it is pointed out how they may perhaps be circumvented.

  2. Amplitude metrics for cellular circadian bioluminescence reporters.

    PubMed

    St John, Peter C; Taylor, Stephanie R; Abel, John H; Doyle, Francis J

    2014-12-02

    Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary

  3. Seismic directional beamforming using cosine amplitude distribution

    NASA Astrophysics Data System (ADS)

    Jiang, T.; Xu, X.; Song, J.; Jia, H.; Ge, L.

    2013-12-01

    o improve the signal-to-noise ratio in seismic exploration, we studied the method of time domain seismic beam-forming based on receiver array (TSBBRA). TSBBRA is useful to extract reflected waves from some target layers and decrease noise from other direction. When noise is strong enough, the control parameter of the method of TSBBRA need to be increased. It means that we have to use more raw records to form a directional seismic record. Therefore, the signal energy in beam is much denser, and the beam becomes narrower accordingly. When the beam can not cover the receiver array, the signal-to-noise ratios in different traces are quite unbalanced and average quality of data probably is still quite low. Therefore, this paper proposes seismic directional beamforming using the cosine amplitude distribution (SDBCAD). SDBCAD can adjust seismic beam shape by introducing cosine amplitude distribution, an amplitude weighting method, in the procedure of beamforming. We studied cosine amplitude weighting function, analyzed the characteristics of uniform and cosine amplitude distribution in beamforming, and compared directivity of beams from the two kind of amplitude pattern. It shows that the main beam of cosine-weighted amplitude is different from uniform distribution. The coverage of main beam from SDBCAD is wider than uniform amplitude, and the width of beam is varied with different number of cosine order. So we simulated the seismic raw record, and used TSBBRA and SDBCAD to process simulated data at the receiving array. The results show that SDBCAD can broaden directional beam, and the main beam from SDBCAD can cover the entire traces instead of partial coverage in TSBBRA. The average signal-to-noise ratio increased 0.2~4.5dB. It concludes that SDBCAD is competent to stretch beam reasonable, and it is useful to boost signal-to-noise ratio when beam from TSBBRA is too narrow to illuminate receiver array properly. Updated results will be presented at the meeting.

  4. Nucleon Distribution Amplitudes from Lattice QCD

    SciTech Connect

    Goeckeler, Meinulf; Kaltenbrunner, Thomas; Warkentin, Nikolaus; Horsley, Roger; Zanotti, James M.; Nakamura, Yoshifumi; Pleiter, Dirk; Schierholz, Gerrit; Rakow, Paul E. L.; Schaefer, Andreas; Stueben, Hinnerk

    2008-09-12

    We calculate low moments of the leading-twist and next-to-leading-twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature.

  5. Amplitude Metrics for Cellular Circadian Bioluminescence Reporters

    PubMed Central

    St. John, Peter C.; Taylor, Stephanie R.; Abel, John H.; Doyle, Francis J.

    2014-01-01

    Bioluminescence rhythms from cellular reporters have become the most common method used to quantify oscillations in circadian gene expression. These experimental systems can reveal phase and amplitude change resulting from circadian disturbances, and can be used in conjunction with mathematical models to lend further insight into the mechanistic basis of clock amplitude regulation. However, bioluminescence experiments track the mean output from thousands of noisy, uncoupled oscillators, obscuring the direct effect of a given stimulus on the genetic regulatory network. In many cases, it is unclear whether changes in amplitude are due to individual changes in gene expression level or to a change in coherence of the population. Although such systems can be modeled using explicit stochastic simulations, these models are computationally cumbersome and limit analytical insight into the mechanisms of amplitude change. We therefore develop theoretical and computational tools to approximate the mean expression level in large populations of noninteracting oscillators, and further define computationally efficient amplitude response calculations to describe phase-dependent amplitude change. At the single-cell level, a mechanistic nonlinear ordinary differential equation model is used to calculate the transient response of each cell to a perturbation, whereas population-level dynamics are captured by coupling this detailed model to a phase density function. Our analysis reveals that amplitude changes mediated at either the individual-cell or the population level can be distinguished in tissue-level bioluminescence data without the need for single-cell measurements. We demonstrate the effectiveness of the method by modeling experimental bioluminescence profiles of light-sensitive fibroblasts, reconciling the conclusions of two seemingly contradictory studies. This modeling framework allows a direct comparison between in vitro bioluminescence experiments and in silico ordinary

  6. Bootstrapping One-Loop QCD Amplitudes

    SciTech Connect

    Berger, Carola F.; /SLAC

    2006-09-08

    We review the recently developed bootstrap method for the computation of high-multiplicity QCD amplitudes at one loop. We illustrate the general algorithm step by step with a six-point example. The method combines (generalized) unitarity with on-shell recursion relations to determine the not cut-constructible, rational terms of these amplitudes. Our bootstrap approach works for arbitrary configurations of gluon helicities and arbitrary numbers of external legs.

  7. Feynman amplitudes and limits of heights

    NASA Astrophysics Data System (ADS)

    Amini, O.; Bloch, S. J.; Burgos Gil, J. I.; Fresán, J.

    2016-10-01

    We investigate from a mathematical perspective how Feynman amplitudes appear in the low-energy limit of string amplitudes. In this paper, we prove the convergence of the integrands. We derive this from results describing the asymptotic behaviour of the height pairing between degree-zero divisors, as a family of curves degenerates. These are obtained by means of the nilpotent orbit theorem in Hodge theory.

  8. Vowel identification by amplitude and phase contrast.

    PubMed

    Molis, Michelle R; Diedesch, Anna; Gallun, Frederick; Leek, Marjorie R

    2013-02-01

    Vowel identification is largely dependent on listeners' access to the frequency of two or three peaks in the amplitude spectrum. Earlier work has demonstrated that, whereas normal-hearing listeners can identify harmonic complexes with vowel-like spectral shapes even with very little amplitude contrast between "formant" components and remaining harmonic components, listeners with hearing loss require greater amplitude differences. This is likely the result of the poor frequency resolution that often accompanies hearing loss. Here, we describe an additional acoustic dimension for emphasizing formant versus non-formant harmonics that may supplement amplitude contrast information. The purpose of this study was to determine whether listeners were able to identify "vowel-like" sounds using temporal (component phase) contrast, which may be less affected by cochlear loss than spectral cues, and whether overall identification improves when congruent temporal and spectral information are provided together. Five normal-hearing and five hearing-impaired listeners identified three vowels over many presentations. Harmonics representing formant peaks were varied in amplitude, phase, or a combination of both. In addition to requiring less amplitude contrast, normal-hearing listeners could accurately identify the sounds with less phase contrast than required by people with hearing loss. However, both normal-hearing and hearing-impaired groups demonstrated the ability to identify vowel-like sounds based solely on component phase shifts, with no amplitude contrast information, and they also showed improved performance when congruent phase and amplitude cues were combined. For nearly all listeners, the combination of spectral and temporal information improved identification in comparison to either dimension alone.

  9. Twistor-strings and gravity tree amplitudes

    NASA Astrophysics Data System (ADS)

    Adamo, Tim; Mason, Lionel

    2013-04-01

    Recently we discussed how Einstein supergravity tree amplitudes might be obtained from the original Witten and Berkovits twistor-string theory when external conformal gravitons are restricted to be Einstein gravitons. Here we obtain a more systematic understanding of the relationship between conformal and Einstein gravity amplitudes in that twistor-string theory. We show that although it does not in general yield Einstein amplitudes, we can nevertheless obtain some partial twistor-string interpretation of the remarkable formulae recently been found by Hodges and generalized to all tree amplitudes by Cachazo and Skinner. The Hodges matrix and its higher degree generalizations encode the world sheet correlators of the twistor string. These matrices control both Einstein amplitudes and those of the conformal gravity arising from the Witten and Berkovits twistor-string. Amplitudes in the latter case arise from products of the diagonal elements of the generalized Hodges matrices and reduced determinants give the former. The reduced determinants arise if the contractions in the worldsheet correlator are restricted to form connected trees at MHV. The (generalized) Hodges matrices arise as weighted Laplacian matrices for the graph of possible contractions in the correlators and the reduced determinants of these weighted Laplacian matrices give the sum of the connected tree contributions by an extension of the matrix-tree theorem.

  10. Stress-dependent ultrasonic scattering in polycrystalline materials.

    PubMed

    Kube, Christopher M; Turner, Joseph A

    2016-02-01

    Stress-dependent elastic moduli of polycrystalline materials are used in a statistically based model for the scattering of ultrasonic waves from randomly oriented grains that are members of a stressed polycrystal. The stress is assumed to be homogeneous and can be either residual or generated from external loads. The stress-dependent elastic properties are incorporated into the definition of the differential scattering cross-section, which defines how strongly an incident wave is scattered into various directions. Nine stress-dependent differential scattering cross-sections or scattering coefficients are defined to include all possibilities of incident and scattered waves, which can be either longitudinal or (two) transverse wave types. The evaluation of the scattering coefficients considers polycrystalline aluminum that is uniaxially stressed. An analysis of the influence of incident wave propagation direction, scattering direction, frequency, and grain size on the stress-dependency of the scattering coefficients follows. Scattering coefficients for aluminum indicate that ultrasonic scattering is much more sensitive to a uniaxial stress than ultrasonic phase velocities. By developing the stress-dependent scattering properties of polycrystals, the influence of acoustoelasticity on the amplitudes of waves propagating in stressed polycrystalline materials can be better understood. This work supports the ongoing development of a technique for monitoring and measuring stresses in metallic materials.

  11. The amplitude of auroral backscatter. I - Model estimates of the dependence on electron density

    NASA Astrophysics Data System (ADS)

    Uspenskii, M. V.; Williams, P. J. S.

    1988-01-01

    A model of the auroral backscatter amplitude, in the form discussed by Uspensky (1985) and Oksman et al. (1986), has been derived for the radar geometry appropriate to joint observations by the PGI auroral radars at Karmaselga and Essoyla and the EISCAT incoherent scatter radar. The model shows how refraction effects cause a strongly nonlinear dependence of backscatter amplitude on electron density in the E-region. It also explains why the macroaspect sensitivity for auroral radar operating at a frequency of about 45 MHz is only 1-2 dB per degree for aspect angles greater than 5 deg.

  12. Renormalization-group evolution of the B-meson light-cone distribution amplitude.

    PubMed

    Lange, Björn O; Neubert, Matthias

    2003-09-05

    An integro-differential equation governing the evolution of the leading-order B-meson light-cone distribution amplitude is derived. The anomalous dimension in this equation contains a logarithm of the renormalization scale, whose coefficient is identified with the cusp anomalous dimension of Wilson loops. The exact solution of the evolution equation is obtained, from which the asymptotic behavior of the distribution amplitude is derived. These results can be used to resum Sudakov logarithms entering the hard-scattering kernels in QCD factorization theorems for exclusive B decays.

  13. Low-energy pion-nucleon scattering

    SciTech Connect

    Gibbs, W.R.; Ai, L.; Kaufmann, W.B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent {pi}{sup {plus_minus}}p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f{sup 2}=0.0756{plus_minus}0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P{sub 31} and P{sub 13} partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the {Sigma} term. Off-shell amplitudes are also provided. {copyright} {ital 1998} {ital The American Physical Society}

  14. Low-energy pion-nucleon scattering

    NASA Astrophysics Data System (ADS)

    Gibbs, W. R.; Ai, Li; Kaufmann, W. B.

    1998-02-01

    An analysis of low-energy charged pion-nucleon data from recent π+/-p experiments is presented. From the scattering lengths and the Goldberger-Miyazawa-Oehme (GMO) sum rule we find a value of the pion-nucleon coupling constant of f2=0.0756+/-0.0007. We also find, contrary to most previous analyses, that the scattering volumes for the P31 and P13 partial waves are equal, within errors, corresponding to a symmetry found in the Hamiltonian of many theories. For the potential models used, the amplitudes are extrapolated into the subthreshold region to estimate the value of the Σ term. Off-shell amplitudes are also provided.

  15. Skyrmion recoil in pion-nucleon scattering

    SciTech Connect

    Hughes, J. Physics Department, University of California at Davis, Davis, California 95616 ); Mathews, G.J. )

    1992-08-01

    We calculate the lowest-order recoil corrections to the pion-nucleon scattering matrix in the SU(2) Skyrme model. The corrections result from a direct semiclassical evaluation of path-integral expressions for relevant finite-time transition amplitudes. The {ital S} matrix for pion-nucleon scattering is extracted from these amplitudes by using a configuration-space representation for the asymptotic nucleons; the quanta are treated just as in the vacuum sector. The recoil corrections result from the Skyrmion freely translating between initial and final positions, and are relevant to a kinematical regime opposite to that where the impulse approximation is valid. The form of the corrections is model independent, unchanged for any chiral model with hedgehog solitary wave solutions. Remarkably, new lowest-lying resonances emerge in the {ital p} channels, whereas the {ital s} and {ital d} waves are not noticeably improved.

  16. Multichannel 1 → 2 transition amplitudes in a finite volume

    SciTech Connect

    Briceno, Raul A.; Hansen, Maxwell T.; Walker-Loud, Andre

    2015-02-03

    We perform a model-independent, non-perturbative investigation of two-point and three-point finite-volume correlation functions in the energy regime where two-particle states can go on-shell. We study three-point functions involving a single incoming particle and an outgoing two-particle state, relevant, for example, for studies of meson decays (e.g., B⁰ → K*l⁺l⁻) or meson photo production (e.g., πγ* → ππ). We observe that, while the spectrum solely depends upon the on-shell scattering amplitude, the correlation functions also depend upon off-shell amplitudes. The main result of this work is a non-perturbative generalization of the Lellouch-Luscher formula relating matrix elements of currents in finite and infinite spatial volumes. We extend that work by considering a theory with multiple, strongly-coupled channels and by accommodating external currents which inject arbitrary four-momentum as well as arbitrary angular-momentum. The result is exact up to exponentially suppressed corrections governed by the pion mass times the box size. We also apply our master equation to various examples, including two processes mentioned above as well as examples where the final state is an admixture of two open channels.

  17. Differential cross sections for muonic atom scattering from hydrogenic molecules

    SciTech Connect

    Adamczak, Andrzej

    2006-10-15

    The differential cross sections for low-energy muonic hydrogen atom scattering from hydrogenic molecules are directly expressed by the corresponding amplitudes for muonic atom scattering from hydrogen-isotope nuclei. The energy and angular dependence of these three-body amplitudes is thus taken naturally into account in scattering from molecules, without involving any pseudopotentials. Effects of the internal motion of nuclei inside the target molecules are included for every initial rotational-vibrational state. These effects are very significant as the considered three-body amplitudes often vary strongly within the energy interval < or approx. 0.1 eV. The differential cross sections, calculated using the presented method, have been successfully used for planning and interpreting many experiments in low-energy muon physics. Studies of {mu}{sup -} nuclear capture in p{mu} and the measurement of the Lamb shift in p{mu} atoms created in H{sub 2} gaseous targets are recent examples.

  18. Collinear limits beyond the leading order from the scattering equations

    NASA Astrophysics Data System (ADS)

    Nandan, Dhritiman; Plefka, Jan; Wormsbecher, Wadim

    2017-02-01

    The structure of tree-level scattering amplitudes for collinear massless bosons is studied beyond their leading splitting function behavior. These near-collinear limits at sub-leading order are best studied using the Cachazo-He-Yuan (CHY) formulation of the S-matrix based on the scattering equations. We compute the collinear limits for gluons, gravitons and scalars. It is shown that the CHY integrand for an n-particle gluon scattering amplitude in the collinear limit at sub-leading order is expressed as a convolution of an ( n - 1)-particle gluon integrand and a collinear kernel integrand, which is universal. Our representation is shown to obey recently proposed amplitude relations in which the collinear gluons of same helicity are replaced by a single graviton. Finally, we extend our analysis to effective field theories and study the collinear limit of the non-linear sigma model, Einstein-Maxwell-Scalar and Yang-Mills-Scalar theory.

  19. Amplitude Modulations of Acoustic Communication Signals

    NASA Astrophysics Data System (ADS)

    Turesson, Hjalmar K.

    2011-12-01

    In human speech, amplitude modulations at 3 -- 8 Hz are important for discrimination and detection. Two different neurophysiological theories have been proposed to explain this effect. The first theory proposes that, as a consequence of neocortical synaptic dynamics, signals that are amplitude modulated at 3 -- 8 Hz are propagated better than un-modulated signals, or signals modulated above 8 Hz. This suggests that neural activity elicited by vocalizations modulated at 3 -- 8 Hz is optimally transmitted, and the vocalizations better discriminated and detected. The second theory proposes that 3 -- 8 Hz amplitude modulations interact with spontaneous neocortical oscillations. Specifically, vocalizations modulated at 3 -- 8 Hz entrain local populations of neurons, which in turn, modulate the amplitude of high frequency gamma oscillations. This suggests that vocalizations modulated at 3 -- 8 Hz should induce stronger cross-frequency coupling. Similar to human speech, we found that macaque monkey vocalizations also are amplitude modulated between 3 and 8 Hz. Humans and macaque monkeys share similarities in vocal production, implying that the auditory systems subserving perception of acoustic communication signals also share similarities. Based on the similarities between human speech and macaque monkey vocalizations, we addressed how amplitude modulated vocalizations are processed in the auditory cortex of macaque monkeys, and what behavioral relevance modulations may have. Recording single neuron activity, as well as, the activity of local populations of neurons allowed us to test both of the neurophysiological theories presented above. We found that single neuron responses to vocalizations amplitude modulated at 3 -- 8 Hz resulted in better stimulus discrimination than vocalizations lacking 3 -- 8 Hz modulations, and that the effect most likely was mediated by synaptic dynamics. In contrast, we failed to find support for the oscillation-based model proposing a

  20. On the frequency dependence and spatial coherence of PKP precursor amplitudes

    NASA Astrophysics Data System (ADS)

    Mancinelli, Nicholas; Shearer, Peter; Thomas, Christine

    2016-03-01

    Studies now agree that small-scale (˜10 km) weak (˜0.1%) velocity perturbations throughout the lowermost mantle generate the globally averaged amplitudes of 1 Hz precursors to the core phase, . The possible frequency dependence and spatial coherence of this scattered phase, however, has been given less attention. Using a large global data set of ˜150,000 PKP precursor recordings, we characterize the frequency dependence of PKP precursors at central frequencies ranging from 0.5 to 4 Hz. At greater frequencies, we observe more scattered energy (relative to the reference phase PKPdf), particularly at shorter ranges. We model this observation by invoking heterogeneity at length scales from 2 to 30 km. Amplitudes at 0.5 Hz, in particular, suggest the presence of more heterogeneity at scales >8 km than present in previously published models. Using a regional bootstrap approach, we identify large (>20°), spatially coherent regions of anomalously strong scattering beneath the West Pacific, Central/North America, and—to a lesser extent—East Africa. Finally, as proof of concept, we use array processing techniques to locate the origin of scattered energy observed in Southern California by the Anza and Southern California Seismic Networks. The energy appears to come primarily from out-of-plane scattering on the receiver side. We suggest that such improvised arrays can increase global coverage and may reveal whether a majority of precursor energy comes from localized heterogeneity in the lowermost mantle.

  1. Including Delbrück scattering in GEANT4

    NASA Astrophysics Data System (ADS)

    Omer, Mohamed; Hajima, Ryoichi

    2017-08-01

    Elastic scattering of γ-rays is a significant interaction among γ-ray interactions with matter. Therefore, the planning of experiments involving measurements of γ-rays using Monte Carlo simulations usually includes elastic scattering. However, current simulation tools do not provide a complete picture of elastic scattering. The majority of these tools assume Rayleigh scattering is the primary contributor to elastic scattering and neglect other elastic scattering processes, such as nuclear Thomson and Delbrück scattering. Here, we develop a tabulation-based method to simulate elastic scattering in one of the most common open-source Monte Carlo simulation toolkits, GEANT4. We collectively include three processes, Rayleigh scattering, nuclear Thomson scattering, and Delbrück scattering. Our simulation more appropriately uses differential cross sections based on the second-order scattering matrix instead of current data, which are based on the form factor approximation. Moreover, the superposition of these processes is carefully taken into account emphasizing the complex nature of the scattering amplitudes. The simulation covers an energy range of 0.01 MeV ≤ E ≤ 3 MeV and all elements with atomic numbers of 1 ≤ Z ≤ 99. In addition, we validated our simulation by comparing the differential cross sections measured in earlier experiments with those extracted from the simulations. We find that the simulations are in good agreement with the experimental measurements. Differences between the experiments and the simulations are 21% for uranium, 24% for lead, 3% for tantalum, and 8% for cerium at 2.754 MeV. Coulomb corrections to the Delbrück amplitudes may account for the relatively large differences that appear at higher Z values.

  2. Double soft limit of the graviton amplitude from the Cachazo-He-Yuan formalism

    NASA Astrophysics Data System (ADS)

    Saha, Arnab Priya

    2017-08-01

    We present a complete analysis for double soft limit of graviton scattering amplitude using the formalism proposed by Cachazo, He, and Yuan. Our results agree with that obtained via Britto-Cachazo-Feng-Witten (BCFW) recursion relations in [T. Klose, T. McLoughlin, D. Nandan, J. Plefka, and G. Travaglini, Double-soft limits of gluons and gravitons, J. High Energy Phys. 07 (2015) 135., 10.1007/JHEP07(2015)135]. In addition we find precise relations between degenerate and nondegenerate solutions of scattering equations with local and nonlocal terms in the soft factor.

  3. Amplitude-masked photoacoustic wavefront shaping: theory and application in flowmetry

    NASA Astrophysics Data System (ADS)

    Liang, Jinyang; Tay, Jian Wei; Hemphill, Ashton S.; Wang, Lihong V.

    2015-03-01

    Optical diffusion in scattering media prevents focusing beyond shallow depths, causing optical imaging and sensing to suffer from low optical intensities, resulting in low signal-to-noise ratios (SNR). Here, we demonstrate focusing using a fast binary-amplitude digital micromirror device to characterize the transmission modes of the scattering medium. We then identify and selectively illuminate the transmission modes which contribute constructively to the intensity at the optical focus. Applying this method to photoacoustic flowmetry, we increased the optical intensity at the focus six-fold, and showed that the corresponding increase in SNR allows particle flow to be measured.

  4. Stimulated Brillouin scattering in the field of a two-dimensionally localized pumping wave

    SciTech Connect

    Solikhov, D. K.; Dvinin, S. A.

    2016-06-15

    Stimulated Brillouin scattering of electromagnetic waves in the field of a two-dimensionally localized pump wave at arbitrary scattering angles in the regime of forward scattering is analyzed. Spatial variations in the amplitudes of interacting waves are studied for different values of the pump field and different dimensions of the pump wave localization region. The intensity of scattered radiation is determined as a function of the scattering angle and the dimensions of the pump wave localization region. It is shown that the intensity increases with increasing scattering angle.

  5. Stimulated Brillouin scattering in the field of a two-dimensionally localized pumping wave

    NASA Astrophysics Data System (ADS)

    Solikhov, D. K.; Dvinin, S. A.

    2016-06-01

    Stimulated Brillouin scattering of electromagnetic waves in the field of a two-dimensionally localized pump wave at arbitrary scattering angles in the regime of forward scattering is analyzed. Spatial variations in the amplitudes of interacting waves are studied for different values of the pump field and different dimensions of the pump wave localization region. The intensity of scattered radiation is determined as a function of the scattering angle and the dimensions of the pump wave localization region. It is shown that the intensity increases with increasing scattering angle.

  6. Kaonic atoms and in-medium K-N amplitudes II: Interplay between theory and phenomenology

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2013-02-01

    A microscopic kaonic-atom optical potential VK-(1) is constructed, using the Ikeda-Hyodo-Weise NLO chiral K-N subthreshold scattering amplitudes constrained by the kaonic hydrogen SIDDHARTA measurement, and incorporating Pauli correlations within the Waas-Rho-Weise generalization of the Ericson-Ericson multiple-scattering approach. Good fits to kaonic atom data over the entire periodic table require additionally sizable K-NN-motivated absorptive and dispersive phenomenological terms, in agreement with our former analysis based on a post-SIDDHARTA in-medium chirally-inspired NLO separable model by Cieplý and Smejkal. Such terms are included by introducing a phenomenological potential VK-(2) and coupling it self-consistently to VK-(1). Properties of resulting kaonic atom potentials are discussed with special attention paid to the role of K--nuclear absorption and to the extraction of density-dependent amplitudes representing K- multi-nucleon processes.

  7. Realizing total reciprocity violation in the phase for photon scattering.

    PubMed

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-22

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

  8. Realizing total reciprocity violation in the phase for photon scattering

    PubMed Central

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-01-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices. PMID:28225031

  9. Realizing total reciprocity violation in the phase for photon scattering

    NASA Astrophysics Data System (ADS)

    Deák, László; Bottyán, László; Fülöp, Tamás; Merkel, Dániel Géza; Nagy, Dénes Lajos; Sajti, Szilárd; Schulze, Kai Sven; Spiering, Hartmut; Uschmann, Ingo; Wille, Hans-Christian

    2017-02-01

    Reciprocity is when wave or quantum scattering satisfies a symmetry property, connecting a scattering process with the reversed one. While reciprocity involves the interchange of source and detector, it is fundamentally different from rotational invariance, and is a generalization of time reversal invariance, occurring in absorptive media as well. Due to its presence at diverse areas of physics, it admits a wide variety of applications. For polarization dependent scatterings, reciprocity is often violated, but violation in the phase of the scattering amplitude is much harder to experimentally observe than violation in magnitude. Enabled by the advantageous properties of nuclear resonance scattering of synchrotron radiation, we have measured maximal, i.e., 180-degree, reciprocity violation in the phase. For accessing phase information, we introduced a new version of stroboscopic detection. The scattering setting was devised based on a generalized reciprocity theorem that opens the way to construct new types of reciprocity related devices.

  10. Periodic amplitude variations in Jovian continuum radiation

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.; Scarf, F. L.

    1986-01-01

    An analysis of periodic variations in the amplitude of continuum radiation near 3 kHz trapped in the Jovian magnetosphere shows structure with periods near both five and ten hours. Contrary to a plausible initial idea, the continuum amplitudes are not organized by position of the observer relative to the dense plasma sheet. Instead, there seem to be preferred orientations of system III longitude with respect to the direction to the sun which account for the peaks. This implies a clock-like modulation of the continuum radiation intensity as opposed to a searchlight effect. The importance of the dipole longitude-solar wind alignment to the amplitude of the continuum radiation implies the source region of the radiation is near the magnetopause and may indirectly tie the generation of the radio waves to the clocklike modulation of energetic electron fluxes from Jupiter.

  11. Cut-constructible part of QCD amplitudes

    SciTech Connect

    Britto, Ruth; Feng Bo; Mastrolia, Pierpaolo

    2006-05-15

    Unitarity cuts are widely used in analytic computation of loop amplitudes in gauge theories such as QCD. We expand upon the technique introduced in hep-ph/0503132 to carry out any finite unitarity cut integral. This technique naturally separates the contributions of bubble, triangle and box integrals in one-loop amplitudes and is not constrained to any particular helicity configurations. Loop momentum integration is reduced to a sequence of algebraic operations. We discuss the extraction of the residues at higher-order poles. Additionally, we offer concise algebraic formulas for expressing coefficients of three-mass triangle integrals. As an application, we compute all remaining coefficients of bubble and triangle integrals for nonsupersymmetric six-gluon amplitudes.

  12. Amplitude-coded color doppler: clinical applications.

    PubMed

    Turetschek, K; Kollmann, C; Dorffner, R; Wunderbaldinger, P; Mostbeck, G

    1999-01-01

    Amplitude-coded color Doppler sonography (ACD) has become an useful adjunct to gray-scale US and conventional color Doppler sonography (CD) for the assessment of vascular diseases and pathologic conditions that might affect or alter tissue vascularization or perfusion. Basically, all US units that generate conventional color Doppler information through autocorrelation technique are capable of displaying ACD. This technique is also referred to as power Doppler, amplitude-mode color Doppler US, color Doppler energy (CDE), or US angiography. Amplitude-coded color Doppler sonography has already emerged as a valuable adjunct to conventional CD, particularly for evaluating flow in parts of the body where CD signal is weak because of slow flow, small blood vessels, or both.

  13. A description of seismic amplitude techniques

    NASA Astrophysics Data System (ADS)

    Shadlow, James

    2014-02-01

    The acquisition of seismic data is a non-invasive technique used for determining the sub surface geology. Changes in lithology and fluid fill affect the seismic wavelet. Analysing seismic data for direct hydrocarbon indicators (DHIs), such as full stack amplitude anomalies, or amplitude variation with offset (AVO), can help a seismic interpreter relate the geophysical response to real geology and, more importantly, to distinguish the presence of hydrocarbons. Inversion is another commonly used technique that attempts to tie the seismic data back to the geology. Much has been written about these techniques, and attempting to gain an understanding on the theory and application of them by reading through various journals can be quite daunting. The purpose of this paper is to briefly outline DHI analysis, including full stack amplitude anomalies, AVO and inversion and show the relationship between all three. The equations presented have been included for completeness, but the reader can pass over the mathematical detail.

  14. Explicit formulae for Yang-Mills-Einstein amplitudes from the double copy

    NASA Astrophysics Data System (ADS)

    Chiodaroli, Marco; Günaydin, Murat; Johansson, Henrik; Roiban, Radu

    2017-07-01

    Using the double-copy construction of Yang-Mills-Einstein theories formulated in our earlier work, we obtain compact presentations for single-trace Yang-Mills-Einstein tree amplitudes with up to five external gravitons and an arbitrary number of gluons. These are written as linear combinations of color-ordered Yang-Mills trees, where the coefficients are given by color/kinematics-satisfying numerators in a Yang-Mills + ϕ 3 theory. The construction outlined in this paper holds in general dimension and extends straightforwardly to supergravity theories. For one, two, and three external gravitons, our expressions give identical or simpler presentations of amplitudes already constructed through string-theory considerations or the scattering equations formalism. Our results are based on color/kinematics duality and gauge invariance, and strongly hint at a recursive structure underlying the single-trace amplitudes with an arbitrary number of gravitons. We also present explicit expressions for all-loop single-graviton Einstein-Yang-Mills amplitudes in terms of Yang-Mills amplitudes and, through gauge invariance, derive new all-loop amplitude relations for Yang-Mills theory.

  15. An Empirical Study of Atmospheric Correction Procedures for Regional Infrasound Amplitudes with Ground Truth.

    NASA Astrophysics Data System (ADS)

    Howard, J. E.

    2014-12-01

    This study focusses on improving methods of accounting for atmospheric effects on infrasound amplitudes observed on arrays at regional distances in the southwestern United States. Recordings at ranges of 150 to nearly 300 km from a repeating ground truth source of small HE explosions are used. The explosions range in actual weight from approximately 2000-4000 lbs. and are detonated year-round which provides signals for a wide range of atmospheric conditions. Three methods of correcting the observed amplitudes for atmospheric effects are investigated with the data set. The first corrects amplitudes for upper stratospheric wind as developed by Mutschlecner and Whitaker (1999) and uses the average wind speed between 45-55 km altitudes in the direction of propagation to derive an empirical correction formula. This approach was developed using large chemical and nuclear explosions and is tested with the smaller explosions for which shorter wavelengths cause the energy to be scattered by the smaller scale structure of the atmosphere. The second approach isa semi-empirical method using ray tracing to determine wind speed at ray turning heights where the wind estimates replace the wind values in the existing formula. Finally, parabolic equation (PE) modeling is used to predict the amplitudes at the arrays at 1 Hz. The PE amplitudes are compared to the observed amplitudes with a narrow band filter centered at 1 Hz. An analysis is performed of the conditions under which the empirical and semi-empirical methods fail and full wave methods must be used.

  16. Yang-Mills amplitude relations at loop level from non-adjacent BCFW shifts

    NASA Astrophysics Data System (ADS)

    Boels, Rutger H.; Isermann, Reinke Sven

    2012-03-01

    This article studies methods to obtain relations for scattering amplitudes at the loop level, with concrete examples at one loop. These methods originate in the analysis of large so-called Britto-Cachazo-Feng-Witten shifts of tree level amplitudes and loop level integrands. In particular BCFW shifts for particles which are not color adjacent and some particular generalizations of this situation are analyzed in some detail in four and higher dimensions. For generic non-adjacent shifts our results are independent of loop order for integrands and hold for generic minimally coupled gauge theories with possible scalar potential and Yukawa terms. By a standard argument this result indicates a generalization of the Bern-Carrasco-Johansson relations for tree level amplitudes exists to the integrand at all loop levels. A concrete relation is presented at one loop. Furthermore, inspired by results in QED it is shown that the results on generalized BCFW shifts of tree level amplitudes imply relations for the so-called rational, bubble and triangle terms of one loop amplitudes in pure Yang-Mills theory. Bubble and triangle terms for instance are shown to obey a five photon decoupling identity, while a three photon decoupling identity is demonstrated for the rational terms. Along the same lines recently conjectured relations for helicity equal amplitudes at one loop are shown to generalize to helicity independent relations for the massive box coefficient of the rational terms.

  17. High-Energy Amplitudes in the Next-to-Leading Order

    SciTech Connect

    Ian Balitsky

    2011-03-01

    High-energy scattering in the saturation region is described by the evolution of color dipoles. In the leading order this evolution is governed by the non-linear BK equation. To see if this equation is relevant for existing or future accelerators (like EIC or LHeC) one needs to know how big are the next-to-leading order (NLO) corrections. I review the calculation of the NLO corrections to high-energy amplitudes in QCD.

  18. Modified π π amplitude with σ pole

    NASA Astrophysics Data System (ADS)

    Bydžovský, P.; Kamiński, R.; Nazari, V.

    2014-12-01

    A set of well-known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel S (π π , K K ¯, and η η ) and P (π π , ρ 2 π , and ρ σ ) wave amplitudes mostly below 1 GeV. Before the modifications, these amplitudes significantly did not satisfy the crossing symmetry condition and did not describe the π π threshold region. Moreover, the pole of the S wave amplitude related with the f0(500 ) meson (former f0(600 ) or σ ) had much smaller imaginary part and bigger real one in comparison with those in the newest Particle Data Group Tables. Here, these amplitudes are supplemented by near threshold expansion polynomials and refitted to the experimental data in the effective two pion mass from the threshold to 1.8 GeV and to the dispersion relations up to 1.1 GeV. In result the self consistent, i.e., unitary and fulfilling the crossing symmetry condition, S and P wave amplitudes are formed and the σ pole becomes much narrower and lighter. To eliminate doubts about the uniqueness of the so obtained sigma pole position short and purely mathematical proof of the uniqueness of the results is also presented. This analysis is addressed to a wide group of physicists and aims at providing a very effective and easy method of modification of, many presently used, π π amplitudes with a heavy and broad σ meson without changing of their original mathematical structure.

  19. Scattering of ultrarelativistic electrons in ultrathin crystals

    NASA Astrophysics Data System (ADS)

    Shul'ga, N. F.; Shulga, S. N.

    2017-06-01

    Quantum theory is proposed of high energy electrons scattering in ultrathin crystals. This theory is based upon a special representation of the scattering amplitude in the form of an integral over the surface surrounding the crystal, and on the spectral method of determination of the wave function. The comparison is performed of quantum and classical differential scattering cross-sections in the transitional range of crystal thicknesses, from those at which the channeling phenomenon is not developed up to those at which it is established. It is shown that in this thickness range the quantum scattering cross-section, unlike the classical one, contains sharp peaks corresponding to some specific scattering angles, that is connected with the diffraction of the incident plane wave onto the periodically distributed crystal atomic strings. It is shown that the value of the scattering cross-section in the peaks varies periodically with the change of the target thickness. We note that this must lead to a new interference effect in radiation that is connected with the rearrangement of incident wave packet in transitional area of crystal thicknesses.

  20. Toward improved photon-atom scattering predictions

    NASA Astrophysics Data System (ADS)

    Kissel, Lynn

    1995-05-01

    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 Delbrück components, processes beyond photoionization contribute. Subtracted cross sections for bound-bound atomic transitions and bound pair annihilation 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.

  1. Toward improved photon-atom scattering predictions

    NASA Astrophysics Data System (ADS)

    Kissel, Lynn

    1994-10-01

    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.

  2. Nonlinear (super)symmetries and amplitudes

    NASA Astrophysics Data System (ADS)

    Kallosh, Renata

    2017-03-01

    There is an increasing interest in nonlinear supersymmetries in cosmological model building. Independently, elegant expressions for the all-tree amplitudes in models with nonlinear symmetries, like D3 brane Dirac-Born-Infeld-Volkov-Akulov theory, were recently discovered. Using the generalized background field method we show how, in general, nonlinear symmetries of the action, bosonic and fermionic, constrain amplitudes beyond soft limits. The same identities control, for example, bosonic E 7(7) scalar sector symmetries as well as the fermionic goldstino symmetries.

  3. Coherent quantum states from classical oscillator amplitudes

    NASA Astrophysics Data System (ADS)

    Briggs, John S.; Eisfeld, Alexander

    2012-05-01

    In the first days of quantum mechanics Dirac pointed out an analogy between the time-dependent coefficients of an expansion of the Schrödinger equation and the classical position and momentum variables solving Hamilton's equations. Here it is shown that the analogy can be made an equivalence in that, in principle, systems of classical oscillators can be constructed whose position and momenta variables form time-dependent amplitudes which are identical to the complex quantum amplitudes of the coupled wave function of an N-level quantum system with real coupling matrix elements. Hence classical motion can reproduce quantum coherence.

  4. Constructing Chaotic Systems with Total Amplitude Control

    NASA Astrophysics Data System (ADS)

    Li, Chunbiao; Sprott, Julien Clinton; Yuan, Zeshi; Li, Hongtao

    A general method is introduced for controlling the amplitude of the variables in chaotic systems by modifying the degree of one or more of the terms in the governing equations. The method is applied to the Sprott B system as an example to show its flexibility and generality. The method may introduce infinite lines of equilibrium points, which influence the dynamics in the neighborhood of the equilibria and reorganize the basins of attraction, altering the multistability. However, the isolated equilibrium points of the original system and their stability are retained with their basic properties. Electrical circuit implementation shows the convenience of amplitude control, and the resulting oscillations agree well with results from simulation.

  5. Topographic quantitative EEG amplitude in recovered alcoholics.

    PubMed

    Pollock, V E; Schneider, L S; Zemansky, M F; Gleason, R P; Pawluczyk, S

    1992-05-01

    Topographic measures of electroencephalographic (EEG) amplitude were used to compare recovered alcoholics (n = 14) with sex- and age-matched control subjects. Delta, alpha, and beta activity did not distinguish the groups, but regional differences in theta distribution did. Recovered alcoholics showed more uniform distributions of theta amplitudes in bilateral anterior and posterior regions compared with controls. Because a minimum of 5 years had elapsed since the recovered alcoholic subjects fulfilled DSM-III-R criteria for alcohol abuse or dependence, it is unlikely these EEG theta differences reflect the effects of withdrawal.

  6. Dual amplitude pulse generator for radiation detectors

    DOEpatents

    Hoggan, Jerry M.; Kynaston, Ronnie L.; Johnson, Larry O.

    2001-01-01

    A pulsing circuit for producing an output signal having a high amplitude pulse and a low amplitude pulse may comprise a current source for providing a high current signal and a low current signal. A gate circuit connected to the current source includes a trigger signal input that is responsive to a first trigger signal and a second trigger signal. The first trigger signal causes the gate circuit to connect the high current signal to a pulse output terminal whereas the second trigger signal causes the gate circuit to connect the low current signal to the pulse output terminal.

  7. Beam normal spin asymmetry in elastic lepton-nucleon scattering

    SciTech Connect

    M. Gorchtein; P.A.M. Guichon; M. Vanderhaeghen

    2004-04-01

    We discuss the two-photon exchange contribution to observables which involve lepton helicity flip in elastic lepton-nucleon scattering. This contribution is accessed through the spin asymmetry for a lepton beam polarized normal to the scattering plane. We estimate this beam normal spin asymmetry at large momentum transfer using a parton model and we express the corresponding amplitude in terms of generalized parton distributions.

  8. Parity nonconserving spin rotation in weak neutron-proton scattering

    NASA Astrophysics Data System (ADS)

    Avishai, Y.

    1984-07-01

    Parity nonconservation in weak n-p scattering is studied at threshold wehre neutron spin rotation might occur. We use the DDH weak NN force and a separable form with S, P and D partial waves in the strong NN interaction. The contribution of various spin-isospin components to the weak NN scattering amplitude is evaluated and the spin rotation angle is found to be -2.35 × 10 -9 rad/cm. The sources of possible errors are indicated.

  9. Strong WW scattering chiral lagrangians, unitarity and resonances

    SciTech Connect

    Pelaez, J.R.

    1996-08-01

    Chiral lagrangians provide a model independent description of the strongly interacting symmetry breaking sector. In this work, first we review the LHC sensitivity to the chiral parameters (in the hardest case of non-resonant low-energy WW scattering). Later we show how to reproduce or predict the resonance spectrum by means of dispersion theory and the inverse amplitude method. We present a parameter space scan that covers many different strong WW scattering scenarios.

  10. Scattering of Second Sound Waves by Quantum Vorticity

    NASA Astrophysics Data System (ADS)

    Lund, Fernando; Steinberg, Victor

    1995-08-01

    A new method of detection and measurement of quantum vorticity by scattering second sound off quantized vortices in superfluid helium is suggested. Theoretical calculations of the relative amplitude of the scattered second sound waves from a single quantum vortex, a vortex lattice, and bulk vorticity are presented. The relevant estimates show that an experimental verification of the method is feasible. Moreover, it can even be used for the detection of a single quantum vortex.

  11. Photoacoustic Doppler flow measurement in optically scattering media

    NASA Astrophysics Data System (ADS)

    Fang, Hui; Maslov, Konstantin; Wang, Lihong V.

    2007-12-01

    We recently observed the photoacoustic Doppler effect from flowing small light-absorbing particles. Here, we apply the effect to measure blood-mimicking fluid flow in an optically scattering medium. The light scattering in the medium decreases the amplitude of the photoacoustic Doppler signal but does not affect either the magnitude or the directional discrimination of the photoacoustic Doppler shift. This technology may hold promise for a new Doppler method for measuring blood flow in microcirculation with high sensitivity.

  12. Speckle-learning-based object recognition through scattering media.

    PubMed

    Ando, Takamasa; Horisaki, Ryoichi; Tanida, Jun

    2015-12-28

    We experimentally demonstrated object recognition through scattering media based on direct machine learning of a number of speckle intensity images. In the experiments, speckle intensity images of amplitude or phase objects on a spatial light modulator between scattering plates were captured by a camera. We used the support vector machine for binary classification of the captured speckle intensity images of face and non-face data. The experimental results showed that speckles are sufficient for machine learning.

  13. Roy-Steiner equations for πN scattering

    NASA Astrophysics Data System (ADS)

    de Elvira, J. Ruiz; Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.

    2015-10-01

    In this talk, we briefly review our ongoing collaboration to precisely determine the low-energy πN scattering amplitude by means of Roy-Steiner equations. After giving a brief overview of this system of dispersive equations and their application to πN scattering, we proceed to solve for the lower partial waves of the s-channel (πN → πN) and the t-channel l( {π π to bar NN} right) sub-problems.

  14. Electromagnetic wave scattering from some vegetation samples

    NASA Technical Reports Server (NTRS)

    Karam, Mostafa A.; Fung, Adrian K.; Antar, Yahia M.

    1988-01-01

    For an incident plane wave, the field inside a thin scatterer (disk and needle) is estimated by the generalized Rayleigh-Gans (GRG) approximation. This leads to a scattering amplitude tensor equal to that obtained via the Rayleigh approximation (dipole term) with a modifying function. For a finite-length cylinder the inner field is estimated by the corresponding field for the same cylinder of infinite lenght. The effects of different approaches in estimating the field inside the scatterer on the backscattering cross section are illustrated numerically for a circular disk, a needle, and a finite-length cylinder as a function of the wave number and the incidence angle. Finally, the modeling predictions are compared with measurements.

  15. Effects of periodic forcing in chaotic scattering.

    PubMed

    Blesa, Fernando; Seoane, Jesús M; Barrio, Roberto; Sanjuán, Miguel A F

    2014-04-01

    The effects of a periodic forcing on chaotic scattering are relevant in certain situations of physical interest. We investigate the effects of the forcing amplitude and the external frequency in both the survival probability of the particles in the scattering region and the exit basins associated to phase space. We have found an exponential decay law for the survival probability of the particles in the scattering region. A resonant-like behavior is uncovered where the critical values of the frequencies ω≃1 and ω≃2 permit the particles to escape faster than for other different values. On the other hand, the computation of the exit basins in phase space reveals the existence of Wada basins depending of the frequency values. We provide some heuristic arguments that are in good agreement with the numerical results. Our results are expected to be relevant for physical phenomena such as the effect of companion galaxies, among others.

  16. Focusing of particles scattered by a surface

    NASA Astrophysics Data System (ADS)

    Babenko, P. Yu.; Zinov'ev, A. N.; Shergin, A. P.

    2015-06-01

    It has been shown by computer simulation that the coefficient of reflection of argon atoms scattered by crystalline aluminum and germanium targets at glancing angles of less than 4° is close to unity and the beam of scattered particles exhibits focusing (the angular distributions of particles are strongly compressed). Whereas beam focusing with respect to the azimuth is well known and has already been studied, sharp focusing in the surface-normal direction at small glancing angles has not been studied so far. This effect is confirmed by the experimental results. It is associated with multiple scattering of incident particles by the atomic chain. The simulation results allowed finding quite accurately the amplitude of thermal vibrations of surface atoms ((0.123 ± 0.007) Å for aluminum), which agrees well with the experiment.

  17. Multipole radiation in charged-particle scattering

    NASA Technical Reports Server (NTRS)

    Gould, Robert J.

    1990-01-01

    This paper formulates the general problem of photon emission in particle scattering using a classical and quantum mechanical approach. The connection between the classical short collision time (SCT) and Born results is examined for various special classifications of problems. In the dipole case the two formulations yield results that can be expressed in the same form and for arbitrary scattering potential. For quadrupole emission the SCT and Born results are the same only for a short-range potential, however. The quadrupole problem is more sensitive to details in the process because the calculation requires an expansion of the total amplitude for the process to lowest order in the photon wave number or momentum. The special case of photon emission associated with spin-flip transitions during scattering is considered for spin-1/2 particles. Like classical magnetic dipole radiation, there is no infrared divergence feature for this type of emission.

  18. True and false symmetries in the classification of optical scatterers

    NASA Astrophysics Data System (ADS)

    Crosta, Giovanni F.; Videen, Gorden

    2014-05-01

    A plane wave is scattered by a potential of bounded support. Translation, rotation and reflection of the potential, q0 induce transformations of the scattered wave. The latter can be represented by means of Born sequences, where q0 appears under the integral sign: non-local formulas are thus derived, the properties of which are discussed. Next, the symmetries induced by the 1st BORN approximation are addressed. Invariance of the squared modulus of the scattering amplitude holds for translation and reflection. The transformation Tɛ := 13 +Σ3ℓ=1ɛℓAℓ, with {ɛℓ;} real and {Aℓ} the generators of rotations in IR3, is investigated. Conditions on the {ɛ ℓ} are derived, by which the scattering amplitude coming from the first BORN approximation is invariant to Tɛ. As an application, these "false symmetries" are compared to those induced by limited angular resolution of a detector in light scattering experiments. Namely, scattering patterns are made available by the TAOS (Two-dimensional Angle-resolved Optical Scattering) method, which consists of detecting single airborne aerosol particles and collecting the intensity of the light they scatter from a pulsed, monochromatic laser beam. The optics and the detector properties determine the resolution at which a pattern is saved. The implications on the performance of TAOS pattern analysis are briefly discussed.

  19. Statistical modeling of in situ hiss amplitudes using ground measurements

    NASA Astrophysics Data System (ADS)

    Golden, D. I.; Spasojevic, M.; Li, W.; Nishimura, Y.

    2012-05-01

    Plasmaspheric hiss is a naturally occurring extremely low frequency electromagnetic emission that is often observed within the Earth's plasmasphere. Plasmaspheric hiss plays a major role in the scattering and loss of electrons from the Earth's radiation belts, thereby contributing to the maintenance of the slot region between the inner and outer electron belt. Traditionally, in situ satellite observations have been the measurement modality of choice for studies of plasmaspheric hiss due to their ability to directly measure the hiss source region. However, satellite studies are relatively short-lived and very few satellite receivers remain operational for an entire 11-year solar cycle. Ground stations, in contrast, may collect multiple solar cycles' worth of data during their lifetime, yet they cannot directly measure the hiss source region. This study aims to determine the extent to which measurements of hiss at midlatitude ground stations may be used to predict the mean amplitude of in situ measurements of plasmaspheric hiss. We use coincident measurements between Palmer Station, Antarctica (L = 2.4, 50°S invariant latitude) and the THEMIS spacecraft from June 2008 through May 2010, during solar minimum. Using an autoregressive multiple regression model, we show that in the local time sector from 00 < MLT < 12, when the ionosphere above Palmer Station is in darkness and hiss is observed at Palmer, the amplitude of plasmaspheric hiss observed by the THEMIS spacecraft is 1.4 times higher than when hiss is not observed at Palmer. In the same local time sector when the ground station is in daylight and hiss is observed, the THEMIS observed amplitudes are not significantly different from those when hiss is not observed on the ground. A stronger relationship is found in the local time sector from 12 < MLT < 24 where, when Palmer is in daylight and hiss is observed, THEMIS plasmaspheric hiss amplitudes are 2 times higher compared to when hiss is not observed at Palmer

  20. QCD amplitudes with 2 initial spacelike legs via generalised BCFW recursion

    NASA Astrophysics Data System (ADS)

    Kutak, Krzysztof; van Hameren, Andreas; Serino, Mirko

    2017-02-01

    We complete the generalisation of the BCFW recursion relation to the off-shell case, allowing for the computation of tree level scattering amplitudes for full High Energy Factorisation (HEF), i.e. with both incoming partons having a non-vanishing transverse momentum. We provide explicit results for color-ordered amplitudes with two off-shell legs in massless QCD up to 4 point, continuing the program begun in two previous papers. For the 4-fermion amplitudes, which are not BCFW-recursible, we perform a diagrammatic computation, so as to offer a complete set of expressions. We explicitly show and discuss some plots of the squared 2 → 2 matrix elements as functions of the differences in rapidity and azimuthal angle of the final state particles.

  1. Manifest Ultraviolet Behavior in the Three-Loop Four-Point Amplitude of N=8 Supergravity

    SciTech Connect

    Bern, Z.; Carrasco, J.J.M.; Dixon, L.J.; Johansson, H.; Roiban, R.; /Penn State U.

    2008-09-03

    Using the method of maximal cuts, we obtain a form of the three-loop four-point scattering amplitude of N = 8 supergravity in which all ultraviolet cancellations are made manifest. The Feynman loop integrals that appear have a graphical representation with only cubic vertices, and numerator factors that are quadratic in the loop momenta, rather than quartic as in the previous form. This quadratic behavior reflects cancellations beyond those required for finiteness, and matches the quadratic behavior of the three-loop four-point scattering amplitude in N = 4 super-Yang-Mills theory. By direct integration we confirm that no additional cancellations remain in the N = 8 supergravity amplitude, thus demonstrating that the critical dimension in which the first ultraviolet divergence occurs at three loops is D{sub c} = 6. We also give the values of the three-loop divergences in D = 7, 9, 11. In addition, we present the explicitly color-dressed three-loop four-point amplitude of N = 4 super-Yang-Mills theory.

  2. Resonances in Coupled πK-ηK Scattering from Quantum Chromodynamics

    DOE PAGES

    Dudek, Jozef J.; Edwards, Robert G.; Thomas, Christopher E.; ...

    2014-10-01

    Using first-principles calculation within Quantum Chromodynamics, we are able to reproduce the pattern of experimental strange resonances which appear as complex singularities within coupled πK, ηK scattering amplitudes. We make use of numerical computation within the lattice discretized approach to QCD, extracting the energy dependence of scattering amplitudes through their relation- ship to the discrete spectrum of the theory in a finite-volume, which we map out in unprecedented detail.

  3. Travel-Time and Amplitude Sensitivity Kernels

    DTIC Science & Technology

    2011-09-01

    amplitude sensitivity kernels shown in the lower panels concentrate about the corresponding eigenrays . Each 3D kernel exhibits a broad negative...in 2 and 3 dimensions have similar 11 shapes to corresponding travel-time sensitivity kernels (TSKs), centered about the respective eigenrays

  4. The CMU Baryon Amplitude Analysis Program

    SciTech Connect

    Matt Bellis

    2007-10-01

    The PWA group at Carnegie Mellon University has developed a comprehensive approach and analysis package for the purpose of extracting the amplitudes for photoproduced baryon resonances. The end goal is to identify any missing resonances that are predicted by the constituent quark model, but not definitively observed in experiments. The data comes from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab.

  5. Consonant confusions in amplitude-expanded speech.

    PubMed

    Freyman, R L; Nerbonne, G P

    1996-12-01

    The perceptual consequences of expanding the amplitude variations in speech were studied under conditions in which spectral information was obscured by signal correlated noise that had an envelope correlated with the speech envelope, but had a flat amplitude spectrum. The noise samples, created individually from 22 vowel-consonant-vowel nonsense words, were used as maskers of those words, with signal-to-noise ratios ranging from -15 to 0 dB. Amplitude expansion was by a factor of 3.0 in terms of decibels. In the first experiment, presentation level for speech peaks was 80 dB SPL. Consonant recognition performance for expanded speech by 50 listeners with normal hearing was as much as 30 percentage points poorer than for unexpanded speech and the types of errors were dramatically different, especially in the midrange of S-N ratios. In a second experiment presentation level was varied to determine whether reductions in consonant levels produced by expansion were responsible for the differences between conditions. Recognition performance for unexpanded speech at 40 dB SPL was nearly equivalent to that for expanded speech at 80 dB SPL. The error patterns obtained in these two conditions were different, suggesting that the differences between conditions in Experiment 1 were due largely to expanded amplitude envelopes rather than differences in audibility.

  6. Audio steganography by amplitude or phase modification

    NASA Astrophysics Data System (ADS)

    Gopalan, Kaliappan; Wenndt, Stanley J.; Adams, Scott F.; Haddad, Darren M.

    2003-06-01

    This paper presents the results of embedding short covert message utterances on a host, or cover, utterance by modifying the phase or amplitude of perceptually masked or significant regions of the host. In the first method, the absolute phase at selected, perceptually masked frequency indices was changed to fixed, covert data-dependent values. Embedded bits were retrieved at the receiver from the phase at the selected frequency indices. Tests on embedding a GSM-coded covert utterance on clean and noisy host utterances showed no noticeable difference in the stego compared to the hosts in speech quality or spectrogram. A bit error rate of 2 out of 2800 was observed for a clean host utterance while no error occurred for a noisy host. In the second method, the absolute phase of 10 or fewer perceptually significant points in the host was set in accordance with covert data. This resulted in a stego with successful data retrieval and a slightly noticeable degradation in speech quality. Modifying the amplitude of perceptually significant points caused perceptible differences in the stego even with small changes of amplitude made at five points per frame. Finally, the stego obtained by altering the amplitude at perceptually masked points showed barely noticeable differences and excellent data recovery.

  7. The CMU Baryon Amplitude Analysis Program

    NASA Astrophysics Data System (ADS)

    Bellis, Matt

    2007-05-01

    The PWA group at Carnegie Mellon University has developed a comprehensive approach and analysis package for the purpose of extracting the amplitudes for photoproduced baryon resonances. The end goal is to identify any missing resonances that are predicted by the constituent quark model, but not definitively observed in experiments. The data comes from the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab.

  8. Amplitude Frequency Response Measurement: A Simple Technique

    ERIC Educational Resources Information Center

    Satish, L.; Vora, S. C.

    2010-01-01

    A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

  9. Large Amplitude Patterns for Two Competing Species.

    DTIC Science & Technology

    1980-06-01

    scalar equation arising in population genetics . Mimura and Nishiura, [14], have obtained small amplitude spatial patterns for a system arising in...A nonlinear eigenvalue problem occuring in population genetics , preprint. [17] Peletier, L. A., Fife, P.: Nonlinear diffusion in population genetics . Arch

  10. Amplitude Frequency Response Measurement: A Simple Technique

    ERIC Educational Resources Information Center

    Satish, L.; Vora, S. C.

    2010-01-01

    A simple method is described to combine a modern function generator and a digital oscilloscope to configure a setup that can directly measure the amplitude frequency response of a system. This is achieved by synchronously triggering both instruments, with the function generator operated in the "Linear-Sweep" frequency mode, while the oscilloscope…

  11. Amplitude of Supersonic Diffuser Flow Pulsations

    NASA Technical Reports Server (NTRS)

    Sterbentz, William H.; Davids, Joseph

    1952-01-01

    A theoretical method for evaluating the stability characteristics and the amplitude and the frequency of pulsation of ram-jet engines without heat addition is presented herein. Experimental verification of the theoretical results are included where data were available. Theory and experiment show that the pulsation amplitude of a high mass-flow-ratio diffuser having no cone surface flow separation increases with decreasing mass flow. The theoretical trends for changes in amplitude, frequency, and mean-pressure recovery with changes in plenum-chamber volume were experimentally confirmed. For perforated convergent-divergent-type diffusers, a stability hysteresis loop was predicted on the pressure-recovery mass-flow-ratio curve. At a given mean mass-flow ratio, the higher.value of mean pressure recovery corresponded to oscillatory flow in the diffuser while the lower branch was stable. This hysteresis has been observed experimentally. The theory indicates that for a ram-jet engine of given diameter, the amplitude of pulsation of a supersonic diffuser is increased by decreasing the relative size of the plenum chamber with respect to the diffuser volume down to a critical value at which oscillations cease. In the region of these critical values, the stable mass-flow range of the diffuser may be increased either by decreasing the combustion chamber volume or by increasing the length of the diffuser.

  12. Optics as Scattering

    ERIC Educational Resources Information Center

    di Francia, Giuliano Toraldo

    1973-01-01

    The art of deriving information about an object from the radiation it scatters was once limited to visible light. Now due to new techniques, much of the modern physical science research utilizes radiation scattering. (DF)

  13. Backward pion-nucleon scattering

    SciTech Connect

    F. Huang; Sibirtsev, Alex; Haidenbauer, Johann; Meissner, Ulf-G.

    2010-02-01

    A global analysis of the world data on differential cross sections and polarization asymmetries of backward pion-nucleon scattering for invariant collision energies above 3 GeV is performed in a Regge model. Including the $N_\\alpha$, $N_\\gamma$, $\\Delta_\\delta$ and $\\Delta_\\beta$ trajectories, we reproduce both angular distributions and polarization data for small values of the Mandelstam variable $u$, in contrast to previous analyses. The model amplitude is used to obtain evidence for baryon resonances with mass below 3 GeV. Our analysis suggests a $G_{39}$ resonance with a mass of 2.83 GeV as member of the $\\Delta_{\\beta}$ trajectory from the corresponding Chew-Frautschi plot.

  14. Scattering in Quantum Lattice Gases

    NASA Astrophysics Data System (ADS)

    O'Hara, Andrew; Love, Peter

    2009-03-01

    Quantum Lattice Gas Automata (QLGA) are of interest for their use in simulating quantum mechanics on both classical and quantum computers. QLGAs are an extension of classical Lattice Gas Automata where the constraint of unitary evolution is added. In the late 1990s, David A. Meyer as well as Bruce Boghosian and Washington Taylor produced similar models of QLGAs. We start by presenting a unified version of these models and study them from the point of view of the physics of wave-packet scattering. We show that the Meyer and Boghosian-Taylor models are actually the same basic model with slightly different parameterizations and limits. We then implement these models computationally using the Python programming language and show that QLGAs are able to replicate the analytic results of quantum mechanics (for example reflected and transmitted amplitudes for step potentials and the Klein paradox).

  15. Aharonov-Bohm scattering in Chern-Simons theory of scalar particles

    SciTech Connect

    Boz, M.; Fainberg, V.; Pak, N.K.

    1996-03-15

    The S-matrix operator for relativistic theory of charged scalar particles interacting via Chern-Simon field is constructed and is shown to be formally the same as S-matrix in relativistic scalar quantum electrodynamics in which the Feynman diagrams with external photon lines are not considered and the propagators of the Chern-Simons particles are substituted in place of the ones for photons. All the one-loop Feynman diagrams for relativistic scattering amplitude of two charged particles are calculated. Due to the renormalizabilty of the theory only two diagrams have linear divergence, which are regularized. The nonrelativistic limit of the scattering amplitude is also finite, unlike the non-relativistic Chern-Simons scattering theory. It is found that for a certain value of the contact interaction, corresponding to the repulsive case, the scattering amplitude coincides with that of Aharonov-Bohm scattering, in the same approximation. 20 refs., 2 fig.

  16. Quantitative laryngeal electromyography: turns and amplitude analysis.

    PubMed

    Statham, Melissa McCarty; Rosen, Clark A; Nandedkar, Sanjeev D; Munin, Michael C

    2010-10-01

    Laryngeal electromyography (LEMG) is primarily a qualitative examination, with no standardized approach to interpretation. The objectives of our study were to establish quantitative norms for motor unit recruitment in controls and to compare with interference pattern analysis in patients with unilateral vocal fold paralysis (VFP). Retrospective case-control study We performed LEMG of the thyroarytenoid-lateral cricoarytenoid muscle complex (TA-LCA) in 21 controls and 16 patients with unilateral VFP. Our standardized protocol used a concentric needle electrode with subjects performing variable force TA-LCA contraction. To quantify the interference pattern density, we measured turns and mean amplitude per turn for ≥10 epochs (each 500 milliseconds). Logarithmic regression analysis between amplitude and turns was used to calculate slope and intercept. Standard deviation was calculated to further define the confidence interval, enabling generation of a linear-scale graphical "cloud" of activity containing ≥90% of data points for controls and patients. Median age of controls and patients was similar (50.7 vs. 48.5 years). In controls, TA-LCA amplitude with variable contraction ranged from 145-1112 μV, and regression analysis comparing mean amplitude per turn to root-mean-square amplitude demonstrated high correlation (R = 0.82). In controls performing variable contraction, median turns per second was significantly higher compared to patients (450 vs. 290, P = .002). We first present interference pattern analysis in the TA-LCA in healthy adults and patients with unilateral VFP. Our findings indicate that motor unit recruitment can be quantitatively measured within the TA-LCA. Additionally, patients with unilateral VFP had significantly reduced turns when compared with controls.

  17. Optical factors influencing the amplitude of accommodation.

    PubMed

    López-Alcón, Diego; Marín-Franch, Iván; Fernández-Sánchez, Vicente; López-Gil, Norberto

    2016-09-23

    The purpose of this work was to find plausible predictors among optical parameters that may explain the inter-individual differences in subjective amplitude of accommodation not explained by age. An exploratory multivariable regression analysis was carried out retrospectively on a dataset with 180 eyes from 97 subjects (ages ranged from 20 to 58years). Subjective amplitudes of accommodation were recorded with the use of a custom-made Badal system. A commercial aberrometer was used to obtain each eye's wavefront during the full range of accommodation. The plausible predictors under study were pupil diameter in the unaccommodated eye, its reduction with accommodation; fourth- and six-order Zernike spherical aberration, their reduction with accommodation, and subjective refraction. At a significance level of 0.05, only fourth- and sixth-order Zernike spherical aberration were found to be predictors of subjective amplitude of accommodation not explained by age, each explaining on their own less than 5% of the variance, and about 9% together. All other optical parameters explained less than 2%. Spherical aberration did not explain the greater variability for younger eyes than for older eyes. The remainder variability in amplitude of accommodation not explained by age or spherical aberration was about ±2.6D for 20year-old subjects, ±1.5D for 40year-old subjects, and about ±0.6D for 55year-old subjects. Optical factors do not seem to account for much of the inter-individual differences in subjective amplitude of accommodation. Most of the variability not explained by age must be due to anatomical differences and physiological, psychological, or other factors. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. Scattering from binary optics

    NASA Technical Reports Server (NTRS)

    Ricks, Douglas W.

    1993-01-01

    There are a number of sources of scattering in binary optics: etch depth errors, line edge errors, quantization errors, roughness, and the binary approximation to the ideal surface. These sources of scattering can be systematic (deterministic) or random. In this paper, scattering formulas for both systematic and random errors are derived using Fourier optics. These formulas can be used to explain the results of scattering measurements and computer simulations.

  19. A method to measure the distance among scatters and the scatters' diameter in artificial composite materials.

    PubMed

    Sun, Li; Ji, Aiming; Hu, Jialing; Zhu, Canyan; Zhang, Lijun; Yang, Jianfeng; Liu, Yongsong; Mao, Ling-Feng

    2016-04-01

    A new method to measure the distance among scatters, the density of scatters, and the scatters' diameter in artificial composite materials has been proposed. This method is based on detecting the reflection amplitude change (amp) of the echo signal reflected from scatters. Simulation results show that such a method is valid for the distance less than four times of the acoustic wavelength, because the coupling between the scatters can be neglected for the distance larger than four times of the acoustic wavelength. Therefore, this new measure method can be always valid by choosing appropriate frequency according to the scaling rule discussed in this paper. At the same time, it is found that the diameter of scatters is the half of the wavelength where the curve peak of the amp vs frequency occurs. It implies that such a new method can also be used to measure the diameter of scatters in solids and liquids, and even in PM2.5 pollution particles in air.

  20. Application of diffraction tomography theory to determine size and shape of spheroidal particles from light scattering

    NASA Astrophysics Data System (ADS)

    Ding, Chizhu; Yang, Kecheng; Li, Wei; Guo, Wenping; Zhang, Xiaohui; Xia, Min

    2014-10-01

    Discerning the geometry of spheroidal scatterers of micron order is an important topic in identifying marine microbes. Optical diffraction tomography theory indicates that under the first-order Born approximation for weak scattering, scattering amplitude in the far zone and scattering potential of the scatterer have a Fourier relationship. In this paper, we describe a method based on diffraction tomography theory and determine the size and the shape of spheroidal scatterers by reconstructing the distribution of scattering potential from angular resolved scattered field. As a demonstration of this method, the scattering from spheroidal particles with equal-volume-sphere radii of 0.5429, 1.00, and 2.00 μm and an aspect ratio that varies from 0.4 to 1.5 was modeled by using T-matrix theory and used as test data. Simulation results show that in the case of low contrast, size and shape determination can be achieved with sub-wavelength precision.

  1. Scattered P'P' waves observed at short distances

    USGS Publications Warehouse

    Earle, Paul S.; Rost, Sebastian; Shearer, Peter M.; Thomas, Christine

    2011-01-01

    We detect previously unreported 1 Hz scattered waves at epicentral distances between 30° and 50° and at times between 2300 and 2450 s after the earthquake origin. These waves likely result from off-azimuth scattering of PKPbc to PKPbc in the upper mantle and crust and provide a new tool for mapping variations in fine-scale (10 km) mantle heterogeneity. Array beams from the Large Aperture Seismic Array (LASA) clearly image the scattered energy gradually emerging from the noise and reaching its peak amplitude about 80 s later, and returning to the noise level after 150 s. Stacks of transverse versus radial slowness (ρt, ρr) show two peaks at about (2, -2) and (-2,-2) s/°, indicating the waves arrive along the major arc path (180° to 360°) and significantly off azimuth. We propose a mantle and surface PKPbc to PKPbc scattering mechanism for these observations because (1) it agrees with the initiation time and distinctive slowness signature of the scattered waves and (2) it follows a scattering path analogous to previously observed deep-mantle PK•KP scattering (Chang and Cleary, 1981). The observed upper-mantle scattered waves and PK•KP waves fit into a broader set of scattered waves that we call P′•d•P′, which can scatter from any depth, d, in the mantle.

  2. Robust discrimination of permanent scatterers using Cameron Decomposition

    NASA Astrophysics Data System (ADS)

    Kouroupis, G.; Elias, P.; Anastassopoulos, V.

    2014-10-01

    One of the main difficulties encountered in Differential Interferometry (DInSAR) applications is temporal and spatial decorrelation over time. Single pixels, called Permanent Scatterers (PS), overcome this difficulty since they are coherent over time and over wide look-angle variations. Permanent Scatterers identification using interferographic techniques is unfeasible since they require the use of many acquisitions. Samsonov and Tiampo have presented a technique that selects Permanent Scatterers by analyzing their Polarization Phase Difference (PPD). The PPD approach would work just fine looking for single bounce scatterers because they are invariant to any initial arbitrary rotation between the scatterer and the radar Line of Sight (LOS). We propose to replace the PPD technique with Cameron's Coherent Target Decomposition (CTD) because it is more accurate in finding the single and double bounce scatterers as it eliminates the initial orientation angle of the scatterer. Additionally, Cameron's CTD is capable of recognizing more scattering mechanisms which means that more pixels, depending on their amplitude and stability over time, can be classified as Permanent Scatterers. A sample scene of fully polarimetric SAR image depicting the San Francisco bay was employed for experimentation. Our results demonstrate the superiority of the Cameron's CTD approach compared to PPD's approach for the selection of pixels classified as Permanent Scatterers.

  3. Diffractive approach to elastic hadron scattering and the {rho} - parameter

    SciTech Connect

    Menon, M.J.; Pimentel, B.M.

    1993-02-01

    Making use of the ISR and SPS experimental data, the free parameters in a diffractive approach to elastic pp and {bar p}p scattering are parametrized as function of the center of mass energy. In this approach the ratio of the forward real and imaginary parts of the scattering amplitude ({rho}) is the only input variable at each energy. With this formalism we then analize the {bar p}p scattering at 1.8 TeV in detail, taking as input the recently reported value of {rho} and showing how the experimental uncertainty in this parameter affects the predictions. 24 refs., 4 figs., 2 tabs.

  4. Isospin odd @pK scattering length [rapid communication

    NASA Astrophysics Data System (ADS)

    Schweizer, J.

    2005-10-01

    We make use of the chiral two-loop representation of the πK scattering amplitude [J. Bijnens, P. Dhonte, P. Talavera, JHEP 0405 (2004) 036] to investigate the isospin odd scattering length at next-to-next-to-leading order in the SU (3) expansion. This scattering length is protected against contributions of ms in the chiral expansion, in the sense that the corrections to the current algebra result are of order Mπ2. In view of the planned lifetime measurement on πK atoms at CERN it is important to understand the size of these corrections.

  5. Characteristics of early, long recovery VLF scattering events

    NASA Astrophysics Data System (ADS)

    Kotovsky, D. A.; Moore, R. C.

    2013-12-01

    Experimental observations of early, long recovery VLF events (LOREs) and their causative radio atmospherics (sferics) are analyzed -- 49 events are presented, including over-sea and over-land events. We demonstrate that the phasor addition of ambient and scattered VLF fields may lead to amplitude and phase changes that have different perturbation characteristics (onset duration, recovery time, etc.), and conclude that VLF perturbations are best categorized by their associated normalized scattered field phasor. Additionally, we present observations which demonstrate that normalized scattered field characteristics can depend upon the receiving antenna orientation.

  6. Electromagnetic model based SAR ATR through attributed scatterers

    NASA Astrophysics Data System (ADS)

    Ma, Conghui; Wen, Gongjian; Gao, Feng; Huang, Xiaohong; Yang, Xiaoliang

    2016-10-01

    Electromagnetic model (em-model) provides a concise and physically relevant description of target through representative scatterers. In a forward built em-model, detailed information about each scatterer's position, scattering amplitude along with its provenance can be predicted. This makes em-model a good candidate for use in synthetic aperture radar (SAR) automatic target recognition (ATR). In this paper, we introduce scatterers' provenance as attributed information into target recognition, and an attributed em-model based target recognition method is proposed. Firstly, according to the purpose of ATR, each scatterer in em-model is endowed with an importance factor based on its provenance. Secondly, a detection is implemented to decide whether the em-model predicted scatterer has a corresponding scatterer in measured data. If the scatterer exist in measured target, evaluate how similar the scatterer pair resembled with each other. Next, similarities of all the scatterer pairs are synthesized as a whole match score between em-model and SAR data. In the synthesis, the importance factor servers as a weighting factor that scatterer with more attention will be more discriminative for recognition. In the end, target in measured SAR data is recognized as the model type or not based on the match score. The novelty of this method comes from taking into account of the provenance information of scatterers as attributed information and endowing the scatterers with different important factors according to their importance in recognition. This makes the attributed scatterer based recognition method pertinent to the purpose of ATR. Experiments on simulated Tank SAR data that produced by a high frequency electromagnetic simulation software verified the effectiveness of this method.

  7. Tip-surface forces, amplitude, and energy dissipation in amplitude-modulation (tapping mode) force microscopy

    NASA Astrophysics Data System (ADS)

    Paulo, Álvaro San; García, Ricardo

    2001-11-01

    Amplitude-modulation (tapping mode) atomic force microscopy is a technique for high resolution imaging of a wide variety of surfaces in air and liquid environments. Here by using the virial theorem and energy conservation principles we have derived analytical relationships between the oscillation amplitude, phase shift, and average tip-surface forces. We find that the average value of the interaction force and oscillation and the average power dissipated by the tip-surface interaction are the quantities that control the amplitude reduction. The agreement obtained between analytical and numerical results supports the analytical method.

  8. High-amplitude, ultrashort strain solitons in solids

    NASA Astrophysics Data System (ADS)

    Muskens, O. L.

    2004-03-01

    In recent years, pressure pulses of very short (picosecond) time duration have found wide application as a diagnostic tool in the semiconductor industry and in fundamental condensed matter research. Next to their application in the studies of nanometer-sized structures, propagation of these short acoustic pulses over millimeter distances at low temperatures has revealed a new field of picosecond acoustics. It has been shown that, for very short strain pulses, phonon dispersion destroys the internal structure of the coherent wavepacket by pulling apart its different frequency components. However, when strain amplitudes are sufficiently increased, a nonlinear pulse-steepening mechanism emerges, that leads to the formation of shock waves. The combined action of the nonlinear and dispersive effects then results in the formation of stable, highly localized solitary waves. In this thesis, we study the development of picosecond pressure pulses into trains of ultrashort acoustic solitons in a bulk crystal. The high-amplitude, bipolar strain wavepackets are generated by femtosecond optical excitation of a thin chromium film evaporated onto the crystal, using high-power optical pulses from an amplified Ti:sapphire laser. Propagation over millimeter distances at low temperatures is studied by means of two complementary experimental methods. First, the development of low-frequency, gigahertz strain components is monitored using Brillouin light-scattering. By monitoring the scattered intensity against traveled distance of the packets, we demonstrate the breakup of the initial single-cycle pulse into an ultrashort acoustic soliton train, reaching transient pressures up to tens of kilobars and soliton widths less than 0.5 picoseconds, corresponding to only several nanometers in the crystal. Further, we show that the ultrashort strain solitons interact coherently with local electronic two-level systems at terahertz frequency, in optically excited ruby. The strain

  9. Two-Photon Exchange in Elastic Electron-Proton Scattering: A QCD Factorization Approach

    SciTech Connect

    Kivel, Nikolai; Vanderhaeghen, Marc

    2009-08-28

    We estimate the two-photon exchange contribution to elastic electron-proton scattering at large momentum transfer Q{sup 2}. It is shown that the leading two-photon exchange amplitude behaves as 1/Q{sup 4}, and can be expressed in a model independent way in terms of the leading twist nucleon distribution amplitudes. Using several models for the nucleon distribution amplitudes, we provide estimates for existing data and for ongoing experiments.

  10. Multiple scattering technique lidar

    NASA Technical Reports Server (NTRS)

    Bissonnette, Luc R.

    1992-01-01

    The Bernouilli-Ricatti equation is based on the single scattering description of the lidar backscatter return. In practice, especially in low visibility conditions, the effects of multiple scattering can be significant. Instead of considering these multiple scattering effects as a nuisance, we propose here to use them to help resolve the problems of having to assume a backscatter-to-extinction relation and specifying a boundary value for a position far remote from the lidar station. To this end, we have built a four-field-of-view lidar receiver to measure the multiple scattering contributions. The system has been described in a number of publications that also discuss preliminary results illustrating the multiple scattering effects for various environmental conditions. Reported here are recent advances made in the development of a method of inverting the multiple scattering data for the determination of the aerosol scattering coefficient.

  11. Stability of amplitude chimeras in oscillator networks

    NASA Astrophysics Data System (ADS)

    Tumash, L.; Zakharova, A.; Lehnert, J.; Just, W.; Schöll, E.

    2017-01-01

    We show that amplitude chimeras in ring networks of Stuart-Landau oscillators with symmetry-breaking nonlocal coupling represent saddle-states in the underlying phase space of the network. Chimera states are composed of coexisting spatial domains of coherent and of incoherent oscillations. We calculate the Floquet exponents and the corresponding eigenvectors in dependence upon the coupling strength and range, and discuss the implications for the phase-space structure. The existence of at least one positive real part of the Floquet exponents indicates an unstable manifold in phase space, which explains the nature of these states as long-living transients. Additionally, we find a Stuart-Landau network of minimum size N = 12 exhibiting amplitude chimeras.

  12. Multilayered models for electromagnetic reflection amplitudes

    NASA Technical Reports Server (NTRS)

    Linlor, W. I.

    1976-01-01

    The remote sensing of snowpack characteristics with surface installations or with an airborne system could have important applications in water resource management and flood prediction. To derive some insight into such applications, the electromagnetic response of multilayer snow models is analyzed. Normally incident plane waves are assumed at frequencies ranging from 10 to the 6th power to 10 to the 10th power Hz, and amplitude reflection coefficients are calculated for models having various snow-layer combinations, including ice sheets. Layers are defined by a thickness, permittivity, and conductivity; the electrical parameters are constant or prescribed functions of frequency. To illustrate the effect of various layering combinations, results are given in the form of curves of amplitude reflection coefficients, versus frequency for a variety of models. Under simplifying assumptions, the snow thickness and effective dielectric constant can be estimated from the reflection coefficient variations as a function of frequency.

  13. Constructing QCD one-loop amplitudes

    SciTech Connect

    Forde, Darren; /SLAC /UCLA

    2008-02-22

    In the context of constructing one-loop amplitudes using a unitarity bootstrap approach we discuss a general systematic procedure for obtaining the coefficients of the scalar bubble and triangle integral functions of one-loop amplitudes. Coefficients are extracted after examining the behavior of the cut integrand as the unconstrained parameters of a specifically chosen parameterization of the cut loop momentum approach infinity. Measurements of new physics at the forthcoming experimental program at CERN's Large Hadron Collider (LHC) will require a precise understanding of processes at next-to-leading order (NLO). This places increased demands for the computation of new one-loop amplitudes. This in turn has spurred recent developments towards improved calculational techniques. Direct calculations using Feynman diagrams are in general inefficient. Developments of more efficient techniques have usually centered around unitarity techniques [1], where tree amplitudes are effectively 'glued' together to form loops. The most straightforward application of this method, in which the cut loop momentum is in D = 4, allows for the computation of 'cut-constructible' terms only, i.e. (poly)logarithmic containing terms and any related constants. QCD amplitudes contain, in addition to such terms, rational pieces which cannot be derived using such cuts. These 'missing' rational parts can be extracted using cut loop momenta in D = 4-2 {var_epsilon}. The greater difficulty of such calculations has restricted the application of this approach, although recent developments [3, 4] have provided new promise for this technique. Recently the application of on-shell recursion relations [5] to obtaining the 'missing' rational parts of one-loop processes [6] has provided an alternative very promising solution to this problem. In combination with unitarity methods an 'on-shell bootstrap' approach provides an efficient technique for computing complete one-loop QCD amplitudes [7]. Additionally

  14. Amplitudes of MHD Waves in Sunspots

    NASA Astrophysics Data System (ADS)

    Norton, Aimee Ann; Cally, Paul; Baldner, Charles; Kleint, Lucia; Tarbell, Theodore D.; De Pontieu, Bart; Scherrer, Philip H.; Rajaguru, Paul

    2016-05-01

    The conversion of p-modes into MHD waves by strong magnetic fields occurs mainly in the sub-photospheric layers. The photospheric signatures of MHD waves are weak due to low amplitudes at the beta=1 equipartion level where mode-conversion occurs. We report on small amplitude oscillations observed in the photosphere with Hinode SOT/SP in which we analyze time series for sunspots ARs 12186 (11.10.2014) and 12434 (17.10.2015). No significant magnetic field oscillations are recovered in the umbra or penumbra in the ME inversion. However, periodicities in the inclination angle are found at the umbral/penumbral boundary with 5 minute periods. Upward propagating waves are indicated in the intensity signals correlated between HMI and AIA at different heights. We compare SP results with the oscillations observed in HMI data. Simultaneous IRIS data shows transition region brightening above the umbral core.

  15. Is DAMAs modulation amplitude changing with time?

    NASA Astrophysics Data System (ADS)

    Kelso, Chris

    2016-06-01

    If dark matter is composed of weakly interacting particles, Earth's orbital motion induces a small annual variation in the rate at which these particles interact in a terrestrial detector. The DAMA collaboration has identified at a 9.3σ confidence level (CL) such an annual modulation in their event rate over two detector iterations, DAMA/NaI and DAMA/LIBRA, each with about 7 years of observations. We examine the nature of this modulation signal and find the modulation amplitude for the two detectors is inconsistent at the 3σ CL over 2-6 keVee. Such a time-dependence in the modulation amplitude is unexpected behavior for a dark matter signal, at least for dark matter halo morphologies consistent with the DAMA signal. We also find unusual behavior over the 5-6 keVee energy range that might indicate problems with the data.

  16. Photon Counting Chirped Amplitude Modulation Ladar

    DTIC Science & Technology

    2008-03-01

    135 S. Taylor Ave., Room 103, Louisville, CO 80027-3025 14. ABSTRACT This work developed a method using Geiger - mode avalanche photodiode (GM-APD...effort to develop a method using Geiger - mode avalanche photodiode (GM-APD) photon counting detectors in the U.S. Army Research Laboratory’s chirped...architecture are discussed. 15. SUBJECT TERMS laser radar, ladar, avalanche photo-detectors, Geiger mode detectors, chirped amplitude modulation

  17. Chiral extrapolation of SU(3) amplitudes

    SciTech Connect

    Ecker, Gerhard

    2011-05-23

    Approximations of chiral SU(3) amplitudes at NNLO are proposed to facilitate the extrapolation of lattice data to the physical meson masses. Inclusion of NNLO terms is essential for investigating convergence properties of chiral SU(3) and for determining low-energy constants in a controllable fashion. The approximations are tested with recent lattice data for the ratio of decay constants F{sub K}/F{sub {pi}}.

  18. Automatic generation of tree level helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Stelzer, T.; Long, W. F.

    1994-11-01

    The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.

  19. Automatic generation of tree level helicity amplitudes

    NASA Astrophysics Data System (ADS)

    Stelzer, T.; Long, W. F.

    1994-07-01

    The program MadGraph is presented which automatically generates postscript Feynman diagrams and Fortran code to calculate arbitrary tree level helicity amplitudes by calling HELAS[1] subroutines. The program is written in Fortran and is available in Unix and VMS versions. MadGraph currently includes standard model interactions of QCD and QFD, but is easily modified to include additional models such as supersymmetry.

  20. Large Amplitude Oscillatory Shear near Jamming

    NASA Astrophysics Data System (ADS)

    Tighe, Brian; Dagois-Bohy, Simon; Somfai, Ellak; van Hecke, Martin

    2014-11-01

    Jammed solids such as foams and emulsions can be driven with oscillatory shear at finite strain amplitude and frequency. On a macro scale, this induces nonlinearities such as strain softening and shear thinning. On the micro scale one observes the onset of irreversibility, caging, and long-time diffusion. Using simulations of soft viscous spheres, we systematically vary the distance to the jamming transition. We correlate crossovers in the microscopic and macroscopic response, and construct scaling arguments to explain their relationships.

  1. Amplitude calibration experiment for SIR-B

    NASA Technical Reports Server (NTRS)

    Held, D. N.; Ulaby, F. T.

    1984-01-01

    The objectives, approach, and expected results of the amplitude calibration experiment for the Shuttle Imaging Radar-B (SIR-B) are outlined. Specific objectives include: (1) the determination of the repeatability (stability) of the SIR-B; (2) the absolute and relative calibration of the system; and (3) the ground truth verification of the calibration accuracy using measurements made by a ground spectrometer and an airborne synthetic aperture radar.

  2. Understanding the amplitudes of noise correlation measurements

    USGS Publications Warehouse

    Tsai, Victor C.

    2011-01-01

    Cross correlation of ambient seismic noise is known to result in time series from which station-station travel-time measurements can be made. Part of the reason that these cross-correlation travel-time measurements are reliable is that there exists a theoretical framework that quantifies how these travel times depend on the features of the ambient noise. However, corresponding theoretical results do not currently exist to describe how the amplitudes of the cross correlation depend on such features. For example, currently it is not possible to take a given distribution of noise sources and calculate the cross correlation amplitudes one would expect from such a distribution. Here, we provide a ray-theoretical framework for calculating cross correlations. This framework differs from previous work in that it explicitly accounts for attenuation as well as the spatial distribution of sources and therefore can address the issue of quantifying amplitudes in noise correlation measurements. After introducing the general framework, we apply it to two specific problems. First, we show that we can quantify the amplitudes of coherency measurements, and find that the decay of coherency with station-station spacing depends crucially on the distribution of noise sources. We suggest that researchers interested in performing attenuation measurements from noise coherency should first determine how the dominant sources of noise are distributed. Second, we show that we can quantify the signal-to-noise ratio of noise correlations more precisely than previous work, and that these signal-to-noise ratios can be estimated for given situations prior to the deployment of seismometers. It is expected that there are applications of the theoretical framework beyond the two specific cases considered, but these applications await future work.

  3. High energy parton-parton elastic scattering in QCD

    SciTech Connect

    Tang, W.K.

    1993-08-01

    We show that the high energy limit of quark-quark, or gluon-gluon, elastic scattering is calculable in terms of the BFKL pomeron when {minus}t {much_gt} {Lambda}{sub QCD}{sup 2}. Surprisingly, this on-shell amplitudes does not have infrared divergences in the high energy limit.

  4. Amplitude Scintillation due to Atmospheric Turbulence for the Deep Space Network Ka-Band Downlink

    NASA Technical Reports Server (NTRS)

    Ho, C.; Wheelon, A.

    2004-01-01

    Fast amplitude variations due to atmospheric scintillation are the main concerns for the Deep Space Network (DSN) Ka-band downlink under clear weather conditions. A theoretical study of the amplitude scintillation variances for a finite aperture antenna is presented. Amplitude variances for weak scattering scenarios are examined using turbulence theory to describe atmospheric irregularities. We first apply the Kolmogorov turbulent spectrum to a point receiver for three different turbulent profile models, especially for an exponential model varying with altitude. These analytic solutions then are extended to a receiver with a finite aperture antenna for the three profile models. Smoothing effects of antenna aperture are expressed by gain factors. A group of scaling factor relations is derived to show the dependences of amplitude variances on signal wavelength, antenna size, and elevation angle. Finally, we use these analytic solutions to estimate the scintillation intensity for a DSN Goldstone 34-m receiving station. We find that the (rms) amplitude fluctuation is 0.13 dB at 20-deg elevation angle for an exponential model, while the fluctuation is 0.05 dB at 90 deg. These results will aid us in telecommunication system design and signal-fading prediction. They also provide a theoretical basis for further comparison with other measurements at Ka-band.

  5. New strings for old Veneziano amplitudes. II. Group-theoretic treatment

    NASA Astrophysics Data System (ADS)

    Kholodenko, A. L.

    2006-09-01

    In this part of our four parts work we use theory of polynomial invariants of finite pseudo-reflection groups in order to reconstruct both the Veneziano and Veneziano-like (tachyon-free) amplitudes and the generating function reproducing these amplitudes. We demonstrate that such generating function and amplitudes associated with it can be recovered with help of finite dimensional exactly solvableN=2 supersymmetric quantum mechanical model known earlier from works of Witten, Stone and others. Using the Lefschetz isomorphism theorem we replace traditional supersymmetric calculations by the group-theoretic thus solving the Veneziano model exactly using standard methods of representation theory. Mathematical correctness of our arguments relies on important theorems by Shepard and Todd, Serre and Solomon proven respectively in the early 50s and 60s and documented in the monograph by Bourbaki. Based on these theorems, we explain why the developed formalism leaves all known results of conformal field theories unchanged. We also explain why these theorems impose stringent requirements connecting analytical properties of scattering amplitudes with symmetries of space-time in which such amplitudes act.

  6. Higgs amplitude mode in a two-dimensional quantum antiferromagnet near the quantum critical point

    NASA Astrophysics Data System (ADS)

    Hong, Tao; Matsumoto, Masashige; Qiu, Yiming; Chen, Wangchun; Gentile, Thomas R.; Watson, Shannon; Awwadi, Firas F.; Turnbull, Mark M.; Dissanayake, Sachith E.; Agrawal, Harish; Toft-Petersen, Rasmus; Klemke, Bastian; Coester, Kris; Schmidt, Kai P.; Tennant, David A.

    2017-07-01

    Spontaneous symmetry-breaking quantum phase transitions play an essential role in condensed-matter physics. The collective excitations in the broken-symmetry phase near the quantum critical point can be characterized by fluctuations of phase and amplitude of the order parameter. The phase oscillations correspond to the massless Nambu-Goldstone modes whereas the massive amplitude mode, analogous to the Higgs boson in particle physics, is prone to decay into a pair of low-energy Nambu-Goldstone modes in low dimensions. Especially, observation of a Higgs amplitude mode in two dimensions is an outstanding experimental challenge. Here, using inelastic neutron scattering and applying the bond-operator theory, we directly and unambiguously identify the Higgs amplitude mode in a two-dimensional S = 1/2 quantum antiferromagnet C9H18N2CuBr4 near a quantum critical point in two dimensions. Owing to an anisotropic energy gap, it kinematically prevents such decay and the Higgs amplitude mode acquires an infinite lifetime.

  7. General solution of the scattering equations

    NASA Astrophysics Data System (ADS)

    Dolan, Louise; Goddard, Peter

    2016-10-01

    The scattering equations, originally introduced by Fairlie and Roberts in 1972 and more recently shown by Cachazo, He and Yuan to provide a kinematic basis for describing tree amplitudes for massless particles in arbitrary space-time dimension, have been reformulated in polynomial form. The scattering equations for N particles are equivalent to N - 3 polynomial equations h m = 0, 1 ≤ m ≤ N - 3, in N - 3 variables, where h m has degree m and is linear in the individual variables. Facilitated by this linearity, elimination theory is used to construct a single variable polynomial equation, Δ N = 0, of degree ( N - 3)! determining the solutions. Δ N is the sparse resultant of the system of polynomial scattering equations and it can be identified as the hyperdeterminant of a multidimensional matrix of border format within the terminology of Gel'fand, Kapranov and Zelevinsky. Macaulay's Unmixedness Theorem is used to show that the polynomials of the scattering equations constitute a regular sequence, enabling the Hilbert series of the variety determined by the scattering equations to be calculated, independently showing that they have ( N - 3)! solutions.

  8. Scattering theory without large-distance asymptotics

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Li, Wen-Du; Dai, Wu-Sheng

    2014-06-01

    In conventional scattering theory, to obtain an explicit result, one imposes a precondition that the distance between target and observer is infinite. With the help of this precondition, one can asymptotically replace the Hankel function and the Bessel function with the sine functions so that one can achieve an explicit result. Nevertheless, after such a treatment, the information of the distance between target and observer is inevitably lost. In this paper, we show that such a precondition is not necessary: without losing any information of distance, one can still obtain an explicit result of a scattering rigorously. In other words, we give an rigorous explicit scattering result which contains the information of distance between target and observer. We show that at a finite distance, a modification factor — the Bessel polynomial — appears in the scattering amplitude, and, consequently, the cross section depends on the distance, the outgoing wave-front surface is no longer a sphere, and, besides the phase shift, there is an additional phase (the argument of the Bessel polynomial) appears in the scattering wave function.

  9. [Amplitude modulation in sound signals by mammals].

    PubMed

    Nikol'skiĭ, A A

    2012-01-01

    Periodic variations in amplitude of a signal, or amplitude modulation (AM), affect the structure of communicative messages spectrum. Within the spectrum of AM-signals, side frequencies are formed both above and below the carrier frequency that is subjected to modulation. In case of harmonic signal structure they are presented near fundamental frequency as well as near harmonics. Thus, AM may by viewed as a relatively simple mechanism for controlling the spectrum of messages transmitted by mammals. Examples of AM affecting the spectrum structure of functionally different sound signals are discussed as applied to representatives of four orders of mammals: rodents (Reodentia), duplicidentates (Lagomorpha), pinnipeds (Pinnipedia), and paridigitates (Artiodactia). For the first time, the classification of AM in animals' sound signals is given. Five forms of AM are picked out in sound signals by mammals: absence of AM, continuous AM, fragmented, heterogeneous, and multilevel one. AM presence/absence is related neither with belonging to any specific order nor with some particular function of a signal. Similar forms of AM can occur in different orders of mammals in parallel. On the contrary, different forms of AM can be detected in signals meant for similar functions. The assumption is made about AM-signals facilitating information encoding and jamprotection of messages transmitted by mammals. Preliminry analysis indicates that hard-driving amplitude modulation is incompatible with hard-driving frequency modulation.

  10. Prominence Seismology Using Small Amplitude Oscillations

    NASA Astrophysics Data System (ADS)

    Oliver, Ramón

    2009-12-01

    Quiescent prominences can be modeled as thin slabs of cold, dense plasma embedded in the much hotter and rarer solar corona. Although their global shape is rather irregular, they are often characterised by an internal structure consisting of a large number of thin, parallel threads piled together. Prominences often display periodic disturbances mostly observed in the Doppler displacement of spectral lines and with an amplitude typically of the order of or smaller than 2-3 km s-1, a value which seems to be much smaller than the characteristic speeds of the prominence plasma (namely the Alfvén and sound velocities). Two particular features of these small amplitude prominence oscillations are that they seem to damp in a few periods and that they seem not to affect the whole prominence structure. In addition, in high spatial resolution observations, in which threads can be discerned, small amplitude oscillations appear to be clearly associated to these fine structure constituents. Prominence seismology tries to bring together the results from these observations (e.g. periods, wavelengths, damping times) and their theoretical modeling (by means of the magnetohydrodynamic theory) to gain insight into physical properties of prominences that cannot be derived from direct observation. In this paper we discuss works that have not been described in previous reviews, namely the first seismological application to solar prominences and theoretical advances on the attenuation of prominence oscillations.

  11. Continuous phase and amplitude holographic elements

    NASA Technical Reports Server (NTRS)

    Maker, Paul D. (Inventor); Muller, Richard E. (Inventor)

    1995-01-01

    A method for producing a phase hologram using e-beam lithography provides n-ary levels of phase and amplitude by first producing an amplitude hologram on a transparent substrate by e-beam exposure of a resist over a film of metal by exposing n is less than or equal to m x m spots of an array of spots for each pixel, where the spots are randomly selected in proportion to the amplitude assigned to each pixel, and then after developing and etching the metal film producing a phase hologram by e-beam lithography using a low contrast resist, such as PMMA, and n-ary levels of low doses less than approximately 200 micro-C/sq cm and preferably in the range of 20-200 micro-C/sq cm, and aggressive development using pure acetone for an empirically determined time (about 6 s) controlled to within 1/10 s to produce partial development of each pixel in proportion to the n-ary level of dose assigned to it.

  12. Zeroing in on Supersymmetric Radiation Amplitude Zeros

    SciTech Connect

    Hewett, JoAnne L.; Ismail, Ahmed; Rizzo, Thomas G.; /SLAC

    2012-02-15

    Radiation amplitude zeros have long been used to test the Standard Model. Here, we consider the supersymmetric radiation amplitude zero in chargino-neutralino associated production, which can be observed at the luminosity upgraded LHC. Such an amplitude zero only occurs if the neutralino has a large wino fraction and hence this observable can be used to determine the neutralino eigenstate content. We find that this observable can be measured by comparing the p{sub T} spectrum of the softest lepton in the trilepton {tilde {chi}}{sub 1}{sup {+-}} {tilde {chi}}{sub 2}{sup 0} decay channel to that of a control process such as {tilde {chi}}{sub 1}{sup +} {tilde {chi}}{sub 1}{sup -} or {tilde {chi}}{sub 2}{sup 0} {tilde {chi}}{sub 2}{sup 0}. We test this technique on a previously generated model sample of the 19 dimensional parameter space of the phenomenological MSSM, and find that it is effective in determining the wino content of the neutralino.

  13. Resonant scattering of surface plasmon polaritons by dressed quantum dots

    SciTech Connect

    Huang, Danhong; Cardimona, Dave; Easter, Michelle; Gumbs, Godfrey; Maradudin, A. A.; Lin, Shawn-Yu; Zhang, Xiang

    2014-06-23

    The resonant scattering of surface plasmon-polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In contrast to non-resonant scattering by a localized dielectric surface defect, a strong resonant peak in the spectrum of the scattered field is predicted that is accompanied by two side valleys. The peak height depends nonlinearly on the amplitude of SPP waves, reflecting the feedback dynamics from a photon-dressed electron-hole plasma inside the quantum dots. This unique behavior in the scattered field peak strength is correlated with the occurrence of a resonant dip in the absorption spectrum of SPP waves due to the interband photon-dressing effect. Our result on the scattering of SPP waves may be experimentally observable and applied to spatially selective illumination and imaging of individual molecules.

  14. Siegert pseudostate formulation of scattering theory: General three-dimensional case

    NASA Astrophysics Data System (ADS)

    Krainov, Lev O.; Batishchev, Pavel A.; Tolstikhin, Oleg I.

    2016-04-01

    This paper generalizes the Siegert pseudostate (SPS) formulation of scattering theory to arbitrary finite-range potentials without any symmetry in the three-dimensional (3D) case. The orthogonality and completeness properties of 3D SPSs are established. The SPS expansions for scattering states, outgoing-wave Green's function, scattering matrix, and scattering amplitude, that is, all major objects of scattering theory, are derived. The theory is illustrated by calculations for several model potentials. The results enable one to apply 3D SPSs as a purely discrete basis capable of representing both discrete and continuous spectra in solving various stationary and time-dependent quantum-mechanical problems.

  15. Nonlinear Generation of Electromagnetic Waves through Induced Scattering by Thermal Plasma

    PubMed Central

    Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.

    2015-01-01

    We demonstrate the conversion of electrostatic pump waves into electromagnetic waves through nonlinear induced scattering by thermal particles in a laboratory plasma. Electrostatic waves in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10−6 times the background magnetic field, wave power is scattered below the pump frequency with wave normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered wave has a perpendicular wavelength that is an order of magnitude larger than the pump wave and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered wave normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment. PMID:26647962

  16. Nonlinear Generation of Electromagnetic Waves through Induced Scattering by Thermal Plasma

    NASA Astrophysics Data System (ADS)

    Tejero, E. M.; Crabtree, C.; Blackwell, D. D.; Amatucci, W. E.; Mithaiwala, M.; Ganguli, G.; Rudakov, L.

    2015-12-01

    We demonstrate the conversion of electrostatic pump waves into electromagnetic waves through nonlinear induced scattering by thermal particles in a laboratory plasma. Electrostatic waves in the whistler branch are launched that propagate near the resonance cone. When the amplitude exceeds a threshold ~5 × 10-6 times the background magnetic field, wave power is scattered below the pump frequency with wave normal angles (~59°), where the scattered wavelength reaches the limits of the plasma column. The scattered wave has a perpendicular wavelength that is an order of magnitude larger than the pump wave and longer than the electron skin depth. The amplitude threshold, scattered frequency spectrum, and scattered wave normal angles are in good agreement with theory. The results may affect the analysis and interpretation of space observations and lead to a comprehensive understanding of the nature of the Earth’s plasma environment.

  17. TOPICAL REVIEW: A first course on twistors, integrability and gluon scattering amplitudes

    NASA Astrophysics Data System (ADS)

    Wolf, Martin

    2010-10-01

    These notes accompany an introductory lecture course on the twistor approach to supersymmetric gauge theories aimed at early stage PhD students. It was held by the author at the University of Cambridge during the Michaelmas term in 2009. The lectures assume a working knowledge of differential geometry and quantum field theory. No prior knowledge of twistor theory is required.

  18. Interference by rain scatter

    NASA Technical Reports Server (NTRS)

    Crane, Robert K.

    1988-01-01

    The data from Japan and the U.S. (the Virginia Precipitation Scatter Experiment) show excellent agreement between the two-component rain scatter model predictions and bistatic scatter measurements. In employing the model, all the scattering geometries should be classified as backscattering as defined by Crane (1974). The forward scatter model should only be used for great circle paths with both antennas pointed at the horizon and at each other in a typical troposcatter communication system geometry. The forward scatter model can also be used for main-lobe, side-lobe coupling when one antenna is pointed toward the other along the great circle path. The forward scatter observations made over the Prospect Hill - Mt Tug path show that the two-component model is incomplete. Much stronger signals were observed at Ku-band than expected based on simultaneous C-band measurements. The discrepancies may be due to: (1) scattering by ice/snow at height (posssible in April) at the 1 km height of the scattering volume), (2) the coherent effects of turbulent fluctuations in the hydrometeor number densities and (3) errors in the modeling of the statistical relationship between attenuation along the path and scattering in the common volume.

  19. Interference by rain scatter

    NASA Astrophysics Data System (ADS)

    Crane, Robert K.

    1988-08-01

    The data from Japan and the U.S. (the Virginia Precipitation Scatter Experiment) show excellent agreement between the two-component rain scatter model predictions and bistatic scatter measurements. In employing the model, all the scattering geometries should be classified as backscattering as defined by Crane (1974). The forward scatter model should only be used for great circle paths with both antennas pointed at the horizon and at each other in a typical troposcatter communication system geometry. The forward scatter model can also be used for main-lobe, side-lobe coupling when one antenna is pointed toward the other along the great circle path. The forward scatter observations made over the Prospect Hill - Mt Tug path show that the two-component model is incomplete. Much stronger signals were observed at Ku-band than expected based on simultaneous C-band measurements. The discrepancies may be due to: (1) scattering by ice/snow at height (posssible in April) at the 1 km height of the scattering volume), (2) the coherent effects of turbulent fluctuations in the hydrometeor number densities and (3) errors in the modeling of the statistical relationship between attenuation along the path and scattering in the common volume.

  20. Pion-nucleon scattering in the P11 channel

    NASA Astrophysics Data System (ADS)

    Morioka, S.; Afnan, I. R.

    1982-09-01

    We present a parametrization of the π-N interaction in the P11 channel in which the amplitude is the sum of a pole part and a non-pole part (t=tpole+tnp) and satisfies two-body unitarity. Here tpole has both the nucleon propagator and the πNN vertex dressed. The final amplitude fits the scattering length and low energy π-N phase shifts (Tlabπ<300 MeV). We study the effect of a resonance in tnp on the phase shifts, πNN coupling constant, and the off-shell behavior of the amplitude. NUCLEAR REACTIONS πN scattering in P11 channel, renormalization, resonance effect.

  1. Refraction and scattering of sound by a shear layer

    NASA Technical Reports Server (NTRS)

    Schlinker, R. H.; Amiet, R. K.

    1980-01-01

    The angle and amplitude changes for acoustic waves refracted by a circular open jet shear layer were determined. The generalized refraction theory was assessed experimentally for on axis and off axis acoustic source locations as source frequency varied from 1 kHz to 10 kHz and free stream Mach number varied from 0.1 to 0.4. Angle and amplitude changes across the shear layer show good agreement with theory. Experiments confirm that the refraction theory is independent of shear layer thickness, acoustic source frequency, and source type. A generalized theory is, thus, available for correcting far field noise data acquired in open jet test facilities. The effect of discrete tone scattering by the open jet turbulent shear layer was also studied. Scattering effects were investigated over the same Mach number range as frequency varied from 5 kHz to 15 kHz. Attenuation of discrete tone amplitude and tone broadening were measured as a function of acoustic source position and radiation angle. Scattering was found to be stronger at angles close to the open jet axis than at 90 deg, and becomes stronger as the acoustic source position shifts downstream. A scattering analysis provided an estimate of the onset of discrete tone scattering.

  2. Time reversal for a single spherical scatterer.

    PubMed

    Chambers, D H; Gautesen, A K

    2001-06-01

    We show that the time reversal operator for a planar time reversal mirror (TRM) can have up to four distinct eigenvalues with a small spherical acoustic scatterer. Each eigenstate represents a resonance between the TRM and an induced scattering moment of the sphere. Their amplitude distributions on the TRM are orthogonal superpositions of the radiation patterns from a monopole and up to three orthogonal dipoles. The induced monopole moment is associated with the compressibility contrast between the sphere and the medium, while the dipole moments are associated with density contrast. The number of eigenstates is related to the number of orthogonal orientations of each induced multipole. For hard spheres (glass, metals) the contribution of the monopole moment to the eigenvalues is much greater than that of the dipole moments, leading to a single dominant eigenvalue. The other eigenvalues are much smaller, making it unlikely multiple eigenvalues could have been observed in previous experiments using hard materials. However, for soft materials such as wood, plastic, or air bubbles the eigenvalues are comparable in magnitude and should be observable. The presence of multiple eigenstates breaks the one-to-one correspondence between eigenstates and distinguishable scatterers discussed previously by Prada and Fink [Wave Motion 20, 151-163 (1994)]. However, eigenfunctions from separate scatterers would have different phases for their eigenfunctions, potentially restoring the ability to distinguish separate scatterers. Since relative magnitudes of the eigenvalues for a single scatterer are governed by the ratio of the compressibility contrast to the density contrast, measurement of the eigenvalue spectrum would provide information on the composition of the scatterer.

  3. Investigation of scattering in lunar seismic coda

    NASA Astrophysics Data System (ADS)

    Blanchette-Guertin, J.-F.; Johnson, C. L.; Lawrence, J. F.

    2012-06-01

    We investigate the intrinsic attenuation and scattering properties of the Moon by parameterizing the coda decay of 369 higher-quality lunar seismograms from 72 events via their characteristic rise and decay times. We investigate any dependence of the decay times on source type, frequency, and epicentral distance. Intrinsic attenuation, scattering, and possible focusing of energy in a near-surface, low-velocity layer all contribute to the coda decay. Although it is not possible to quantify the exact contribution of each of these effects in the seismograms, results suggest that scattering in a near-surface global layer dominates the records of shallow events (˜0-200 km depth), particularly at frequencies above 2 Hz, and for increasing epicentral distance. We propose that the scattering layer is the megaregolith and that energy from shallow sources encounters more scatterers as it travels longer distances in the layer, increasing the coda decay times. A size distribution of ejecta blocks that has more small-scale than large-scale scatterers intensifies this effect for increasing frequencies. Deep moonquakes (700-1100 km depth) exhibit no dependence of the decay time on epicentral distance. We suggest that because of their large depths and small amplitudes, deep moonquakes from any distance sample a similar region near a given receiver. Near-station structure and geology may also control the decay times of local events, as evidenced by two natural impact records. This study provides constraints and testable hypotheses for waveform modeling of the lunar interior that includes the effects of intense scattering and shallow, low-velocity layers.

  4. Resonance scattering by fish schools: A comparison of two models.

    PubMed

    Raveau, M; Feuillade, C

    2016-01-01

    The effective medium method is used to investigate resonance scattering from schools of fish with gas-filled swim bladders, as a function of frequency and azimuth. Calculations are also performed with a coupled differential equation model, which incorporates both multiple scattering between fish and wave interference interactions of their scattered fields [Feuillade, Nero, and Love, J. Acoust. Soc. Am. 99, 196-208 (1996)]. A theoretical comparison of the models for idealized spherical schools shows good agreement over the entire resonance region in the forward direction, where interference interactions have a minimal effect. Good agreement is also seen in back scattering at low frequencies, where the wavelength λ≥4s, and s is the average nearest neighbor fish separation. If λ<4s, the models diverge in back scattering, and the effective medium method fails. This can be critically important when migrations of schools to deeper water cause the collective resonance frequency to increase. Multiple scattering interactions are negligible when |4πnf(b)(2)/k|⪅0.01, where n is the fish number density, f(b) is the individual fish scattering amplitude, and k=2π/λ. A comparison with forward scattering data shows very good agreement for both models, and indicates a method for estimating fish abundance. For back scattering data, the effective medium method diverges strongly when λ<4s.

  5. Scattering process in the Scalar Duffin-Kemmer-Petiau gauge theory

    NASA Astrophysics Data System (ADS)

    Beltran, J.; Pimentel, B. M.; Soto, D. E.

    2016-04-01

    In this work we calculate the cross section of the scattering process of the Duffin-Kemmer-Petiau theory coupling with the Maxwell’s electromagnetic field. Specifically, we find the propagator of the free theory, the scattering amplitudes and cross sections at Born level for the Moeller and Compton scattering process of this model. For this purpose we use the analytic representation for free propagators and take account the framework of the Causal Perturbation Theory of Epstein and Glaser.

  6. Theory of direct scattering of neutral and charged atoms

    NASA Technical Reports Server (NTRS)

    Franco, V.

    1979-01-01

    The theory for direct elastic and inelastic collisions between composite atomic systems formulated within the framework of the Glauber approximation is presented. It is shown that the phase-shift function is the sum of a point Coulomb contribution and of an expression in terms of the known electron-hydrogen-atom and proton-hydrogen-atom phase shift function. The scattering amplitude is reexpressed, the pure Coulomb scattering in the case of elastic collisions between ions is isolated, and the exact optical profile function is approximated by a first-order expansion in Glauber theory which takes into account some multiple collisions. The approximate optical profile function terms corresponding to interactions involving one and two electrons are obtained in forms of Meijer G functions and as a one-dimensional integral, and for collisions involving one or two neutral atoms, the scattering amplitude is further reduced to a simple closed-form expression.

  7. Theory of direct scattering of neutral and charged atoms

    NASA Technical Reports Server (NTRS)

    Franco, V.

    1979-01-01

    The theory for direct elastic and inelastic collisions between composite atomic systems formulated within the framework of the Glauber approximation is presented. It is shown that the phase-shift function is the sum of a point Coulomb contribution and of an expression in terms of the known electron-hydrogen-atom and proton-hydrogen-atom phase shift function. The scattering amplitude is reexpressed, the pure Coulomb scattering in the case of elastic collisions between ions is isolated, and the exact optical profile function is approximated by a first-order expansion in Glauber theory which takes into account some multiple collisions. The approximate optical profile function terms corresponding to interactions involving one and two electrons are obtained in forms of Meijer G functions and as a one-dimensional integral, and for collisions involving one or two neutral atoms, the scattering amplitude is further reduced to a simple closed-form expression.

  8. Halo-independent methods for inelastic dark matter scattering

    SciTech Connect

    Bozorgnia, Nassim; Schwetz, Thomas; Herrero-Garcia, Juan; Zupan, Jure E-mail: juan.a.herrero@uv.es E-mail: jure.zupan@cern.ch

    2013-07-01

    We present halo-independent methods to analyze the results of dark matter direct detection experiments assuming inelastic scattering. We focus on the annual modulation signal reported by DAMA/LIBRA and present three different halo-independent tests. First, we compare it to the upper limit on the unmodulated rate from XENON100 using (a) the trivial requirement that the amplitude of the annual modulation has to be smaller than the bound on the unmodulated rate, and (b) a bound on the annual modulation amplitude based on an expansion in the Earth's velocity. The third test uses the special predictions of the signal shape for inelastic scattering and allows for an internal consistency check of the data without referring to any astrophysics. We conclude that a strong conflict between DAMA/LIBRA and XENON100 in the framework of spin-independent inelastic scattering can be established independently of the local properties of the dark matter halo.

  9. Supersymmetric Regularization Two-Loop QCD Amplitudes and Coupling Shifts

    SciTech Connect

    Dixon, Lance

    2002-03-08

    We present a definition of the four-dimensional helicity (FDH) regularization scheme valid for two or more loops. This scheme was previously defined and utilized at one loop. It amounts to a variation on the standard 't Hooft-Veltman scheme and is designed to be compatible with the use of helicity states for ''observed'' particles. It is similar to dimensional reduction in that it maintains an equal number of bosonic and fermionic states, as required for preserving supersymmetry. Supersymmetry Ward identities relate different helicity amplitudes in supersymmetric theories. As a check that the FDH scheme preserves supersymmetry, at least through two loops, we explicitly verify a number of these identities for gluon-gluon scattering (gg {yields} gg) in supersymmetric QCD. These results also cross-check recent non-trivial two-loop calculations in ordinary QCD. Finally, we compute the two-loop shift between the FDH coupling and the standard {bar M}{bar S} coupling, {alpha}{sub s}. The FDH shift is identical to the one for dimensional reduction. The two-loop coupling shifts are then used to obtain the three-loop QCD {beta} function in the FDH and dimensional reduction schemes.

  10. K-N amplitudes below threshold constrained by multinucleon absorption

    NASA Astrophysics Data System (ADS)

    Friedman, E.; Gal, A.

    2017-03-01

    Six widely different subthreshold K- N scattering amplitudes obtained in SU(3) chiral-model EFT approaches by fitting to low-energy and threshold data are employed in optical-potential studies of kaonic atoms. Phenomenological terms representing K- multinucleon interactions are added to the EFT-inspired single-nucleon part of the K--nucleus optical potential in order to obtain good fits to kaonic-atom strong-interaction level shifts and widths across the periodic table. Introducing as a further constraint the fractions of single-nucleon K- absorption at rest from old bubble-chamber experiments, it is found that only two of the models considered here reproduce these absorption fractions. Within these two models, the interplay between single-nucleon and multinucleon K- interactions explains features observed previously with fully phenomenological optical potentials. Radial sensitivities of kaonic atom observables are re-examined, and remarks are made on the role of 'subthreshold kinematics' in absorption-at-rest calculations.

  11. Momentum space dipole amplitude for DIS and inclusive hadron production

    SciTech Connect

    Basso, E. A.; Gay Ducati, M. B.; De Oliveira, E. G.

    2013-03-25

    We show how the AGBS model, originally developed for deep inelastic scattering applied to HERA data on the proton structure function, can also describe the RHIC data on single inclusive hadron yield for d+Au and p+p collisions through a new simultaneous fit. The single inclusive hadron production is modeled through the color glass condensate, which uses the quark(and gluon) condensate amplitudes in momentum space. The AGBS model is also a momentum space model based on the asymptotic solutions of the BK equation, although a different definition of the Fourier transform is used. This description entirely in transverse momentum of both processes arises for the first time. The small difference between the simultaneous fit and the one for HERA data alone suggests that the AGBS model describes very well both kind of processes and thus emerges as a good tool to investigate the inclusive hadron production data. We use this model for predictions at LHC energies, which agree quite well with available experimental data.

  12. Nonlinear amplitude approximation for bilinear systems

    NASA Astrophysics Data System (ADS)

    Jung, Chulwoo; D'Souza, Kiran; Epureanu, Bogdan I.

    2014-06-01

    An efficient method to predict vibration amplitudes at the resonant frequencies of dynamical systems with piecewise-linear nonlinearity is developed. This technique is referred to as bilinear amplitude approximation (BAA). BAA constructs a single vibration cycle at each resonant frequency to approximate the periodic steady-state response of the system. It is postulated that the steady-state response is piece-wise linear and can be approximated by analyzing the response over two time intervals during which the system behaves linearly. Overall the dynamics is nonlinear, but the system is in a distinct linear state during each of the two time intervals. Thus, the approximated vibration cycle is constructed using linear analyses. The equation of motion for analyzing the vibration of each state is projected along the overlapping space spanned by the linear mode shapes active in each of the states. This overlapping space is where the vibratory energy is transferred from one state to the other when the system switches from one state to the other. The overlapping space can be obtained using singular value decomposition. The space where the energy is transferred is used together with transition conditions of displacement and velocity compatibility to construct a single vibration cycle and to compute the amplitude of the dynamics. Since the BAA method does not require numerical integration of nonlinear models, computational costs are very low. In this paper, the BAA method is first applied to a single-degree-of-freedom system. Then, a three-degree-of-freedom system is introduced to demonstrate a more general application of BAA. Finally, the BAA method is applied to a full bladed disk with a crack. Results comparing numerical solutions from full-order nonlinear analysis and results obtained using BAA are presented for all systems.

  13. Loop-quantum-gravity vertex amplitude.

    PubMed

    Engle, Jonathan; Pereira, Roberto; Rovelli, Carlo

    2007-10-19

    Spin foam models are hoped to provide the dynamics of loop-quantum gravity. However, the most popular of these, the Barrett-Crane model, does not have the good boundary state space and there are indications that it fails to yield good low-energy n-point functions. We present an alternative dynamics that can be derived as a quantization of a Regge discretization of Euclidean general relativity, where second class constraints are imposed weakly. Its state space matches the SO(3) loop gravity one and it yields an SO(4)-covariant vertex amplitude for Euclidean loop gravity.

  14. Fatigue damage analysis under variable amplitude cycling

    NASA Technical Reports Server (NTRS)

    Leis, B. N.; Forte, T. P.

    1983-01-01

    This paper explores the suitability of a recently proposed mean stress parameter and introduces a nonlinear damage accumulation procedure. Data covering a range of positive and negative stress ratios from +0.6 to -2.66, for several aluminum alloys and steels, are assembled and shown to be well correlated by a simple damage parameter. A nonlinear damage accumulation postulate is advanced to replace the usual linear procedure. Results of critical experiments performed to assess the suitability of the postulate are introduced and shown to support a non-linear criterion. The implications of this work related to variable amplitude life prediction are discussed.

  15. Fatigue crack growth under variable amplitude loading

    NASA Astrophysics Data System (ADS)

    Sidawi, Jihad A.

    1994-09-01

    Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.

  16. Fatigue crack growth under variable amplitude loading

    NASA Technical Reports Server (NTRS)

    Sidawi, Jihad A.

    1994-01-01

    Fatigue crack growth tests were conducted on an Fe 510 E C-Mn steel and a submerged arc welded joint from the same material under constant, variable, and random loading amplitudes. Paris-Erdogan's crack growth rate law was tested for the evaluation of m and C using the stress intensity factor K, the J-integral, the effective stress intensity factor K(sub eff), and the root mean square stress intensity factor K(sub rms) fracture mechanics concepts. The effect of retardation and residual stresses resulting from welding was also considered. It was found that all concepts gave good life predictions in all cases.

  17. Phase amplitude conformal symmetry in Fourier transforms

    NASA Astrophysics Data System (ADS)

    Kuwata, S.

    2015-04-01

    For the Fourier transform ℑ : L2(R) → L2(R) of a complex-valued even or odd function ψ, it is found that the amplitude invariance |ℑψ| = |ψ| leads to a phase invariance or inversion as arg(ℑψ) = ±argψ + θ (θ = constant). The converse holds unless arg ψ = constant. The condition |ψ| = |ℑψ| is required in dealing with, for example, the minimum uncertainty relation between position and momentum. Without the evenness or oddness of ψ, |ℑψ| = |ψ| does not necessarily imply arg(ℑψ) = ±argψ + θ, nor is the converse.

  18. In-Medium Pion Valence Distribution Amplitude

    NASA Astrophysics Data System (ADS)

    Tsushima, K.; de Melo, J. P. B. C.

    2017-03-01

    After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant.

  19. The small amplitude magnetohydrodynamic Riemann problem

    NASA Technical Reports Server (NTRS)

    Wu, C. C.; Kennel, C. F.

    1993-01-01

    The small-amplitude MHD Riemann problem is studied using the Cohen-Kulsrud-Burgers equations. Unlike the coplanar Riemann problem, the evolution of noncoplanar Riemann problems is not self-similar and its flow structures could change in time. But its large-time behavior is very simple and a time-dependent 2 - 3 intermediate shock is always involved for the noncoplanar field rotations. The time-dependent 2 - 3 intermediate shock has a well-defined structure and exists for any degree of field rotation.

  20. Stochastic aspects of nuclear large amplitude motion

    SciTech Connect

    Kolomietz, V.M.

    1995-08-01

    A consistent description of the macroscopic large amplitude dynamics and processes of internal excitation of a nucleus is suggested. The cranking model approach is used for the calculation of the response function of the nucleus in a moving frame. Using spectral statistics smearing, the collective mass, friction, and diffusion coefficients are derived. The relation of the response function in a moving frame to the correlation function in a classical chaotic system is established. The rate of dissipation due to the Landau-Zener transitions and through the Kubo mechanism is considered.

  1. Elastic scattering phenomenology

    NASA Astrophysics Data System (ADS)

    Mackintosh, R. S.

    2017-04-01

    We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered "good", are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions.

  2. Partially strong WW scattering

    SciTech Connect

    Cheung Kingman; Chiang Chengwei; Yuan Tzuchiang

    2008-09-01

    What if only a light Higgs boson is discovered at the CERN LHC? Conventional wisdom tells us that the scattering of longitudinal weak gauge bosons would not grow strong at high energies. However, this is generally not true. In some composite models or general two-Higgs-doublet models, the presence of a light Higgs boson does not guarantee complete unitarization of the WW scattering. After partial unitarization by the light Higgs boson, the WW scattering becomes strongly interacting until it hits one or more heavier Higgs bosons or other strong dynamics. We analyze how LHC experiments can reveal this interesting possibility of partially strong WW scattering.

  3. Large Amplitude Whistler Waves and Electron Acceleration in the Earth's Radiation Belts: A Review of STEREO and Wind Observations

    NASA Technical Reports Server (NTRS)

    Cattell, Cynthia; Breneman, A.; Goetz, K.; Kellogg, P.; Kersten, K.; Wygant, J.; Wilson, L. B., III; Looper, Mark D.; Blake, J. Bernard; Roth, I.

    2012-01-01

    One of the critical problems for understanding the dynamics of Earth's radiation belts is determining the physical processes that energize and scatter relativistic electrons. We review measurements from the Wind/Waves and STEREO S/Waves waveform capture instruments of large amplitude whistler-mode waves. These observations have provided strong evidence that large amplitude (100s mV/m) whistler-mode waves are common during magnetically active periods. The large amplitude whistlers have characteristics that are different from typical chorus. They are usually nondispersive and obliquely propagating, with a large longitudinal electric field and significant parallel electric field. We will also review comparisons of STEREO and Wind wave observations with SAMPEX observations of electron microbursts. Simulations show that the waves can result in energization by many MeV and/or scattering by large angles during a single wave packet encounter due to coherent, nonlinear processes including trapping. The experimental observations combined with simulations suggest that quasilinear theoretical models of electron energization and scattering via small-amplitude waves, with timescales of hours to days, may be inadequate for understanding radiation belt dynamics.

  4. Multigluon scattering in open superstring theory

    SciTech Connect

    Stieberger, Stephan; Taylor, Tomasz R.

    2006-12-15

    We discuss the amplitudes describing N-gluon scattering in type I superstring theory, on a disk world sheet. After reviewing the general structure of amplitudes and the complications created by the presence of a large number of vertices at the boundary, we focus on the most promising case of maximally helicity violating (MHV) configurations because in this case, the zero Regge slope limit ({alpha}{sup '}{yields}0) is particularly simple. We obtain the full-fledged MHV disk amplitudes for N=4, 5, and N=6 gluons, expressed in terms of one, two and six functions of kinematic invariants, respectively. These functions represent certain boundary integrals--generalized Euler integrals--which for N{>=}6 correspond to multiple hypergeometric series (generalized Kampe de Feriet functions). Their {alpha}{sup '} expansions lead to Euler-Zagier sums. For arbitrary N, we show that the leading string corrections to the Yang-Mills amplitude, of order O({alpha}{sup '2}), originate from the well-known {alpha}{sup '2} TrF{sup 4} effective interactions of four gauge field strength tensors. By using iteration based on the soft gluon limit, we derive a simple formula valid to that order for arbitrary N. We argue that such a procedure can be extended to all orders in {alpha}{sup '}. If nature gracefully picked a sufficiently low string mass scale, our results would be important for studying string effects in multijet production at the Large Hadron Collider (LHC)

  5. PERIOD AND AMPLITUDE VARIABILITY OF THE HIGH-AMPLITUDE {delta} SCUTI STAR GP ANDROMEDAE

    SciTech Connect

    Zhou, A.-Y.; Jiang, S.-Y.

    2011-10-15

    Extensive differential time-series CCD photometry has been carried out between 2003 and 2009 for the high-amplitude {delta} Scuti (HADS) star GP And. We acquired 12,583 new measurements consisting of 41 nights (153.3 hr) spanning over 2221 days. This is the largest time-series data set to date for the star. Based upon these data and others available in the literature, a comprehensive analysis has been conducted to investigate the pulsational properties of the star. Except for the known fundamental period and its harmonics we failed to detect any additional pulsation periods either radial or nonradial. We show clear amplitude variability, but we failed to verify the previously claimed periodic amplitude modulation. Classic O-C analysis indicates that the fundamental pulsation period of GP And is slowly increasing at a rate of P-dot /P = (5.49 {+-} 0.1)x10{sup -8} yr{sup -1} in accordance with the predictions of stellar evolutionary models. Findings of nonradial oscillations in previously known radial high-amplitude pulsators are being increasingly reported. We have briefly reviewed the current status of multiperiodicity and nonradial pulsation features among the high-amplitude pulsators in the classic instability strip.

  6. Small-amplitude synchrotron tune near transition

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-05-01

    The separatrices of the rf buckets near transition are mapped when the synchronous phase is neither 0 or {pi}. The small-amplitude synchronous tune is derived when the rf frequency is changed. Synchrotron radiation is present in all electron storage ring. As a result, the synchronous phase is always offset from {phi}{sub s} = {pi} to compensate for the power loss. Even for proton storage rings with negligible synchrotron radiation, the synchronous phase is also required to be offset from {phi}{sub s} = 0 or {pi} slightly to compensate for beam loading. Thus for all storage rings operating near transition, beam particles reside in accelerating buckets instead of stationary bucket. It is of interest to map these buckets and see how they evolve near transition. When the rf frequency is varied, the closed orbit is pushed radially inward or outward. The momentum of the particle synchronous with the rf is thus changed. By measuring the small-amplitude synchrotron tune as a function of the rf frequency, the lowest first few orders of the slip factor can be inferred. Here, we derive this relationship up to the lowest first three orders of the slip factor when the particle velocity is not ultra-relativistic.

  7. Amplitude enhancement by a gold dimer

    NASA Astrophysics Data System (ADS)

    Hong, Xin; Wang, Jingxin; Jin, Zheng

    2016-10-01

    The unique optical properties such as brightness, non-bleaching, good bio-compatibility make gold particles ideal label candidates for molecular probes. Due to the strongly enhanced field, aggregation of gold nanoparticles finds themselves plenty of applications in bio-imaging. But limited by its small cross-section associated with nanometer sized particle, it is a big challenge to employ it in a single molecular detection. The field enhancement results from the effect of plasmonic coupling between two closely attached gold nanoparticle under the right excitation condition. With the aim to apply the gold dimer probe to find the molecules in our recently established optical detection method, we compared of the amplitude enhancement by the dimer relative to a single particle. The amplitude distribution under a highly focused illumination objective was calculated, whose results suggest that at the optimized excitation condition, the local field can be enhanced 190 fold. In consequence, experimental detection was carried out. Gold dimers were linked together by the hybridization of two single chain DNAs. Dimer and single particle probes were mixed together in one detection. Overwhelming contrast between these two kinds of probes were clearly exhibited in the experimental detection image. This method can provide a way to a high specific detection in early diagnosis.

  8. Wrist Proprioception: Amplitude or Position Coding?

    PubMed Central

    Marini, Francesca; Squeri, Valentina; Morasso, Pietro; Masia, Lorenzo

    2016-01-01

    This work examines physiological mechanisms underlying the position sense of the wrist, namely, the codification of proprioceptive information related to pointing movements of the wrist toward kinesthetic targets. Twenty-four healthy subjects participated to a robot-aided assessment of their wrist proprioceptive acuity to investigate if the sensorimotor transformation involved in matching targets located by proprioceptive receptors relies on amplitude or positional cues. A joint position matching test was performed in order to explore such dichotomy. In this test, the wrist of a blindfolded participant is passively moved by a robotic device to a preset target position and, after a removal movement from this position, the participant has to actively replicate and match it as accurately as possible. The test involved two separate conditions: in the first, the matching movements started from the same initial location; in the second one, the initial location was randomly assigned. Target matching accuracy, precision, and bias in the two conditions were then compared. Overall results showed a consistent higher performance in the former condition than in the latter, thus supporting the hypothesis that the joint position sense is based on vectorial or amplitude coding rather than positional. PMID:27807417

  9. Optical scatter: an overview

    NASA Astrophysics Data System (ADS)

    Stover, John C.

    1991-12-01

    Optical scatter is a bothersome source of optical noise, limits resolution and reduces system throughput. However, it is also an extremely sensitive metrology tool. It is employed in a wide variety of applications in the optics industry (where direct scatter measurement is of concern) and is becoming a popular indirect measurement in other industries where its measurement in some form is an indicator of another component property - like roughness, contamination or position. This paper presents a brief review of the current state of this technology as it emerges from university and government laboratories into more general industry use. The bidirectional scatter distribution function (or BSDF) has become the common format for expressing scatter data and is now used almost universally. Measurements made at dozens of laboratories around the country cover the spectrum from the uv to the mid- IR. Data analysis of optical component scatter has progressed to the point where a variety of analysis tools are becoming available for discriminating between the various sources of scatter. Work has progressed on the analysis of rough surface scatter and the application of these techniques to some challenging problems outside the optical industry. Scatter metrology is acquiring standards and formal test procedures. The available scatter data base is rapidly expanding as the number and sophistication of measurement facilities increases. Scatter from contaminants is continuing to be a major area of work as scatterometers appear in vacuum chambers at various laboratories across the country. Another area of research driven by space applications is understanding the non-topographic sources of mid-IR scatter that are associated with Beryllium and other materials. The current flurry of work in this growing area of metrology can be expected to continue for several more years and to further expand to applications in other industries.

  10. Low energy neutron deuteron scattering to N3LO

    NASA Astrophysics Data System (ADS)

    Margaryan, Arman; Vanasse, Jared; Springer, Roxanne

    2015-10-01

    We calculate the next-to-next-to-next-to-leading order (N3LO) nd scattering amplitude in the framework of nonrelativistic pionless effective field theory (EFTπ/). This theory is only valid when the typical momentum exchange in the scattering is smaller then the mass of the pion. The power counting parameter for EFTπ/ is the ratio Q/Λπ /, where Q is the typical momentum exchange in the scattering and Λπ / is the EFTπ/ breakdown scale, Λπ / amplitude for nd scattering at leading order requires summing an infinite set of diagrams. The first nonzero polarization-dependent observables occur at N2LO. At N3LO new 2-body forces appear, which introduce four new EFTπ/ coefficients. These coefficients are fixed by the 3PJ and 1P1 phase shifts of NN scattering. We find that these terms have an important impact. The results of this calculation at N3LO will be important for understanding spin polarization observables in nd scattering, in particular the longstanding Ay puzzle. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics, under Award Number DE-FG02-05ER41368.

  11. Two space scatterer formalism calculation of bulk parameters of thunderclouds

    NASA Technical Reports Server (NTRS)

    Phanord, Dieudonne D.

    1994-01-01

    In a previous study, we used a modified two-space scatterer formalism of Twersky to establish for a cloud modeled as a statistically homogeneous distribution of spherical water droplets, the dispersion relations that determine its bulk propagation numbers and bulk indexes of refraction in terms of the vector equivalent scattering amplitude and the dyadic scattering amplitude of the single water droplet in isolation. The results were specialized to the forward direction of scattering while demanding that the scatterers preserve the incident polarization. We apply this approach to obtain specific numerical values for the macroscopic parameters of the cloud. We work with a cloud of density rho = 100 cm(exp -3), a wavelength lambda = 0.7774 microns, and with spherical water droplets of common radius alpha = 10 microns. In addition, the scattering medium is divided into three parts, the medium outside the cloud, moist air (the medium inside the cloud but outside the droplets), and the medium inside the spherical water droplets. The results of this report are applicable to a cloud of any geometry since the boundary does not interfere with the calculations. Also, it is important to notice the plane wave nature of the incidence wave in the moist atmosphere.

  12. Reconstruction of Rain Microstructure From Spectrum of Scattering Light

    NASA Astrophysics Data System (ADS)

    Sterlyadkin, V.; Gluschenko, A.

    Night photoregistration of light, scattered by drops had proved that practically all drops oscillate as they fall. As drop oscillation frequency W monotony diminish with drop volume V rise, so different fractions of rain form different parts of spectrum. Thereby it is possible to reconstruct rain microstructure from remote optical measure- ments. In common case the form of spectrum depends not only on drop size distri- bution N(V) but also on oscillation amplitudes function, scattering phase function for oscillating drops and on frequency dependence W(V). The statistical treatment of our field data had shown that average oscillation amplitude rise with drop volume V as , where A is a some constant. This result allows to solve the inverse problem: to re- construct drop size distribution N(V) from the power spectrum of light, scattering by rain. Scattering phase function for nonspherical and oscillating drops was calculated in straight-line approximation. Analysis of optical properties of oscillating water drop had shown some optimal measurement geometry for registration of rain microstruc- ture. For low intensity rains it is reasonable to use the effect of abnormal high modu- lation of light scattered by oscillating drops, which we discovered earlier in laboratory condition and under field measurements. (The effect of abnormal high modulation al- lows us to detect 2-3 mm raindrop deformations from 5 m distance). The results of reconstruction of drop size distributions from spectra of light, scattered by rains are presented and discussed.

  13. Estimation of guided wave scattering matrices from spatially distributed transducer arrays

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Michaels, Jennifer E.; Michaels, Thomas E.

    2013-01-01

    Because of their ability to travel relatively long distances with low attenuation, guided waves are being considered as a tool for the detection of defects in plate-like structures for aerospace, civil, and petrochemical applications. When a guided wave encounters a defect, a scattered field related to the characteristics of the defect is generated. The far field scattering behavior can be described by a scattering matrix that quantifies the amplitude of the scattered signal as a function of incident and scattered angles. Because of the mode and frequency dependence of guided waves interacting with defects, the scattering matrix is typically defined for specific guided wave modes (incident and scattered) at a designated frequency. Prior work has utilized finite element modeling and full wavefield scanning to estimate scattering matrices, but these approaches may be impractical because of either computational requirements or experimental issues. Here, we propose a methodology for estimating a scattering matrix based upon limited experimental data recorded from a spatially distributed transducer array. After applying baseline subtraction to extract changes in received signals resulting from the introduction of a scatterer, we further process differenced signals to obtain a limited number of scattering matrix data points corresponding to the incident and scattered angles for each transducer pair. We perform radial basis function interpolation of these initial points to estimate the complete scattering matrix and evaluate the efficacy of the proposed method via experiments with a glued-on linear scatterer.

  14. Color-kinematic duality in ABJM theory without amplitude relations

    NASA Astrophysics Data System (ADS)

    Sivaramakrishnan, Allic

    2017-01-01

    We explicitly show that the Bern-Carrasco-Johansson color-kinematic duality holds at tree level through at least eight points in Aharony-Bergman-Jafferis-Maldacena theory with gauge group SU(N) × SU(N). At six points we give the explicit form of numerators in terms of amplitudes, displaying the generalized gauge freedom that leads to amplitude relations. However, at eight points no amplitude relations follow from the duality, so the diagram numerators are fixed unique functions of partial amplitudes. We provide the explicit amplitude-numerator decomposition and the numerator relations for eight-point amplitudes.

  15. Spurious cross-frequency amplitude-amplitude coupling in nonstationary, nonlinear signals

    NASA Astrophysics Data System (ADS)

    Yeh, Chien-Hung; Lo, Men-Tzung; Hu, Kun

    2016-07-01

    Recent studies of brain activities show that cross-frequency coupling (CFC) plays an important role in memory and learning. Many measures have been proposed to investigate the CFC phenomenon, including the correlation between the amplitude envelopes of two brain waves at different frequencies - cross-frequency amplitude-amplitude coupling (AAC). In this short communication, we describe how nonstationary, nonlinear oscillatory signals may produce spurious cross-frequency AAC. Utilizing the empirical mode decomposition, we also propose a new method for assessment of AAC that can potentially reduce the effects of nonlinearity and nonstationarity and, thus, help to avoid the detection of artificial AACs. We compare the performances of this new method and the traditional Fourier-based AAC method. We also discuss the strategies to identify potential spurious AACs.

  16. Systematics of meson-Skyrmion scattering

    SciTech Connect

    Mattis, M.P.

    1986-02-01

    The S-matrix characterizing the scattering of pions from nucleons is calculated in the context of skyrmion models of the nucleon. These are models in which the nucleon is considered a soliton in the field of pions. The spectrum of nucleon and delta resonances in the Skyrme model is calculated and found to be in overall good agreement with Nature. Model-independent sum rules between amplitudes in the same partial wave are derived and examined. An extension of the formalism to the case of three light flavors is presented. 31 refs., 26 figs., 6 tabs.

  17. Deeply Virtual Compton Scattering off the Neutron

    NASA Astrophysics Data System (ADS)

    Mazouz, M.; Camsonne, A.; Camacho, C. Muñoz; Ferdi, C.; Gavalian, G.; Kuchina, E.; Amarian, M.; Aniol, K. A.; Beaumel, M.; Benaoum, H.; Bertin, P.; Brossard, M.; Chen, J.-P.; Chudakov, E.; Craver, B.; Cusanno, F.; de Jager, C. W.; Deur, A.; Feuerbach, R.; Fieschi, J.-M.; Frullani, S.; Garçon, M.; Garibaldi, F.; Gayou, O.; Gilman, R.; Gomez, J.; Gueye, P.; Guichon, P. A. M.; Guillon, B.; Hansen, O.; Hayes, D.; Higinbotham, D.; Holmstrom, T.; Hyde, C. E.; Ibrahim, H.; Igarashi, R.; Jiang, X.; Jo, H. S.; Kaufman, L. J.; Kelleher, A.; Kolarkar, A.; Kumbartzki, G.; Laveissiere, G.; Lerose, J. J.; Lindgren, R.; Liyanage, N.; Lu, H.-J.; Margaziotis, D. J.; Meziani, Z.-E.; McCormick, K.; Michaels, R.; Michel, B.; Moffit, B.; Monaghan, P.; Nanda, S.; Nelyubin, V.; Potokar, M.; Qiang, Y.; Ransome, R. D.; Réal, J.-S.; Reitz, B.; Roblin, Y.; Roche, J.; Sabatié, F.; Saha, A.; Sirca, S.; Slifer, K.; Solvignon, P.; Subedi, R.; Sulkosky, V.; Ulmer, P. E.; Voutier, E.; Wang, K.; Weinstein, L. B.; Wojtsekhowski, B.; Zheng, X.; Zhu, L.

    2007-12-01

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e→,e'γ)X cross section measured at Q2=1.9GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to Eq, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  18. Deeply virtual compton scattering off the neutron.

    PubMed

    Mazouz, M; Camsonne, A; Camacho, C Muñoz; Ferdi, C; Gavalian, G; Kuchina, E; Amarian, M; Aniol, K A; Beaumel, M; Benaoum, H; Bertin, P; Brossard, M; Chen, J-P; Chudakov, E; Craver, B; Cusanno, F; de Jager, C W; Deur, A; Feuerbach, R; Fieschi, J-M; Frullani, S; Garçon, M; Garibaldi, F; Gayou, O; Gilman, R; Gomez, J; Gueye, P; Guichon, P A M; Guillon, B; Hansen, O; Hayes, D; Higinbotham, D; Holmstrom, T; Hyde, C E; Ibrahim, H; Igarashi, R; Jiang, X; Jo, H S; Kaufman, L J; Kelleher, A; Kolarkar, A; Kumbartzki, G; Laveissiere, G; Lerose, J J; Lindgren, R; Liyanage, N; Lu, H-J; Margaziotis, D J; Meziani, Z-E; McCormick, K; Michaels, R; Michel, B; Moffit, B; Monaghan, P; Nanda, S; Nelyubin, V; Potokar, M; Qiang, Y; Ransome, R D; Réal, J-S; Reitz, B; Roblin, Y; Roche, J; Sabatié, F; Saha, A; Sirca, S; Slifer, K; Solvignon, P; Subedi, R; Sulkosky, V; Ulmer, P E; Voutier, E; Wang, K; Weinstein, L B; Wojtsekhowski, B; Zheng, X; Zhu, L

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e,e'gamma)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E_{q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  19. Quadratic electroweak corrections for polarized Moller scattering

    SciTech Connect

    A. Aleksejevs, S. Barkanova, Y. Kolomensky, E. Kuraev, V. Zykunov

    2012-01-01

    The paper discusses the two-loop (NNLO) electroweak radiative corrections to the parity violating electron-electron scattering asymmetry induced by squaring one-loop diagrams. The calculations are relevant for the ultra-precise 11 GeV MOLLER experiment planned at Jefferson Laboratory and experiments at high-energy future electron colliders. The imaginary parts of the amplitudes are taken into consideration consistently in both the infrared-finite and divergent terms. The size of the obtained partial correction is significant, which indicates a need for a complete study of the two-loop electroweak radiative corrections in order to meet the precision goals of future experiments.

  20. Deeply Virtual Compton Scattering off the Neutron

    SciTech Connect

    Mazouz, M.; Guillon, B.; Real, J.-S.; Voutier, E.

    2007-12-14

    The present experiment exploits the interference between the deeply virtual Compton scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D(e-vector,e{sup '}{gamma})X cross section measured at Q{sup 2}=1.9 GeV{sup 2} and x{sub B}=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to E{sub q}, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.

  1. Scattering of matter waves in spatially inhomogeneous environments

    SciTech Connect

    Tsitoura, F.; Krüger, P.; Kevrekidis, P. G.; Frantzeskakis, D. J.

    2015-03-30

    In this article, we study scattering of quasi-one-dimensional matter waves at an interface of two spatial domains, one with repulsive and one with attractive interatomic interactions. It is shown that the incidence of a Gaussian wave packet from the repulsive to the attractive region gives rise to generation of a soliton train. More specifically, the number of emergent solitons can be controlled, e.g., by the variation of the amplitude or the width of the incoming wave packet. Furthermore, we study the reflectivity of a soliton incident from the attractive region to the repulsive one. We find the reflection coefficient numerically and employ analytical methods, which treat the soliton as a particle (for moderate and large amplitudes) or a quasilinear wave packet (for small amplitudes), to determine the critical soliton momentum (as a function of the soliton amplitude) for which total reflection is observed.

  2. Scattering of matter waves in spatially inhomogeneous environments

    DOE PAGES

    Tsitoura, F.; Krüger, P.; Kevrekidis, P. G.; ...

    2015-03-30

    In this article, we study scattering of quasi-one-dimensional matter waves at an interface of two spatial domains, one with repulsive and one with attractive interatomic interactions. It is shown that the incidence of a Gaussian wave packet from the repulsive to the attractive region gives rise to generation of a soliton train. More specifically, the number of emergent solitons can be controlled, e.g., by the variation of the amplitude or the width of the incoming wave packet. Furthermore, we study the reflectivity of a soliton incident from the attractive region to the repulsive one. We find the reflection coefficient numericallymore » and employ analytical methods, which treat the soliton as a particle (for moderate and large amplitudes) or a quasilinear wave packet (for small amplitudes), to determine the critical soliton momentum (as a function of the soliton amplitude) for which total reflection is observed.« less

  3. Compton scattering overview

    SciTech Connect

    Hartemann, F V

    2008-12-01

    An overview of linear and nonlinear Compton scattering is presented, along with a comparison with Thomson scattering. Two distinct processes play important roles in the nonlinear regime: multi-photon interactions, leading to the generation of harmonics, and radiation pressure, yielding a downshift of the radiated spectral features. These mechanisms, their influence on the source brightness, and different modeling strategies are also briefly discussed.

  4. Limitations in scatter propagation

    NASA Astrophysics Data System (ADS)

    Lampert, E. W.

    1982-04-01

    A short description of the main scatter propagation mechanisms is presented; troposcatter, meteor burst communication and chaff scatter. For these propagation modes, in particular for troposcatter, the important specific limitations discussed are: link budget and resulting hardware consequences, diversity, mobility, information transfer and intermodulation and intersymbol interference, frequency range and future extension in frequency range for troposcatter, and compatibility with other services (EMC).

  5. Multiple Scattering in Clouds

    DTIC Science & Technology

    1979-09-01

    Equation .................................. 35 Boundary Conditions ................................ 37SIrradiance at Cloud Exit...mathematical description of the multiple scatter- ing problem is given by the nonstationary radiative transport equation of Chandrasekhar [2]. Written in...function, S0 is the source function, and X is the single-scatter albedo. Unfortunately, the nonstationary transport equation has not been solved in a

  6. Bubble nonlinear dynamics and stimulated scattering process

    NASA Astrophysics Data System (ADS)

    Jie, Shi; De-Sen, Yang; Sheng-Guo, Shi; Bo, Hu; Hao-Yang, Zhang; Shi-Yong, Hu

    2016-02-01

    A complete understanding of the bubble dynamics is deemed necessary in order to achieve their full potential applications in industry and medicine. For this purpose it is first needed to expand our knowledge of a single bubble behavior under different possible conditions including the frequency and pressure variations of the sound field. In addition, stimulated scattering of sound on a bubble is a special effect in sound field, and its characteristics are associated with bubble oscillation mode. A bubble in liquid can be considered as a representative example of nonlinear dynamical system theory with its resonance, and its dynamics characteristics can be described by the Keller-Miksis equation. The nonlinear dynamics of an acoustically excited gas bubble in water is investigated by using theoretical and numerical analysis methods. Our results show its strongly nonlinear behavior with respect to the pressure amplitude and excitation frequency as the control parameters, and give an intuitive insight into stimulated sound scattering on a bubble. It is seen that the stimulated sound scattering is different from common dynamical behaviors, such as bifurcation and chaos, which is the result of the nonlinear resonance of a bubble under the excitation of a high amplitude acoustic sound wave essentially. The numerical analysis results show that the threshold of stimulated sound scattering is smaller than those of bifurcation and chaos in the common condition. Project supported by the Program for Changjiang Scholars and Innovative Research Team in University, China (Grant No. IRT1228) and the Young Scientists Fund of the National Natural Science Foundation of China (Grant Nos. 11204050 and 11204049).

  7. A scattering model for forested area

    NASA Technical Reports Server (NTRS)

    Karam, M. A.; Fung, A. K.

    1988-01-01

    A forested area is modeled as a volume of randomly oriented and distributed disc-shaped, or needle-shaped leaves shading a distribution of branches modeled as randomly oriented finite-length, dielectric cylinders above an irregular soil surface. Since the radii of branches have a wide range of sizes, the model only requires the length of a branch to be large compared with its radius which may be any size relative to the incident wavelength. In addition, the model also assumes the thickness of a disc-shaped leaf or the radius of a needle-shaped leaf is much smaller than the electromagnetic wavelength. The scattering phase matrices for disc, needle, and cylinder are developed in terms of the scattering amplitudes of the corresponding fields which are computed by the forward scattering theorem. These quantities along with the Kirchoff scattering model for a randomly rough surface are used in the standard radiative transfer formulation to compute the backscattering coefficient. Numerical illustrations for the backscattering coefficient are given as a function of the shading factor, incidence angle, leaf orientation distribution, branch orientation distribution, and the number density of leaves. Also illustrated are the properties of the extinction coefficient as a function of leaf and branch orientation distributions. Comparisons are made with measured backscattering coefficients from forested areas reported in the literature.

  8. Single spin asymmetry AN in polarized proton-proton elastic scattering at s=200 GeV

    NASA Astrophysics Data System (ADS)

    STAR Collaboration; Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied, R.; Betancourt, M. J.; Betts, R. R.; Bhasin, A.; Bhati, A. K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bruna, E.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Cai, X. Z.; Caines, H.; Calderón de la Barca Sánchez, M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, J. Y.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chung, P.; Chwastowski, J.; Codrington, M. J. M.; Corliss, R.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derradi de Souza, R.; Dhamija, S.; Didenko, L.; Ding, F.; Dion, A.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elnimr, M.; Engelage, J.; Eppley, G.; Eun, L.; Evdokimov, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Fersch, R. G.; Filip, P.; Finch, E.; Fisyak, Y.; Gagliardi, C. A.; Gangadharan, D. R.; Geurts, F.; Gibson, A.; Gliske, S.; Gorbunov, Y. N.; Grebenyuk, O. G.; Grosnick, D.; Gupta, S.; Guryn, W.; Haag, B.; Hajkova, O.; Hamed, A.; Han, L.-X.; Harris, J. W.; Hays-Wehle, J. P.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Huo, L.; Igo, G.; Jacobs, W. W.; Jena, C.; Judd, E. G.; Kabana, S.; Kang, K.; Kapitan, J.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Kikola, D. P.; Kiryluk, J.; Kisel, I.; Kisiel, A.; Kizka, V.; Klein, S. R.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Koroleva, L.; Korsch, W.; Kotchenda, L.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; LaPointe, S.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Leight, W.; LeVine, M. J.; Li, C.; Li, L.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lima, L. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Longacre, R. S.; Lu, Y.; Luo, X.; Luszczak, A.; Ma, G. L.; Ma, Y. G.; Madagodagettige Don, D. M. M. D.; Mahapatra, D. P.; Majka, R.; Mall, O. I.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Mioduszewski, S.; Mitrovski, M. K.; Mohammed, Y.; Mohanty, B.; Mondal, M. M.; Morozov, B.; Munhoz, M. G.; Mustafa, M. K.; Naglis, M.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nogach, L. V.; Novak, J.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Oliveira, R. A. N.; Olson, D.; Ostrowski, P.; Pachr, M.; Page, B. S.; Pal, S. K.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Peryt, W.; Pile, P.; Planinic, M.; Pluta, J.; Plyku, D.; Poljak, N.; Porter, J.; Poskanzer, A. M.; Powell, C. B.; Pruneau, C.; Pruthi, N. K.; Przybycien, M.; Pujahari, P. R.; Putschke, J.; Qiu, H.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Redwine, R.; Reed, R.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Ruan, L.; Rusnak, J.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandacz, A.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, B.; Schmitz, N.; Schuster, T. R.; Seele, J.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shao, M.; Sharma, B.; Sharma, M.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Singaraju, R. N.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; deSouza, U. G.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Steadman, S. G.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Suarez, M. C.; Sumbera, M.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szanto de Toledo, A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarini, L. H.; Tarnowsky, T.; Thein, D.; Thomas, J. H.; Tian, J.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, Q.; Wang, X. L.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Whitten, C.; Wieman, H.; Wissink, S. W.; Witt, R.; Witzke, W.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, N.; Xu, Q. H.; Xu, W.; Xu, Y.; Xu, Z.; Xue, L.; Yang, Y.; Yang, Y.; Yepes, P.; Yi, Y.; Yip, K.; Yoo, I.-K.; Zawisza, M.; Zbroszczyk, H.; Zhang, J. B.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.

    2013-02-01

    We report a high precision measurement of the transverse single spin asymmetry AN at the center of mass energy s=200 GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The AN was measured in the four-momentum transfer squared t range 0.003⩽|t|⩽0.035 (, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of AN and its t-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this s, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.

  9. Single spin asymmetry AN in polarized proton-proton elastic scattering at √{ s} = 200 GeV

    NASA Astrophysics Data System (ADS)

    Adamczyk, L.; Agakishiev, G.; Aggarwal, M. M.; Ahammed, Z.; Alakhverdyants, A. V.; Alekseev, I.; Alford, J.; Anson, C. D.; Arkhipkin, D.; Aschenauer, E.; Averichev, G. S.; Balewski, J.; Banerjee, A.; Barnovska, Z.; Beavis, D. R.; Bellwied, R.; Betancourt, M. J.; Betts, R. R.; Bhasin, A.; Bhati, A. K.; Bichsel, H.; Bielcik, J.; Bielcikova, J.; Bland, L. C.; Bordyuzhin, I. G.; Borowski, W.; Bouchet, J.; Brandin, A. V.; Brovko, S. G.; Bruna, E.; Bültmann, S.; Bunzarov, I.; Burton, T. P.; Butterworth, J.; Cai, X. Z.; Caines, H.; Calderón de la Barca Sánchez, M.; Cebra, D.; Cendejas, R.; Cervantes, M. C.; Chaloupka, P.; Chang, Z.; Chattopadhyay, S.; Chen, H. F.; Chen, J. H.; Chen, J. Y.; Chen, L.; Cheng, J.; Cherney, M.; Chikanian, A.; Christie, W.; Chung, P.; Chwastowski, J.; Codrington, M. J. M.; Corliss, R.; Cramer, J. G.; Crawford, H. J.; Cui, X.; Das, S.; Davila Leyva, A.; De Silva, L. C.; Debbe, R. R.; Dedovich, T. G.; Deng, J.; Derradi de Souza, R.; Dhamija, S.; Didenko, L.; Ding, F.; Dion, A.; Djawotho, P.; Dong, X.; Drachenberg, J. L.; Draper, J. E.; Du, C. M.; Dunkelberger, L. E.; Dunlop, J. C.; Efimov, L. G.; Elnimr, M.; Engelage, J.; Eppley, G.; Eun, L.; Evdokimov, O.; Fatemi, R.; Fazio, S.; Fedorisin, J.; Fersch, R. G.; Filip, P.; Finch, E.; Fisyak, Y.; Gagliardi, C. A.; Gangadharan, D. R.; Geurts, F.; Gibson, A.; Gliske, S.; Gorbunov, Y. N.; Grebenyuk, O. G.; Grosnick, D.; Gupta, S.; Guryn, W.; Haag, B.; Hajkova, O.; Hamed, A.; Han, L.-X.; Harris, J. W.; Hays-Wehle, J. P.; Heppelmann, S.; Hirsch, A.; Hoffmann, G. W.; Hofman, D. J.; Horvat, S.; Huang, B.; Huang, H. Z.; Huck, P.; Humanic, T. J.; Huo, L.; Igo, G.; Jacobs, W. W.; Jena, C.; Judd, E. G.; Kabana, S.; Kang, K.; Kapitan, J.; Kauder, K.; Ke, H. W.; Keane, D.; Kechechyan, A.; Kesich, A.; Kikola, D. P.; Kiryluk, J.; Kisel, I.; Kisiel, A.; Kizka, V.; Klein, S. R.; Koetke, D. D.; Kollegger, T.; Konzer, J.; Koralt, I.; Koroleva, L.; Korsch, W.; Kotchenda, L.; Kravtsov, P.; Krueger, K.; Kulakov, I.; Kumar, L.; Lamont, M. A. C.; Landgraf, J. M.; LaPointe, S.; Lauret, J.; Lebedev, A.; Lednicky, R.; Lee, J. H.; Leight, W.; LeVine, M. J.; Li, C.; Li, L.; Li, W.; Li, X.; Li, X.; Li, Y.; Li, Z. M.; Lima, L. M.; Lisa, M. A.; Liu, F.; Ljubicic, T.; Llope, W. J.; Longacre, R. S.; Lu, Y.; Luo, X.; Luszczak, A.; Ma, G. L.; Ma, Y. G.; Madagodagettige Don, D. M. M. D.; Mahapatra, D. P.; Majka, R.; Mall, O. I.; Margetis, S.; Markert, C.; Masui, H.; Matis, H. S.; McDonald, D.; McShane, T. S.; Mioduszewski, S.; Mitrovski, M. K.; Mohammed, Y.; Mohanty, B.; Mondal, M. M.; Morozov, B.; Munhoz, M. G.; Mustafa, M. K.; Naglis, M.; Nandi, B. K.; Nasim, Md.; Nayak, T. K.; Nelson, J. M.; Nogach, L. V.; Novak, J.; Odyniec, G.; Ogawa, A.; Oh, K.; Ohlson, A.; Okorokov, V.; Oldag, E. W.; Oliveira, R. A. N.; Olson, D.; Ostrowski, P.; Pachr, M.; Page, B. S.; Pal, S. K.; Pan, Y. X.; Pandit, Y.; Panebratsev, Y.; Pawlak, T.; Pawlik, B.; Pei, H.; Perkins, C.; Peryt, W.; Pile, P.; Planinic, M.; Pluta, J.; Plyku, D.; Poljak, N.; Porter, J.; Poskanzer, A. M.; Powell, C. B.; Pruneau, C.; Pruthi, N. K.; Przybycien, M.; Pujahari, P. R.; Putschke, J.; Qiu, H.; Raniwala, R.; Raniwala, S.; Ray, R. L.; Redwine, R.; Reed, R.; Riley, C. K.; Ritter, H. G.; Roberts, J. B.; Rogachevskiy, O. V.; Romero, J. L.; Ross, J. F.; Ruan, L.; Rusnak, J.; Sahoo, N. R.; Sahu, P. K.; Sakrejda, I.; Salur, S.; Sandacz, A.; Sandweiss, J.; Sangaline, E.; Sarkar, A.; Schambach, J.; Scharenberg, R. P.; Schmah, A. M.; Schmidke, B.; Schmitz, N.; Schuster, T. R.; Seele, J.; Seger, J.; Seyboth, P.; Shah, N.; Shahaliev, E.; Shao, M.; Sharma, B.; Sharma, M.; Shi, S. S.; Shou, Q. Y.; Sichtermann, E. P.; Singaraju, R. N.; Skoby, M. J.; Smirnov, D.; Smirnov, N.; Solanki, D.; Sorensen, P.; deSouza, U. G.; Spinka, H. M.; Srivastava, B.; Stanislaus, T. D. S.; Steadman, S. G.; Stevens, J. R.; Stock, R.; Strikhanov, M.; Stringfellow, B.; Suaide, A. A. P.; Suarez, M. C.; Sumbera, M.; Sun, X. M.; Sun, Y.; Sun, Z.; Surrow, B.; Svirida, D. N.; Symons, T. J. M.; Szanto de Toledo, A.; Takahashi, J.; Tang, A. H.; Tang, Z.; Tarini, L. H.; Tarnowsky, T.; Thein, D.; Thomas, J. H.; Tian, J.; Timmins, A. R.; Tlusty, D.; Tokarev, M.; Trentalange, S.; Tribble, R. E.; Tribedy, P.; Trzeciak, B. A.; Tsai, O. D.; Turnau, J.; Ullrich, T.; Underwood, D. G.; Van Buren, G.; van Nieuwenhuizen, G.; Vanfossen, J. A.; Varma, R.; Vasconcelos, G. M. S.; Videbæk, F.; Viyogi, Y. P.; Vokal, S.; Voloshin, S. A.; Vossen, A.; Wada, M.; Wang, F.; Wang, G.; Wang, H.; Wang, J. S.; Wang, Q.; Wang, X. L.; Wang, Y.; Webb, G.; Webb, J. C.; Westfall, G. D.; Whitten, C.; Wieman, H.; Wissink, S. W.; Witt, R.; Witzke, W.; Wu, Y. F.; Xiao, Z.; Xie, W.; Xin, K.; Xu, H.; Xu, N.; Xu, Q. H.; Xu, W.; Xu, Y.; Xu, Z.; Xue, L.; Yang, Y.; Yang, Y.; Yepes, P.; Yi, Y.; Yip, K.; Yoo, I.-K.; Zawisza, M.; Zbroszczyk, H.; Zhang, J. B.; Zhang, S.; Zhang, X. P.; Zhang, Y.; Zhang, Z. P.; Zhao, F.; Zhao, J.; Zhong, C.; Zhu, X.; Zhu, Y. H.; Zoulkarneeva, Y.; Zyzak, M.; STAR Collaboration

    2013-02-01

    We report a high precision measurement of the transverse single spin asymmetry AN at the center of mass energy √{ s} = 200 GeV in elastic proton-proton scattering by the STAR experiment at RHIC. The AN was measured in the four-momentum transfer squared t range 0.003 ⩽ | t | ⩽ 0.035 (GeV / c) 2, the region of a significant interference between the electromagnetic and hadronic scattering amplitudes. The measured values of AN and its t-dependence are consistent with a vanishing hadronic spin-flip amplitude, thus providing strong constraints on the ratio of the single spin-flip to the non-flip amplitudes. Since the hadronic amplitude is dominated by the Pomeron amplitude at this √{ s}, we conclude that this measurement addresses the question about the presence of a hadronic spin flip due to the Pomeron exchange in polarized proton-proton elastic scattering.

  10. Analytic Form of the Two-Loop Planar Five-Gluon All-Plus-Helicity Amplitude in QCD.

    PubMed

    Gehrmann, T; Henn, J M; Lo Presti, N A

    2016-02-12

    Virtual two-loop corrections to scattering amplitudes are a key ingredient to precision physics at collider experiments. We compute the full set of planar master integrals relevant to five-point functions in massless QCD, and use these to derive an analytical expression for the two-loop five-gluon all-plus-helicity amplitude. After subtracting terms that are related to the universal infrared and ultraviolet pole structure, we obtain a remarkably simple and compact finite remainder function, consisting only of dilogarithms.

  11. Focusing through a turbid medium by amplitude modulation with genetic algorithm

    NASA Astrophysics Data System (ADS)

    Dai, Weijia; Peng, Ligen; Shao, Xiaopeng

    2014-05-01

    Multiple scattering of light in opaque materials such as white paint and human tissue forms a volume speckle field, will greatly reduce the imaging depth and degrade the imaging quality. A novel approach is proposed to focus light through a turbid medium using amplitude modulation with genetic algorithm (GA) from speckle patterns. Compared with phase modulation method, amplitude modulation approach, in which the each element of spatial light modulator (SLM) is either zero or one, is much easier to achieve. Theoretical and experimental results show that, the advantage of GA is more suitable for low the signal to noise ratio (SNR) environments in comparison to the existing amplitude control algorithms such as binary amplitude modulation. The circular Gaussian distribution model and Rayleigh Sommerfeld diffraction theory are employed in our simulations to describe the turbid medium and light propagation between optical devices, respectively. It is demonstrated that the GA technique can achieve a higher overall enhancement, and converge much faster than others, and outperform all algorithms at high noise. Focusing through a turbid medium has potential in the observation of cells and protein molecules in biological tissues and other structures in micro/nano scale.

  12. Research progress on a focal plane array ladar system using chirped amplitude modulation

    NASA Astrophysics Data System (ADS)

    Stann, Barry L.; Abou-Auf, Ahmed; Aliberti, Keith; Dammann, John; Giza, Mark; Dang, Gerard; Ovrebo, Greg; Redman, Brian; Ruff, William; Simon, Deborah

    2003-08-01

    The Army Research Laboratory is researching a focal plane array (FPA) ladar architecture that is applicable for smart munitions, reconnaissance, face recognition, robotic navigation, etc.. Here we report on progress and test results attained over the past year related to the construction of a 32x32 pixel FPA ladar laboratory breadboard. The near-term objective of this effort is to evaluate and demonstrate an FPA ladar using chirped amplitude modulation; knowledge gained will then be used to build a field testable version with a larger array format. The ladar architecture achieves ranging based on a frequency modulation/continuous wave technique implemented by directly amplitude modulating a near-IR diode laser transmitter with a radio frequency (rf) subcarrier that is linearly frequency modulated (chirped amplitude modulation). The diode's output is collected and projected to form an illumination field in the downrange image area. The returned signal is focused onto an array of optoelectronic mixing, metal-semiconductor-metal detectors where it is detected and mixed with a delayed replica of the laser modulation signal that modulates the responsivity of each detector. The output of each detector is an intermediate frequency (IF) signal resulting from the mixing process whose frequency is proportional to the target range. This IF signal is continuously sampled over a period of the rf modulation. Following this, a signal processor calculates the discrete fast Fourier transform over the IF waveform in each pixel to establish the ranges and amplitudes of all scatterers.

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

    SciTech Connect

    M. T. Pena; Franz Gross; Yohanes Surya

    1996-05-01

    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.

  14. Tissue characterization of skin ulcer for bacterial infection by multiple statistical analysis of echo amplitude envelope

    NASA Astrophysics Data System (ADS)

    Omura, Masaaki; Yoshida, Kenji; Kohta, Masushi; Kubo, Takabumi; Ishiguro, Toshimichi; Kobayashi, Kazuto; Hozumi, Naohiro; Yamaguchi, Tadashi

    2016-07-01

    To characterize skin ulcers for bacterial infection, quantitative ultrasound (QUS) parameters were estimated by the multiple statistical analysis of the echo amplitude envelope based on both Weibull and generalized gamma distributions and the ratio of mean to standard deviation of the echo amplitude envelope. Measurement objects were three rat models (noninfection, critical colonization, and infection models). Ultrasound data were acquired using a modified ultrasonic diagnosis system with a center frequency of 11 MHz. In parallel, histopathological images and two-dimensional map of speed of sound (SoS) were observed. It was possible to detect typical tissue characteristics such as infection by focusing on the relationship of QUS parameters and to indicate the characteristic differences that were consistent with the scatterer structure. Additionally, the histopathological characteristics and SoS of noninfected and infected tissues were matched to the characteristics of QUS parameters in each rat model.

  15. Computational complexity of exterior products and multiparticle amplitudes of noninteracting fermions in entangled states

    NASA Astrophysics Data System (ADS)

    Ivanov, Dmitri A.

    2017-07-01

    Noninteracting bosons were proposed to be used for a demonstration of quantum-computing supremacy in a boson-sampling setup. A similar demonstration with fermions would require that the fermions are initially prepared in an entangled state. I suggest that pairwise entanglement of fermions would be sufficient for this purpose. Namely, it is shown that computing multiparticle scattering amplitudes for fermions entangled pairwise in groups of four single-particle states is #P-hard. In linear algebra, such amplitudes are expressed as exterior products of two-forms of rank 2. In particular, a permanent of a N ×N matrix may be expressed as an exterior product of N2 two forms of rank 2 in dimension 2 N2 , which establishes the #P-hardness of the latter.

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

    SciTech Connect

    Pena, M.T.; Gross, F.; Surya, Y.

    1996-11-01

    We discuss the two-pion-exchange (TPE) 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}{ital N} scattering amplitude which includes {Delta}, Roper, and {ital D}{sub 13} isobars, as well as contact terms and off-shell (nonpole) dressed nucleon terms. The {pi}{ital N} amplitude satisfies chiral symmetry constraints and fits {pi}{ital N} data below {approximately} 700 MeV pion energy. We 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 {ital NN} data below the pion production threshold. {copyright} {ital 1996 The American Physical Society.}

  17. Evaluation of new spin foam vertex amplitudes

    NASA Astrophysics Data System (ADS)

    Khavkine, Igor

    2009-06-01

    The Christensen-Egan algorithm is extended and generalized to efficiently evaluate new spin foam vertex amplitudes proposed by Engle, Pereira and Rovelli and Freidel and Krasnov, with or without (factored) boundary states. A concrete pragmatic proposal is made for comparing the different models using uniform methodologies, applicable to the behavior of large spin asymptotics and of expectation values of specific semiclassical observables. The asymptotics of the new models exhibit non-oscillatory, power-law decay similar to that of the Barrett-Crane model, though with different exponents. Also, an analysis of the semiclassical wave packet propagation problem indicates that the Magliaro, Rovelli and Perini's conjecture of good semiclassical behavior of the new models does not hold for generic factored states, which neglect spin-spin correlations.

  18. Amplitude Scaling of Active Separation Control

    NASA Technical Reports Server (NTRS)

    Stalnov, Oksana; Seifert, Avraham

    2010-01-01

    Three existing and two new excitation magnitude scaling options for active separation control at Reynolds numbers below one Million. The physical background for the scaling options was discussed and their relevance was evaluated using two different sets of experimental data. For F+ approx. 1, 2D excitation: a) The traditional VR and C(mu) - do not scale the data. b) Only the Re*C(mu) is valid. This conclusion is also limited for positive lift increment.. For F+ > 10, 3D excitation, the Re corrected C(mu), the St corrected velocity ratio and the vorticity flux coefficient, all scale the amplitudes equally well. Therefore, the Reynolds weighted C(mu) is the preferred choice, relevant to both excitation modes. Incidence also considered, using Ue from local Cp.

  19. Low Amplitude Impact of Damaged PBX 9501

    NASA Astrophysics Data System (ADS)

    Idar, Deanne

    1999-06-01

    Low amplitude impact tests on damaged, baseline and aged, PBX 9501 specimens have been performed to determine the critical impact-velocity threshold for violent reaction. Tests were performed using 3.0-in. diameter, 2 kg. mild-steel projectiles launched from a spigot gun at lightly confined modified Steven targets. Prior damage on the seven targets was induced by a single impact ranging in velocity from 36.9 to 52.7 m/s. External blast gauge data were coupled with ballistic pendulum data to evaluate the level of reaction violence relative to a steady-state detonation. Strain gage data were used to evaluate the response of the explosive to impact and characterize subsequent reaction profiles. The effect of PBX 9501 lots, age, and prior level of damage on threshold behavior will be discussed and compared to single impact test results.

  20. Speech recognition with amplitude and frequency modulations

    NASA Astrophysics Data System (ADS)

    Zeng, Fan-Gang; Nie, Kaibao; Stickney, Ginger S.; Kong, Ying-Yee; Vongphoe, Michael; Bhargave, Ashish; Wei, Chaogang; Cao, Keli

    2005-02-01

    Amplitude modulation (AM) and frequency modulation (FM) are commonly used in communication, but their relative contributions to speech recognition have not been fully explored. To bridge this gap, we derived slowly varying AM and FM from speech sounds and conducted listening tests using stimuli with different modulations in normal-hearing and cochlear-implant subjects. We found that although AM from a limited number of spectral bands may be sufficient for speech recognition in quiet, FM significantly enhances speech recognition in noise, as well as speaker and tone recognition. Additional speech reception threshold measures revealed that FM is particularly critical for speech recognition with a competing voice and is independent of spectral resolution and similarity. These results suggest that AM and FM provide independent yet complementary contributions to support robust speech recognition under realistic listening situations. Encoding FM may improve auditory scene analysis, cochlear-implant, and audiocoding performance. auditory analysis | cochlear implant | neural code | phase | scene analysis