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Angular distribution of neutrons from a plane surface

Description: From introduction: "This report determines lattice losses by considering the angular distribution of the neutrons emitted from the interior faces of the lattice and the exterior faces of the target. The purpose of this report is to investigate this problem by considering the dimensions of the faces to be large compared to the total mean free path."
Date: 1951
Creator: Harker, Wesley H.
Partner: UNT Libraries Government Documents Department

Classical two-slit interference effects in double photoionization of molecular hydrogen at high energies

Description: Recent experiments on double photoionization of H$_2$ with photon energies between 160 and 240 eV have revealed body-frame angular distributions that suggest classical two-slit interference effects may be present when one electron carries most of the available energy and the second electron is not observed. We report precise quantum mechanical calculations that reproduce the experimental findings. They reveal that the interpretation in terms of classical diffraction is only appropriate atsubstantially higher photon energies. At the energies considered in the experiment we offer an alternative explanation based on the mixing of two non-diffractive contributions by circularly polarized light.
Date: July 6, 2008
Creator: Horner, Daniel A.; Miyabe, Shungo; Rescigno, Thomas N; McCurdy, C. William; Morales, Felipe & Martin, Fernando
Partner: UNT Libraries Government Documents Department

Fragmentation pathwaysfor selected electronic states of theacetylene dication

Description: Coincident measurement of the Auger electron and fragmention momenta emitted after carbon core-level photoionization of acetylenehas yielded new understanding of how the dication fragments. Ab initiocalculations and experimental data, including body-frame Auger angulardistributions, are used to identify the parent electronic states andtogether yield a comprehensive map of the dissociation pathways whichinclude surface crossings and barriers to direct dissociation. The Augerangular distributions show evidence of core-holelocalization.
Date: December 18, 2007
Creator: Osipov, Timur; Rescigno, Thomas N.; Weber, Thorsten; Miyabe,Shungo; Jahnke, T.; Alnaser, A. et al.
Partner: UNT Libraries Government Documents Department

Photoelectron angular distributions beyond the dipole approximation

Description: This paper reports the measurement of nondipolar asymmetry parameters for the angular distributions of Ar 1s, Kr 2s, and Kr 2p photoemission within 2-3 keV above their respective thresholds. Pronounced asymmetries with respect to direction of photon propagation are present even at low electron kinetic energies. The energy dependence of the asymmetry is Z- and subshell-specific and causes the direction of preferred electron emission to change sign at least once in each case. Towards higher energies, the asymmetry increases and the photoelectron emission pattern is forward-skewed for all 3 cases. Measured asymmetry parameters are in good agreement with recent predictions from nonrelativistic calculations which include interference between electric-dipole and electric-quadrupole transition amplitudes in the photoabsorption process.
Date: August 1996
Creator: Kraessig, B.; Jung, M.; Gemmell, D. S.; Kanter, E. P.; LeBrun, T.; Southworth, S. H. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the angular distribution of electrons from W {right arrow} e{nu} decays observed in p pbar collisions at {squareroot}s = 1.8 TeV

Description: We present a preliminary measurement of the electron angular distribution parameter {alpha}<sub>2</sub> in W {yields} e{nu} events using data collected by the D0 detector during the 1994-1995 Tevatron run. We compare our results with next-to- leading order perturbative QCD, which predicts an angular distribution of (1±{alpha}<sub>1</sub> cos{theta}* +{alpha}<sub>2</sub> cos²{theta}*), where {theta}* is the angle between the charged lepton and the antiproton in the Collins-Soper frame. In the presence of QCD corrections, the parameters {alpha}<sub>1</sub> and {alpha}<sub>2</sub> become functions of p<sup>W</sup><sub>T</sub> , the W boson transverse momentum. We present the first measurement of {alpha}<sub>2</sub> as a function of p<sup>W</sup><sub>T</sub>. This measurement is of importance, because it provides a test of next-to-leading order QCD corrections which are a non-negligible contribution to the W mass measurement.
Date: July 26, 1999
Creator: Abbott, B.
Partner: UNT Libraries Government Documents Department

Initial Measurements on the Angular Distribution of Deuterium Plasma Produced by a Pulsed Spark Source

Description: Abstract: "The deuterium plasma which is ejected by a 6000-ampere pulsed current through a rail-type spark source has a yield in the forward direction which is a factor of 5 to 10 greater than that in the perpendicular direction. This effect is believed to be due to the magnetic propulsion of the plasma."
Date: March 24, 1955
Creator: Bostick, W. H.
Partner: UNT Libraries Government Documents Department


Description: The 60-in. scattering chamber used with the external beam of the Argonne 60-in. cyclotron is described. The scattering chamber permits operation over an angular range from 4 deg to 176 deg with an accuracy of plus or minus 3 min. of arc. The geometrical factors involved in the measurement of cross sections are known to plus or minus 0.1% or better. The angular positions of the detectors, the target changer, and an absorber foil system in front of the detection units are operated by remote control so as to permit continuous operation of the cyclotron when these parameters are varied. It is possible to operate several detectors simultaneously; and in order to permit angular correlation studies, the angular position of one detector can be varied by remote control with respect to the other detector units. A summary of some of the experimental work performed with this instrument is given. (auth)
Date: April 1, 1961
Creator: Yntema, J.L. & Ostrander, H.W.
Partner: UNT Libraries Government Documents Department

The Simplest Double Slit: Interference and Entanglement in Double Photoionization of H2

Description: The wave nature of particles is rarely seen in nature. One reason is their very short de Broglie wavelengths in most situations. However, even with wavelengths close to the size of their surroundings, they couple to their environment, e.g. by gravity, Coulomb interaction, or thermal radiation. These couplings shift the phase of the waves, often in an uncontrolled way, hence yielding varying amounts of decoherence i.e. loss of phase integrity. Decoherence is thought to be a main cause of the transition from quantum to classical behavior. How much interaction is necessary and how big an environment is needed to induce the onset of classical behavior? Here we show that a photoelectron and two protons form a minimum particle/slit system, and that a minimum environment can be no more than a single additional electron. We observe interference 'fringes' in the angular distribution of a single electron and the loss of fringe visibility caused by its Coulomb interaction with a second electron. While, at the same time, the correlated momenta of the entangled electron pair continue to exhibit quantum interference.
Date: September 18, 2007
Creator: Akoury , D.; Kreidi, K.; Jahnke , T.; Weber, Th.; Staudte , A.; Schoffler, M. et al.
Partner: UNT Libraries Government Documents Department

A hybridGaussian-discrete variable representation approach to molecular continuum processes II: application to photoionization of diatomic Li2+

Description: We describe an approach for studying molecular photoionization with a hybrid basis that combines the functionality of analytic basis sets to represent electronic coordinates near the nuclei of a molecule with numerically-defined grid-based functions. We discuss the evaluation of the various classes of two-electron integrals that occur in a hybrid basis consisting of Gaussian type orbitals (GTOs) and discrete variable representation (DVR) functions. This combined basis is applied to calculate single photoionization cross sections for molecular Li_2+, which has a large equilibrium bond distance (R=5.86a_0). The highly non-spherical nature of Li_2+ molecules causes higher angular momentum components to contribute significantly to the cross section even at low photoelectron energies, resulting in angular distributions that appear to be f-wave dominated near the photoionization threshold. At higher energies, where the de Broglie wavelength of the photoelectron becomes comparable with the bond distance, interference effects appear in the photoionization cross section. These interference phenomena appear at much lower energies than would be expected for diatomic targets with shorter internuclear separations.
Date: August 1, 2008
Creator: Rescigno, Thomas N; Yip, Frank L.; McCurdy, C. William & Rescigno, Thomas N.
Partner: UNT Libraries Government Documents Department


Description: The energy and angular distributions of N{sub 2}H{sup +} and N{sub 2}D{sup +} formed when a beam of N+2 passes through a scattering cell containing H{sub 2}, D{sub 2}, or HD have been measured at relative kinetic energies ranging from 2.3 to 11.6 eV. From some experiments, intensity contour maps that show the complete product velocity vector distribution in the centre of mass system have been generated. Although backward recoil scattering occurs at all energies, most products are scattered forward in the centre of mass system. The shape and position of the forward scattered product peak are largely consistent with the stripping model modified to account for target motion.
Date: June 1, 1967
Creator: Gentry, W.R.; Gislason, E.A.; Lee, Yuan-tseh; Mahan, B.H. & Tsao,Chi-wing.
Partner: UNT Libraries Government Documents Department

Strange-Particle Production by 1170-MeV/c pi- Mesons

Description: Production of {Lambda} + K{sup 0}, {Sigma}{sup 0} + K{sup 0}, and {Sigma}{sup -} + K{sup +} by 1170-MeV/c {pi}{sup -} mesons has been studied in the Lawrence Radiation Laboratory 72-inch hydrogen bubble chamber, Cross sections, angular distributions, and polarizations are presented. The polarization of the {Sigma}{sup 0} is determined at four center-of-mass angles and found to be small everywhere. Based on published results for the reaction {pi}{sup +} + p {yields} {Sigma}{sup +}, K{sup +}, a comparison of the polarizations of {Sigma}{sup +}, {Sigma}{sup -}, and {Sigma}{sup 0} is made from the charge-independence triangle. A conclusion is reached that the {Sigma}{sup -} polarization should be large, and that the {Sigma}{sup -} and {Sigma}{sup +} polarizations should be opposite in sign.
Date: May 27, 1963
Creator: Anderson, Jared Arnold
Partner: UNT Libraries Government Documents Department


Description: The systematics of bulk entropy production in experimental data on Ai-A, p + y and e{sup +}e{sup -} interactions at high energies and large {mu}{sub B} is discussed. It is proposed that scenarios with very early thermalization, such as Landau's hydrodynamical model, capture several essential features of the experimental results. It is also pointed out that the dynamics of systems which reach the hydrodynamic regime give similar multiplicities and angular distributions as those calculated in weak-coupling approximations (e.g. pQCD) over a wide range of beam energies. Finally, it is shown that the dynamics of baryon stopping are relevant to the physics of total entropy production, explaining why A+A and e{sup +}e{sup -} multiplicities are different at low beam energies.
Date: July 3, 2006
Partner: UNT Libraries Government Documents Department

Collider Signals Of Top Quark Flavor Violation From A Warped ExtraDimension

Description: We study top quark flavor violation in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. Such a scenario provides solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM without inducing a flavor problem. We find that, generically, tcZ couplings receive a huge enhancement, in particular the right handed ones can be {Omicron}(1%). This results in BR (t {yields} cZ) at or above the sensitivity of the Large Hadron Collider (LHC). At the International Linear Collider (ILC), single top production, via e{sup +}e{sup -} {yields} t{bar c}, can be a striking signal for this scenario. In particular, it represents a physics topic of critical importance that can be explored even with a relatively low energy option, close to the tc threshold. At both the LHC and the ILC, angular distributions can probe the above prediction of dominance of right-handed couplings.
Date: August 29, 2006
Creator: Agashe, Kaustubh; Perez, Gilad & Soni, Amarjit
Partner: UNT Libraries Government Documents Department

Background neutral veto: Background reduction in eta(c) --> gamma-gamma

Description: Several upgrades of the E760 detector have been discussed at various stages. One of these considered the possibility of covering with a photon detector the backward region (i.e. lab. poar angle {theta}{sub lab} &gt; 70{sup o}). In this memo the author limited the study to the effect of an extensive coverage in the backward region on the {gamma}{gamma} background at the {eta}{sub c}. This is a rather important channel. In effect at this time and as far as the author knows, they don't have a clear signal and the Signal/Background ratio is poor. (Signal/Background {approx_equal} 1. {divided_by} 1.5 are the values so far obtained from different analyses). Nevertheless the {gamma}{gamma} final state remains the ''strong channel'' for the {eta}{sub c} detection. The author considered as background sources the {pi}{sup 0}{pi}{sup 0} and {pi}{sup 0}{gamma} final states and the author required |cos{theta}*| &lt; 0.25. Events p{bar p} {yields} {pi}{sup 0}{pi}{sup 0} and {pi}{sup 0}{gamma} were Monte Carlo generated at E{sub CM} = 2.985 GeV with the angular distribution as measured by E760 [1].
Date: June 1, 1992
Creator: Marchetto, F. & /INFN, Turin /Turin U.
Partner: UNT Libraries Government Documents Department

Common Origin of the Circular-dichroism Pattern in ARPES of SrTiO3 and CuxBi2Se3

Description: We investigate circular dichroism in the angular distribution (CDAD) of photoelectrons from SrTiO{sub 3}:Nb and Cu{sub x}Bi{sub 2}Se{sub 3} recorded by 7-eV laser ARPES. In addition to the well-known node that occurs in CDAD when the incidence plane matches the mirror plane of the crystal, we show that another type of node occurs when the mirror plane of the crystal is vertical to the incidence plane and the electronic state is two dimensional. The flower-shaped CDAD's occurring around the Fermi level of SrTiO{sub 3}:Nb and around the Dirac point of Cu{sub x}Bi{sub 2}Se{sub 3} are explained on equal footings. A surface-state-to-surface-resonance transition is indicated for the topological state of Cu{sub x}Bi{sub 2}Se{sub 3}.
Date: August 19, 2011
Creator: Bell, Christopher
Partner: UNT Libraries Government Documents Department

Angular Distributions in the Decays B to K*l+l-

Description: The authors use a sample of 384 million B{bar B} events collected with the BABAR detector at the PEP-II e{sup +}e{sup -} collider to study angular distributions in the rare decays B {yields} K*{ell}{sup +}{ell}{sup -}, where {ell}{sup +}{ell}{sup -} is either e{sup +}e{sup -} or {mu}{sup +}{mu}{sup -}. For low dilepton invariant masses, m{sub {ell}{ell}} &lt; 2.5 GeV/c{sup 2}, they measure a lepton forward-backward asymmetry {Alpha}{sub FB} = 0.24{sub -0.23}{sup +0.18} {+-} 0.05 and K* longitudinal polarization F{sub L} = 0.35 {+-} 0.16 {+-} 0.04. For m{sub {ell}{ell}} &gt; 3.2 GeV/c{sup 2}, they measure {Alpha}{sub FB} = 0.76{sub -0.32}{sup +0.52} {+-} 0.07 and F{sub L} = 0.71{sub -0.22}{sup 0.20} {+-} 0.04.
Date: May 2, 2008
Creator: Collaboration, The BABAR & Aubert, B.
Partner: UNT Libraries Government Documents Department

Neutron Production by Muon Spallation I: Theory

Description: We describe the physics and codes developed in the Muon Physics Package. This package is a self-contained Fortran90 module that is intended to be used with the Monte Carlo package MCNPX. We calculate simulated energy spectra, multiplicities, and angular distributions of direct neutrons and pions from muon spallation.
Date: November 13, 2006
Creator: Luu, T & Hagmann, C
Partner: UNT Libraries Government Documents Department

Towards a Microscopic Reaction Description Based on Energy Density Functionals

Description: A microscopic calculation of reaction cross sections for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all particle-hole excitations in the target and one-nucleon pickup channels. The particle-hole states may be regarded as doorway states through which the flux flows to more complicated configurations, and subsequently to long-lived compound nucleus resonances. Target excitations for {sup 40,48}Ca, {sup 58}Ni, {sup 90}Zr and {sup 144}Sm were described in a random-phase framework using a Skyrme functional. Reaction cross sections obtained agree very well with experimental data and predictions of a state-of-the-art fitted optical potential. Couplings between inelastic states were found to be negligible, while the pickup channels contribute significantly. The effect of resonances from higher-order channels was assessed. Elastic angular distributions were also calculated within the same method, achieving good agreement with experimental data. For the first time observed absorptions are completely accounted for by explicit channel coupling, for incident energies between 10 and 70 MeV, with consistent angular distribution results.
Date: September 26, 2011
Creator: Nobre, G A; DIetrich, F S; Escher, J E; Thompson, I J; Dupuis, M; Terasaki, J et al.
Partner: UNT Libraries Government Documents Department

Grid-based methods for diatomic quantum scattering problems II: Time-dependent treatment of single- and two-photon ionization of H2+

Description: The time-dependent Schr\&quot;odinger equation for H2+ in a time-varying electromagnetic field is solved in the fixed-nuclei approximation using a previously developed finite-element/ discrete variable representation in prolate spheroidal coordinates. Amplitudes for single- and two-photon ionization are obtained using the method of exterior complex scaling to effectively propagate the field-free solutions from the end of the radiation pulse to infinite times. Cross sections are presented for one-and two-photon ionization for both parallel and perpendicular polarization of the photon field, as well as photoelectron angular distributions for two-photon ionization.
Date: April 20, 2009
Creator: Rescigno, Thomas N.; Tao, L. & McCurdy, C.W.
Partner: UNT Libraries Government Documents Department

Transverse momentum dependent quark distributions and polarized Drell-Yan processes

Description: We study the spin-dependent quark distributions at large transverse momentum. We derive their transverse momentum behaviors in the collinear factorization approach in this region. We further calculate the angular distribution of the Drell-Yan lepton pair production with polarized beams and present the results in terms of the collinear twist-three quark-gluon correlation functions. In the intermediate transverse momentum region, we find that the two pproaches: the collinear factorization and the transverse momentum dependent factorization approaches are consistent in the description of the lepton pair angular distributions.
Date: September 11, 2009
Creator: Zhou, J.; Yuan, F. & Liang, Z.-T.
Partner: UNT Libraries Government Documents Department