Angular anisotropy representation by probability tables
In this paper, we improve point-wise or group-wise angular anisotropy representation by using probability tables. The starting point of this study was to give more flexibility (sensitivity analysis) and more accuracy (ray effect) to group-wise anisotropy representation by Dirac functions, independently introduced at CEA (Mao, 1998) and at IRSN (Le Cocq, 1998) ten years ago. Basing ourselves on our experience of cross-section description, acquired in CALENDF (Sublet et al., 2006), we introduce two kinds of moment based probability tables, Dirac (DPT) and Step-wise (SPT) Probability Tables where the angular probability distribution is respectively represented by Dirac functions or by a step-wise function. First, we show how we can improve equi-probable cosine representation of point-wise anisotropy by using step-wise probability tables. Then we show, by Monte Carlo techniques, how we can obtain a more accurate description of group-wise anisotropy than the one usually given by a finite expansion on a Legendre polynomial basis (that can induce negative values) and finally, we describe it by Dirac probability tables. This study is carried out in the framework of GALILEE project R and D activities (Coste-Delclaux, 2008). (authors)
UTOE, UKNDL to ENDF/B Format Conversion with Log-Log Interpolation and Angular Distribution Tables
1 - Nature of physical problem solved: The programme performs a fully automated translation from UKNDL into ENDF/B (version 1) format. 2 - Method of solution: Each reaction is cropped to reduce the number of redundant points; log-log interpolation scheme is adopted everywhere. Angular distributions are given in tabular form. 3 - Restrictions on the complexity of the problem: The existing array size limitations which apply to both UKNDL and ENDF/B have been taken into account. Secondary energy distributions as formulated by UKNDL are not considered; a simple evaporation spectrum is introduced everywhere for the (n,n') continuum and (n,2n) reactions
Perturbed angular correlations and distributions
The present index comprises original works and review papers on the perturbed angular correlations (PAC) and distributions (PAD). The articles published in the Soviet and foreign journals as well as the materials of conferences, monographs and collections published in the USSR and abroad, the preprints produced by various institutes and abstracts of disertations are included from 1948 up to 1973. The whole material compiled in this index is divided into three parts. Part one is a bibliographic index. All papers in this part are divided into three sections. Section one comprises the papers devoted to the theoretical works on PAC, review papers, monographs, materials of conferences. Section two deals with the works of methodical character where correlation spectrometers as well as the treatment of experimental data are described. In section three experimental works with concrete nuclei are compiled. Part two gives the characteristic of works performed with concrete nuclei. This part is presented in the form of the table in which the works are systematized according to the chemical elements and isotopes. The table shows the characteristics of the nuclear levels used in the investigations by PAC as well as brief characteristics of experiments and results obtained. Part three - appendix contains alphabetic index of the authors, the list of the used editions with the abbreviations of the titles of these editions. The lists indicating the dynamic of the quantity of works on PAC and the distribution according to the literature sources are also given
Fission fragment angular distributions
Recently a Letter appeared (Phys. Rev. Lett., 522, 414(1984)) claiming that the usual expression for describing the angula distribution of fission fragments from compound nuclear decay is not a necessarily valid limit of a more general expression. In this comment we wish to point out that the two expressions arise from distinctly different models, and that the new expression as used in the cited reference is internally inconsistent
Angular distribution of coherent bremsstrahlung
The angular distribution of the linearly polarised photon beam produced by coherent bremsstrahlung from an aligned diamond radiator has been measured at the MAMI A2 tagged photon facility. The measurements were made with a prototype position sensitive photon detector which utilises the pair production process and a double sided silicon strip detector. This polarised photon beam is used for nuclear and hadronic experiments and in their analysis the polarisation is obtained from a calculation, which matches the experimental intensity spectrum. As the polarisation is related to the photon beam angular distribution, the present measurements can be used to test this calculation. The overall agreement is found to be good although there are some regions where significant discrepancies exist.
Wigner distributions and quark orbital angular momentum
Cedric LorceOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
We discuss the quark phase-space or Wigner distributions of the nucleon which combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-front constituent quark model. We show how the quark orbital angular momentum can be extracted from the Wigner distributions a...
Angular distribution of oriented nucleus fission neutrons
Calculations of anisotropy of angular distribution of oriented 235U nuclei thermal fission neutrons have been carried out. the neutrons were assumed to evaporate isotropically by completely accelerated fragements in the fragment system with only its small part, i. e. fission-producing neutrons, emitted at the moment of neck break. It has been found out that at low energies of neutrons Esub(n)=1-2 MeV the sensitivity of the angular distribution anisotropy to variations of spectrum of neutron evaporation from fragments and the magnitude of a share of fission-producing neutrons reaches approximately 100%, which at high energies, Esub(n) > 5 MeV it does not exceed approximately 20%. Therefore the angular distribution of fast neutrons to a greater degree of confidence may be used for restoring the angular distribution anisotropy of fragments while the angular distribution of low energy neutrons may be used for deriving information on the fission process, but only in case 6f the experiment accuracy is better than approximately 3%
Moliere angular and lateral distributions with ionization
The Moliere distribution for arbitrary linear combination between the deflection angle and the lateral displacement is improved to take into account ionization loss. The analytical results for lateral distribution derived through numerical integrations for dilogarithm function are compared with our detailed Monte Carlo results. Goudsmit-Saunderson angular distribution derived with Moliere parameters, is also confirmed to agree with our detailed Monte Carlo results. (author)
Quark Wigner distributions and orbital angular momentum
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions and the transverse-momentum dependent parton distributions. We focus the discussion on the distributions of unpolarized/longitudinally polarized quark in an unpolarized/longitudinally polarized nucleon. In this way, we can study the role of the orbital angular momentum of the quark in shaping the nucleon and its correlations with the quark and nucleon polarizations. The quark orbital angular momentum is also calculated from its phase-space average weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. The corresponding results obtained within different light-cone quark models are compared with alternative definitions of the quark orbital angular momentum, as given in terms of generalized parton distributions and transverse-momentum dependent parton distributions.
Jet angular distribution from quantum chromodynamics
The quantum chromodynamic correction to jet (defined a la Sterman and Weinberg) angular distribution in energetic e+e- annihilation is calculated to order α/sub s/ keeping exact dependence on epsilon and delta. Deviations from the zeroth order distribution, 1 + cos2theta, for are found relatively large values of epsilon and delta. This effect could be tested at the existing e+e- colliding beam facilities
Angular momentum distributions in subbarrier fusion reactions
Interest in subbarrier heavy-ion fusion was stimulated by the realization that subbarrier fusion cross sections were enhanced by many orders of magnitude over what would be expected from quantum mechanical one-dimensional barrier penetration. This review focuses on the angular momentum (spin) distributions in heavy-ion fusion reactions. Experimental probes, theoretical considerations, and a comparison of experimental results with model calculations are given. 86 refs., 10 figs
Quark Orbital-Angular-Momentum Distribution in the Nucleon
Hoodbhoy, Pervez; Ji, Xiangdong; Lu, Wei
1998-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {\\it orbital} angular momentum distribution $L_q(x)$. The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution $E(x)$ in the forward limit. We comment upon the evolution equations o...
Study of the Angular Distribution of Scintillation Photons
Fornaro, Giulia Alice; Ghezzi, Alessio; Knapitsch, Arno; Modrzynski, Pawel; Pizzichemi, Marco; Lecoq, Paul; Auffray, Etiennette
2014-01-01
This paper presents a characterization method to experimentally determine the angular distribution of scintillation light. By exciting LYSO crystals with a radioactive source, we measured the light angular profiles obtained with samples of different geometries in different conditions of wrapping. We also measured the angular distribution of light emitting in glue and compared it with the one emitting in air. Angular distribution of light output of photonic crystals is also provided. Consistency of the measurements is verified with conventional light output measurements.
Quark orbital-angular-momentum distribution in the nucleon
Hoodbhoy, P.; Ji, X.; Lu, W. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)
1999-01-01
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark {ital orbital} angular momentum distribution L{sub q}(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. {copyright} {ital 1998} {ital The American Physical Society}
Quark orbital-angular-momentum distribution in the nucleon
We introduce gauge-invariant quark and gluon angular momentum distributions after making a generalization of the angular momentum density operators. From the quark angular momentum distribution, we define the gauge-invariant and leading-twist quark orbital angular momentum distribution Lq(x). The latter can be extracted from data on the polarized and unpolarized quark distributions and the off-forward distribution E(x) in the forward limit. We comment upon the evolution equations obeyed by this as well as other orbital distributions considered in the literature. copyright 1998 The American Physical Society
Phase-space distributions and orbital angular momentum
Pasquini B.
2014-06-01
Full Text Available We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Phase-space distributions and orbital angular momentum
Pasquini B.; Lorcé C.
2014-01-01
We review the concept of Wigner distributions to describe the phase-space distributions of quarks in the nucleon, emphasizing the information encoded in these functions about the quark orbital angular momentum.
Imaging the Earth's Interior: the Angular Distribution of Terrestrial Neutrinos
Fields, Brian D
2004-01-01
Decays of radionuclides throughout the Earth's interior produce geothermal heat, but also are a source of antineutrinos. The (angle-integrated) geoneutrino flux places an integral constraint on the terrestrial radionuclide distribution. In this paper, we calculate the angular distribution of geoneutrinos, which opens a window on the differential radionuclide distribution. We develop the general formalism for the neutrino angular distribution, and we present the inverse transformation which recovers the terrestrial radioisotope distribution given a measurement of the neutrino angular distribution. Thus, geoneutrinos not only allow a means to image the Earth's interior, but offering a direct measure of the radioactive Earth, both (1) revealing the Earth's inner structure as probed by radionuclides, and (2) allowing for a complete determination of the radioactive heat generation as a function of radius. We present the geoneutrino angular distribution for the favored Earth model which has been used to calculate g...
Orbital Angular Momentum Parton Distributions in Light-Front Dynamics
Cano, F.; Faccioli, P.; Scopetta, S.; Traini, M.(Dipartimento di Fisica, Università degli studi di Trento and INFN — TIFPA, Via Sommarive 14, I-38123, Povo (Trento), Italy)
2000-01-01
We study the quark angular momentum distribution in the nucleon within a light-front covariant quark model. Special emphasis is put into the orbital angular momentum: a quantity which is very sensitive to the relativistic treatment of the spin in a light-front dynamical approach. Discrepancies with the predictions of the low-energy traditional quark models where relativistic spin effects are neglected, are visible also after perturbative evolution to higher momentum scales. Orbital angular mo...
Observables for Quarks and Gluons Orbital Angular Momentum Distributions
Liuti, Simonetta; Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Rajan, Abha
2015-02-01
We discuss the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term - Ji decomposition - or a canonical term - Jaffe-Manohar decomposition. Orbital angular momentum has been connected in each decomposition to a different observable, a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and a twist three Generalized Parton Distribution (GPD) for the kinetic term. While the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
Evolution Equations for Higher Moments of Angular Momentum Distributions
Haegler, P.; Schaefer, A
1998-01-01
Based on a sumrule for the nucleon spin we expand quark and gluon orbital angular momentum operators and derive an evolution matrix for higher moments of the corresponding distributions. In combination with the spin-dependent DGLAP-matrix we find a complete set of spin and orbital angular momentum evolution equations.
Quantum optimal control of photoelectron spectra and angular distributions
Goetz, R Esteban; Santra, Robin; Koch, Christiane P
2016-01-01
Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on e.g. charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.
Quantum optimal control of photoelectron spectra and angular distributions
Goetz, R. Esteban; Karamatskou, Antonia; Santra, Robin; Koch, Christiane P.
2016-01-01
Photoelectron spectra and photoelectron angular distributions obtained in photoionization reveal important information on, e.g., charge transfer or hole coherence in the parent ion. Here we show that optimal control of the underlying quantum dynamics can be used to enhance desired features in the photoelectron spectra and angular distributions. To this end, we combine Krotov's method for optimal control theory with the time-dependent configuration interaction singles formalism and a splitting approach to calculate photoelectron spectra and angular distributions. The optimization target can account for specific desired properties in the photoelectron angular distribution alone, in the photoelectron spectrum, or in both. We demonstrate the method for hydrogen and then apply it to argon under strong XUV radiation, maximizing the difference of emission into the upper and lower hemispheres, in order to realize directed electron emission in the XUV regime.
A new detection system for time-optimized heavy-ion angular distribution measurements has been designed and constructed. This device is composed by an ionization chamber with a segmented-grid anode and three position-sensitive silicon detectors. This particular arrangement allows identifying reaction products emitted within a 30° wide angular range with better than 1° angular resolution. As a demonstration of its capabilities, angular distributions of the elastic scattering cross-section and the production of alpha particles in the 7Li+27Al system, at an energy above the Coulomb barrier, are presented. -- Highlights: • We constructed a detection system for time-optimized heavy-ion angular distribution measurements. • We characterized this device and obtained an energy resolution of 3% and an angular resolution of 1°. • We measured elastic scattering cross-sections in 7Li+27Al finding good agreement with previous data. • The performed tests included the measurement of alpha particle production cross-sections in 7Li+27Al
Asymmetry in the angular distributions of spectator-nucleons
The asymmetry in the angular distributions of spectator-nucleons has been studied in dp interactions, and it has been found that the sign of the asymmetry depends on the reaction channel. It is shown that in the momentum interval 0-200 MeV/c of spectators basic features of the angular distributions can be reproduced in the framework of the spectator model taking into account the energy dependence of the NN cross section and the flux-factor
Quark Wigner Distributions and Orbital Angular Momentum
Lorce, Cédric; Pasquini, B.
2011-01-01
We study the Wigner functions of the nucleon which provide multidimensional images of the quark distributions in phase space. These functions can be obtained through a Fourier transform in the transverse space of the generalized transverse-momentum dependent parton distributions. They depend on both the transverse position and the three-momentum of the quark relative to the nucleon, and therefore combine in a single picture all the information contained in the generalized parton distributions...
Angular distributions by the conventional and the Doppler shift method
The angular distribution of elastically scattered metastable Ne*(3P2) has been measured by the conventional and the Doppler shift method. The conventional method shows a good angular resolution and signal to noise ratio. For the Doppler shift method, the angular resolution and the signal to noise ratio are much worse. By Monte Carlo-calculations it is shown that the influence of the residual velocity profiles of the supersonic atomic beams is large for the Doppler method, but can nearly be neglected for the conventional method. For nonsymmetric systems (such as Na2-Xe) and for inelastic processes the Doppler method is expected to be more successful. (Auth.)
Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strat...
Angular distributions and total yield of laser ablated silver
Svendsen, Winnie Edith; Nordskov, A.; Schou, Jørgen; Thestrup Nielsen, Birgitte; Ellegaard, Ole
1997-01-01
The angular distribution of laser ablated silver has been measured in situ with a newly constructed setup with an array of microbalances. The distribution is strongly peaked in the forward direction corresponding to cospθ, where p varies between 5 and 9 for laser fluences from 2 to 7 J/cm2 at 355...
Measurements of angular distributions of degraded protons in thick absorbers
This chapter examines the behavior of a proton beam with a kinetic energy corresponding to the lower energy limit of the Low-Energy Antiproton Ring (LEAR), which is degraded by thick absorbers suffering an energy loss comparable to its initial energy. Angular distributions of protons are measured with an initial energy around 3.5 MeV, degraded by thick aluminium, polyethylene, and lead absorbers. Using the Erlangen Tandem accelerator, the measurements indicate that in all cases the variation of the width of the straggling distribution (fwhm) and of their mean energy as a function of the scattering angle was found to be small in the angular region between 00 and 150. It is concluded that degraders with low proton number are superior to those with high proton number, due to their narrower angular distributions
On the Observability of the Quark Orbital Angular Momentum Distribution
Courtoy, Aurore; Hernandez, J Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha
2013-01-01
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated to orbital angular momentum %to deeply virtual Compton scattering provide observables related to orbital angular momentum and are related to the target-spin asymmetry in deeply virtual Compton scattering, already mea...
Generalized Parton Distributions Describing Partonic Orbital Angular Momentum
Liuti, Simonetta; Engelhardt, Michael; Rajan, Abha; Courtoy, Aurore
2015-04-01
We discuss orbital angular momentum in QCD, in particular, its observability, and its partonic interpretation. Orbital momentum can be defined in QCD using two different decomposition schemes that yield a kinetic and a canonical definition, respectively. We argue that kinetic orbital angular momentum is intrinsically associated with twist three Generalized Parton Distributions (GPDs), and it is therefore readily observable in Deeply Virtual Compton Scattering experiments. On the other hand, canonical angular momentum is defined in terms of a Generalized Transverse Momentum Distribution (GTMD) and it can be therefore observed in scattering processes involving an additional hadronic reaction plane. A comparison between the two definitions can be performed by extending to GTMDs the techniques previously developed for lattice calculations of Transverse Momentum Distributions (TMDs) evaluating the matrix elements of quark bilocal operators containing a staple-shaped Wilson connection. This work was funded in part by U.S. D.O.E. Grant DE-FG02-01ER4120.
Practical derivation of Moliere angular distribution with ionization
Approximation methods for practical and efficient derivations of Moliere angular distribution are attempted. The scale factor ν characterizing the ionization process, solved in numerical integrals, is well approximated by a series expansion of the solution with rest-mass up to the second order. Moliere screening model is found well approximated by a simpler Born-type model for wide variety of substances, so that the characteristic constants B and θM of angular distribution for mixed or compound substances are derived far simply and enough accurately from the Kamata-Nishimura constants for mixture without taking as many integrations as the number of mixed substances for stochastic means. These confirmations will be valuable for rapid derivations of Moliere angular distribution, especially in tracing tracks of charged particle in Monte Carlo simulations. (author)
Angular Distribution of Clustersin Skewed CDM Models
Borgani, S; Plionis, M
1994-01-01
We perform a detailed investigation of the statistical properties of the projected distribution of galaxy clusters obtained in Cold Dark Matter (CDM) models with both Gaussian and skewed primordial density fluctuations. We use N-body simulations to construct a set artificial Lick maps. An objective cluster--finding algorithm is used to identify clusters of different richness. For Gaussian models, the overall number of clusters is too small in the standard CDM case, but a model with higher normalisation fares much better; non--Gaussian models with negative skewness also fit faily well. We apply several statistical tests to compare real and simulated cluster samples, such as the 2-point correlation function, the minimal spanning tree construction, the multifractal analysis and the skewness of cell counts. The emerging picture is that Gaussian models, even with a higher normalization, are in trouble. Skew-positive models are also ruled out, while skew-negative models can reproduce the observed clustering of gala...
Distributed MIMO Radar Monopulse Angular Estimation
Jin Zhen
2014-08-01
Full Text Available The linear zone of the S-curve, which is formed with the digital beamforming (DBF method, is extremely narrow for monopulse angle measurements with distributed Multiple-Input and Multiple-Output (MIMO radar. Based on the transmitting-receiving beam pattern without gratelobe, the DBF method is proposed to form the ΣΔ-beam by using the absolute value of the echo signal. The ideal null depth can be achieved and the linear zone of the S-curve is expanded because the main lobe of the Δ-beam is enveloped by the Σ-beam. The monopulse angle for a target with high angle velocity was estimated. When the Signal-to-Noise Ratio (SNR was higher than −15 dB , the accuracy of the proposed method was better than that of conventional methods. When the SNR was equal to −15 dB , the accuracy of the proposed method was similar to
The calculation of angular and energy-angular distributions for n+D reactions
The energy-angular distributions for secondary neutrons and protons of breakup reactions and the elastic angular distributions of n+D were calculated by the computer code TSD which was developed by Chu and his co-workers from the three-body integral equations based on Faddeev-AGS theory. The results are compiled in the ENDF/B-6 format, and they are stored in the second version of Chinese Evaluated Nuclear DAta Library, CENDL-2. Their errors of energy conservation for breakup are less than one percent. The differential cross sections of the elastic scattering and the double-differential cross sections for secondary neutrons and protons of breakup reactions were calculated from CENDL-2, the results are in good agreement with the experimental data
Predicted angular distribution of fast charged particles with ionization
Moliere theory of angular distribution for fast charged particles is improved to take into account ionization loss, by using Kamata-Nishimura formulation of the theory. Decrease of the particle energy along the passage hence increase of the screening angle brings a slight different results from those derived by Moliere-Bethe formulation for fixed energies. The present results are reduced to the same Moliere distribution with modified values of the expansion parameter and the unit of Moliere angle. Properties of the new distribution and differences from the traditional one are discussed. Angular distributions of particles penetrating through the mixed or compound substances are also investigated both under the relativistic and the nonrelativistic conditions, together with the Kamata-Nishimura constants characterizing their formulation. (author)
Orbital angular momentum and generalized transverse momentum distribution
Zhao, Yong; Liu, Keh-Fei; Yang, Yi-Bo
2016-03-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.
Orbital Angular Momentum and Generalized Transverse Momentum Distribution
Zhao, Yong; Yang, Yibo
2015-01-01
We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally, and discuss the strategies of calculating them in lattice QCD.
Spin and Orbital Angular Momentum Distribution Functions of the Nucleon
Wakamatsu, M.; Watabe, T
1999-01-01
A theoretical prediction is given for the spin and orbital angular momentum distribution functions of the nucleon within the framework of an effective quark model of QCD, i.e. the chiral quark soliton model. An outstanding feature of the model is that it predicts fairly small quark spin fraction of the nucleon $\\Delta \\Sigma \\simeq 0.35$, which in turn dictates that the remaining 65% of the nucleon spin is carried by the orbital angular momentum of quarks and antiquarks at the model energy sc...
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Roux, Filippus S; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation decays to zero.
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on parton...
Experimental orbital angular momentum based quantum key distribution through turbulence
Goyal, Sandeep; Ibrahim, Alpha Hamadou; Roux, Filippus S.; Konrad, Thomas; Forbes, Andrew
2014-01-01
Using an experimental setup that simulates a turbulent atmosphere, we study the secret key rate for quantum key distribution protocols in orbital angular momentum based free space quantum communication. The quantum key distribution protocols under consideration include the Ekert 91 protocol for different choices of mutually unbiased bases and the six-state protocol. We find that the secret key rate of these protocols decay to zero roughly at the same scale where the entanglement of formation ...
Energy and angular distributions of atmospheric muons at the Earth
Shukla, Prashant
2016-01-01
A fair knowledge of the atmospheric muon distributions at Earth is a prerequisite for the simulations of cosmic ray setups and rare event search detectors. A modified power law is proposed for atmospheric muon energy distribution which gives good description of the cosmic muon data in low as well as high energy regime. Using this distribution, analytical forms for zenith angle ($\\theta$) distribution are obtained. Assuming a flat Earth, it leads to the $\\cos^{n-1}\\theta$ form where it is shown that the parameter $n$ is nothing but the power of the energy distribution. A new analytical form for zenith angle distribution is obtained without assuming a flat Earth which gives an improved description of the data at all angles even above $70^o$. These distributions are tested with the available atmospheric muon data of energy and angular distributions. The parameters of these distributions can be used to characterize the cosmic muon data as a function of energy, angle and altitude.
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore, E-mail: aurore.courtoy@ulg.be [IFPA, AGO Department, Université de Liège, Bât. B5, Sart Tilman, B-4000 Liège (Belgium); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Goldstein, Gary R., E-mail: gary.goldstein@tufts.edu [Department of Physics and Astronomy, Tufts University, Medford, MA 02155 (United States); Osvaldo Gonzalez Hernandez, J., E-mail: jog4m@virginia.edu [Istituto Nazionale di Fisica Nucleare (INFN) – Sezione di Torino, via P. Giuria, 1, 10125 Torino (Italy); Liuti, Simonetta, E-mail: sl4y@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States); Laboratori Nazionali di Frascati, INFN, Frascati (Italy); Rajan, Abha, E-mail: ar5xc@virginia.edu [University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904 (United States)
2014-04-04
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions – the generalized transverse momentum distributions – that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore; Goldstein, Gary R.; Osvaldo Gonzalez Hernandez, J.; Liuti, Simonetta; Rajan, Abha
2014-04-01
We argue that due to parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions - the generalized transverse momentum distributions - that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light-cone operators projections in the transverse direction, or they appear in the deeply virtual Compton scattering amplitude at twist three. Orbital angular momentum or the spin structure of the nucleon was a major reason for these various distributions and amplitudes to have been introduced. We show that the twist three contributions associated with orbital angular momentum are related to the target-spin asymmetry in deeply virtual Compton scattering, already measured at HERMES.
Twist Three Generalized Parton Distributions for Orbital Angular Momentum
Rajan, Abha
2016-01-01
We study the orbital angular momentum contribution to the spin structure of the proton. It is well known that the quark and gluon spin contributions do not add up to the proton spin. We motivate the connection between the Generalized Transverse Momentum Distribution (GTMD) $F_{14}$, and orbital angular momentum by exploring the underlying quark proton helicity amplitude structure. The twist three Generalized Parton Distribution (GPD) $\\tilde{E}_{2T}$, was shown to connect to OAM. We study these functions using a diquark model calculation. The GTMD $F_{14}$ is unique in that it can describe both Jaffe-Manohar and Ji OAM depending on choice of gauge link, i.e. whether final state interactions are included or not. We perform a calculation of $F_{14}$ in both scenarios.
Parton Transverse Momentum and Orbital Angular Momentum Distributions
Rajan, Abha; Engelhardt, Michael; Liuti, Simonetta
2016-01-01
The quark orbital angular momentum component of proton spin, $L_q$, can be defined in QCD as the integral of a Wigner phase space distribution weighting the cross product of the quark's transverse position and momentum. It can also be independently defined from the operator product expansion for the off-forward Compton amplitude in terms of a twist-three generalized parton distribution. We provide an explicit link between the two definitions, connecting them through their dependence on partonic intrinsic transverse momentum. Connecting the definitions provides the key for correlating direct experimental determinations of $L_q$, and evaluations through Lattice QCD calculations. The direct observation of quark orbital angular momentum does not require transverse spin polarization, but can occur using longitudinally polarized targets.
Dijet angular distributions in direct and resolved photoproduction at HERA
Jet photoproduction, where the two highest transverse energy (ETjet) jets have ETjet above 6 GeV and a jet-jet invariant mass above 23 GeV, has been studied with the ZEUS detector at the HERA ep collider. Resolved and direct photoproduction samples have been separated. The cross section as a function of the angle between the jet-jet axis and the beam direction in the dijet rest frame has been measured for the two samples. The measured angular distributions differ markedly from each other. They agree with the predictions of QCD calculations, where the different angular distributions reflect the different spins of the quark and gluon exchanged in the hard subprocess. (orig.)
Angular distribution and atomic effects in condensed phase photoelectron spectroscopy
A general concept of condensed phase photoelectron spectroscopy is that angular distribution and atomic effects in the photoemission intensity are determined by different mechanisms, the former being determined largely by ordering phenomena such as crystal momentum conservation and photoelectron diffraction while the latter are manifested in the total (angle-integrated) cross section. In this work, the physics of the photoemission process is investigated in several very different experiments to elucidate the mechanisms of, and correlation between, atomic and angular distribution effects. Theoretical models are discussed and the connection betweeen the two effects is clearly established. The remainder of this thesis, which describes experiments utilizing both angle-resolved and angle-integrated photoemission in conjunction with synchrotron radiation in the energy range 6 eV less than or equal to h ν less than or equal to 360 eV and laboratory sources, is divided into three parts
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L 2, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L 2). Instead, we require that when integrating N(E, L 2) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L 2) we show how the distribution of particles in L 2 is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L 2, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
Statistical mechanics of collisionless orbits. IV. Distribution of angular momentum
Williams, Liliya L. R. [School of Physics and Astronomy, University of Minnesota, 116 Church Street SE, Minneapolis, MN 55455 (United States); Hjorth, Jens; Wojtak, Radosław, E-mail: llrw@astro.umn.edu, E-mail: jens@dark-cosmology.dk, E-mail: wojtak@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø (Denmark)
2014-03-01
It has been shown in previous work that DARKexp, which is a theoretically derived, maximum entropy, one shape parameter model for isotropic collisionless systems, provides very good fits to simulated and observed dark matter halos. Specifically, it fits the energy distribution, N(E), and the density profiles, including the central cusp. Here, we extend DARKexp N(E) to include the distribution in angular momentum, L {sup 2}, for spherically symmetric systems. First, we argue, based on theoretical, semi-analytical, and simulation results, that while dark matter halos are relaxed in energy, they are not nearly as relaxed in angular momentum, which precludes using maximum entropy to uniquely derive N(E, L {sup 2}). Instead, we require that when integrating N(E, L {sup 2}) over squared angular momenta one retrieves the DARKexp N(E). Starting with a general expression for N(E, L {sup 2}) we show how the distribution of particles in L {sup 2} is related to the shape of the velocity distribution function, VDF, and velocity anisotropy profile, β(r). We then demonstrate that astrophysically realistic halos, as judged by the VDF shape and β(r), must have linear or convex distributions in L {sup 2}, for each separate energy bin. The distribution in energy of the most bound particles must be nearly flat, and become more tilted in favor of radial orbits for less bound particles. These results are consistent with numerical simulations and represent an important step toward deriving the full distribution function for spherically symmetric dark matter halos.
Reconstructing the galaxy redshift distribution from angular cross power spectra
Sun, L; Tao, C
2015-01-01
The control of photometric redshift (photo-$z$) errors is a crucial and challenging task for precision weak lensing cosmology. The spacial cross-correlations (equivalently, the angular cross power spectra) of galaxies between tomographic photo-$z$ bins are sensitive to the true redshift distribution $n_i(z)$ of each bin and hence can help calibrate the photo-$z$ error distribution for weak lensing surveys. Using Fisher matrix analysis, we investigate the contributions of various components of the angular power spectra to the constraints of $n_i(z)$ parameters and demonstrate the importance of the cross power spectra therein, especially when catastrophic photo-$z$ errors are present. We further study the feasibility of reconstructing $n_i(z)$ from galaxy angular power spectra using Markov Chain Monte Carlo estimation. Considering an LSST-like survey with $10$ photo-$z$ bins, we find that the underlying redshift distribution can be determined with a fractional precision ($\\sigma(\\theta)/\\theta$ for parameter $\\...
Accessing the quark orbital angular momentum with Wigner distributions
Lorce, Cedric [IPNO, Universite Paris-Sud, CNRS/IN2P3, 91406 Orsay, France and LPT, Universite Paris-Sud, CNRS, 91406 Orsay (France); Pasquini, Barbara [Dipartimento di Fisica, Universita degli Studi di Pavia, Pavia, Italy and Istituto Nazionale di Fisica Nucleare, Sezione di Pavia, Pavia (Italy)
2013-04-15
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Accessing the quark orbital angular momentum with Wigner distributions
Cedric, Lorce
2012-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Accessing the quark orbital angular momentum with Wigner distributions
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wigner distributions. We discuss the concept of Wigner distributions in the context of quantum field theory and show how they are related to the GPDs and the TMDs. We summarize the different definitions discussed in the literature for the quark OAM and show how they can in principle be extracted from the Wigner distributions.
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D.; Maji, T.; Mondal, C.; Mukherjee, A.
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact pa...
Accessing the quark orbital angular momentum with Wigner distributions
Cedric LorceIPNO and LPT, Orsay; Barbara Pasquini(Pavia U. and INFN, Pavia)
2015-01-01
The quark orbital angular momentum (OAM) has been recognized as an important piece of the proton spin puzzle. A lot of effort has been invested in trying to extract it quantitatively from the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs), which are accessed in high-energy processes and provide three-dimensional pictures of the nucleon. Recently, we have shown that it is more natural to access the quark OAM from the phase-space or Wig...
Wigner distribution and orbital angular momentum of a proton
Chakrabarti, D; Mondal, C; Mukherjee, A
2016-01-01
The Wigner distributions for u and d quarks in a proton are calculated using the light front wave functions (LFWFs) of the scalar quark-diquark model for nucleon constructed from the soft-wall AdS/QCD correspondence. We present a detail study of the quark orbital angular momentum(OAM) and its correlation with quark spin and proton spin. The quark density distributions, considering the different polarizations of quarks and proton, in transverse momentum plane as well as in transverse impact parameter plane are presented for both u and d quarks.
Proton angular distribution following multiphoton dissociative ionization of H2
The angular distribution of protons ejected following resonant (2+1)-photon dissociative ionization of H2 by 193-nm radiation through the E,F state has been obtained. The analysis shows that the Π character of the degenerate continuum states is approximately eight times larger than the Σ character, which is consistent with previous single-photon measurements. The analysis presented here, together with a previous analysis of the proton energy distribution, reveals the ionization channel to be significantly stronger than both the dissociation and dissociative ionization channels
On the angular distribution and spin polarization of the photoelectrons from semi-filled shell atoms
Amusia, M Ya
2007-01-01
We present here the results of calculations of photoelectrons' angular anisotropy and spin-polarization parameters for a number of semi-filled shell atoms. We consider ionization of outer or in some cases next to the outer electrons in a number of elements from I, V, and VI groups of the Periodic Table. All calculations are performed with account of multi-electron correlations in the frame of the Spin Polarized version of the Random Phase Approximation with Exchange - SP RPAE. We consider the dipole angular distribution and spin polarization of photoelectrons from semi-filled subshells and from closed shells that are neighbors to the semi-filled shells. We have considered also angular anisotropy and spin-polarization of photoelectrons from some excited atoms that are formed by spin-flip of one of the outer electrons. To check the accuracy and consistency of the applied SP RPAE approach and to see the role of the nuclear charge variation only, we have calculated the dipole angular anisotropy and spin-polarizat...
Precision angular velocity response of a fiber-optic gyroscope using a piezo-nano-rotation table
Modern fiber-optic gyroscopes are calibrated using the Earth's rotation or stepper motor actuated rotation tables. We investigated the angular velocity resolution of the Optolink SRS-1000 fiber-optic gyroscope using a piezo-activated rotation table down to angular velocity steps of 1 × 10−7 rad s−1 with an accuracy of 1.5 × 10−8 rad s−1. To our knowledge, these are the smallest velocity steps resolved and reported in the literature so far. Our results show that such a gyroscope may be also used for nanopositioning purposes in addition to its usual navigation application. (technical design note)
Partons Transverse Momentum and Orbital Angular Momentum Distributions
Liuti, Simonetta; Rajan, Abha; Courtoy, Aurore; Engelhardt, Michael
2015-10-01
We discuss the two definitions of partonic orbital angular momentum given by Ji and by Jaffe and Manohar, respectively. It is by now established that the two definitions are described by the same generalized transverse momentum distribution, F14, while they differ through their gauge link structure. They can also be both described in terms of a twist three generalized parton distribution, G2 which can be measured in DVCS type experiments. Here, starting from nonlocal, kT unintegrated, off-forward matrix elements, instead of the standard OPE, we show how G2 can be written as the sum of twist two, quark mass, and interaction dependent (twist three) terms, thus emphasizing the role of quark intrinsic transverse momentum and off-shellness. The twist two term in particular is given by the kT2 moment of F14. We therefore uncover a relation/sum rule connecting the two definitions of orbital angular momentum, F14 and G2. We explore both the spin and the intrinsic transverse momentum/transverse space correlations as well as the gauge link structure behind the two decomposition frameworks, which are necessary to extract orbital angular momentum from experiment.
Electric octupole contribution to the angular distribution of the krypton 4p photoelectrons
The angular distribution of Kr 4p photoelectrons was measured with linearly polarized synchrotron radiation in the function of the photon energy. The shape of the measured angular distributions indicates the presence of octupol interaction.
Angular Distribution and Angular Dispersion in Collision of 19F+27A1 at 114 MeV
WANG Qi; Li Zhi-Chang; LU Xiu-Qin; ZHAO Kui; LIU Jian-Cheng; SERGEY Yu-Kun; DONG Yu-Chuan; LI Song-Lin; DUAN Li-Min; XU Hu-Shan; XU Hua-Gen; CHEN Ruo-Fu; WU He-Yu; HAN Jian-Long
2004-01-01
Angular distributions of fragments B, C, N, O, F, Ne, Na, Mg and Al induced by the collision of 19F+27 A1 at 114MeV have been measured. Angular dispersion parameters are extracted from the experimental data and compared with the theoretical ones. The dynamic dispersions for dissipative products depend strongly on the charge number Z of the fragments.
Probes of initial-state interactions in dilepton angular distributions
We discuss the angular distribution of dileptons d sigma/d4Qd OMEGA, emphasizing phase sensitivity as a probe of initial-state interactions in QCD. The coherent nature of Sudakov effects is discussed, along with the presence of imaginary parts related by analyticity. Angular-distribution structure functions which describe interference between longitudinal and transverse virtual photons, e.g., can be used to probe phase differences that depend on large momenta. These evolve according to exp(ic ln ln(Q2/lambda/sub QCD2)) where Q2 is a large scale. We report on a complete calculation at O(α/sub s/2) of the q anti q → #betta#* + gluons channel which confirms the cancellation of small (cutoff) scales, and describe a complementary experiment involving spin. We discuss the limit x → 1 of the distribution d sigma/dQ2dxdcos theta, and point out an unusual and interesting effect that a momentum-dependent phase can produce here
Dijet Angular Distributions in Direct and Resolved Photoproduction at HERA
ZEUS Collaboration
1996-01-01
Jet photoproduction, where the two highest transverse energy ($\\ETJ$) jets have $\\ETJ$ above 6 GeV and a jet-jet invariant mass above 23~GeV, has been studied with the ZEUS detector at the HERA $ep$ collider. Resolved and direct photoproduction samples have been separated. The cross section as a function of the angle between the jet-jet axis and the beam direction in the dijet rest frame has been measured for the two samples. The measured angular distributions differ markedly from each other....
Measurements of the angular distribution of diffuse irradiance
Andersen, Elsa; Nielsen, Kristian Pagh; Dragsted, Janne; Furbo, Simon
2015-01-01
Advanced solar resource assessment and forecasting is necessary for optimal solar energy utilization. In order to investigate the short-term resource variability, for instance caused by clouds it is necessary to investigate how clouds affect the solar irradiance, including the angular distributio...... the solar irradiance from 8 different parts of the sky as well as horizontal measurements of the total beam and total diffuse irradiance....... of the solar irradiance. The investigation is part of the Danish contribution to the taskforce 46 within the International Energy Agency and financed by the Danish Energy Agency. The investigation focuses on the distribution of the diffuse solar irradiance and is based on horizontal measurements of...
Photon Angular Distribution and Polarization of Radiative Recombination
OU Wei-Ying; SHEN Tian-Ming; CHEN Chong-Yang; Roger Hutton; ZOU Ya-Ming
2005-01-01
@@ A systematic study is carried out on the angular distribution and polarization of photons emitted following radiative-recombination of bare and He-like ions of Ne, Ar, Ni and Mo with a unidirectional electron beam. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave method is used. Scaling rules for polarization of the photon following radiative recombination to both bare and He-like ions are given for the incident energy regions up to six times the ionization threshold energy of the final state.
Orbital Angular Momentum Parton Distributions in Quark Models
Scopetta, S.; Vento, V.
1999-01-01
At the low energy, {\\sl hadronic}, scale we calculate Orbital Angular Momentum (OAM) twist-two parton distributions for the relativistic MIT bag model and for non-relativistic quark models. We reach the scale of the data by leading order evolution in perturbative QCD. We confirm that the contribution of quarks and gluons OAM to the nucleon spin grows with $Q^2$, and it can be relevant at the experimental scale, even if it is negligible at the hadronic scale, irrespective of the model used. Th...
Angular Distribution of Photons in Coherent Bremsstrahlung in Deformed Crystals
Parazian, V V
2010-01-01
We investigate the angular distribution of photons in the coherent bremsstrahlung process by high-energy electrons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The case is considered in detail when the electron enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO2 single crystal and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S -type.
Theoretical Manifestation of the Broadening Effect on Photoelectron Angular Distributions
ZHANG Jing-Tao(张敬涛); ZHOU Lan(周岚); ZHANG Wen-Qi(张文琦); XU Zhi-Zhan(徐至展); GUO Dong-Sheng(郭东升); R.R.Freeman
2003-01-01
The broadening effect in photoelectron angular distributions (PADs) observed by Freeman et al. Is studied theoretically. Using a nonperturbative scattering theory developed for multiphoton ionization with the inclusion of spontaneous emission, we calculate the PADs for above-threshold ionization (ATI) peaks. The numerical calculations from our theory reproduce the kinetic-energy dependence and the laser-intensity dependence of PADs of ATI peaks observed by Freeman et al., [Phys. Rev. Lett. 57 (1986) 3156] and provide an evidence for the existence of the ponderomotive momentum of intense laser fields.
Nucleon form factors, generalized parton distributions and quark angular momentum
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale μ=2 GeV to be Juv=0.230+0.009-0.024 and Jdv=-0.004+0.010-0.016.
Angular distribution of 6He+p elastic scattering
LIU Xin; SU Jun; ZENG Sheng; YAN Sheng-Quan; LIAN Gang; HUANG Wu-Zhen; LIU Wei-Ping; WANG You-Bao; LI Zhi-Hong; JIN Sun-Jun; WANG Bao-Xiang; LI Yun-Ju; LI Er-Tao; BAI Xi-Xiang; GUO Bing
2012-01-01
The angular distribution of 1H(6He,p)6He elastic scattering has been measured at Ec.m.=4.3 MeV by using a thick-target inverse kinematic method.The experimental differential cross sections are reproduced by the distorted-wave Born approximation calculation utilizing the CH89 global optical potential parameter set.The real part of CH89 is reduced comparing with other potentials,which may be attributed to the couplings necessary for the weakly bound nuclei.
Angular distribution in the neutron-induced fission of actinides
Leong L.S.
2013-12-01
Full Text Available Above 1 MeV of incident neutron energy the fission fragment angular distribution (FFAD has generally a strong anisotropic behavior due to the combination of the incident orbital momentum and the intrinsic spin of the fissioning nucleus. This effect has to be taken into account for the efficiency estimation of devices used for fission cross section measurements. In addition it bears information on the spin deposition mechanism and on the structure of transitional states. We designed and constructed a detection device, based on Parallel Plate Avalanche Counters (PPAC, for measuring the fission fragment angular distributions of several isotopes, in particular 232Th. The measurement has been performed at n_TOF at CERN taking advantage of the very broad energy spectrum of the neutron beam. Fission events were recognized by back to back detection in coincidence in two position-sensitive detectors surrounding the targets. The detection efficiency, depending mostly on the stopping of fission fragments in backings and electrodes, has been computed with a Geant4 simulation and validated by the comparison to the measured case of 235U below 3 keV where the emission is isotropic. In the case of 232Th, the result is in good agreement with previous data below 10 MeV, with a good reproduction of the structures associated to vibrational states and the opening of second chance fission. In the 14 MeV region our data are much more accurate than previous ones which are broadly scattered.
Spin O decay angular distribution for interfering mesons in electroproduction
Self analyzing meson electroproduction experiments are currently being planned for the CEBAF CLAS detector. These experiments deduce the spin polarization of outgoing unstable spin s (?)0 mesons from their decay angular distribution, W(θ,ψ). The large angular acceptance of the CLAS detector permits kinematic tracking of a sufficient number of these events to accurately determine electroproduction amplitudes from the deduced polarization. Maximum polarization information is obtained from W(θ,ψ) for decay into spin 0 daughters. The helicity of the decaying meson is transferred to the daughter's relative orbital angular momentum m-projection; none is open-quotes absorbedclose quotes into daughter helicities. The decaying meson's helicity maximally appears in W(θ,ψ). W(θ,ψ) for spin 0 daughters has been derived for (1) vector meson electroproduction and (2) general interfering mesons produced by incident pions. This paper derives W(θ,ψ) for electroproduction of two interfering mesons that decay into spin 0 daughters. An application is made to the case of interfering scalar and vector mesons. The derivation is an extension of work by Schil using the general decay formalism of Martin. The expressions can be easily extended to the case of N interfering mesons since interference occurs pairwise in the observable W (θ,ψ), a quadratic function of the meson amplitudes. The derivation uses the virtual photon density matrix of Schil which is transformed by a meson electroproduction transition operator, T. The resulting density matrix for the interfering mesons is then converted into a corresponding statistical tensor and contracted into the efficiency tensor for spin 0 daughters
DISTRIBUTION OF ACCRETING GAS AND ANGULAR MOMENTUM ONTO CIRCUMPLANETARY DISKS
We investigate gas accretion flow onto a circumplanetary disk from a protoplanetary disk in detail by using high-resolution three-dimensional nested-grid hydrodynamic simulations, in order to provide a basis of formation processes of satellites around giant planets. Based on detailed analyses of gas accretion flow, we find that most of gas accretion onto circumplanetary disks occurs nearly vertically toward the disk surface from high altitude, which generates a shock surface at several scale heights of the circumplanetary disk. The gas that has passed through the shock surface moves inward because its specific angular momentum is smaller than that of the local Keplerian rotation, while gas near the midplane in the protoplanetary disk cannot accrete to the circumplanetary disk. Gas near the midplane within the planet's Hill sphere spirals outward and escapes from the Hill sphere through the two Lagrangian points L1 and L2. We also analyze fluxes of accreting mass and angular momentum in detail and find that the distributions of the fluxes onto the disk surface are well described by power-law functions and that a large fraction of gas accretion occurs at the outer region of the disk, i.e., at about 0.1 times the Hill radius. The nature of power-law functions indicates that, other than the outer edge, there is no specific radius where gas accretion is concentrated. These source functions of mass and angular momentum in the circumplanetary disk would provide us with useful constraints on the structure and evolution of the circumplanetary disk, which is important for satellite formation.
Spin O decay angular distribution for interfering mesons in electroproduction
Funsten, H.; Gilfoyle, G.
1994-04-01
Self analyzing meson electroproduction experiments are currently being planned for the CEBAF CLAS detector. These experiments deduce the spin polarization of outgoing unstable spin s (?)0 mesons from their decay angular distribution, W({theta},{psi}). The large angular acceptance of the CLAS detector permits kinematic tracking of a sufficient number of these events to accurately determine electroproduction amplitudes from the deduced polarization. Maximum polarization information is obtained from W({theta},{psi}) for decay into spin 0 daughters. The helicity of the decaying meson is transferred to the daughter`s relative orbital angular momentum m-projection; none is {open_quotes}absorbed{close_quotes} into daughter helicities. The decaying meson`s helicity maximally appears in W({theta},{psi}). W({theta},{psi}) for spin 0 daughters has been derived for (1) vector meson electroproduction and (2) general interfering mesons produced by incident pions. This paper derives W({theta},{psi}) for electroproduction of two interfering mesons that decay into spin 0 daughters. An application is made to the case of interfering scalar and vector mesons. The derivation is an extension of work by Schil using the general decay formalism of Martin. The expressions can be easily extended to the case of N interfering mesons since interference occurs pairwise in the observable W ({theta},{psi}), a quadratic function of the meson amplitudes. The derivation uses the virtual photon density matrix of Schil which is transformed by a meson electroproduction transition operator, T. The resulting density matrix for the interfering mesons is then converted into a corresponding statistical tensor and contracted into the efficiency tensor for spin 0 daughters.
Angular momentum of disc galaxies with a lognormal density distribution
Marr, John Herbert
2015-01-01
Whilst most galaxy properties scale with galaxy mass, similar scaling relations for angular momentum are harder to demonstrate. A lognormal (LN) density distribution for disc mass provides a good overall fit to the observational data for disc rotation curves for a wide variety of galaxy types and luminosities. In this paper, the total angular momentum J and energy $\\vert{}$E$\\vert{}$ were computed for 38 disc galaxies from the published rotation curves and plotted against the derived disc masses, with best fit slopes of 1.683$\\pm{}$0.018 and 1.643$\\pm{}$0.038 respectively, using a theoretical model with a LN density profile. The derived mean disc spin parameter was $\\lambda{}$=0.423$\\pm{}$0.014. Using the rotation curve parameters V$_{max}$ and R$_{max}$ as surrogates for the virial velocity and radius, the virial mass estimator $M_{disc}\\propto{}R_{max}V_{max}^2$ was also generated, with a log-log slope of 1.024$\\pm{}$0.014 for the 38 galaxies, and a proportionality constant ${\\lambda{}}^*=1.47\\pm{}0.20\\time...
Drell-Yan Lepton Angular Distribution at Small Transverse Momentum
Boer, D; Boer, Daniel; Vogelsang, Werner
2006-01-01
We investigate the dependence of the Drell-Yan cross section on lepton polar and azimuthal angles, as generated by the lowest-order QCD annihilation and Compton processes. We focus in particular on the azimuthal-angular distributions, which are of the form cos(phi) and cos(2phi). At small transverse momentum q_T of the lepton pair, q_T << Q, with Q the pair mass, these terms are known to be suppressed relative to the phi-independent part of the Drell-Yan cross section by one or two powers of the transverse momentum. Nonetheless, as we show, like the phi-independent part they are subject to large logarithmic corrections, whose precise form however depends on the reference frame chosen. These logarithmic contributions ultimately require resummation to all orders in the strong coupling. We discuss the potential effects of resummation on the various angular terms in the cross section and on the Lam-Tung relation.
Nucleon form factors, generalized parton distributions and quark angular momentum
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Low energy level spacing distribution in the atomic table ensemble
We have analysed the nearest neighbour spacing distributions for the atomic table ensemble. The analysis carried out indicates that the random matrix theory arguments extend even to the ground state domain of atoms. (orig.)
Non-dipole effects in photoelectron angular distributions for rare gas atoms
The authors present a theoretical study of O(ka) and O(k2a2) corrections to the dipole approximation in photoionization of rare gas atoms, where k is the magnitude of the photon wave vector and a is the radius of the ionized subshell. In the dipole approximation, the photoelectron angular distribution is characterized by the single parameter Β. The O(ka) corrections are characterized by two parameters γ and delta, and the O(k2a2) corrections are characterized by three parameters λ, μ, and ν, constrained by the relation λ + μ + ν = 0 and a correction ΔΒ to the dipole parameter Β. Formulas are given for the non-dipole parameters in terms of reduced matrix elements of electric and magnetic multipole operators. Tables and graphs of the seven angular distribution parameters, calculated in the relativistic independent-particle approximation (IPA), are given for electron energies ranging from 20 to 5,000 eV for all 41 subshells of the rare gas atoms He,NE,Ar,Kr, and Xe. Tables and graphs of the O(ka) parameters are also given in the energy range 2--60 eV for the n = 3 and 4 shells of Kr, and for the n = 4 and 5 shells of Xe, where interesting non-dipole effects are found. Comparisons of the IPA calculations with correlated relativistic random-phase approximation calculations are made for selected subshells of Ar and Kr, illustrating the influence of correlation on the non-dipole parameters
Karras, G.; Kosmidis, C.
2010-10-01
The angular distribution of the fragment ions ejected from the interaction of methyl iodide clusters with 20 fs strong laser pulses is studied by means of a mass spectrometer. Three types of angular distributions, one isotropic and two anisotropic, have been observed and their dependence on the laser intensity has been studied. There is strong evidence that the ions exhibiting anisotropic angular distribution with a maximum in the direction parallel to the laser polarization vector are produced via an electron impact ionization process.
Orbital angular momentum from marginals of quadrature distributions
Sanchez-Soto, L. L.; Klimov, A. B.; de la Hoz, P.; Rigas, I.; J. Rehacek; Hradil, Z.; Leuchs, G.
2013-01-01
We set forth a method to analyze the orbital angular momentum of a light field. Instead of using the canonical formalism for the conjugate pair angle-angular momentum, we model this latter variable by the superposition of two independent harmonic oscillators along two orthogonal axes. By describing each oscillator by a standard Wigner function, we derive, via a consistent change of variables, a comprehensive picture of the orbital angular momentum. We compare with previous approaches and show...
Fission fragment angular distribution in heavy ion induced fission
S. Soheyli
2006-06-01
Full Text Available We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a without neutron correction and b with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the average emitted neutron from compound nuclei considering the best fit for each system.
Fission fragment angular distribution in heavy ion induced fission
S. Soheyli; I. Ziaeian
2006-01-01
We have calculated the fission fragment angular anisotropy for 16O + 232Th,12C + 236U , 11B + 237 Np , 14 N + 232 Th , 11B + 235U , 12C + 232Th systems with the saddle point statistical model and compared the fission fragment angular anisotropy for these systems. This comparison was done with two methods a) without neutron correction and b) with neutron correction. Also we studied normal and anomalous behavior of the fission fragment angular anisotropy. Finally, we have predicted the averag...
Angular distributions of four neutron groups from the 10B(d, n)11C reaction
Paris, C.H.; Endt, P.M.
1954-01-01
Measurements are described of the angular distributions of the four most energetic neutron groups from the 10B(d, n)11C reaction at a deuteron energy of 0.6 MeV. Neutrons were detected by their recoil protons in nuclear emulsions. The angular distributions have been analyzed in terms of a stripping
Fission fragment angular distribution measurements in 18O+194Pt reaction
Fission fragment angular distributions were measured for 18O + 194Pt in energy range 78.2 - 87.3 MeV. The normal nature of angular anisotropy suggests that the reaction proceeded through true CN formation. The present results are consistent with result obtained from fission fragment mass distribution measurements carried out for reaction using other isotopes of platinum
Angular distributions of target black fragments in nucleus–nucleus collisions at high energy
The experimental results of space, azimuthal, and projected angular distributions of target black fragments produced in silicon-emulsion collisions at 4.5A GeV/c (the Dubna energy) are reported. A multi-source ideal gas model is suggested to describe the experimental angular distributions. The Monte Carlo calculated results are in agreement with the experimental data. (author)
Brady, J.W. Jr.; Doll, J.D.; Thompson, D.L.
1978-10-15
The angular and velocity distributions for gas/solid-surface collisions are examined. It is shown that the envelope of the scattered phase-space distribution is quite sensitive to the gas/surface interaction potential.
Fission fragment angular distributions and fission cross section validation
The present knowledge of angular distributions of neutron-induced fission is limited to a maximal energy of 15 MeV, with large discrepancies around 14 MeV. Only 238U and 232Th have been investigated up to 100 MeV in a single experiment. The n-TOF Collaboration performed the fission cross section measurement of several actinides (232Th, 235U, 238U, 234U, 237Np) at the n-TOF facility using an experimental set-up made of Parallel Plate Avalanche Counters (PPAC), extending the energy domain of the incident neutron above hundreds of MeV. The method based on the detection of the 2 fragments in coincidence allowed to clearly disentangle the fission reactions among other types of reactions occurring in the spallation domain. I will show the methods we used to reconstruct the full angular resolution by the tracking of fission fragments. Below 10 MeV our results are consistent with existing data. For example in the case of 232Th, below 10 MeV the results show clearly the variation occurring at the first (1 MeV) and second (7 MeV) chance fission, corresponding to transition states of given J and K (total spin and its projection on the fission axis), and a much more accurate energy dependence at the 3. chance threshold (14 MeV) has been obtained. In the spallation domain, above 30 MeV we confirm the high anisotropy revealed in 232Th by the single existing data set. I'll discuss the implications of this finding, related to the low anisotropy exhibited in proton-induced fission. I also explore the critical experiments which is valuable checks of nuclear data. The 237Np neutron-induced fission cross section has recently been measured in a large energy range (from eV to GeV) at the n-TOF facility at CERN. When compared to previous measurements, the n-TOF fission cross section appears to be higher by 5-7 % beyond the fission threshold. To check the relevance of n-TOF data, we simulate a criticality experiment performed at Los Alamos with a 6 kg sphere of 237Np. This sphere was
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azimuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments. (author)
Defining the Observables for Quarks and Gluons Orbital Angular Momentum Distributions
Liuti, S.; Courtoy, A.; Goldstein, G. R.; Gonzalez Hernandez, J. O.; Rajan, A.
2015-09-01
We present a critical discussion of the observables that have been recently put forth to describe quarks and gluons orbital angular momentum distributions. Starting from a standard parameterization of the energy momentum tensor in QCD one can single out two forms of angular momentum, a so-called kinetic term, generally associated with the Ji decomposition, and a canonical term from the Jaffe Manohar decomposition. Orbital angular momentum has been connected to a Generalized Transverse Momentum Distribution (GTMD), for the canonical term, and to a twist three Generalized Parton Distribution for the kinetic term. We argue that while the latter appears as an azymuthal angular modulation in the longitudinal target spin asymmetry in deeply virtual Compton scattering, due to parity constraints, the GTMD associated with canonical angular momentum cannot be measured in a similar set of experiments.
On the theories of angular distribution and correlation of beta and gamma radiation
Groot, S.R. de
1952-01-01
In both phenomena of angular distribution and angular correlation, one has nuclear radiation from ensembles of nuclei with an unequal population of the magnetic sub-levels. This population is described by appropriate “orientation parameters”. On this basis the theories of the directional as well as
Measurement of the angular distribution of neutron-proton scattering at 10 MeV
The relative angular distribution of neutrons scattered from protons was measured at an incident neutron energy of 10 MeV at the Ohio University Accelerator Laboratory. An array of 11 detector telescopes at laboratory angles of 0 to 60 degrees was used to detect recoil protons from neutron interactions with a CH2 (polypropylene) target. Data for 7 of these telescopes were obtained with one set of electronics and are presented here. These data, from 108 to 180 degrees for the center-of-mass scattering angles, have a small slope which agrees better with angular distributions predicted by the Arndt phase shifts than with the ENDF/B-VI angular distribution
Continuum angular distributions in nuclear reactions: Physical basis for the Kalbach systematics
We show how the conservation of linear momentum is fundamental to the description of angular distributions in preequilibrium nuclear reactions. By using state densities with linear momentum to describe the phase space during the preequilibrium cascade, angular distributions can be derived in a transparent way. Fermi-motion and Pauli-blocking effects are included, and correlations between the emission particle's energy and angle are obtained for all orders of scattering. Our model provides a physical basis for the widely-used phenomenological systematics of Kalbach, and provides a framework for understanding the systematical properties of continuum angular distributions
Spectral dependence of angular distribution halfwidths of Vavilov-Cherenkov radiation
Angular distributions of Vavilov-Cherenkov radiation have been measured. This radiaiton is excited during 210 keV electron propagation in a mica 2.5 mm thick target in a spectral range from 2500 up to 5000 A. A formula for diffraction halfwidth of angular distribution has been derived, its applicability limits are pointed out. Experimental halfwidth agrees with the calculated ones. The deviation of angular distribution maximum from Vavilov-Cherenkov radiation angle is analyzed. This deviation is due to radiator boundaries and multiple scattering of electrons
Angular distribution of photofission fragments in 238U at 5.43 MeV
The angular distribution of photofission fragments of 238U, produced by 5.43 MeV monochromatic photons from the η,γ reaction in sulphur, has been measured using glass plates as detectors. In the analysis of the results only the contributions from the (Jπ, K) 1= (1-,0), (1-,1) and (2+,0) terms were considered. The coefficients of the angular distributions of the fission fragments were obtained. An analysis of the data available in the literature on the angular distribution near the photofission threshold is also presented. (author)
Role of electron-molecule angular scattering in shaping the electron-velocity distribution
Kunhardt, E.E.; Tzeng, Y.
1986-09-01
Five models has been studied to elucidate the role of electron-molecule angular scattering in shaping the velocity distribution for electrons in nitrogen at E/N values of 300 and 1500 Td. The angular dependence of the differential scattering cross sections for elastic and inelastic collisions has been observed to have significant effects on the shape of the velocity distribution, the rate coefficients, and the transport parameters. The velocity distribution is most sensitive to the angular dependence of elastic scattering. Moreover, for a given elastic differential scattering cross section, variations in the angular dependence of inelastic scattering cause significant changes in the distribution. The magnitude of these changes depends on the relative action of the inelastic collisions with respect to the elastic collisions for a given energy interval, i.e., whether the scattering by the inelastic collisions is isotropic, forward, or backward in a given energy interval.
Ren Xiang-He; Wu Yan; Zhang Jing-Tao; Ma Hui; Xu Yu-Long
2013-01-01
We theoretically investigate the strong-field ionization of H2+ molecules in four different electronic states by calculating photoelectron angular distributions in circularly polarized fields.We find that the structure of photoelectron angular distribution depends on the molecular orbital as well as the energy of the photoelectron.The location of main lobes changes with the symmetric property of the molecular orbital.Generally,for molecules with bonding electronic states,the photoelectron's angular distribution shows a rotation of π/2 with respect to the molecular axis,while for molecules with antibonding electronic states,no rotation occurs.We use an interference scenario to interpret these phenomena.We also find that,due to the interference effect,a new pair of jets appears in the waist of the main lobes,and the main lobes or jets of the photoelectron's angular distribution are split into two parts if the photoelectron energy is sufficiently high.
Jouanne, C.
2014-04-01
This article is intended to present the use of the covariance matrices of cross section and of angular distributions for 56Fe scattering reactions using a benchmark on neutron propagation in an iron bulk.
Yuan, Kai-Jun; Bandrauk, André D.
2012-01-01
Angular distributions of molecular above-threshold ionization (MATI) in bichromatic attosecond extreme ultraviolet (XUV) linear polarization laser pulses have been theoretically investigated. Multiphoton ionization in a prealigned molecular ion H2+ produces clear MATI spectra which show a forward-backward asymmetry in angular and momentum distributions which is critically sensitive to the carrier envelope phase (CEP) φ, the time delay Δτ between the two laser pulses, and the photoelectron kinetic energies Ee. The features of the asymmetry in MATI angular distributions are described well by multiphoton perturbative ionization models. Phase differences of continuum electron wave functions can be extracted from the CEP φ and time delay Δτ dependent ionization asymmetry ratio created by interfering multiphoton ionization pathways. At large internuclear distances MATI angular distributions exhibit more complex features due to laser-induced electron diffraction where continuum electron wavelengths are less than the internuclear distance.
Angular distribution and azimuthal asymmetry for pentaquark production in proton-proton collisions
Angular distributions for production of the Θ+ pentaquark are calculated for the collisions of polarized protons with polarized target protons. We compare calculations based on different assumptions concerning spin and parity (J=1/2±,3/2±) of the Θ+ state. For a wide class of interactions the spin correlation parameters describing the asymmetric angular distributions are calculated up to 250 MeV above production threshold. The deviations from the near-threshold behavior are investigated
3He(e,d)e'p isochromats and angular distribution measurements
An angular distribution and isochromats for the reaction 3He(e,d)e'p were measured to determine the importance of E2 strength near the peak of the 3He(#betta#,d)p cross section. The angular distribution was analyzed using both a complete and approximate virtual photon spectrum. The isochromats were compared to a plane wave model prediction and least squares fitted to determine the relative amounts of E1 and E2 strength
Fission fragment angular distribution in 24Mg induced reactions on 192Os and 197Au
Angular distributions of fission fragments have been measured in 24Mg + 192Os and 24Mg + 197Au reactions at Elab = 128 MeV which is close to entrance channel Coulomb barrier. Experimental angular anisotropies were in reasonably good agreement with those calculated using the statistical theory. Analysis of the angular distribution data of the present study and of our earlier measurement in 19F + 197Au reaction has shown that contribution from non-compound nucleus fission in these systems is not significant. (author)
The quark orbital angular momentum from Wigner distributions and light-cone wave functions
Lorce, Cédric; Pasquini, Barbara; Xiong, Xiaonu; Yuan, Feng
2012-01-01
We investigate the quark orbital angular momentum of the nucleon in the absence of gauge-field degrees of freedom, by using the concept of the Wigner distribution and the light-cone wave functions of the Fock state expansion of the nucleon. The quark orbital angular momentum is obtained from the phase-space average of the orbital angular momentum operator weighted with the Wigner distribution of unpolarized quarks in a longitudinally polarized nucleon. We also derive the light-cone wave funct...
Dose rate distribution of commercially available I-125 seeds is strongly anisotropic due to self absorption. Effects of this anisotropy to dose distribution of linear, planar and volume implants are studied. Results suggest that this anisotropy should be taken into account especially when one is considering dose distribution near the seeds. Angularly averaged distribution of single seed is found to cause serious deflections to isodoses of the implant in high dose region. To use true anisotropic dose rate distribution one must be able to evaluate angular orientation of seeds in the implant. A method is presented to compute this orientation also when seeds are poorly visible in radiographs. (orig.)
ELECTRON ANGULAR DISTRIBUTIONS IN DISSOCIATIVE PHOTOIONIZATION OF THE HYDROGEN MOLECULE.
Jhon F. Pérez-Torres
2009-06-01
Full Text Available Se propone un método para calcular distribuciones angulares de electrones ionizados en la molécula de hidrógeno fija en el espacio sometida a pulsos láser intensos y ultracortos, basado en la solución desde primeros principios de la ecuación de Schrödinger dependiente del tiempo. Esta solución nos permite tener una visión temporal de la interferencias generadas en el canal de ionización disociativa (en el espectro de energía cinética de los protones debido a la presencia de la autoionización de estados doblemente excitados de la molécula de hidrógeno. Se muestra específicamente cómo la autoionización durante el proceso de fotoionización disociativa también puede inducir una asimetría en la distribución angular del electrón ionizado con respecto a la inversión nuclear, un efecto no intuitivo a pesar de estar tratando con un sistema homonuclear.
Quark phase-space distributions and orbital angular momentum
Cédric LorcéOrsay, IPN and Orsay, LPT; Barbara Pasquini(Pavia U. and INFN, Pavia)
2012-01-01
We discuss the Wigner functions of the nucleon which provide multi-dimensional images of the quark distributions in phase space. They combine in a single picture all the information contained in the generalized parton distributions (GPDs) and the transverse-momentum dependent parton distributions (TMDs). In particular, we present results for the distribution of unpolarized quarks in a longitudinally polarized nucleon obtained in a light-cone constituent quark model. We show how quark orbital ...
Energy and angular distributions of atmospheric muons at the Earth
Shukla, Prashant
2016-01-01
A fair knowledge of the atmospheric muon distributions at Earth is a prerequisite for the simulations of cosmic ray setups and rare event search detectors. A modified power law is proposed for atmospheric muon energy distribution which gives good description of the cosmic muon data in low as well as high energy regime. Using this distribution, analytical forms for zenith angle ($\\theta$) distribution are obtained. Assuming a flat Earth, it leads to the $\\cos^{n-1}\\theta$ form where it is show...
The angular distribution of photon energy spectra emitted from an I-125 brachytherapy source was measured using a specially designed jig in the range of ±70° in the plane of the long axis of the source. It is important to investigate the angular dependence of photon emissions from these sources for the calibration of the air kerma rate. The results show that the influence of the distributions between 0° and ±8° is small enough to allow a calibration using current primary instruments which have a large entrance window. - Highlights: ► Angular energy distribution for an I-125 brachytherapy source was measured. ► Variation of the distribution is sufficiently small. ► It is acceptable for primary calibration of the source strength. ► Distributions should be taken into consideration in some instruments.
Angular distributions of higher order splitting functions in the vacuum and in dense QCD matter
Fickinger, Michael; Vitev, Ivan
2013-01-01
We study the collinear splitting functions needed for next-to-next-to-leading order calculations of jet production in the vacuum and in dense QCD matter. These splitting functions describe the probability of a parton to evolve into three-parton final state and are generalizations of the traditional DGLAP splitting kernels to a higher perturbative order. Of particular interest are the angular distributions of such splitting functions, which can elucidate the significance of multiple parton branching for jet observables and guide the construction of parton shower Monte Carlo generators. We find that to ${\\cal O}(\\alpha_s^2)$ both the vacuum and the in-medium collinear splitting functions are neither angular ordered nor anti-angular ordered. Specifically, in dense QCD matter they retain the characteristic broad angular distribution already found in the ${\\cal O}(\\alpha_s)$ result.
Power law in the angular velocity distribution of a granular needle
Piasecki, J.; Viot, P.
2005-01-01
We show how inelastic collisions induce a power law with exponent -3 in the decay of the angular velocity distribution of anisotropic particles with sufficiently small moment of inertia. We investigate this question within the Boltzmann kinetic theory for an elongated granular particle immersed in a bath. The power law persists so long as the collisions are inelastic for a large range of angular velocities provided the mass ratio of the anisotropic particle and the bath particles remains smal...
Angular distribution of x-rays emitted in the process of Dielectronic Recombination (DR) was studied at the Electron Beam Ion Trap. For this the photon emission spectra were observed along and perpendicular the electron beam propagation direction. X-ray line intensities differ drastically between the two acquired spectra. This indicates a strong alignment of the total angular momentum vector of the excited states populated by DR with respect to the electron beam propagation direction.
L-subshell resolved photon angular distribution of radiative electron capture into He-like uranium
The photon angular distributions for radiative electron capture (REC) into the j=1/2 and j=3/2 L-subshell levels were measured and calculated for U90+→C collisions at 89 MeV/u. The experiment provides the first study of the photon angular distribution of REC into a projectile p-state (j=3/2) which was found to exhibit a slight backward peaking in the laboratory frame. For radiative capture to the j=1/2 states the measured angular distribution deviates considerably from symmetry around 90 . The results demonstrate that the usual sin2θlab distribution is not valid in the high-Z regime. (orig.)
The angular distribution of neutron scattering from hydrogen at 27.3 MeV
The angular distribution for np scattering at 27.3 MeV has been measured at 7 angles between 170 and 57.90 in the lab system. The neutrons scattered by a small plastic scintillator were detected in another plastic scintillator whose absolute efficiency had been measured between 5 and 25 MeV by use of the associated particle method. It was found to be necessary to investigate the effect on the angular distribution of the 12C(n,n'y) reaction occurring in the target scintillator. The data overlap, and are combined with, existing distribution data at the same energy obtained by detecting recoil protons. The asymmetry about 1/2π of the resulting angular distribution is in better agreement with predictions from phase-shift analyses than with those from meson-theoretical models. (Auth.)
Angular distribution of ions and extreme ultraviolet emission in laser-produced tin droplet plasma
Chen, Hong; Duan, Lian; Lan, Hui [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Wang, Xinbing, E-mail: xbwang@hust.edu.cn; Chen, Ziqi; Zuo, Duluo [Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074 (China); Lu, Peixiang [School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)
2015-05-21
Angular-resolved ion time-of-flight spectra as well as extreme ultraviolet radiation in laser-produced tin droplet plasma are investigated experimentally and theoretically. Tin droplets with a diameter of 150 μm are irradiated by a pulsed Nd:YAG laser. The ion time-of-flight spectra measured from the plasma formed by laser irradiation of the tin droplets are interpreted in terms of a theoretical elliptical Druyvesteyn distribution to deduce ion density distributions including kinetic temperatures of the plasma. The opacity of the plasma for extreme ultraviolet radiation is calculated based on the deduced ion densities and temperatures, and the angular distribution of extreme ultraviolet radiation is expressed as a function of the opacity using the Beer–Lambert law. Our results show that the calculated angular distribution of extreme ultraviolet radiation is in satisfactory agreement with the experimental data.
The angular distribution of 40 keV argon sputtered copper has been measured. Comparison is made of the distributions from a flat surface (featureless at 10.000X) and from a pyramid-covered surface. Three different orientations of the single crystal have been used to bring the low index directions and as well as the into the plane of the collector foil. Enhanced ejections from the low index directions are seen to decrease in the order , low index directions not in but near the collector plane can also influence the angular distributions. Generally, the total yield is higher from the pyramid-covered surface than from the flat. (Auth.)
Measured multipole moments of continuum electron transfer angular distributions
The velocity space distribution of electrons emitted near the forward direction from collisions involving fast, highly stripped oxygen ions with gaseous and solid targets is presented and described in terms of multipole moments of the ejected charge distribution, which permits direct comparison with recent theory. The measurements are produced by employing position-sensitive electron detection to combine emission angle definition with conventional electrostatic spectrometry. Agreement obtained between theory and distributions observed for binary continuum electron loss processes coupled with a similar multipole content observed with solid targets suggests a model of convoy electron production dominated by electron loss from the projectile within the bulk of the target. Further, the connection between multipoles of the projectile electron emission distribution in single collisions and the state of excitation of that projectile excited states may provide the basis for a probe of the state of ions traversing bulk solid matter. 14 refs., 3 figs., 1 tab
On the observability of the quark orbital angular momentum distribution
Courtoy, Aurore; Goldstein, Gary R.; Hernandez, J. Osvaldo Gonzalez; Liuti, Simonetta; Rajan, Abha(University of Virginia – Physics Department, 382 McCormick Rd., Charlottesville, VA 22904, USA)
2014-01-01
We argue that due to Parity constraints, the helicity combination of the purely momentum space counterparts of the Wigner distributions -- the generalized transverse momentum distributions -- that describes the configuration of an unpolarized quark in a longitudinally polarized nucleon, can enter the deeply virtual Compton scattering amplitude only through matrix elements involving a final state interaction. The relevant matrix elements in turn involve light cone operators projections in the ...
We have studied the angular distributions for 6--30-MeV Cq+ (q=4--6) and 2--9-MeV H+ ions axially channeled in the [001] direction of a thin silicon crystal (1792 and 1900 A). We report highly structured two-dimensional angular distributions that depend sensitively on the projectile's velocity and incident charge state and the target's thickness and azimuthal orientation. Some structure in the angular contour maps is the result of a rainbow effect in axial channeling (i.e., extrema in the classical deflection function). State-to-state charge-state distributions, which are required to interpret the data accurately, have also been measured. All measured angular distributions have been explained via Monte Carlo trajectory calculations using Moliere's approximation to the Thomas-Fermi screening function and a screening length given by target electrons alone. The calculations indicate that all projectile velocity and charge-state effects and the target-thickness effects observed are the result of the projectile's transverse oscillatory motion in the channel. Using this information, we show that swift heavy-ion and proton angular distributions are simply related using a scaling law that depends only on the projectile's velocity and charge-to-mass ratio and on the crystal thickness
Angular distribution of atoms ejected by laser ablation of different metals
Angular distributions of 13 different metals ejected by laser ablation using fourth harmonics (wavelength=266 nm) of neodymium doped yttrium aluminum garnet laser and a fluence close to near-threshold value (2.3 J/cm2) have been investigated with a high angular resolution. The angular distribution which is characterized by the exponent n of cosn θ distribution showed very broad range of values between 3 and 24 for different metals. A simple relation that the exponent n is proportional to the square root of particle atomic weight as reported previously has not been observed. Instead, a general trend has been found that the metals with higher sublimation energy such as Ta and Zr show narrower angular distribution than those with lower sublimation energy such as Sn and In. While the sublimation energy of metals has a great influence on the angular distribution of ejected atoms, a simple consideration suggests that their thermal conductivity and specific heat have little effect on it.
Angular distributions of emitted particles by laser ablation of silver at 355 nm
Svendsen, Winnie Edith; Schou, Jørgen; Hansen, T.; Ellegaard, Ole
1998-01-01
The angular distribution of laser ablated silver in vacuum has been measured in situ with an array of quartz-crystal microbalances. The silver surface was irradiated by ns pulses from a Nd:YAG laser operating at 355 nm for fluences ranging from 0.7 J/cm2 to 8 J/cm2. The distribution is strongly...
Computerized method for X-ray angular distribution simulation in radiological systems
A method to simulate the changes in X-ray angular distribution (the Heel effect) for radiologic imaging systems is presented. This simulation method is described as to predict images for any exposure technique considering that the distribution is the cause of the intensity variation along the radiation field
Eremenko, D. O.; Drozdov, V. A.; Fotina, O. V.; Platonov, S. Yu.; Yuminov, O. A.
2016-07-01
Background: It is well known that the anomalous behavior of angular anisotropies of fission fragments at sub- and near-barrier energies is associated with a memory of conditions in the entrance channel of the heavy-ion reactions, particularly, deformations and spins of colliding nuclei that determine the initial distributions for the components of the total angular momentum over the symmetry axis of the fissioning system and the beam axis. Purpose: We develop a new dynamic approach, which allows the description of the memory effects in the fission fragment angular distributions and provides new information on fusion and fission dynamics. Methods: The approach is based on the dynamic model of the fission fragment angular distributions which takes into account stochastic aspects of nuclear fission and thermal fluctuations for the tilting mode that is characterized by the projection of the total angular momentum onto the symmetry axis of the fissioning system. Another base of our approach is the quantum mechanical method to calculate the initial distributions over the components of the total angular momentum of the nuclear system immediately following complete fusion. Results: A method is suggested for calculating the initial distributions of the total angular momentum projection onto the symmetry axis for the nuclear systems formed in the reactions of complete fusion of deformed nuclei with spins. The angular distributions of fission fragments for the 16O+232Th,12C+235,236,238, and 13C+235U reactions have been analyzed within the dynamic approach over a range of sub- and above-barrier energies. The analysis allowed us to determine the relaxation time for the tilting mode and the fraction of fission events occurring in times not larger than the relaxation time for the tilting mode. Conclusions: It is shown that the memory effects play an important role in the formation of the angular distributions of fission fragments for the reactions induced by heavy ions. The
Buss, R.J.
1979-04-01
The study of seven radical-molecule reactions using the crossed molecular beam technique with supersonic nozzle beams is reported. Product angular and velocity distributions were obtained and compared with statistical calculations in order to identify dynamical features of the reactions. In the reaction of chlorine and fluorine atoms with vinyl bromide, the product energy distributions are found to deviate from predictions of the statistical model. A similar effect is observed in the reaction of chlorine atoms with 1, 2 and 3-bromopropene. The reaction of oxygen atoms with ICl and CF/sub 3/I has been used to obtain an improved value of the IO bond energy, 55.0 +- 2.0 kcal mol/sup -1/. In all reactions studied, the product energy and angular distributions are found to be coupled, and this is attributed to a kinematic effect of the conservation of angular momentum.
Buica, Gabriela; 10.1103/PhysRevA.72.053416
2013-01-01
We theoretically investigate the effects of laser polarization on photoelectron angular distribution through laser-induced continuum structure. We focus on a polarization geometry where the probe and dressing lasers are both linearly polarized, and change the relative polarization angle between them. We find that the total ionization yield and the branching ratio into different ionization channels change as a function of the relative polarization angle, and accordingly the photoelectron angular distribution is altered. We present specific results for the $4p_{1/2}$-$6p_{1/2}$ and $4p_{3/2}$-$6p_{3/2}$ systems of the K atom, and show that the change of the polarization angle leads to the significant modification of photoelectron angular distribution.
Carbon K-shell photoelectron angular distribution from fixed-in-space CO2 molecules
Measurements of photoelectron angular distributions for carbon K-shell ionization of fixed-in-space CO2 molecules with the molecular axis oriented along, perpendicular and at 45 degrees to the electric vector of the light are reported. The major features of these measured spectra are fairly well reproduced by calculations employing a relaxed-core Hartree-Fock approach. In contrast to the angular distribution for K-shell ionization of N2, which exhibits a rich structure dominated by the f-wave (l=3) at the shape resonance, the angular distribution for carbon K-shell photoionization of CO2 is quite unstructured over the entire observed range across the shape resonance. (letter to the editor)
The Large Hadron Collider (LHC) at the Conseil Europeen pour la Recherche Nucleaire (CERN) allows to study the interactions of quarks and gluons in a yet unexplored energy regime. In 2010, the LHC delivered an integrated luminosity of more than 36 pb-1 of proton-proton collisions at a center-of-mass energy of √(s)=7 TeV. In these proton-proton collisions, the interactions of the constituent quarks and gluons produced a considerable amount of jets of particles with transverse momenta above 1 TeV. Well suited for the study of these jet processes is the Compact Muon Solenoid (CMS) experiment situated at the LHC point 5 as it can measure jets with the necessary energy and angular resolutions over a large range of transverse momentum (∝30 GeVTdijet = e verticalstrokey1-y2verticalstroke, where y1 and y2 are the rapidities of the two jets, y ≡ (1)/(2)ln [(E+pz)/(E-pz)], and pz is the projection of the jet momentum along the beam axis. The choice of the variable χdijet is motivated by the fact that the normalized differential cross section (1)/(σ) (dσ)/(dχdijet) (the dijet angular distribution) is flat in this variable for Rutherford scattering, characteristic for spin-1 particle exchange. In contrast to QCD which predicts a dijet angular distribution similar to Rutherford scattering, new physics, such as quark compositeness, that might have a more isotropic dijet angular distribution would produce an excess at low values of χdijet. Since the shapes of the dijet angular distributions for the qg →qg, qq' →qq' and gg →gg scattering processes are similar, the QCD prediction does not strongly depend on the parton distribution functions (PDFs) which describe the momentum distribution of the partons inside the protons. Due to the normalization, the dijet angular distribution has a reduced sensitivity to several predominant experimental uncertainties (e.g. the jet energy scale and luminosity uncertainties). The dijet angular distribution is therefore well suited
Angular momentum distributions for {sup 16}O + {sup 144}Nd
Duchene, G.; Romain, P.; Beck, F.A.; Benet, P.; Disdier, D.; Haas, B.; Lott, B.; Rauch, V.; Scheibling, F.; Vivien, J.P. [Strasbourg-1 Univ., 67 (France). Centre de Recherches Nucleaires]|[Strasbourg-1 Univ., 67 (France); Basu, S.K. [Bhabha Atomic Research Centre, Calcutta (India). Variable Energy Cyclotron Project; Bozek, E.; Zuber, K. [Institute of Nuclear Physics, Cracow (Poland); Di Gregorio, D.E.; Fernandez-Niello, J. [Comision Nacional de Energia Atomica, Buenos Aires (Argentina). Dept. de Fisica
1992-12-31
Fusion cross sections have been measured for the system {sup 16} O + {sup 144} Nd at bombarding energies in the range 67 MeV {<=}E{sub lab} {<=} 90 MeV by detecting directly evaporation residues in Si detectors and in the range 60 MeV {<=}E{sub lab}{<=} 75 MeV by off-line detection of the K X-rays emitted by the radioactive evaporation residues and daughters. In order to obtain the spin distributions in the compound system gamma-ray multiplicity distributions for the most important neutron evaporation channels were also measured using a 4{pi} - BaF{sub 2} array, in conjunction with Ge detectors. Results are compared with calculations based on models that consider fluctuations in barrier height due to ground state zero point vibrations as well as couplings to various inelastic and transfer channels.
Angular momentum distributions for 16O+144Nd
Fusion cross sections have been measured for the system 16O+144Nd at bombarding energies in the range 67 MeV≤Elab≤90 MeV by detecting directly evaporation residues in Si detectors and in the range 60 MeV≤Elab≤75 MeV by off-line detection of the K x rays emitted by the radioactive evaporation residues and daughters. In order to obtain the spin distributions in the compound system gamma-ray multiplicity distributions for the most important neutron evaporation channels were also measured using a 4π BaF2 array, in conjunction with Ge detectors. Results are compared with calculations based on models that consider fluctuations in barrier height due to ground-state zero-point vibrations as well as couplings to various inelastic and transfer channels
Angular Distribution of the 12C(6He, 7Li)11B Reaction
LI Er-Tao; LI Zhi-Hong; LI Yun-Ju; YAN Sheng-Quan; BAI Xi-Xiang; GUO Bing; SU Jun; WANG You-Bao; WANG Bao-Xiang; LIAN Gang; ZENG Sheng; FANG Xiao; ZHAO Wei-Juan; LIU Wei-Ping
2009-01-01
Angular distribution of the 12C(6He, 7Li)11B transfer reaction is measured with a secondary 6He beam of 36.4 Me V for the first time. The experimental angular distribution is well reproduced by the distorted-wave Born approxima-tion (DWBA) calculation. The success of the present experiment shows that it is feasible to measure one-nucleon transfer reaction on a light nucleus target with the secondary beam facility of the HI-13 tandem accelerator at China Institute of Atomic Energy (CIAE), Beifing.
Angular and velocity distributions of NO scattered from the Pt(111) crystal surface
Guthrie, W.L.; Lin, T.; Ceyer, S.T.; Somorjai, G.A.
1982-06-15
The angular and velocity distributions of NO scattered from the Pt(111) surface have been measured for a crystal temperature range of 475--1200 K and for an incident beam energy range of 265--1390 K. Both angular and velocity distributions confirm the coexistence of inelastic and trapping-desorption scattering processes. For beams with a kinetic energy of
Near-field angular distributions of high velocity ions for low-power hall thrusters
Sullivan, Regina M.; Yost, Allison; Johnson, Lee K.
2009-01-01
Experimental angular distributions of high-energy primary ions in the near-field region of a small Hall thruster between 50-200 mm downstream of the thruster exit plane at a range of centerline angles have been determined using a highly-collimated, energy-selective diagnostic probe. The measurements reveal a wide angular distribution of ions exiting the thruster channel and the formation of a strong, axially-directed jet of ions along the thruster centerline. Comparisons are made to other exp...
This paper presents a way to determine the angular and spatial distributions of the thermal neutron source strength of a boron neutron capture therapy (BNCT) beam. The experiments applied 1) the indirect neutron radiography, 2) the cadmium difference method, and 3) the instrumental neutron activation analysis. The measured data were processed by the spectrum deconvolution technique to resolve into a proper set of angular and spatial distributions. This paper took the epithermal neutron beam of the BNCT facility at the Tsing Hua Open-pool Reactor as an example.
Energy-loss effects in multiple-scattering angular distributions of ions in matter
The standard theory of multiple scattering of ions traversing matter assumes that the energy loss of a particle, during transit through a medium, is very small compared with its initial energy. Here we consider the effect of finite-energy losses on the multiple-scattering angular distributions, by taking into account the variation of the energy-dependent scattering cross section as a function of the depth penetrated into the material. The theory is generalized to account for a continuous slowing down of the beam particles. We study in particular, for the case of slow ions, the increased spread of the angular distributions due to the energy-loss effect
Twofold angular distributions in two-color, two-photon ionization
The ejected electron angular distributions for two-color ionization of hydrogen are studied using a new approach which takes into account the radiative corrections to both the bound and the continuous states. One considers ionization processes in which one high frequency, linearly polarized photon has enough energy to ionize the atom, meanwhile, one extra-photon is exchanged between the atomic system and the low frequency, circularly polarized field. Asymmetric angular distributions are predicted for this case and their origin is discussed. Numerical evaluations, made for the Nd:YAG laser and high frequencies which are near the value of the ionization threshold are presented. (author). 34 refs, 2 figs
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Avakian, Harut; Brodsky, Stanley J.; Deur, Alexandre; Yuan, Feng
2007-01-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis sho...
Yuan, Kai-Jun; Bandrauk, André D.
2012-05-01
Photoionization of aligned and fixed nuclei three-dimensional H2+ and two-dimensional H2 by intense circularly polarized attosecond extreme ultraviolet laser pulses is investigated from numerical solutions of the time-dependent Schrödinger equation. Molecular above-threshold-ionization angular distributions are found to be rotated with respect to the two laser perpendicular polarizations or, equivalently the symmetry axes of the molecule. The angle of rotation is critically sensitive to laser wavelength λ, photoelectron energy Een, and molecular internuclear distance R. The correlated interaction of the two electrons in H2 is shown to also influence such angular distribution rotations in different electronic states.
Radiative angular distributions from charmonium states directly produced by bar pp annihilation
We calculate the combined angular distributions of the photon and the electron in the cascade process p bar p→χJ→ψγ→(e+e-)γ (J=2,1,0), in terms of the helicity or the multipole transition amplitudes in χJ→ψγ. Our expressions for them differ from those found previously. We describe the origin of these differences. The effect of the motion of ψ in the χJ rest frame on the angular-distribution functions is taken into account
Angular distribution of electron temperature and density in a laser-ablation plume
Toftmann, B.; Schou, Jørgen; Hansen, T.N.; Lunney, J.G.
2000-01-01
The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy is ...... about 2 orders of magnitude larger, and its angular distribution is mon peaked about the target normal. The derived Values of the electron density are in agreement with the measured values of ion density....
Quark Wigner Distributions and Orbital Angular Momentum in Light-front Dressed Quark Model
Mukherjee, Asmita; Ojha, Vikash Kumar
2014-01-01
We calculate the Wigner functions for a quark target dressed with a gluon. These give a combined position and momentum space information of the quark distributions and are related to both generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs). We calculate and compare the different definitions of quark orbital angular momentum in this model. We compare our results with other model calculations.
Compton scattering of twisted light: angular distribution and polarization of scattered photons
Stock, S; Fritzsche, S; Seipt, D
2015-01-01
Compton scattering of twisted photons is investigated within a non-relativistic framework using first-order perturbation theory. We formulate the problem in the density matrix theory, which enables one to gain new insights into scattering processes of twisted particles by exploiting the symmetries of the system. In particular, we analyze how the angular distribution and polarization of the scattered photons are affected by the parameters of the initial beam such as the opening angle and the projection of orbital angular momentum. We present analytical and numerical results for the angular distribution and the polarization of Compton scattered photons for initially twisted light and compare them with the standard case of plane-wave light.
Compton scattering of twisted light: Angular distribution and polarization of scattered photons
Stock, S.; Surzhykov, A.; Fritzsche, S.; Seipt, D.
2015-07-01
Compton scattering of twisted photons is investigated within a nonrelativistic framework using first-order perturbation theory. We formulate the problem in the density-matrix theory, which enables one to gain new insights into scattering processes of twisted particles by exploiting the symmetries of the system. In particular, we analyze how the angular distribution and polarization of the scattered photons are affected by the parameters of the initial beam such as the opening angle and the projection of orbital angular momentum. We present analytical and numerical results for the angular distribution and the polarization of Compton scattered photons for initially twisted light and compare them with the standard case of plane-wave light.
Fission cross sections and angular distributions of fission fragments from fissions induced by 14.1 and 15.8 MeV neutrons, respectively, in 232Th, 231Pa, 233U, 235U, 238U, 237Np, 239Pu and 241Am have been studied using Lexan plastic track detectors. A novel experimental set-up evolved from considerations of neutron economy allows simultaneous measurement of angular distribution of fission fragments from five independently fissioning nuclides at a time. The data on angular anistropy were analysed in the perspective of different chances of fissions taking place simultaneously in this energy region. Third-chance fission thresholds for 231Pa and 241Am were estimated from the measured anisotropy values to be 13.2 and 11.1 MeV, respectively. (author)
A review is given of the angular distribution of particles or radiation produced as a result of interaction processes of primary radiation with matter. Equally important as the angular distribution of the particles or radiation is their energy distribution and energy losses or the mean path in the matter. (author)
Quasifission role in the anisotropy of fragment angular distribution of 19F+208Pb reaction
Full text: Role of quasifission was analyzed in the angular anisotropy of the fission-like reaction fragments in the framework of the model based on the conception of dinuclear system (DNS) and used to calculate the partial capture and complete fusion cross sections [1,2,3]. This model allows us to calculate the entrance channel dynamics of the nuclei to be captured with different orientation angles of their axes. We theoretically analyzed the experimental data for mean square values 2> and the angular anisotropy A for the 19F+208Pb reaction which was studied in Ref. [4, 5]. The experimental studies of fission angular distributions in heavy ion reactions show distinct deviation from the SSM theory. Our results of the reaction cross sections showed the presence of quasifission process. Considering the quasifission as 'fission' of the dinuclear system from a non compact shape we estimated mean square values of the angular momentum and anisotropy of the angular distribution of reaction fragments. This was possible with the known angular momentum distributions of complete fusion and quasifission calculated in our model. Comparison of the results with the experimental data shows that the fission data presented in Ref. [4, 5] are in good agreement with our fusion cross sections at energies near the barrier and contain contributions of quasifission at higher energies. Our results of the mean square values of the angular momentum and anisotropy of the angular distributions of reaction fragments are in good agreement with the experimental data if we include quasifission contributions. From a fit of the experimental data for fusion-fission cross section we found which part of quasifission fragments is mixed with the fragments from the compound nucleus fission. So, we conclude that the main reason of the failure of the standard statistical model for the description of the angular anisotropy of the fission fragments at higher than Coulomb barrier is the presence of the
Photoelectron angular distribution and photoionization cross sections for H2
Photoionization of H2 from its ground 1μ/sub g/+ state is studied theoretically. The rotational quantization is introduced in addition to the conventional vibrational-electronic transitions during the photoionization process. The photoionization differential cross section of this rotating system is derived and proved to be expressible in the simple form of [sigma(v')/4π][1 + #betta#(v')P2(cos theta)] for H2+ in the vibrational level v' or in the well-known form of (sigma/sub T//4π) [1 + #betta#P2(cos theta)] after summing over all of the vibrational levels of H2+. The angle theta of the ejected electron is measured from the polarization direction of the radiation for the linearly polarized light or measured from the light propagation direction for the unpolarized light. The asymmetry parameters #betta#(v') and #betta#, which are expressed explicitly here in terms of Racah and Clebsch-Gordan coefficients and electronic transition moments, are shown to equal approximately to 2 for the case of linearly polarized light and -1 for the case of unpolarized light. The differential cross section is also proved to be independent of the initial rotational quantum number N'' (of H2) by neglecting vibrational-rotational interactions. Using single-center electronic wave functions for both the molecular system and the outgoing electron and including partial waves l = 1, 3 and 5 in the continuum (Coulomb) wave functions, sigma(v') and #betta#(v') are computed as a function of v' at 584 A. The calculated ratios sigma(v')/sigma(v'=2) agree with the measured vibrational intensity distributions. sigma/sub T/ and #betta# are computed in the incident photon energy range of 600 A to 440 A and the results compare favorably with previous calculations
The dijet mass spectrum and angular distributions with the D0 detector
We present preliminary results from an analysis of dijet data collected during the 1994-95 Tevatron Collider run with an integrated luminosity of 91 pb-1. Measurements of dijet mass spectra and dijet angular distributions in anti pp collisions at √s- = 1.8 TeV are compared with next-to-leading order QCD theory
Angular Ion and Neutral Energy-Distribution in a Collisional Rf Sheath
Manenschijn, A.; W. J. Goedheer,
1991-01-01
A numerical study on the ion and neutral angular impact energy distribution at the rf-driven electrode of a reactive ion etcher is presented. The calculations for the ions are performed using a Monte Carlo method that includes charge exchange and elastic scattering. The contribution of both collisio
State-selective velocity and angular distributions of NO molecules scattered from a graphite surface
Hager, J.; Shen, Y.R.; Walther, H.
1985-03-01
Laser ionization was used to measure the state-selective angular and velocity distributions of NO molecules scattered from a graphite surface. The data showed that at sufficiently low surface temperatures, the scattered molecules were generally composed of quasispecular reflected part and a diffusive scattered part with different translational and rotational behavior.
Hansen, Jonas Lerche; Stapelfeldt, Henrik; Dimitrovski, Darko;
2011-01-01
A nanosecond laser pulse confines the spatial orientation of naphthalene in 1D or 3D while a femtosecond kick pulse initiates rotation of the molecular plane around the fixed long axis. Time-dependent photoelectron angular distributions (PADs), resulting from ionization by an intense femtosecond...
Angular distribution of neutral hydrogen following collisional electron detachment from H-
The angular distribution of neutral hydrogen following electron detachment from H- has been measured for H- on nitrogen and hydrogen gas, both for neutral atoms left in the 2S state, and for all neutrals independent of the state of excitation. The results are essentially in agreement with calculations based on the Born approximation, although there is some disagreement in detail
Alpha particle angular distribution of oriented 189,191,193Bi
Angular distribution data for α particles emitted in the enhanced decay of on-line oriented neutron deficient isotopes 189,191,193Bi near mid-shell (N=104) are presented. They give additional support for the recent finding that anisotropic α emission in enhanced decays from near-spherical nuclei is mainly determined by nuclear structure effects. (authors)
Palov, A. P.; Mankelevich, Yu A.; Rakhimova, T. V.; Baklanov, M. R.
2016-03-01
Ion-stimulated etching of dielectrics in radio frequency plasma results in positive charging of a trench bottom because of the significant difference in the angular distribution functions of ions and electrons. They are anisotropic for ions and quasi-isotropic for electrons. The charging leads to a decrease in the energy of the ions bombarding the trench bottom and to undesirable sputtering of the walls near the trench bottom because of the curving of the ion trajectories. This process is normally investigated by Monte Carlo methods in the absence of experimental data. In this paper the analytical dependence of the ion flux bombarding the trench bottom on a trench aspect ratio and ion angular distribution function is obtained. Numerical calculations of the electric potential on the trench bottom for a set of trench aspect ratios and angles of the ion angular distribution function were performed based on a Monte Carlo method to demonstrate the ion flux and electric potential correlated well with each other. The proposed formula for an ion flux is suggested to be helpful for analyzing charging the trenches with different aspect ratios in plasma with an arbitrary angular ion distribution function.
Polarization and angular distributions in elastic pp scattering at 100 and 300 GeV
Measurements of the polarization parameter and angular distributions in pp elastic scattering at incident energies of 100 and 300 GeV are reported. The data cover the kinematic range 0.18 2. They are found to be consistent with absorption-model predictions
Angular distribution of electron temperature and density in a laser-ablation plume
Toftmann, B.; Schou, Jørgen; Hansen, T.N.; Lunney, J.G.
2000-01-01
The angular distribution of electron temperature and density in a laser-ablation plume has been studied for the first time. The electron temperature ranges from 0.1 to 0.5 eV and is only weakly dependent on the angle in the low-intensity range studied here. In contrast, the typical ion energy is...
Quiescence and late time activity in collapsars due to critical angular momentum distributions
Lopez-Camara, D
2010-01-01
Even thought a large amount of long gamma ray bursts (LGRBs) present quiescent periods, their origin remains unclear. In this talk, it is shown how different angular momentum distributions, as a function of the stellar radius), can lead to neutrino luminosity variability and the possibility of quiescent epochs in LGRBs.
The statistical properties of the angular distribution of beta delayed protons from oriented nuclei
Stone, N J; Wöhr, A
2000-01-01
Statistical model of beta -delayed proton emission is briefly reviewed. Theory of angular distribution of beta -delayed proton emission from nuclear states oriented at low temperatures is discussed and the design of the first trial experiment using /sup 118 /Cs oriented at low temperature at the ISOLDE/NICOLE facility at CERN is described. (14 refs).
A relatively simple formalism for calculating the average neutron elastic angular distribution dσel/dΩ in the resonance region below several hundred keV is presented. The expression for dσel/dΩ depends mainly on the R-matrix parameters S0, R', S1, and R1∞. Comparisons between calculated and experimental angular distributions are presented for 103Rh, 139La, 232Th, and 238U. A fit to 238U data at 75 keV led to a value of the p-wave strength function of S1=1.81±0.35x10-4. Except for measuring a complete set of individual l=1 resonances, determining the p-wave strength function by fitting low-energy angular distributions is probably more reliable than, or competitive with, other techniques which are available. An analysis of elastic angular distributions as a function of neutron energy is also well suited to a search for intermediate structure in the s- or p-wave strength function. copyright 1997 The American Physical Society
The validity of the hypothesis that the angular distribution of shower particles produced in hadron - nucleus interactions can be parametrized by the number of slow particles emitted from the struck nucleus is tested. Relation between the mean number of slow particles and the mass number A of the target nucleus or the corresponding average number of collisions inside the target nucleus is found. (author)
Angular distribution of species in pulsed energy beam deposition of oxide films
Nistor, M., E-mail: mnistor@infim.ro [National Institute for Lasers, Plasmas and Radiation Physics, L22 P.O. Box MG-36, 77125 Bucharest-Magurele (Romania); Gherendi, F.; Mandache, N.B. [National Institute for Lasers, Plasmas and Radiation Physics, L22 P.O. Box MG-36, 77125 Bucharest-Magurele (Romania)
2012-09-15
Highlights: Black-Right-Pointing-Pointer Thickness profiles of Ba{sub x}Sr{sub 1-x}TiO{sub 3} thin films were measured. Black-Right-Pointing-Pointer Comparison between pulsed laser (PLD) and pulsed electron beam deposition (PED). Black-Right-Pointing-Pointer The film thicknesses profile of PED has a slightly broader shape than that of PLD. Black-Right-Pointing-Pointer The film stoichiometry is preserved at all angles. - Abstract: Pulsed energy beam deposition methods like pulsed-laser deposition (PLD) or pulsed-electron beam deposition (PED) allow the formation of smooth, dense and crystalline oxide thin films. The angular distribution of the ablated flux from the target and the thin film thickness profile were extensively studied for PLD for a wide range of materials and growth conditions. In the case of complex oxide compounds, the angular distribution of the various species emitted by the target will determine the precise composition of the films. In this work we report on the determination of the angular distributions of the species emitted from a Ba{sub x}Sr{sub 1-x}TiO{sub 3} (BST) target. A comparison between these results obtained by PED and PLD methods is presented and discussed in the frame of Anisimov's model. A slightly broader shape of the angular distribution for PED than that for PLD is explained taking into account the differences in the spot size and fluence between the pulsed electron beam and laser beam and a small collisional broadening of the angular distribution in the case of PED. The stoichiometry is preserved at all angles.
Calculation of the angular distribution of delay times in neutron scattering on 58Ni nuclei
Angular distributions of average delay times and time variances are calculated for resonance-neutron scattering on 58Ni nuclei at neutron energies in the range E = 600−700 keV. The effect of the energy spectrum and polarization of the beam on the scattering-process time is discussed. The angular dependence of the time law is also considered for the decay of an intermediate compound nuclear system. It is shown that the results of stationary and nonstationary calculations are in good agreement.
Calculation of the angular distribution of delay times in neutron scattering on {sup 58}Ni nuclei
Prokopets, G. A., E-mail: gaprok@uos.net.ua [National University of Kyiv-Mohyla Academy (Ukraine)
2011-05-15
Angular distributions of average delay times and time variances are calculated for resonance-neutron scattering on {sup 58}Ni nuclei at neutron energies in the range E = 600-700 keV. The effect of the energy spectrum and polarization of the beam on the scattering-process time is discussed. The angular dependence of the time law is also considered for the decay of an intermediate compound nuclear system. It is shown that the results of stationary and nonstationary calculations are in good agreement.
Towards a Direct Measurement of the Quark Orbital Angular Momentum Distribution
Liuti, Simonetta; Engelhardt, Michael; Rajan, Abha
2015-01-01
We discuss two different definitions of partonic orbital angular momentum given in the literature in terms of the Fourier transform of a Wigner distribution, $F_{14}$, and a twist three generalized parton distribution, $\\tilde{E}_{2T}$, respectively. We derive a relation between the two definitions which reflects their specific spin and intrinsic transverse momentum/transverse space correlations as well as their gauge link structure.
Angular Distribution of Protons Measured by the Energetic Particle Telescope on PROBA-V
Borisov, Stanislav; Benck, Sylvie; Cyamukungu, Mathias
2014-01-01
Angular distribution and contamination of proton spectra measured at LEO are considered as possible sources of discrepancies between fluxes obtained by different instruments. In particular, not accounted for pitch angle distribution and East/West asymmetry of energetic proton fluxes have been suspected of leading to the reported underestimates of these fluxes by the NASA Model AP8. The Energetic Particle Telescope (EPT) was designed as a science-class instrument aimed at providing uncontamina...
Simulation of ion implantation into deep trenches demands the exact evaluation of ion fluxes backscattered from the sidewalls. In this paper an application of Boltzmann Transport Equation (BTE) to backscattered ion energy and angular distribution calculations is presented. Characteristic examples of grazing implantation of Sb, As and P in Si are considered and good agreement with Monte-Carlo (MC) calculations are found. It was also found that BTE gives a more smooth distribution without statistical fluctuations and essentially saves computational time. (author)
Angular distributions of photoelectrons and non-thermal photoions from atoms and molecules. [Review
Dehmer, Joseph L.
1977-01-01
During the last ten years, photoelectron angular distributions have been used extensively to study the dynamics of the photoionization process in atoms and molecules. Some major advances in this body of work are reviewed with special emphasis on results emerging since the last Conference on VUV Radiation Physics three years ago. By far the greatest progress has occurred for atoms, where interest is focussed on improving zero-order (Hartree-Slater, Cooper-Zare) understanding of the asymmetry parameter β(ϵ), by considering electron correlations, relativistic effects, and anisotropic final-state interactions. The study of the rare gases has benefitted from extensive coordination between experiment and theory, whereas work on nonspherical atoms has been mainly theoretical, with the only measurements being performed very recently on atomic oxygen. Angular distribution studies on molecules are in a much earlier stage of development. Progress has been impeded by the lack of practical, realistic theoretical methods and wavelength-dependent measurements, both of which are becoming available only now. This recent work, together with selected topics from earlier resonance-line work on molecules will be reviewed. In addition, a new class of angular-dependent studies of molecules will be discussed--the angular distribution of nonthermal ions formed by dissociative photoionization--which provides information complementary to the related measurements on photoelectrons.
Modelling of atmospheric effects on the angular distribution of a backscattering peak
If off-nadir satellite sensing of vegetative surfaces is considered, understanding the angular distribution of the radiance exiting the atmosphere in all upward directions is of interest. Of particular interest is the discovery of those reflectance features which are invariant to atmospheric perturbations. When mono-directional radiation is incident on a vegetative scene a characteristic angular signature called the hot-spot is produced in the solar retro-direction. The remotely sensed hot-spot is modified by atmospheric extinction of the direct and reflected solar radiation, atmospheric backscattering, and the diffuse sky irradiance incident on the surface. It is demonstrated, however, by radiative transfer calculations through model atmospheres that at least one parameter which characterizes the canopy hot-spot, namely its angular half width, is invariant to atmospheric perturbations. 7 refs., 4 figs., 1 tab
Effect of Orbital Angular Momentum on Valence-Quark Helicity Distributions
Harut Avakian; Stanley J. Brodsky; Alexandre Deur; Feng Yuan
2007-08-01
We study the quark helicity distributions at large x in perturbative QCD, taking into account contributions from the valence Fock states of the nucleon which have nonzero orbital angular momentum. These states are necessary to have a nonzero anomalous magnetic moment. We find that the quark orbital angular momentum contributes a large logarithm to the negative helicity quark distributions in addition to its power behavior, scaling as (1-x)^5\\log^2(1-x) in the limit of x\\to 1. Our analysis shows that the ratio of the polarized over unpolarized down quark distributions, \\Delta d/d, will still approach 1 in this limit. By comparing with the experimental data, we find that this ratio should cross zero at x\\approx 0.75.
Probability distribution of primordial angular momentum and formation of massive black holes
Susa, H; Tanaka, T; Hajime Susa; Misao Sasaki; Takahiro Tanaka
1994-01-01
Abstract{ We consider the joint probability distribution function for the mass contrast and angular momentum of over-density regions on the proto- galactic scale and investigate the formation of massive black holes at redshift z\\gsim10. We estimate the growth rate of the angular momentum by the linear perturbation theory and the decay rate by the Compton drag and apply the Press-Schechter theory to obtain the formation rate of massive black holes, assuming the full reionization of the universe at z=z_{ion}\\gg 10. We find the correlation between the mass contrast and angular momentum vanishes in the linear theory. However, application of the Press-Schechter theory introduces a correlation between the mass contrast and angular momentum of bound objects. Using thus obtained probability distribution, we calculate the mass fraction of black holes with M\\sim10^6-10^8M_{\\odot} in the universe. We find that it crucially depends on the reionization epoch z_{ion}. Specifically, for the standard CDM power spectrum with ...
Bogdanov, O. V.; Fiks, E. I.; Pivovarov, Yu. L.
2012-09-01
Numerical methods are used to study the dependence of the structure and the width of the angular distribution of Vavilov-Cherenkov radiation with a fixed wavelength in the vicinity of the Cherenkov cone on the radiator parameters (thickness and refractive index), as well as on the parameters of the relativistic heavy ion beam (charge and initial energy). The deceleration of relativistic heavy ions in the radiator, which decreases the velocity of ions, modifies the condition of structural interference of the waves emitted from various segments of the trajectory; as a result, a complex distribution of Vavilov-Cherenkov radiation appears. The main quantity is the stopping power of a thin layer of the radiator (average loss of the ion energy), which is calculated by the Bethe-Bloch formula and using the SRIM code package. A simple formula is obtained to estimate the angular distribution width of Cherenkov radiation (with a fixed wavelength) from relativistic heavy ions taking into account the deceleration in the radiator. The measurement of this width can provide direct information on the charge of the ion that passes through the radiator, which extends the potentialities of Cherenkov detectors. The isotopic effect (dependence of the angular distribution of Vavilov-Cherenkov radiation on the ion mass) is also considered.
Influence of the halo upon angular distributions for elastic scattering and breakup
The angular distributions for elastic scattering and breakup of halo nuclei are analysed using a near-side/far-side decomposition within the framework of the dynamical eikonal approximation. This analysis is performed for 11Be impinging on Pb at 69 MeV/nucleon. These distributions exhibit very similar features. In particular they are both near-side dominated, as expected from Coulomb-dominated reactions. The general shape of these distributions is sensitive mostly to the projectile-target interactions, but is also affected by the extension of the halo. This suggests the elastic scattering not to be affected by a loss of flux towards the breakup channel.
Hinzmann, Andreas Dominik
2011-10-07
{sub 2}} {sup vertical} {sup stroke}, where y{sub 1} and y{sub 2} are the rapidities of the two jets, y {identical_to} (1)/(2)ln [(E+p{sub z})/(E-p{sub z})], and p{sub z} is the projection of the jet momentum along the beam axis. The choice of the variable {chi}{sub dijet} is motivated by the fact that the normalized differential cross section (1)/({sigma}) (d{sigma})/(d{chi}{sub dijet}) (the dijet angular distribution) is flat in this variable for Rutherford scattering, characteristic for spin-1 particle exchange. In contrast to QCD which predicts a dijet angular distribution similar to Rutherford scattering, new physics, such as quark compositeness, that might have a more isotropic dijet angular distribution would produce an excess at low values of {chi}{sub dijet}. Since the shapes of the dijet angular distributions for the qg {yields}qg, qq{sup '} {yields}qq{sup '} and gg {yields}gg scattering processes are similar, the QCD prediction does not strongly depend on the parton distribution functions (PDFs) which describe the momentum distribution of the partons inside the protons. Due to the normalization, the dijet angular distribution has a reduced sensitivity to several predominant experimental uncertainties (e.g. the jet energy scale and luminosity uncertainties). The dijet angular distribution is therefore well suited to test the predictions of QCD and to search for signals of new physics, in particular for signs of quark compositeness. In the following a measurement of the dijet angular distributions and a search for quark compositeness with the CMS experiment is presented. (orig.)
The angular distribution of sputtered particles measured by RBS analysis of the collected patticles
The angular distributions of sputtered polycrystalline Ag and W have been measured. The ion beams were He+ or Ar+ in the energy range 15-80 keV. The sputtered particles were collected on a band in the form of a half-circle, in order to avoid projection distortions. The collector was made of high purity Al and was analysed by backscattering technique. The sensitivity of this method makes it possible to determine less than one monolayer, and one can therefore assume that the sticking probability does not change during a run. The results show that the angular distribution varies from a cos2theta to a costheta function for different targets. For the interpretation of the results, it is important to discuss the influence of the work function and the beam energy. (Auth.)
Neutron angular distribution in a plasma focus obtained using nuclear track detectors.
Castillo-Mejía, F; Herrera, J J E; Rangel, J; Golzarri, J I; Espinosa, G
2002-01-01
The dense plasma focus (DPF) is a coaxial plasma gun in which a high-density, high-temperature plasma is obtained in a focused column for a few nanoseconds. When the filling gas is deuterium, neutrons can be obtained from fusion reactions. These are partially due to a beam of deuterons which are accelerated against the background hot plasma by large electric fields originating from plasma instabilities. Due to a beam-target effect, the angular distribution of the neutron emission is anisotropic, peaked in the forward direction along the axis of the gun. The purpose of this work is to illustrate the use of CR-39 nuclear track detectors as a diagnostic tool in the determination of the time-integrated neutron angular distribution. For the case studied in this work, neutron emission is found to have a 70% contribution from isotropic radiation and a 30% contribution from anisotropic radiation. PMID:12382811
Hsi, W.; Kwiatkowski, K.; Wang, G.; Bracken, D.S.; Cornell, E.; Ginger, D.S.; Viola, V.E.; Yoder, N.R. [Department of Chemistry and IUCF, Indiana University, Bloomington, Indiana 47405 (United States); Korteling, R.G. [Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6 (CANADA); Gimeno-Nogues, F.; Ramakrishnan, E.; Rowland, D.; Yennello, S.J. [Department of Chemistry and Cyclotron Institute, Texas AM University, College Station, Texas 77843 (United States); Huang, R.; Lynch, W.G.; Tsang, M.B.; Xi, H. [Department of Physics and NSCL, Michigan State University, East Lansing, Michigan 44824 (United States); Breuer, H. [Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Morley, K.B. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Gushue, S.; Remsberg, L.P. [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Friedman, W.A. [Department of Physics, University of Wisconsin, Madison, Wisconsin 53706 (United States); Botvina, A. [Department of Physics, Bologna University, Bologna 40126 (Italy)
1998-07-01
Exclusive studies of sideways-peaked angular distributions for intermediate-mass fragments (IMFs) produced in hadron-induced reactions have been performed with the Indiana silicon sphere (ISiS) detector array. The effect becomes prominent for beam momenta above about 10thinspGeV/c. Both the magnitude of the effect and the peak angle increase as a function of fragment multiplicity and charge. When gated on IMF kinetic energy, the angular distributions evolve from forward peaked to nearly isotropic as the fragment energy decreases. Fragment-fragment correlation studies show no evidence for a preferred angle that might signal a fast dynamic breakup mechanism. Moving-source and intranuclear cascade simulations suggest a possible kinematic origin arising from significant transverse momentum imparted to the recoil nucleus during the fast cascade. A two-step cascade and statistical multifragmentation calculation is consistent with the data. {copyright} {ital 1998} {ital The American Physical Society}
Angular distributions of electrons emitted from free and deposited Na{sub 8} clusters
Baer, Matthias [Institut fuer Theoretische Physik, Universitaet Erlangen (Germany); Dinh, Phuong Mai; Suraud, Eric [Laboratoire de Physique Theorique, IRSAMC, UPS and CNRS, Universite de Toulouse (France); Moskaleva, Lyudmila V.; Roesch, Notker [Department Chemie and Catalysis Research Center, Theoretische Chemie, Technische Universitaet Muenchen, Garching (Germany); Reinhard, Paul-Gerhard [Institut fuer Theoretische Physik, Universitaet Erlangen (Germany); Laboratoire de Physique Theorique, IRSAMC, UPS and CNRS, Universite de Toulouse (France)
2010-05-15
We explore from a theoretical perspective angular distributions of electrons emitted from a Na{sub 8} cluster after excitation by a short laser pulse. The tool of the study is time-dependent density-functional theory (TDDFT) at the level of the local-density approximation (LDA) augmented by a self-interaction correction (SIC) to put emission properties in order. We consider free Na{sub 8} and Na{sub 8} deposited on the surfaces MgO(001) or Ar(001). For the case of free Na{sub 8}, we distinguish between a hypothetical situation of known cluster orientation and a more realistic ensemble of orientations. We also consider the angular distributions for emission from separate single-electron levels. (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Ogawa Tatsuhiko
2016-01-01
Full Text Available To predict angular distribution of fragments produced in nucleusnucleus collisions, JAERI quantum molecular dynamics model (JQMD was improved. Because JQMD underestimated fragments in the forward angle, which were mainly produced by peripheral collisions, JQMD was revised so as to simulate peripheral collisions accurately. Density-dependent in-medium effect and relativistic effect on nucleonnucleon interactions were incorporated for this purpose. The revised version of JQMD coupled with a statistical decay model was used to calculate differential fragment production cross sections measured in earlier studies. Comparison of the measured data and calculation by the revised and old JQMD showed that the revised JQMD can predict fragment angular distribution better than old JQMD. Particularly, agreement of fragment yield in the forward angle is substantially improved.
Measurement of the Angular Distribution of Electrons from $W\\to e\
Abbott, B
2001-01-01
We present a preliminary measurement of the electron angular distribution parameter alpha2 in W to 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 +/- alpha1 cos theta* +alpha_2 cos^2 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 alpha1 and alpha2 become functions of pT(W), the W boson transverse momentum. We present the first measurement of alpha_2 as a function of pT(W). 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.
2p-2h excitations in neutrino scattering: angular distribution and frozen approximation
Simo, I Ruiz; Amaro, J E; Barbaro, M B; Caballero, J A; Donnelly, T W
2015-01-01
We study the phase-space dependence of 2p-2h excitations in neutrino scattering using the relativistic Fermi gas model. We follow a similar approach to other authors, but focusing in the phase-space properties, comparing with the non-relativistic model. A careful mathematical analysis of the angular distribution function for the outgoing nucleons is performed. Our goals are to optimize the CPU time of the 7D integral to compute the hadron tensor in neutrino scattering, and to conciliate the different relativistic and non relativistic models by describing general properties independently of the two-body current. For some emission angles the angular distribution becomes infinite in the Lab system, and we derive a method to integrate analytically around the divergence. Our results show that the frozen approximation, obtained by neglecting the momenta of the two initial nucleons inside the integral of the hadron tensor, reproduces fairly the exact response functions for constant current matrix elements.
Depth dose and angular dose distribution experiments with high energy electron-photon radiation
India's first synchrotron radiation source, Indus-1, is commissioned at the Centre for Advanced Technology (CAT), Indore. Radiation environment of this facility is quite different in comparison to that of nuclear or irradiator facilities and proton or heavy ion accelerator facilities. The primary particle accelerated being the electron, the radiation environment mainly comprises of Bremsstrahlung photons followed by photo-neutrons, whereas electron contamination too exists within the containment area. Due to the complex nature of the radiation viz. high energy, broad energy spectrum, pulsed, mixed field, sharp angular distribution etc. quantification of radiation dose becomes a difficult task. In this paper, experiments on depth dose and angular dose distribution done with 450 MeV electron-photon radiation are described
Uncertainty files for neutron cross sections and elastic angular scattering distributions on 56Fe
Based on a consistent theory calculation by means of UNF code, a evaluation of neutron induced reaction data on 56Fe, including cross section, angular distribution, double differential cross section and gamma ray production data, has been completed. The evaluations on covariance files for the data above are going on and some of the evaluation methods and results are reported. Five methods are used to evaluate the uncertainty files for cross sections and angular distributions. The comparisons between these results and other evaluations for uncertainty files are carried out. The agreements is good in the case of plenty measured data available as a basis of the evaluation. 56Fe(n,p) cross section is a typical example
Monte Carlo Calculation of Sensitivities to Secondary Angular Distributions. Theory and Validation
The basic methods for solution of the transport equation that are in practical use today are the discrete ordinates (SN) method, and the Monte Carlo (Monte Carlo) method. While the SN method is typically less computation time consuming, the Monte Carlo method is often preferred for detailed and general description of three-dimensional geometries, and for calculations using cross sections that are point-wise energy dependent. For analysis of experimental and calculated results, sensitivities are needed. Sensitivities to material parameters in general, and to the angular distribution of the secondary (scattered) neutrons in particular, can be calculated by well known SN methods, using the fluxes obtained from solution of the direct and the adjoint transport equations. Algorithms to calculate sensitivities to cross-sections with Monte Carlo methods have been known for quite a time. However, only just recently we have developed a general Monte Carlo algorithm for the calculation of sensitivities to the angular distribution of the secondary neutrons
Zhou, Yun, E-mail: zhou.yun.x@gmail.com; Pollak, Eli, E-mail: eli.pollak@weizmann.ac.il [Chemical Physics Department, Weizmann Institute of Science, 76100 Rehovot (Israel); Miret-Artés, Salvador, E-mail: s.miret@iff.csic.es [Instituto de Fisica Fundamental, Consejo Superior de Investigaciones Cientificas, Serrano 123, 28006 Madrid (Spain)
2014-01-14
A second order classical perturbation theory is developed and applied to elastic atom corrugated surface scattering. The resulting theory accounts for experimentally observed asymmetry in the final angular distributions. These include qualitative features, such as reduction of the asymmetry in the intensity of the rainbow peaks with increased incidence energy as well as the asymmetry in the location of the rainbow peaks with respect to the specular scattering angle. The theory is especially applicable to “soft” corrugated potentials. Expressions for the angular distribution are derived for the exponential repulsive and Morse potential models. The theory is implemented numerically to a simplified model of the scattering of an Ar atom from a LiF(100) surface.
Angular distribution of species in pulsed laser deposition of LaxCa1−xMnO3
Highlights: • The angular distribution of species was analyzed for different pressures. • Results show a non-congruent transfer of composition from target to substrate. • Film thickness and composition show different angular distributions. - Abstract: The angular distribution of species from a La0.4Ca0.6MnO3 target irradiated with a 248 nm nanosecond pulsed laser was investigated by Rutherford backscattering spectrometry for four different Ar pressures. The film thickness angular distribution was also analyzed using profilometry. Depending on the background gas pressure, the target to substrate distance, and the angular location the film thickness and composition varies considerably. In particular the film composition could vary by up to 17% with respect to the composition of the target material
Testing the anisotropy in the angular distribution of $Fermi$/GBM gamma-ray bursts
Tarnopolski, Mariusz
2015-01-01
Gamma-ray bursts (GRBs) were confirmed to be of extragalactic origin due to their isotropic angular distribution, combined with the fact that they exhibited an intensity distribution that deviated strongly from the $-3/2$ power law. This finding was later confirmed with the first redshift, equal to at least $z=0.835$, measured for GRB970508. Despite this result, the data from $CGRO$/BATSE and $Swift$/BAT indicate that long GRBs are indeed distributed isotropically, but the distribution of short GRBs is anisotropic. $Fermi$/GBM has detected 1669 GRBs up to date, and their sky distribution is examined in this paper. A number of statistical tests is applied: nearest neighbour analysis, fractal dimension, dipole and quadrupole moments of the distribution function decomposed into spherical harmonics, binomial test, and the two point angular correlation function. Monte Carlo benchmark testing of each test is performed in order to evaluate its reliability. It is found that short GRBs are distributed anisotropically ...
Photoelectron angular distributions from strong-field ionization of oriented molecules
Holmegaard, L.; Hansen, J.; Kalhøj, L.; Kragh, S.; Stapelfeldt, H.; Filsinger, F.; Küpper, J.; Meijer, G.; Dimitrovski, D.; Abu-samha, M.; Martiny, C.; Madsen, L.
2010-01-01
The combination of photoelectron spectroscopy and ultrafast light sources is on track to set new standards for detailed interrogation of dynamics and reactivity of molecules. A crucial prerequisite for further progress is the ability to not only detect the electron kinetic energy, as done in traditional photoelectron spectroscopy, but also the photoelectron angular distributions (PADs) in the molecular frame. Here carbonylsulfide (OCS) and benzonitrile molecules, fixed in space by combined la...
On the use of Makrofol KG to study fission fragment angular distributions
Makrofol KG nuclear track detector processing and analysis is carefully regulated and assessed to reveal fission fragments' tracks and their angular distributions. For this purpose, foils of this detector are irradiated by a thin 252Cf source and are subjected to chemical etching followed by a two-step sparking process. The detector efficiency as a function of fission fragment incidence angle and different etching parameters is carried out with a good reproducibility
Angular velocity distribution of a granular planar rotator in a thermalized bath
Piasecki, J.; Talbot, J.; Viot, P.
2006-01-01
The kinetics of a granular planar rotator with a fixed center undergoing inelastic collisions with bath particles is analyzed both numerically and analytically by means of the Boltzmann equation. The angular velocity distribution evolves from quasi-gaussian in the Brownian limit to an algebraic decay in the limit of an infinitely light particle. In addition, we compare this model with a planar rotator with a free center. We propose experimental tests that might confirm the predicted behaviors.
Angular velocity distribution of a granular planar rotator in a thermalized bath.
Piasecki, J; Talbot, J; Viot, P
2007-05-01
The kinetics of a granular planar rotator with a fixed center undergoing inelastic collisions with bath particles is analyzed both numerically and analytically by means of the Boltzmann equation. The angular velocity distribution evolves from quasi-Gaussian in the Brownian limit to an algebraic decay in the limit of an infinitely light particle. In addition, we compare this model to that of a planar rotator with a free center and discuss the prospects for experimental confirmation of these results. PMID:17677054
Zakowicz, S; Harman, Z; Scheid, W
2003-01-01
In collisions of heavy few-electron projectile ions with light targets, an electron can be transferred from the target with the simultaneous excitation of a projectile electron. We study the angular distribution of de-excitation X rays following the resonant capture process. Our results are compared to experimental values of Ma et al. [Phys. Rev. A (joint to this issue)] for collisions of U91+ ions with a hydrogen gas target.
Borka, D.; Mowbray, D. J.; Mišković, Z. L.; Petrović, S.; Nešković, N.
2008-01-01
The best level of ordering and straightening of carbon nanotube arrays is often achieved when they are grown in a dielectric matrix, so such structures present the most suitable candidates for future channeling experiments with carbon nanotubes. Consequently, we investigate here how the dynamic polarization of carbon valence electrons in the presence of various surrounding dielectric media affects the angular distributions of protons channeled through (11,~9) single-wall carbon nanotubes. Pro...
The angular distribution of neutron-proton scattering at 27.3 MeV
The results of experimental investigations are presented to study a forward-backward asymmetry in the n-p scattering angular distribution for angles from 34 deg to 116 deg. To improve the precision of the measurements the neutron detector efficiency factor was analyzed in the 5-25 MeV energy range. Features of the time-of-flight spectrum are discussed. The data obtained confirm the asymmetry predicted by the phase shift evaluations
Compton scattering of twisted light: angular distribution and polarization of scattered photons
Stock, S; SURZHYKOV, A.; Fritzsche, S.; Seipt, D.
2015-01-01
Compton scattering of twisted photons is investigated within a non-relativistic framework using first-order perturbation theory. We formulate the problem in the density matrix theory, which enables one to gain new insights into scattering processes of twisted particles by exploiting the symmetries of the system. In particular, we analyze how the angular distribution and polarization of the scattered photons are affected by the parameters of the initial beam such as the opening angle and the p...
The Angular Distribution of Gamma-Rays from the Fission of U235
The angular distribution of gamma-rays from thermal-neutron-induced fission has been measured with respect to the axis of fission. The gamma radiation intensities were found to be higher in the direction of fission-fragment motion than in that normal to it. The anisotropy proved to be nearly the same for photon threshold energies of 120 keV and 600 keV. (author)
HAWSER is a computer program which calculates gamma-ray angular distributions. A revised version of HAWSER, called MANANU is now available. This program calculates population parameters correctly and uses the Rose and Brink sign convention for mixing ratios (due to a programming error, HAWSER uses the opposite convention). In addition, the new version requires less input data, and has a more convenient output format. (author)
chi_{c1} and chi_{c2} decay angular distributions at the Fermilab Tevatron
Kniehl, Bernd A; Palisoc, C P
2003-01-01
We consider the hadroproduction of chi_{c1} and chi_{c2} mesons and their subsequent radiative decays to J/psi mesons and photons in the factorization formalism of nonrelativistic quantum chromodynamics, and study the decay angular distributions, by means of helicity density matrices, in view of their sensitivity to color-octet processes. We present numerical results appropriate for the Fermilab Tevatron.
Angular distribution of cosmic muons using INO–ICAL prototype detector at TIFR
S Pal; G Majumder; M K Mondal; D Samuel; B Satyanarayana
2012-11-01
The India-based Neutrino Observatory Collaboration is planning to set up a magnetized 50 kt iron calorimeter (ICAL) with resistive plate chambers (RPC) as active detectors to study neutrino oscillations and precisely measure its parameters. A prototype detector stack is set up at TIFR (18°54'N, 72°48'E) to track cosmic ray muons. Using the muon data, angular distribution of cosmic ray muons at the sea level is studied here.
Application of in-beam perturbed angular distribution to the study of high-Tc oxides
The time differential perturbed angular distribution method was applied to the study of high-Tc oxides. Spin rotation signals of the 19F isomer (τ = 128 nsec) produced from oxygen nuclei via 16O(α,p)19F were observed in various high-Tc oxides above Tc. The internal field was determined with the accuracy of about 1%. This method is an alternative to the 17O substituted NMR. (author)
Retrieving orbital angular momentum distribution of light with plasmonic vortex lens
Zhou, Hailong; Dong, Jianji; Zhang, Jihua; Zhang, Xinliang
2016-06-01
We utilize a plasmonic vortex lens (PVL) to retrieve the orbital angular momentum (OAM) distribution of light. The OAM modes are coupled to the surface plasmon polaritons (SPPs) in the form of various Bessel functions respectively. By decomposing the interference pattern of SPPs into these Bessel functions, we can retrieve the relative amplitude and the relative phase of input OAM modes simultaneously. Our scheme shows advantage in integration and can measure hybrid OAM states by one measurement.
Angular distribution of GaAs sputtered under oblique Cs{sup +} bombardment
Verdeil, C. [Department ' Science and Analysis of Materials' (SAM), Centre de Recherche Public - Gabriel Lippmann, 41 rue du Brill, L-4422 Belvaux (Luxembourg); Wirtz, T. [Department ' Science and Analysis of Materials' (SAM), Centre de Recherche Public - Gabriel Lippmann, 41 rue du Brill, L-4422 Belvaux (Luxembourg)], E-mail: wirtz@lippmann.lu; Scherrer, H. [Laboratoire de Physique des Materiaux, Ecole des Mines, Parc de Saurupt, F-54042 Nancy Cedex (France)
2009-08-15
The angular distribution of Ga and As sputtered from Gallium Arsenide (1 0 0) by a Cs{sup +} ion beam was experimentally measured through a collector technique allowing modifications of the energy and incidence angle of the ion beam. The impact energy was varied in the range of 2-10 keV and the angle of incidence from 30 deg. to 60 deg. The angular distributions of emitted matter are determined by means of SIMS depth profiles. Our series of experiments show an evolution of the preferential direction of emission as well as the spreading around this direction in function of the characteristics of the ion beam. The second objective is the study of the evolution of the stoichiometry of the deposit in function of the emission angle. A decrease of the As/Ga ratio around the preferential direction of emission and an increase of this ratio for oblique emission are observed for different conditions of primary bombardment. Considering that the angular distribution depends on the depth of origin, our results suggest that the Cs{sup +} bombardment changes the stoichiometry of the near-surface layers of the sample with an enrichment of As in the outmost layers while the sub-surface region is impoverished in As due to preferential sputtering.
Angular distribution of GaAs sputtered under oblique Cs+ bombardment
The angular distribution of Ga and As sputtered from Gallium Arsenide (1 0 0) by a Cs+ ion beam was experimentally measured through a collector technique allowing modifications of the energy and incidence angle of the ion beam. The impact energy was varied in the range of 2-10 keV and the angle of incidence from 30 deg. to 60 deg. The angular distributions of emitted matter are determined by means of SIMS depth profiles. Our series of experiments show an evolution of the preferential direction of emission as well as the spreading around this direction in function of the characteristics of the ion beam. The second objective is the study of the evolution of the stoichiometry of the deposit in function of the emission angle. A decrease of the As/Ga ratio around the preferential direction of emission and an increase of this ratio for oblique emission are observed for different conditions of primary bombardment. Considering that the angular distribution depends on the depth of origin, our results suggest that the Cs+ bombardment changes the stoichiometry of the near-surface layers of the sample with an enrichment of As in the outmost layers while the sub-surface region is impoverished in As due to preferential sputtering.
Inner Engine Shutdown from Transitions in the Angular Momentum Distribution in Collapsars
Batta, Aldo
2016-01-01
For the collapsar scenario to be effective in the production of Gamma Ray Bursts, the infalling star's angular momentum $J(r)$ must be larger than the critical angular momentum needed to form an accretion disk around a blackhole (BH), namely $J_{\\rm crit} = 2r_{g}c$ for a Schwarzschild BH. By means of 3D SPH simulations, here we study the collapse and accretion onto black holes of spherical rotating envelopes, whose angular momentum distribution has transitions between supercritical ($J>J_{\\rm crit}$) and subcritical ($J
Inner engine shutdown from transitions in the angular momentum distribution in collapsars
Batta, Aldo; Lee, William H.
2016-06-01
For the collapsar scenario to be effective in the production of gamma ray bursts (GRBs), the infalling star's angular momentum J(r) must be larger than the critical angular momentum needed to form an accretion disc around a black hole (BH), namely Jcrit = 2rgc for a Schwarzschild BH. By means of 3D smoothed particle hydrodynamics simulations, here we study the collapse and accretion on to BHs of spherical rotating envelopes, whose angular momentum distribution has transitions between supercritical (J > Jcrit) and subcritical (J 2D hydrodynamical simulations, we find that a substantial amount of subcritical material fed to the accretion disc, lingers around long enough to contribute significantly to the energy loss rate. Increasing the amount of angular momentum in the subcritical material increases the time spent at the accretion disc, and only when the bulk of this subcritical material is accreted before it is replenished by a massive outermost supercritical shell, the inner engine experiences a shutdown. Once the muffled accretion disc is provided again with enough supercritical material, the shutdown will be over and a quiescent time in the long GRB produced afterwards could be observed.
Ceyer, S.T.; Siekhaus, W.J.; Somorjai, G.A.
1981-09-01
A molecular beam surface scattering apparatus designed for the study of corrosion and catalytic surface reactions is described. The apparatus incorporates two molecular or atomic beams aimed at a surface characterized by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES), a rotatable, differentially pumped quadrupole mass spectrometer, and a versatile manipulator. Angular distributions and energy distributions as a function of angle and independent of the surface residence time can be measured. Typical data for the oxidation of deuterium to D/sub 2/O on a Pt(111) crystal surface are presented.
Ceyer, S. T.; Siekhaus, W. J.; Somorjai, G. A.
1980-11-01
A molecular beam surface scattering apparatus designed for the study of corrosion and catalyticsurfacereactions is described. The apparatus incorporates two molecular or atomic beams aimed at a surface characterized by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES), a rotatable, differentially pumped quadrupole mass spectrometer, and a versatile manipulator. Angular distributions and energy distributions as a funcion of angle and independent of the surface residence time can be measured. Typical data for the oxidation of deuterium to D{sub 2}O on a Pt(lll) crystal surface are presented.
Aleshin, A M; Egorov, V V; Zakrevskij, Y A
2002-01-01
The procedures, designed for measuring angular distributions a gamma radiation from aggregations of radioactive materials located in object 'Shelter' are described. The first procedure is based on application of the original multidetector device DB1, permitting to get the data on an angular distribution in a complete solid angle (4 pi). The second procedure is based on application of the modernized dosimeter DKS-04 with the collimated detector. The main observed data on the angular distributions of intensity of gamma radiation in the zones of the works on 'Shelter' stabilization (the measurements have been carried out in frameworks of the exploratory design) are presented. 9 refs., 49 figs.
It is known that secondary cosmic rays are high energetic particles which are products of shower particles, when primary cosmic rays from outer space hit the atmosphere molecules. Many studies of cosmic rays show that cosmic flux depends on the depth of atmosphere. At ground level, most secondary cosmic rays are muons, a type of charged particle, and have angular dependence. The purpose of this article was to develop the telescope with two plastic scintillation detectors to investigate the angular distribution of cosmic rays at ground level. Directions of investigation were carried out vertical, 45-degree oblique and horizontal directions with respect to earth surface, approximately from North to South. Electronic readout system was developed from Flash Analog Digital Converter (Flash-ADC) of 8 bits-250Ms/sec, and Embedded Field Programmable Gate Array (FPGA)-based trigger. LabVIEW trademark interface was written for controlling trigger system and taking data. For each direction measurement, the deposited energy spectra in the scintillators were obtained. The interest of cosmic-ray events was analyzed for counting. Angular distribution was obtained quantitatively. The experiment has been done at University of Science-HCMC. (orig.)
Angular momentum distribution during the collapse of primordial star-forming clouds
Dutta, Jayanta
2015-01-01
It is generally believed that angular momentum is distributed during the gravitational collapse of the primordial star forming cloud. However, so far there has been little understanding of the exact details of the distribution. We use the modified version of the Gadget-2 code, a three-dimensional smoothed-particle hydrodynamics simulation, to follow the evolution of the collapsing gas in both idealized as well as more realistic minihalos. We find that, despite the lack of any initial turbulence and magnetic fields in the clouds the angular momentum profile follows the same characteristic power-law that has been reported in studies that employed fully self-consistent cosmological initial conditions. The fit of the power-law appears to be roughly constant regardless of the initial rotation of the cloud. We conclude that the specific angular momentum of the self-gravitating rotating gas in the primordial minihalos maintains a scaling relation with the gas mass as $L \\propto M^{1.125}$. We also discuss the plausi...
We performed calculations of Vavilov–Cherenkov radiation (VChR) angular distributions from relativistic heavy ions (RHI) taking account of their slowing-down in a radiator. The results of calculations show that the slowing-down of RHI in radiator leads to specific broadening of VChR ring thus forming specific VChR angular distribution which is different compared to well-known Tamm–Frank distribution. The key parameters which change drastically the VChR angular distribution from RHI are: energy, charge and mass of an ion; emission wave length and corresponding refractive index; stopping power and radiator thickness. The theory developed has been applied to the analysis of the earlier experiments (1996–2001) devoted to studies of the VChR angular distribution from Au RHI beam with energies ∼0.9 GeV/u at SIS-18 heavy ion accelerator (GSI, Darmstadt, Germany)
Photoelectron angular distributions from photodetachment of negative ions in strong laser fields
Using a nonperturbative scattering theory, the photoelectron angular distributions (PADs) of negative ions irradiated by intense laser fields are studied. Various PADs are obtained. Similar to that of atoms, PADs of negative ions show main lobes and jet-like structures. Here, the main lobe means the formation of the detached photoelectrons around the direction of laser polarization, while the jet-like structure means a peaked-out formation of photoelectrons emitted from the waist between the two main lobes. For a set of above-threshold-detachment peaks, with one-more-photon absorption, the number of the jet-like structures is not always increased by one, which verifies that the jet-like structures are irrelevant to photoelectron angular momentum.
Photoelectron angular distributions from photodetachment of negative ions in strong laser fields
Bai Lihua; Liu Yuheng; Cui Tingting; Wang Yan; Zhang Huifang; Deng Dongmei [Department of Physics, Shanghai University, Shanghai 200444 (China); Ren Xianghe, E-mail: lhbai@163.com [Institute of Advance Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan)
2011-02-01
Using a nonperturbative scattering theory, the photoelectron angular distributions (PADs) of negative ions irradiated by intense laser fields are studied. Various PADs are obtained. Similar to that of atoms, PADs of negative ions show main lobes and jet-like structures. Here, the main lobe means the formation of the detached photoelectrons around the direction of laser polarization, while the jet-like structure means a peaked-out formation of photoelectrons emitted from the waist between the two main lobes. For a set of above-threshold-detachment peaks, with one-more-photon absorption, the number of the jet-like structures is not always increased by one, which verifies that the jet-like structures are irrelevant to photoelectron angular momentum.
Dasgupta, Basudeb; Sen, Manibrata
2016-01-01
It has been recently pointed out that neutrino fluxes from a supernova can show substantial flavor conversions almost immediately above the core. Using linear stability analyses and numerical solutions of the fully nonlinear equations of motion, we perform a detailed study of these fast conversions, focussing on the region just above the supernova core. We carefully specify the instabilities for evolution in space or time, and find that neutrinos travelling towards the core make fast conversions more generic, i.e., possible for a wider range of flux ratios and angular asymmetries. Using fluxes and angular distributions predicted by supernova simulations, we find that fast conversions can occur within tens of nanoseconds, only a few meters away from the putative neutrinospheres. If these fast flavor conversions indeed take place, they would have important implications for the supernova explosion mechanism and nucleosynthesis.
Inquiry into antineutrino angular distribution in the experiments on polarized neutron β-decay
So far as γ-radiation unescapably accompanies β-decay and thereby the final state of neutron β-decay involves photon beside proton, electron and antineutrino, i.e., not three but four particles, the antineutrino kinematics cannot be reconstructed unambiguously when the proton and electron momenta are given only, the γ-radiation momenta being unknown. Consequently, in the experiments on the polarized neutron β-decay where the electron and proton momentum distributions are observed only, without registering the γ-radiation, the asymmetry factor B of the antineutrino angular distribution cannot be acquired rigorously, but the B value is to be estimated only on the average by drawing into consideration the expectation (mean) value and the dispersion ΔB. The correspondent unavoidable ambiguities in B attainment amount to several percent which is significant for the now-a-days experimental attempts to obtain the B value with the very high precision ∼ (0.1 - 1) %. With allowance for the electromagnetic interaction, experimental measurement of the electron and proton momentum distributions is seen also to be instructive to verify with high accuracy the gA value obtained previously from the electron angular distribution
Angular distribution of fission fragments from 236U(d,pf)
Complete text of publication follows. 236U is the only isotope in the actinide region in which transmission fission resonances observed and at the same time a superdeformed fission isomer is well-established. We have been investigating these transmission resonances for several years. The aim of our latest experiment was to measure the angular distribution of the fission fragments in order to determine the spin and K-values of the resonances and to improve the statistics compared to the previous experiment. An experiment was performed to study the fission resonances of 236U at the Munich Tandem Laboratory using 235U(d,p) reaction at 13 MeV. A 235U2O3 target was used with a thickness of 90 μg/cm2. The outgoing proton energy was determined by a Q3D magnetic spectrometer at an angle 139.4 deg. An energy resolution of ΔE = 5keV was achieved. Fission fragments were detected by two position sensitive avalanche detectors (PSAD) consisting of two wire planes corresponding to horizontal and vertical directions. Thus, the spatial positions of the fragments and their angular correlation with respect to the recoil axis could be determined. High resolution measurement of the angular distribution allowed us to determine the spin and K-values of the observed resonances individually. The angular correlation was parametrized with coefficients a2 and a4 of even Legendre polynomials. Fig. 1b) shows the a2 coefficient belonging to the different resonances. The a2 values are agree with the values of Ref. [4], which were used to determine the K-values in the data analysis of the previous experiment. The most interesting energy region is around 5.1 MeV, where hyperdeformed resonances were identified recently in contrast to the superdeformed interpretation published so far. The high-resolution excitation energy spectrum, which was deduced from the proton kinetic energy is shown in Fig. 1a). A combined analysis of the energy spectrum and the angular distribution confirms that the
Full-spectrum k-distribution look-up table for nonhomogeneous gas-soot mixtures
Wang, Chaojun; Modest, Michael F.; He, Boshu
2016-06-01
Full-spectrum k-distribution (FSK) look-up tables provide great accuracy combined with outstanding numerical efficiency for the evaluation of radiative transfer in nonhomogeneous gaseous media. However, previously published tables cannot be used for gas-soot mixtures that are found in most combustion scenarios since it is impossible to assemble k-distributions for a gas mixed with nongray absorbing particles from gas-only full-spectrum k-distributions. Consequently, a new FSK look-up table has been constructed by optimizing the previous table recently published by the authors and then adding one soot volume fraction to this optimized table. Two steps comprise the optimization scheme: (1) direct calculation of the nongray stretching factors (a-values) using the k-distributions (k-values) rather than tabulating them; (2) deletion of unnecessary mole fractions at many thermodynamic states. Results show that after optimization, the size of the new table is reduced from 5 GB (including the k-values and the a-values for gases only) to 3.2 GB (including the k-values for both gases and soot) while both accuracy and efficiency remain the same. Two scaled flames are used to validate the new table. It is shown that the new table gives results of excellent accuracy for those benchmark results together with cheap computational cost for both gas mixtures and gas-soot mixtures.
Higher Order Moments of the Angular Distribution of Galaxies from Early SDSS Data
Szapudi, I; Scoccimarro, R; Szalay, A S; Connolly, A J; Dodelson, S; Eisenstein, D J; Gunn, J E; Johnston, D; Kent, S; Loveday, J; Meiksin, A; Nichol, R C; Scranton, R; Stebbins, A; Vogeley, M S; Szapudi, Istv\\'an; Frieman, Joshua A.; Scoccimarro, Roman; Szalay, Alexander S.; Connolly, Andrew J.; Dodelson, Scott; Eisenstein, Daniel J.; Gunn, James E.; Johnston, David; Kent, Stephen; Loveday, Jon; Meiksin, Avery; Nichol, Robert C.; Scranton, Ryan; Stebbins, Albert; Vogeley, Michael S.
2002-01-01
We present initial results for counts in cells statistics of the angular distribution of galaxies in early data from the Sloan Digital Sky Survey (SDSS). We analyze a rectangular stripe $2.5^\\circ$ wide, covering approximately 160 sq. degrees, containing over $10^6$ galaxies in the apparent magnitude range $18 < r^\\prime < 22$, with areas of bad seeing, contamination from bright stars, ghosts, and high galactic extinction masked out. This survey region, which forms part of the SDSS Early Data Release, is the same as that for which two-point angular clustering statistics have recently been computed. The third and fourth moments of the cell counts, $s_3$ (skewness) and $s_4$ (kurtosis), constitute the most accurate measurements to date of these quantities (for $r^\\prime < 21$) over angular scales $0.015^\\circ-0.3^\\circ$. They display the approximate hierarchical scaling expected from non-linear structure formation models and are in reasonable agreement with the predictions of $\\Lambda$-dominated cold d...
A Monte Carlo method for calculation of the distribution of angular deflections of fast charged particles passing through thin layer of matter is described on the basis of Moliere theory of multiple scattering. The distribution of the angular deflections obtained as the result of calculations is compared with Moliere theory. The method proposed is useful to calculate the electron transport in matter by Monte Carlo method. (author)
Shen Tian-Ming; Chen Chong-Yang; Wang Yan-Sen
2007-01-01
In this paper a systematic study is carried out on the angular distribution and polarization of photons emitted following radiative recombination of H-like ions by a non-relativistic dipole approximation. In order to incorporate the screening effect due to inner-shell electrons, a distorted wave approach is used. The dependences of the calculated angular distribution and polarization on the reduced energy and nuclear charge are fitted by the corresponding empirical formulas respectively.
This study of the energy stability along the macropulse of the Tesla test facility Linac (TTFL) (1) was obtained by the measurement of the angular distribution of the optical transition radiation (OTR). This technique does not require a dispersive section and can be performed at any point of the beam line. Measurements have been performed with different settings of the RF low level control and at different values of the beam current. An energy variation along the macropulse was spread of the whole macrobunch. The analysis of the OTR angular distribution pattern allows also, to some extent, to evaluate the beam angular spread
Plésiat, Etienne; Decleva, Piero; Martín, Fernando
2013-01-01
We present a theoretical study of vibrationally resolved and unresolved molecular-frame photoelectron angular distributions (MFPADs) resulting from K-shell photoionization of N2, CO, C2H2, NH3, CH4, CF4, BF3, and SF6 in the range of photoelectron energies 0–500 eV. We show that the MFPADs of NH3 and CH4, averaged over the polarization direction, image the molecular geometry at very low energies but also at selected higher energies. For all other molecules, the MFPADs do not image the system’s...
Measurement of angular distribution of neutrons emitted from plasma focus using NTD
Antanasijevic, R; Banjanac, R; Dragic, A; Stanojevic, J; Dordevic, D; Joksimovic, D; Udovicic, V; Vukovic, J
1999-01-01
Mica detectors together with thick uranium foils were used for detection and angular distribution measurement of the neutrons emitted from the d-plasma focus (DPF). The distance between detectors and plasma pinch was 4 cm. For reason of detector protection from the thermal shock, they were covered with the mica layer of 1 mm thickness. Annealing of the detectors were measured after the irradiation with neutrons from an Am-Be source and treated with thermal shock H-plasma focus (HPF). Geometry of detectors in both experiments was the same.
Mechanisms on the photoelectron angular distributions of atoms ionized in mid-infrared laser fields
By solving the time-dependent Schrodinger equation, we show conclusively that low energy/momenta structure in the photoelectron angular distribution originates from multiple scatterings of the tunnel-ionized electron with the ion. We also show that two conditions must be satisfied simultaneously in order to observe prominent low-energy features. First, multiple scattering of the tunnel-ionized electron wave packet is necessary. Second, tunnel ionization must dominate over multiphoton ionization. While the first condition is generally satisfied for all laser wavelengths, the second condition is satisfied only for longer laser wavelengths.
Six-State Quantum Key Distribution Using Photons with Orbital Angular Momentum
LI Jun-Lin; WANG Chuan
2010-01-01
@@ A new implementation of high-dimensional quantum key distribution (QKD) protocol is discussed. Using three mutual unbiased bases, we present a d-level six-state QKD protocol that exploits the orbital angular momentum with the spatial mode of the light beam. The protocol shows that the feature of a high capacity since keys are encoded using photon modes in d-level Hilbert space. The devices for state preparation and measurement are also discussed. This protocol has high security and the alignment of shared reference frames is not needed between sender and receiver.
Angular distribution of positrons in coherent pair production in deformed crystals
Parazian, V V
2008-01-01
We investigate the angular distribution of positrons in the coherent process electron-positron pair creation process by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross-section is derived for an arbitrary deformation field. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for ${\\mathrm{SiO}}_{2}$ single crystal and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by the acoustic wave of S -type.
Angular distribution of positrons in coherent pair production in deformed crystals
Parazian, V. V.
2009-05-01
We investigate the angular distribution of positrons in the coherent process electron-positron pair creation process by high-energy photons in a periodically deformed single crystal with a complex base. The formula for the corresponding differential cross section is derived for an arbitrary deformation field. The case is considered in detail when the photon enters into the crystal at small angles with respect to a crystallographic axis. The results of the numerical calculations are presented for SiO2 and diamond single crystals and Moliere parameterization of the screened atomic potentials in the case of the deformation field generated by an acoustic wave of S-type.
Vibrationally resolved molecular frame photoelectron angular distributions (MFPADs) of fixed-in-space molecules have been evaluated for diatomic and polyatomic molecules. Calculations have been performed by using an extension of the static-exchange density functional theory formerly developed by P. Decleva [1] and coworkers and extended in order to include the nuclear motion in the Born-Oppenheimer approximation. The method proved to be very accurate for diatomic molecules [2, 3, 5], particularly at high energy of the photoelectron. In this work, we present the results obtained for the inner shell photoionization of C2H2, NH3, CH4, CF4, BF3 and SF6.
The calculation of photoionization angular distribution parameter β of atomic Na
刘锦超; 蒲丰年; 刘汉奎; 郭建军; 程延松; 杨向东
1999-01-01
The differential cross sections and angular distribution parameter of the photoionization processes 2p~63s→2p~53skl of atomic Na have been calculated by using many-body perturbation theory. In the calculation, the resonant structure of the excitation process 2s→3p has been included. The electron correlation interaction was analyzed by using the effective diagram method. The summation of specific classes of these diagrams is to an infinite order. The results of calculations are compared with experimental data, which are in good agreement with the experiment.
Angular distributions in J/ψ(ρ0,ω) states near threshold
A resonance X(3872), first observed in the decays B→KX, has been seen to decay to J/ψπ+π-. The π+π- mass spectrum peaks near its kinematic upper limit, prompting speculation that the dipion system may be in a ρ0. The decay X(3872)→J/ψω also has been observed. The reaction γγ→J/ψπ+π- has been studied. Consequently, angular distributions in decays of J/ψ(ρ0,ω) states near threshold are of interest, and results are presented
Photoelectron angular distributions in negative-ion photodetachment from mixed sp states.
Grumbling, Emily R; Sanov, Andrei
2011-10-28
We describe an approach for constructing analytical models for the energy-dependence of photoelectron angular distributions in the one-electron, non-relativistic approximation. We construct such a model for electron emission from an orbital described as a superposition of s- and p-type functions, using linearly polarized light. In the limits of pure s or pure p electron photodetachment or photoionization, the model correctly reproduces the familiar Cooper-Zare formula. The model predictions are compared to experimental results for strongly solvated H(-) and NH(2)(-), corresponding to predominantly s and predominantly p character parent states, respectively. PMID:22047234
Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.
2014-01-01
We investigate effects of intermediate resonant electronic states on molecular photoelectron angular distributions (MPADs) by intense circularly polarized attosecond UV laser pulses. Simulations are performed on aligned H2+ by numerically solving the corresponding three dimensional time dependent Schrödinger equations. MPADs exhibit signature of rotations, which is shown to be critically sensitive to the symmetry of the intermediate resonant electronic state and the pulse intensity. This sensitivity is attributed to the coherent population transfer in the initial and intermediate resonant states, thus suggesting a method to control molecular photoionization on attosecond time scale.
A Large-alphabet Quantum Key Distribution Protocol Using Orbital Angular Momentum Entanglement
Zhao, Sheng-Mei; Gong, Long-Yan; Li, Yong-Qiang; Yang, Hua; Sheng, Yu-Bo; Cheng, Wei-Wen
2013-06-01
We experimentally demonstrate a quantum key distribution protocol using entangled photon pairs in orbital angular momentum (OAM). Here Alice uses a fixed phase hologram to modulate her OAM state on one photon with a spatial light modulator (SLM), while Bob uses the designed N different phase holograms for his N-based keys on the other photon with his SLM. With coincidences, Alice can fully retrieve the keys sent by Bob without reconciliation. We report the experiment results with N = 3 and OAM eigenmodes |l = ±1>, and discuss the security from the light path and typical attacks.
WASP package is a C++ program aimed to analyze angular distributions of secondary particles generated in nuclear interactions. (WASP is designed for data analysis of the STAR and ALICE experiments). It uses a wavelet analysis for this purpose and the vanishing momentum or gaussian wavelets are chosen for transformations. WASP provides an user-friendly Graphical User Interface (GUI) which makes it quite simple to use. WASP design, a brief description of the used wavelet transformation algorithm and GUI are presented in this user's guide
The theory for determination of molecular alignment from circular dichroism in photoelectron angular distributions is generalized to treat the case in which the excitation polarization direction and the laboratory z axis do not coincide. A new method of data analysis is presented here. Alignment created by surface scattering or photofragmentation should be obtainable by these procedures. For studies of orientation with elliptically polarized excitation, differential cross sections at a given collection angle are found to be, to a good approximation, independent of excited-state alignment. Orientation can thus be obtained from differential cross sections by the methods developed by Kummel, Sitz, and Zare [J. Chem. Phys. 88, 6707 (1988)
Measurement of neutron yield and angular distribution for thick natLi(p,n+x) reaction
The low energy accelerators have been used to produce intense neutron flux for various applications employing lower threshold reactions involving light targets. Among those p+7Li, 9Be, 13C, D+D,T are the popular ones. In the present work the total neutron yield has been measured for thick Lithium target up to 5.5 proton energy using BF3 counter. Angular distribution of the neutrons at 4.5 and 5.5 MeV also measured to investigate the feasibility of a neutron time of flight facility at FOTIA
We present quantifiable images of the angular distributions (AD's) of parametric x radiation (PXR), and vacuum-ultraviolet transition radiation (vuv TR) from 230 MeV electrons interacting with a silicon crystal. Both AD's are highly polarized. The vuv TR and optical TR data provide measurements of the beam energy and effective divergence angle. Using these quantities and separately known values of the electronic susceptibility |χ0|, we show that the measured PXR AD is in good agreement with the predictions of single crystal theory. Our analysis suggests a method to measure |χ0| using PXR AD's
Angular Distribution of Element Contents in Tree Rings and the Environmental Information
KESHANZHE; QIANJUNLONG; 等
1999-01-01
Element contents of tree rings and soils near tree roots collected from Deodar cedar (Cedrus deodara (Roxb.) G.Don) and Masson pine(Pinus massoniana lamb).were determined to study the relationship between the angular distribution of element contents in tree rings and the environmental information.The chemical composition and properties of soil are very much cmoplicated,which leads to the non-uniform distribution of the element contents in tree rings.The statistical multi-varialbe regression method was used to get the information of the tree-centered distribution of element contents in the environment(soil),(C'),C'(Z,θj),from the distribtuion of element contents in tree rings(C),C(Z,θi),which depends on the plane azimuth angle(θi),i.e.,C=C(Z,θi),where Z is the atomic number of the element,with a satisfactory result though this study is only a primary one.
The angular distributions for dileptons arising from decays of a virtual photon and the Z0 produced in hadronic collisions are calculated at large mass and finite transverse momentum of dileptons in the lowest order of the quantum chromodynamics and the Weinberg-Salam model with three fermion generations. Numerical evaluation for coefficients of the distributions is carried out for anti pp collision at √s=540 GeV and pp at √s=800 GeV in different (helicity, Gottfried-Jackson and Collins-Soper) reference frames. Coefficients of parity violating terms in the distributions exhibit clean signs of the Z0-boson, while those of parity conserving terms are quite insensitive to the presence of the Z0-boson. (author)
Analyzing angular distributions for two-step dissociation mechanisms in velocity map imaging.
Straus, Daniel B; Butler, Lynne M; Alligood, Bridget W; Butler, Laurie J
2013-08-15
Increasingly, velocity map imaging is becoming the method of choice to study photoinduced molecular dissociation processes. This paper introduces an algorithm to analyze the measured net speed, P(vnet), and angular, β(vnet), distributions of the products from a two-step dissociation mechanism, where the first step but not the second is induced by absorption of linearly polarized laser light. Typically, this might be the photodissociation of a C-X bond (X = halogen or other atom) to produce an atom and a momentum-matched radical that has enough internal energy to subsequently dissociate (without the absorption of an additional photon). It is this second step, the dissociation of the unstable radicals, that one wishes to study, but the measured net velocity of the final products is the vector sum of the velocity imparted to the radical in the primary photodissociation (which is determined by taking data on the momentum-matched atomic cophotofragment) and the additional velocity vector imparted in the subsequent dissociation of the unstable radical. The algorithm allows one to determine, from the forward-convolution fitting of the net velocity distribution, the distribution of velocity vectors imparted in the second step of the mechanism. One can thus deduce the secondary velocity distribution, characterized by a speed distribution P(v1,2°) and an angular distribution I(θ2°), where θ2° is the angle between the dissociating radical's velocity vector and the additional velocity vector imparted to the product detected from the subsequent dissociation of the radical. PMID:23464815
Using the previously proposed method of calculating diffracted photon yields in thin perfect crystals, analyzed a relative contribution of parametric X-ray radiation and diffracted photons in thin crystals. It is shown that for average energy of electrons and the center of the PXR spot diffracted real photon contribution is comparable to the yield of parametric X-ray radiation and determines the shape of the angular distribution of the total emission in this range of observation angles. The possibility of estimating electron beams parameters based on the results of PXR angular distribution measurements is discussed. It is shown that for energy of electrons by far larger than 1 GeV yield of diffracted transition radiation in narrow angular cone becomes predominating and determines the shape of the angular distribution of total emission in the center of radiation spot
We calculate the combined angular distribution of the final electron, of the γ photon, and of the π0 meson produced in the cascade process bar pp→1D2→1P1+γ→(ψπ0) +γ→(e+e-)+π0+γ, where bar p and p are unpolarized. Our final result is valid in the bar pp c.m. frame and it is expressed in terms of the Wigner DJ functions and the spherical harmonics whose arguments are the angles representing the various directions involved. The coefficients of the terms involving the spherical harmonics and the Wigner DJ functions are functions of the angular momentum helicity amplitudes or equivalently of the multipole amplitudes of the individual processes. Once the combined angular distribution is measured, our expressions will enable one to calculate the relative magnitudes as well as the cosines of the relative phases of all the angular momentum helicity amplitudes or equivalently of all the multipole amplitudes in the decay processes 1D2→1P1+γ and 1P1→ψ+π0. We also derive six different partially integrated angular distribution functions which give the angular distributions of one or two particles in the final state. They can all be expressed entirely in terms of the spherical harmonics. By measuring these simpler angular distributions in the six different cases we get as much information on the helicity amplitudes as we obtained by measuring the combined angular distribution of the three particles, namely, the electron, the γ photon, and the π0 meson
Dang, N Dinh; Kmiecik, M; Maj, A
2013-01-01
The line shapes of giant dipole resonance (GDR) in the decay of the compound nucleus $^{88}$Mo, which is formed after the fusion-evaporation reaction $^{48}$Ti + $^{40}$Ca at various excitation energies $E^{*}$ from 58 to 308 MeV, are generated by averaging the GDR strength functions predicted within the phonon damping model (PDM) using the empirical probabilities for temperature and angular momentum. The average strength functions are compared with the PDM strength functions calculated at the mean temperature and mean angular momentum, which are obtained by averaging the values of temperature and angular momentum using the same temperature and angular-momentum probability distributions, respectively. It is seen that these two ways of generating the GDR linear line shape yield very similar results. It is also shown that the GDR width approaches a saturation at angular momentum $J\\geq$ 50$\\hbar$ at $T=$ 4 MeV and at $J\\geq$ 70$\\hbar$ at any $T$.
Angular Distribution of Electrons in Photoionization of Atoms Adsorbed on a Graphene Sheet
Baltenkov, A S
2013-01-01
Within the framework of a model representing the potential of a graphene sheet U(z) as an electro-neutral layer formed by smeared carbon atoms, the effect of this potential on spectral characteristics of atoms adsorbed on a graphene sheet has been studied. Since the distance between the adsorbed atom nucleus and sheet surface significantly exceeds the radii of inner atomic shells the potential U(z) makes influence on the continuum wave functions only. Their behavior in the upper semi-space (z>0) and in the lower one (z<0) where the adsorbed atom is located is defined by a jump of the logarithmic derivative of the wave function for z=0. The photoelectron angular distributions have been calculated for different mutual positions of the polarization vector e and the axis Z normal to the sheet surface. It has been shown that the existence of the electron waves reflected from the potential U(z) leads to evident asymmetry of the angular distribution relative to the plane z=0. The experimental observation of this ...
Anomalous angular distributions in pion and α particle scattering to the 22+ state of 52Cr
Inelastic scattering of 180 MeV π+ and π- from 52Cr shows an angular distribution for the 22+ state at 2.96 MeV that differs greatly from the usual L = 2 shapes for 2+ states. This state is perhaps the only case from pion-inelastic scattering in which standard distorted-wave impulse approximation models (including multistep and single-step responses) fail to reproduce the measured angular distribution. Furthermore, this unique excitation has been shown to have the features expected of a seniority-four proton excitation yet the pion data show charge symmetry. While coupled-channel calculations are not able to reproduce the pion data, they do agree with the shape observed for 42 MeV α particle scattering to this state, but the magnitude of the α scattering data is not consistent with a collective model and known γ ray deexcitations. Scattering to the first and third 2+ states of 52Cr with pions and α particles is also considered, and found to match the usual result for 2+ states in general, accentuating the anomaly of this 22+ transition. copyright 1996 The American Physical Society
W production at LHC: lepton angular distributions and reference frames for probing hard QCD
Richter-Was, E
2016-01-01
Precision tests of the Standard Model in the Strong and Electroweak sectors play an important role, among the physics goals of LHC experiments. Because of the nature of proton-proton processes, observables based on the measurement of the direction and energy of leptons provide the most precise signatures. In the present paper, we concentrate on the angular distribution of leptons from W to l nu decays in the lepton-pair rest-frame. The vector nature of the intermediate state imposes that distributions are to a good precision described by spherical polynomials of at most second order. We argue, that contrary to general belief often expressed in the literature, the full set of angular coefficients can be measured experimentally, despite the presence in the final state of neutrino escaping detection. There is thus no principle difference with respect to the phenomenology of the Z/gamma to l^+ l^- Drell-Yan process. We show also, that with the proper choice of the coordinate frames, only one coefficient in this p...
Photoelectron angular distributions from two-photon ionization of atoms near ionization threshold
Lihua Bai; Tingting Cui; Yuheng Liu; Yan Wang; Dongmei Deng; Jihui Tao
2011-01-01
@@ Photoelectron angular distributions (PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory. We also study the influence of laser wavelength on PADs. For two-photon ionization very close to the ionization threshold, most of the ionized electrons are vertically ejected to the laser polarization. PADs from twophoton ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role. In terms of dependence of PADs on laser wavelength,corresponding variations for the ponderomotive parameter are demonstrated.%Photoelectron angular distributions (PADs) from two-photon ionization of atoms in linearly polarized strong laser fields are obtained in accordance with the nonperturbative quantum scattering theory. We also study the influence of laser wavelength on PADs. For two-photon ionization very close to the ionization threshold, most of the ionized electrons are vertically ejected to the laser polarization. PADs from twophoton ionization of atoms are determined by the second order generalized phased Bessel function at which the ponderomotive parameter plays a key role. In terms of dependence of PADs on laser wavelength,corresponding variations for the ponderomotive parameter are demonstrated.
Simplified neutron detector for angular distribution measurement of p-Li neutron source
Boron Neutron Capture Therapy (BNCT) is one of the most promising cancer therapies using 10B(n, α)7Li nuclear reaction. Because nuclear reactor is currently used for BNCT, the therapy is much restricted. Many kinds of accelerator based neutron sources for BNCT are being investigated worldwide and p-Li reaction is one of the most promising candidates because the emitted neutron energy is comparatively low and no gamma-ray is produced. To use p-Li neutron source for BNCT, measurement of the angular distribution is important. However, the energy of neutrons changes depending on the angle with respect to the proton beam, e.g., the energy of forward emitted neutrons are about 700 keV and it is 100 keV for backward direction. So a neutron detector, the efficiency of which is not dependent on energy, is needed. Though so-called “Long Counter” is known to be available, its structure is complicated and moreover it is expensive. Thus we have designed and developed a simplified neutron detector using Monte Carlo simulation. We verified the developed detector experimentally and measured the angular distribution in detail for p-Li reaction by using it. The obtained results were compared with analytical calculations. (author)