The Mathematical Foundations of 3D Compton Scatter Emission Imaging
T. T. Truong
2007-01-01
Full Text Available The mathematical principles of tomographic imaging using detected (unscattered X- or gamma-rays are based on the two-dimensional Radon transform and many of its variants. In this paper, we show that two new generalizations, called conical Radon transforms, are related to three-dimensional imaging processes based on detected Compton scattered radiation. The first class of conical Radon transform has been introduced recently to support imaging principles of collimated detector systems. The second class is new and is closely related to the Compton camera imaging principles and invertible under special conditions. As they are poised to play a major role in future designs of biomedical imaging systems, we present an account of their most important properties which may be relevant for active researchers in the field.
Applications of Compton scattering
LUO Guang; ZHOU Shang-qi; HAN Zhong; CHEN Shuang-kou
2006-01-01
Compton scattering is used very widely. In this article, we depict an overall picture for its applications which are based on two basic theories. The first is the electron densitometry theory related to electron density. According to this theory its applications are in two fields: one is Compton scatter densitometry (CSD), the other is Compton scatter imaging (CSI). The second technique involves the electron momentum distribution and Compton profile. Applications of this technique are mainly the Compton profile analysis (CPA) and the Compton profile or the electron momentum distribution in physics and chemistry.Future research fields are suggested according to the current situation and limits of this technique and a promising prospect is unfolded.
Watson, Greg
1996-01-01
Neutron Compton scattering measurements have the potential to provide direct information about atomic momentum distributions and adiabatic energy surfaces in condensed matter. First applied to measuring the condensate fraction in superfluid helium, the technique has recently been extended to study a variety of classical and quantum liquids and solids. This article reviews the theoretical background for the interpretation of neutron Compton scattering, with emphasis on studies of solids.
Helene Fonvieille
2003-05-01
Virtual Compton Scattering off the proton: {gamma}^+p --> {gamma}p is a new field of investigation of nucleon structure. Several dedicated experiments have been performed at low c.m. energy and various momentum transfers, yielding specific information on the proton. This talk reviews the concept of nucleon Generalized Polarizabilities and the present experimental status.
We have investigated the electron momentum density of Co-3d electrons in LaCoO3 using X-ray Compton scattering in order to demonstrate the symmetry change of the Co(3d) electron orbital states through the spin-state transition. The electron momentum density reconstructed from the Compton profiles indicates the symmetry change in the 3d electron-orbital states between below and above 100 K, which provides the first microscopic direct evidence for the orbital symmetry change of occupied electronic state associated with the spin-state transition in LaCoO3. The reproduced electron orbital states show a covalent bond with O-2p orbitals, which is responsible for the collectiveness in the characteristics of the spin-state transition. (author)
Fanelli, Cristiano V. [Sapienza Univ. of Rome (Italy)
2015-03-01
In this thesis work, results of the analysis of the polarization transfers measured in real Compton scattering (RCS) by the Collaboration E07-002 at the Je fferson Lab Hall-C are presented. The data were collected at large scattering angle (theta_cm = 70deg) and with a polarized incident photon beam at an average energy of 3.8 GeV. Such a kind of experiments allows one to understand more deeply the reaction mechanism, that involves a real photon, by extracting both Compton form factors and Generalized Parton Distributions (GPDs) (also relevant for possibly shedding light on the total angular momentum of the nucleon). The obtained results for the longitudinal and transverse polarization transfers K_LL and K_LT, are of crucial importance, since they confirm unambiguously the disagreement between experimental data and pQCD prediction, as it was found in E99-114 experiment, and favor the Handbag mechanism. The E99-114 and E07-002 results can contribute to attract new interest on the great yield of the Compton scattering by a nucleon target, as demonstrated by the recent approval of an experimental proposal submitted to the Jefferson Lab PAC 42 for a Wide-angle Compton Scattering experiment, at 8 and 10 GeV Photon Energies. The new experiments approved to run with the updated 12 GeV electron beam at JLab, are characterized by much higher luminosities, and a new GEM tracker is under development to tackle the challenging backgrounds. Within this context, we present a new multistep tracking algorithm, based on (i) a Neural Network (NN) designed for a fast and efficient association of the hits measured by the GEM detector which allows the track identification, and (ii) the application of both a Kalman filter and Rauch-Tung-Striebel smoother to further improve the track reconstruction. The full procedure, i.e. NN and filtering, appears very promising, with high performances in terms of both association effciency and reconstruction accuracy, and these preliminary results will
Compton scattering on hadronic systems
Compton scattering with real photons is studied for several hadronic systems, where special care is taken of the internal structure of the systems. The scattering on the deuteron is treated in terms of an analytically solvable model in the low energy region as in illustration for the general theory of low energy Compton scattering. For the 208Pb target nucleus a consistent treatment of the retardation leads to an interpretation of scattering data below and above the giant resonances up to energies of 50 MeV. Compton scattering in the Δ-resonance region is studied for the nucleon. The internal structure is described via a constituent quark model resulting in a proper treatment of the polarizabilities of the nucleon. The effect of binding on the polarizabilities is discussed on the basis of kinematical effects and modifictions due to the retardation. (orig.)
Compton Scattering on Light Nuclei
Shukla D.
2010-04-01
Full Text Available Compton scattering on light nuclei (A = 2, 3 has emerged as an eﬀective avenue to search for signatures of neutron polarizabilities, both spin–independent and spin–dependent ones. In this discussion I will focus on the theoretical aspect of Compton scattering on light nuclei; giving ﬁrst a brief overview and therafter concentrating on our Compton scattering calculations based on Chiral eﬀective theory at energies of the order of pion mass. These elastic γd and γHe-3 calculations include nucleons, pions as the basic degrees of freedom. I will also discuss γd results where the ∆-isobar has been included explicitly. Our results on unpolarized and polarization observables suggest that a combination of experiments and further theoretical eﬀorts will provide an extraction of the neutron polarizabilities.
3D Image Reconstruction from Compton camera data
Kuchment, Peter
2016-01-01
In this paper, we address analytically and numerically the inversion of the integral transform (\\emph{cone} or \\emph{Compton} transform) that maps a function on $\\mathbb{R}^3$ to its integrals over conical surfaces. It arises in a variety of imaging techniques, e.g. in astronomy, optical imaging, and homeland security imaging, especially when the so called Compton cameras are involved. Several inversion formulas are developed and implemented numerically in $3D$ (the much simpler $2D$ case was considered in a previous publication).
"Stereo Compton cameras" for the 3-D localization of radioisotopes
Takeuchi, K.; Kataoka, J.; Nishiyama, T.; Fujita, T.; Kishimoto, A.; Ohsuka, S.; Nakamura, S.; Adachi, S.; Hirayanagi, M.; Uchiyama, T.; Ishikawa, Y.; Kato, T.
2014-11-01
The Compton camera is a viable and convenient tool used to visualize the distribution of radioactive isotopes that emit gamma rays. After the nuclear disaster in Fukushima in 2011, there is a particularly urgent need to develop "gamma cameras", which can visualize the distribution of such radioisotopes. In response, we propose a portable Compton camera, which comprises 3-D position-sensitive GAGG scintillators coupled with thin monolithic MPPC arrays. The pulse-height ratio of two MPPC-arrays allocated at both ends of the scintillator block determines the depth of interaction (DOI), which dramatically improves the position resolution of the scintillation detectors. We report on the detailed optimization of the detector design, based on Geant4 simulation. The results indicate that detection efficiency reaches up to 0.54%, or more than 10 times that of other cameras being tested in Fukushima, along with a moderate angular resolution of 8.1° (FWHM). By applying the triangular surveying method, we also propose a new concept for the stereo measurement of gamma rays by using two Compton cameras, thus enabling the 3-D positional measurement of radioactive isotopes for the first time. From one point source simulation data, we ensured that the source position and the distance to the same could be determined typically to within 2 meters' accuracy and we also confirmed that more than two sources are clearly separated by the event selection from two point sources of simulation data.
Compton scattering in strong gravity
Bursa, Michal; Adámek, K.
Opava: Silesian University, 2014 - (Stuchlík, Z.), S.31-37. (Publications of the Institute of Physics. 7). ISBN 9788075101266. ISSN 2336-5668. [RAGtime /14.-16./. Opava (CZ), 18.09.2012-22.09.2012] R&D Projects: GA MŠk(CZ) LH14049 Institutional support: RVO:67985815 Keywords : radiation transport * relativity * Compton scattering Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Compton Scattering by the Proton
Galler, G; Kondratev, R; Massone, A M; Wolf, S; Ahrens, J; Arends, H J; Beck, R; Camen, M; Capitani, G P; Grabmayr, P; Hall, S J; Härter, F; Hehl, T; Jennewein, P; Kossert, K; Lvov, A I; Molinari, C; Ottonello, P; Peise, J; Preobrajenskij, I; Proff, S; Robbiano, A; Sanzone, M; Schumacher, M; Schmitz, M; Wissmann, F
2001-01-01
Compton scattering by the proton has been measured over a wide range covering photon energies 250 MeV < E_\\gamma < 800 MeV and photon scattering angles 30^0 < \\theta^{lab}_\\gamma < 150^0, using the tagged-photon facility at MAMI (Mainz) and the large-acceptance arrangement LARA. The data are in good agreement with the dispersion theory based on the SAID-SM99K parameterization of photo-meson amplitudes. From the subset of data between 280 and 360 MeV the resonance pion-photoproduction amplitudes were evaluated leading to the multipole E2/M1 ratio EMR(340 MeV) =(-1.6 \\pm 0.4(stat+syst) \\pm 0.2(model)%. From all data below 455 MeV the proton's backward spin polarizability was determined to be \\gamma_\\pi=(-37.9 \\pm 0.6(stat+syst) \\pm 3.5(model))x10^{-4}fm^4.
Radiative corrections to pion Compton scattering
Kaiser, N.(Physik Department T39, Technische Universität München, Garching, D-85747, Germany); Friedrich, J. M.
2008-01-01
We calculate the one-photon loop radiative corrections to charged pion Compton scattering, $\\pi^- \\gamma \\to \\pi^- \\gamma $. Ultraviolet and infrared divergencies are both treated in dimensional regularization. Analytical expressions for the ${\\cal O}(\\alpha)$ corrections to the invariant Compton scattering amplitudes, $A(s,u)$ and $B(s,u)$, are presented for 11 classes of contributing one-loop diagrams. Infrared finiteness of the virtual radiative corrections is achieved (in the standard way...
Electron Compton scattering in the electron microscope
Inelastic scattering of electrons or photons on target electrons at rest results in a definite increase of wavelength of the incident wave. The change in wavelength is known as Compton shift. For a moving scatterer, the Compton shift will be different in general, but it will still have a definite value. The resulting Compton profile in the spectrum is a direct image of the momentum distribution of the target electrons in the ground state. Therefore Compton scattering can be used to obtain information on the electronic properties of solids, directly in momentum representation. In 1981 B.G. Williams showed that ECOSS can be done in a transmission electron microscope. The scope of this thesis is the investigation and further development of ECOSS on the example of silicon, a well documented test system. After a short introduction into the theoretical concepts of Compton scattering and the investigation of the influence of coherent scattering effects when using single crystal specimens, the inevitable problem of multiple scattering will be discussed in detail and solutions concerning the plasmon-Compton channel coupling as well as the elastic background will be presented. The count rate of Compton-scattered electrons at the detector is notoriously low. The sensitivity of the electron detection system had to be enhanced as a prerequisite for ECOSS to be useful, which has been achieved by the installation of a parallel detection system. The performance of the parallel electron energy-loss spectrometer was investigated concerning its usefulness in electron Compton scattering. A method to eliminate the intrinsic noise of a parallel detector due to varying detector element properties is presented and discussed. Aiming at the measurement of directional anisotropies in the Compton profile one has to use single crystal specimens. To avoid problems with Bragg-Compton channel coupling a new kind of scattering geometry taking advantage of crystal symmetry was introduced and tested
CP-violation in Compton scattering
Gorchtein, Mikhail
2008-01-01
I consider Compton scattering off the nucleon in the presence of $CP$ violation. I construct the Compton tensor which possesses these features and consider low energy expansion (LEX) of the corresponding amplitudes. It allows to separate out the Born contribution which only depends on the static properties of the nucleon, such as the electric charge, the mass, the magnetic moment, and the electric dipole moment (EDM). I introduce new structure constants, the $T$-odd nucleon polarizabilities w...
Compton scattering and the complementarity principle
We explain briefly why Compton scattering from a crystal gives a featureless continuous x-ray background while Bragg scattering from the same crystal produces sharp diffraction peaks. It is shown that the answer lies at the heart of quantum mechanics, namely the uncertainty and the complementarity principles. (author)
Proton polarizabilities from polarized Compton scattering
We study the low-energy expansion of polarized Compton scattering off the proton. We show that the leading non-Born contribution to the beam asymmetry of low-energy Compton scattering is given by the magnetic polarizability alone, the electric polarizability cancels out. Based on this fact we propose to determine the magnetic dipole polarizability of the proton from the beam asymmetry. Computing the higher-order (recoil) effects of polarizabilities on beam asymmetry, we show that they are suppressed in forward kinematics. We also present the low-energy expansion of doubly-polarized observables, from which the spin polarizabilities can be extracted.
Compton Scattering with a Vortex Light Beam
Nairat, Mazen; Voelz, David
2014-03-01
The Compton effect is applied to a vortex light beam. A photon in a vortex beam possesses spin angular momentum associated with the polarization and orbital angular momentum that consists of two orthogonal components: azimuthal and axial. The azimuthal part is directly proportional to the axial part. This study considers inelastic collision of a photon possessing angular momentum with a free electron. The conservation of angular momentum as well as total energy is applied to the photon-electron system to generalize the Compton scattering model. We describe the momentum exchange and characterize the Compton effect beyond the well-known photon wavelength shift to include other parameters such as the radius of gyration. Our analysis suggests that upon an exchange of angular momentum with an electron, it is possible for the scattered photon to have no wavelength to shift. Air Force Research Laboratory.
Real Compton scattering for ELFE at DESY
Real Compton scattering at large s and t is a hard and exclusive reaction which allows to determine the valence quark wave function. An experiment could be carried out at DESY with a Laser backscattering photon beam produced in the internal ring and with a reasonably large acceptance detector for both photons and protons. (authors)
Proton Tomography Through Deeply Virtual Compton Scattering
Ji, Xiangdong
2016-01-01
In this prize talk, I recall some of the history surrounding the discovery of deeply virtual Compton scattering, and explain why it is an exciting experimental tool to obtain novel tomographic pictures of the nucleons at Jefferson Lab 12 GeV facility and the planned Electron-Ion Collider in the United States.
Neutron Compton scattering studies of stretched polyethylene
Gabrys, B J; Mayers, J; Kalhoro, M S
2002-01-01
The mean kinetic energy of hydrogen and carbon atoms in unstretched and stretched polyethylene samples has been measured by neutron Compton scattering. The vibrational frequencies of the ground state and torsional energies have been calculated and compared with the existing data and calculations. The results obtained on deuterated and non-deuterated samples are compared. (orig.)
Nonlinear X-ray Compton Scattering
Fuchs, Matthias; Trigo, Mariano; Chen, Jian; Ghimire, Shambhu; Shwartz, Sharon; Kozina, Michael; Jiang, Mason; Henighan, Thomas; Bray, Crystal; Ndabashimiye, Georges; Bucksbaum, P. H.; Feng, Yiping; Herrmann, Sven; Carini, Gabriella; Pines, Jack
2015-01-01
X-ray scattering is a weak linear probe of matter. It is primarily sensitive to the position of electrons and their momentum distribution. Elastic X-ray scattering forms the basis of atomic structural determination while inelastic Compton scattering is often used as a spectroscopic probe of both single-particle excitations and collective modes. X-ray free-electron lasers (XFELs) are unique tools for studying matter on its natural time and length scales due to their bright and coherent ultrash...
Induced Compton-scattering effects in radiation-transport approximations
The method of characteristics is used to solve radiation transport problems with induced Compton scattering effects included. The methods used to date have only addressed problems in which either induced Compton scattering is ignored, or problems in which linear scattering is ignored. Also, problems which include both induced Compton scattering and spatial effects have not been considered previously. The introduction of induced scattering into the radiation transport equation results in a quadratic nonlinearity. Methods are developed to solve problems in which both linear and nonlinear Compton scattering are important. Solutions to scattering problems are found for a variety of initial photon energy distributions
Virtual Compton Scattering on the Proton
Hyde-Wright, Charles E.
1997-04-01
Virtual compton scattering (VCS), measured via the reaction e + p arrow e' + p' + γ is a new tool for the study of proton structure. Below pion threshold, the cross section can be described in terms of generalized polarizabilities of the proton (P.A.M. Guichon, G.Q. Liu, and A.W. Thomas, Nucl Phys A591), 606 (1995).. These Q^2-dependent observables generalize the electric and magnetic polarizabilities measured in real compton scattering. At high energies, VCS generalizes the structure functions of deep inelastic scattering, and can be related to the quark spin- and orbital-angular momentum decomposition of the nucleon spin (X. Ji, hep-ph/9603249, 7 Mar 96; X. Ji, hep-ph/9609381, 17 Sep 96) (A.V. Radyushkin, Phys Lett B380) (1996) 417; hep-ph/9604317, 15 Apr 96.. In this talk I will present the physical motivation of virtual compton scattering at low and high energies, the recent experimental results from MAMI, and the measurements planned for TJNAF.
Theory of Compton scattering by anisotropic electrons
Poutanen, Juri
2010-01-01
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, and relativistic jets, clusters of galaxies as well as the early Universe. In most of the calculations it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or anisotropic cooling by synchrotron radiation, or anisotropic source of seed soft photons. We develop here an analytical theory of Compton scattering by anisotropic distribution of electrons that can simplify significantly the calculations. Assuming that the electron angular distribution can be represented by a second order polynomial over cosine of some angle (dipole and quadrupole anisotropy), we integrate the exact Klein-Nishina cross-section over the angles. Exact analytical and approximate formulae valid for any photon and electron energies are derived for the redistribution functions describin...
Hard photon production by inverse Compton scattering
The controlled production of hard photons (X and γ-rays) is of relevance in many medical, industrial and science applications. In this work an alternative method for producing both X and γ-rays via Inverse Compton Scattering with both electron and proton beams is discussed. We present results for the cross section for this process with non static electron and protons. The results are evaluated for a particular energy interval, and an experimental design is proposed.
Theory of Compton scattering by anisotropic electrons
Poutanen, Juri; Vurm, Indrek
2010-01-01
Compton scattering plays an important role in various astrophysical objects such as accreting black holes and neutron stars, pulsars, and relativistic jets, clusters of galaxies as well as the early Universe. In most of the calculations it is assumed that the electrons have isotropic angular distribution in some frame. However, there are situations where the anisotropy may be significant due to the bulk motions, or anisotropic cooling by synchrotron radiation, or anisotropic source of seed so...
Electron distributions in nonlinear Compton scattering
Boca, Madalina; Dinu, Victor; Florescu, Viorica
2012-01-01
Based on quantum theory, we investigate the distribution of the electrons scattered in nonlinear Compton effect by an electromagnetic plane wave. Deviations of the final electron momentum from its initial value are solely due to quantum effects. The monochromatic case, examined in detail, reveals features of the electron distribution, useful in the understanding of the pulsed plane wave case for particular intensity and electron energy regimes. The graphs displayed focus on the case of head-o...
Deeply Virtual Compton Scattering Facing Nonforward Distributions
Radyushkin, A V
1997-01-01
Applications of perturbative QCD to deeply virtual Compton scattering process require a generalization of usual parton distributions for the case when long-distance information is accumulated in nonforward matrix elements of quark and gluon operators. We discuss two types of functions parametrizing such matrix elements: double distributions F(x,y;t) and nonforward distribution functions \\cal F_\\zeta (X;t) and also their relation to usual parton densities f(x).
Momentum-space magnetism studied by magnetic Compton scattering
Sakai, Nobuhiko; Koizumi, Akihisa; Miyamoto, Naoki; Tanaka, Yoshikazu
1997-01-01
The usefulness of magnetic Compton-profile spectroscopy to derive momentum-space information about the spin states of electrons is described with examples. The reconstructed three-dimensional momentum density of spin-polarized electrons in ferromagnetic iron reveals information on the spin states in momentum space in a straightforward fashion. The analysis of Mn-ion states in the intermetallic compound MnSb illustrates that atomic orbital wavefunctions in momentum-space representation can be used for the MCP analysis. The separate determination of the magnetic moments of 3d and 4f electrons together with wide band itinerant electrons in amorphous GdxY1-xFe20Al20 alloy are presented. The spin magnetic moments of Sm and Co atoms in SmCo5 have been evaluated for the first time by utilizing the fact that the magnetic Compton-scattering cross section does not depend on atomic orbital angular momenta.
Electronic structure of Mg studied by compton scattering
Kontrym-Sznajd, Grazyna; Samsel-Czekala, Malgorzata [W. Trzebiatowski Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P. O. Box 1410, 50-950 Wroclaw 2 (Poland); Pylak, Maciej [The Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Dobrzynski, Ludwik [The Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk (Poland); Faculty of Physics, University of Bialystok, ul. Lipowa 41, 15-424 Bialystok (Poland); Brancewicz, Marek; Andrejczuk, Andrzej; Zukowski, Eugeniusz [Faculty of Physics, University of Bialystok, ul. Lipowa 41, 15-424 Bialystok (Poland); Kaprzyk, Stanislaw [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Krakow (Poland)
2011-03-15
The electronic structure of divalent hexagonal close packed Mg is investigated by means of the high-resolution Compton scattering. Two-dimensional (2D) electron momentum densities are reconstructed using their line integrals, derived from the plane integrals of three-dimensional (3D) electron momentum densities measured directly in the Compton experiment. The analysis is performed both in the extended and reduced zone schemes. The results are compared with corresponding densities calculated within Korringa-Kohn-Rostoker in the local density approximation (KKR-LDA) band structure theory and electron-positron densities measured in the angular correlation of annihilation radiation (ACAR) experiment. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Radiative corrections to pion Compton scattering
We calculate the one-photon loop radiative corrections to charged pion Compton scattering, π-γ→π-γ. Ultraviolet and infrared divergencies are both treated in dimensional regularization. Analytical expressions for the O(α) corrections to the invariant Compton scattering amplitudes, A(s,u) and B(s,u), are presented for 11 classes of contributing one-loop diagrams. Infrared finiteness of the virtual radiative corrections is achieved (in the standard way) by including soft photon radiation below an energy cut-off λ, and its relation to the experimental detection threshold is discussed. We find that the radiative corrections are maximal in backward directions, reaching e.g. -2.4% for a center-of-mass energy of √(s)=4mπ and λ=5MeV. Furthermore, we extend our calculation of the radiative corrections by including the leading pion structure effect (at low energies) in form of its electric and magnetic polarizability difference, απ-βπ≅6x10-4fm3. We find that this structure effect does not change the relative size and angular dependence of the radiative corrections to pion Compton scattering. Our results are particularly relevant for analyzing the COMPASS experiment at CERN which aims at measuring the pion electric and magnetic polarizabilities with high statistics using the Primakoff effect
3D Ordered Subset Expectation Maximization (OSEM) Algorithm for a Compton camera
Kim, Soo Mee; Lee, Jae Sung; Kim, Joong Hyun; Lee, Dong Soo [Seoul National University College of Medicine, Seoul (Korea, Republic of); Lee, Mi No; Lee, Soo Jin [Paichai University, Daejeon (Korea, Republic of); Lee, Ju Hahn; Lee, Chun Sik [Chungang University, Seoul (Korea, Republic of); Kim, Chan Hyeong [Hanyang University, Seoul (Korea, Republic of)
2007-07-01
The Compton camera is an single-photon imaging device that employs an electronic collimation based on the relationship between energy transfer and Compton scattering angle of {gamma}-ray in the detector. In this study, the expectation maximization (EM) approach along with its accelerated version based on the ordered subsets principle was applied to the problem of image reconstruction for a Compton camera, which is known to be computationally challenging. This study also compared several methods of constructing subsets for the optimal performance of these algorithms.
Radiative corrections to virtual Compton scattering
Radiative corrections to virtual Compton scattering are calculated for the first time at the first order in α. We use the dimensional regularization scheme to treat both Ultra-Violet and Indra-Red divergences. After the compensation of divergences, the expression of the correction contains analytical terms and a numerical term which has to be computed. For a scattered photon of centre of mass energy q'= 45 MeV, a preliminary result of the comparison between theory and experimental data is presented taking into account only analytical terms. (authors)
Nonlinear X-ray Compton Scattering
Fuchs, Matthias; Chen, Jian; Ghimire, Shambhu; Shwartz, Sharon; Kozina, Michael; Jiang, Mason; Henighan, Thomas; Bray, Crystal; Ndabashimiye, Georges; Bucksbaum, P H; Feng, Yiping; Herrmann, Sven; Carini, Gabriella; Pines, Jack; Hart, Philip; Kenney, Christopher; Guillet, Serge; Boutet, Sebastien; Williams, Garth; Messerschmidt, Marc; Seibert, Marvin; Moeller, Stefan; Hastings, Jerome B; Reis, David A
2015-01-01
X-ray scattering is a weak linear probe of matter. It is primarily sensitive to the position of electrons and their momentum distribution. Elastic X-ray scattering forms the basis of atomic structural determination while inelastic Compton scattering is often used as a spectroscopic probe of both single-particle excitations and collective modes. X-ray free-electron lasers (XFELs) are unique tools for studying matter on its natural time and length scales due to their bright and coherent ultrashort pulses. However, in the focus of an XFEL the assumption of a weak linear probe breaks down, and nonlinear light-matter interactions can become ubiquitous. The field can be sufficiently high that even non-resonant multiphoton interactions at hard X-rays wavelengths become relevant. Here we report the observation of one of the most fundamental nonlinear X-ray-matter interactions, the simultaneous Compton scattering of two identical photons producing a single photon at nearly twice the photon energy. We measure scattered...
CP-violation in Compton scattering
Gorchtein, Mikhail
2008-01-01
I consider Compton scattering off the nucleon in the presence of $CP$ violation. I construct the Compton tensor which possesses these features and consider low energy expansion (LEX) of the corresponding amplitudes. It allows to separate out the Born contribution which only depends on the static properties of the nucleon, such as the electric charge, the mass, the magnetic moment, and the electric dipole moment (EDM). I introduce new structure constants, the $T$-odd nucleon polarizabilities which parametrize the unknown non-Born part. These constants describe the response of the $T$-violating content of the nucleon to the external quasistatic electromagnetic field. As an estimate, I provide a HBChPT calculation for these new polarizabilities and discuss the implications for the experiment.
Classical theory of nonlinear Compton scattering
The covariant dynamics of a single electron subjected to the electromagnetic field of an intense, ultrashort laser pulse in vacuum is studied theoretically at arbitrary intensities, in the context of the Dirac-Lorentz equation, which has long been suggested as a possible theory including the radiative reaction due to the electron self-interaction. A brief review of the Lorentz-Maxwell electrodynamics including canonical invariants and scattered light spectra will be given, with a special emphasis on frequency modulation effects associated to the nonlinear relativistic Doppler shift induced by radiation pressure on the backscattered radiation. For circular polarization, an exact analytical expression for the full nonlinear spectrum is derived, and is presented. It is found that the scattering of coherent light by an electron describing a well-behaved trajectory can yield chaotic spectra when the laser ponderomotive force strongly modulates the electron's proper time. The Dirac-Lorentz equation is then derived and integrated numerically backward in time to ensure convergence towards the unique acausal solution satisfying the Dirac-Rohrlich asymptotic conditions (no runaway, law of inertia), and its consequences are investigated in terms of nonlinear Compton scattering. The relevance of this work to laser acceleration, as well as ongoing nonlinear Compton scattering experiments at SLAC and to the proposed γ-γ collider will also be discussed
Recently, a mathematical procedure was reported to unfold the density profile of wood panels from the measurement of the integrated scatter signal that contains prevalently the Compton component. An experimental device (patent claimed) has been used for these measurements. It uses reflection geometry to maximize the Compton signal. The influence of multiple scattering (MS) is not negligible as has been estimated using the Monte Carlo code MCSHAPE3D. However, Monte Carlo computations are time consuming. Therefore, in practice, the MS correction is computed off-line for few thicknesses of the specimen assuming known composition and density. Then, an original 2D interpolation algorithm is used to apply the MS correction to an arbitrary thickness scatterer, in order to improve the precision of the unfolded density profile in real time at the production line. The MS corrected density profiles are in good agreement with direct measurements performed with other means
Virtual compton scattering at high energy
The virtual Compton scattering (VCS) reaction (ep→e'p' gamma) at high energy will provide new information on the proton structure. The invariant momentum transfer (t=(q-q')2) de pendence of high energy VCS is related to the flavor dependent vector and axial-vector form factors of the the proton. Thus VCS can provide information that is complementary to parity violating electron scattering measurements. For small t and large Q2, VCS generalizes the structure functions of deep inelastic lepton scattering. These generalized structure functions have a sum rule which yields the net contribution of quark spin and orbital angular momentum to the proton spin. A large acceptance detector such as the MEMUS design, capable of running at a luminosity 1035/cm2/sec at incident electron energies from 10 to 30 GeV can measure the VCS process in a broad and exciting kinematic range. (orig.)
Exclusive compton scattering on the proton
An experiment is proposed to measure the cross sections for Real Compton Scattering from the proton in the energy range 3-6 GeV and over a wide angular range, and to measure the longitudinal and transverse components of the polarization transfer to the recoil proton at a single kinematic point. Together, these measurements will test models of the reaction mechanism and determine new structure functions of the proton that are related to the same non-forward parton densities that determine the elastic electron scattering form factors and the parton densities. The experiment utilizes an untagged Bremsstrahlung photon beam and the standard Hall A cryogenic targets. The scattered photon is detected in a photon spectrometer, currently under construction. The coincident recoil proton is detected in one of the Hall A magnetic spectrometers and its polarization components are measured in the existing Focal Plane Polarimeter. This proposal extends and supersedes E97 - 108 which was approved by PAC13. (author)
Higher twist effects in deeply virtual Compton scattering
Pirnay, Björn Michael
2016-01-01
We calculate suppressed power corrections to deeply virtual Compton scattering amplitudes using operator product expansion. The numerical impact of these results to present day experiments is investigated.
Compton scattering measurements from dense plasmas
Glenzer, S H; Neumayer, P; Doeppner, T; Landen, L; Lee, R W; Wallace, R; Weber, S; Lee, H J; Kritcher, A L; Falcone, R; Regan, S P; Sawada, H; Meyerhofer, D D; Gregori, G; Fortmann, C; Schwarz, V; Redmer, R
2007-10-02
Compton scattering has been developed for accurate measurements of densities and temperatures in dense plasmas. One future challenge is the application of this technique to characterize compressed matter on the National Ignition Facility where hydrogen and beryllium will approach extremely dense states of matter of up to 1000 g/cc. In this regime, the density, compressibility, and capsule fuel adiabat may be directly measured from the Compton scattered spectrum of a high-energy x-ray line source. Specifically, the scattered spectra directly reflect the electron velocity distribution. In non-degenerate plasmas, the width provides an accurate measure of the electron temperatures, while in partially Fermi degenerate systems that occur in laser-compressed matter it provides the Fermi energy and hence the electron density. Both of these regimes have been accessed in experiments at the Omega laser by employing isochorically heated solid-density beryllium and moderately compressed beryllium foil targets. In the latter experiment, compressions by a factor of 3 at pressures of 40 Mbar have been measured in excellent agreement with radiation hydrodynamic modeling.
Deeply Virtual Compton Scattering off the neutron
The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D((rvec e), e'γ)X cross section measured at Q2=1.9 GeV2 and xB=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to Eq, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced
Deeply Virtual Compton Scattering off the neutron
M. Mazouz; A. Camsonne; C. Munoz Camacho; C. Ferdi; G. Gavalian; E. Kuchina; M. Amarian; K. A. Aniol; M. Beaumel; H. Benaoum; P. Bertin; M. Brossard; J.-P. Chen; E. Chudakov; B. Craver; F. Cusanno; C.W. de Jager; A. Deur; R. Feuerbach; J.-M. Fieschi; S. Frullani; M. Garcon; F. Garibaldi; O. Gayou; R. Gilman; J. Gomez; P. Gueye; P.A.M. Guichon; B. Guillon; O. Hansen; D. Hayes; D. Higinbotham; T. Holmstrom; C.E. Hyde; H. Ibrahim; R. Igarashi; X. Jiang; H.S. Jo; L.J. Kaufman; A. Kelleher; A. Kolarkar; G. Kumbartzki; G. Laveissiere; J.J. LeRose; R. Lindgren; N. Liyanage; H.-J. Lu; D.J. Margaziotis; Z.-E. Meziani; K. McCormick; R. Michaels; B. Michel; B. Moffit; P. Monaghan; S. Nanda; V. Nelyubin; M. Potokar; Y. Qiang; R.D. Ransome; J.-S. Real; B. Reitz; Y. Roblin; J. Roche; F. Sabatie; A. Saha; S. Sirca; K. Slifer; P. Solvignon; R. Subedi; V. Sulkosky; P.E. Ulmer; E. Voutier; K. Wang; L.B. Weinstein; B. Wojtsekhowski; X. Zheng; L. Zhu
2007-12-01
The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\\vec e},e'\\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
Deeply Virtual Compton Scattering off the neutron
Mazouz, M; Ferdi, C; Gavalian, G; Kuchina, E; Amarian, M; Aniol, K A; Beaumel, M; Benaoum, H; Bertin, P; Brossard, M; Chen, J P; Chudakov, E; Craver, B; Cusanno, F; De Jager, C W; Deur, A; Feuerbach, R; Fieschi, J M; Frullani, S; Garçon, M; Garibaldi, F; Gayou, O; Gilman, R; Gómez, J; Gueye, P; Guichon, P A M; Guillon, B; Hansen, O; Hayes, D; Higinbotham, D; Holmstrom, T; Hyde, C E; Ibrahim, H; Igarashi, R; Jiang, X; Jo, H S; Kaufman, L J; Kelleher, A; Kolarkar, A; Kumbartzki, G; Laveissière, G; Le Rose, J J; Lindgren, R; Liyanage, N; Lu, H J; Margaziotis, D J; Meziani, Z E; McCormick, K; Michaels, R; Michel, B; Moffit, B; Monaghan, P; Nanda, S; Nelyubin, V; Potokar, M; Qiang, Y; Ransome, R D; Real, J S; Reitz, B; Roblin, Y; Roche, J; Sabatie, F; Saha, A; Sirca, S; Slifer, K; Solvignon, P; Subedi, R; Sulkosky, V; Ulmer, P E; Voutier, E; Wang, K; Weinstein, L B; Wojtsekhowski, B; Zheng, X; Zhu, L
2007-01-01
The present experiment exploits the interference between the Deeply Virtual Compton Scattering (DVCS) and the Bethe-Heitler processes to extract the imaginary part of DVCS amplitudes on the neutron and on the deuteron from the helicity-dependent D$({\\vec e},e'\\gamma)X$ cross section measured at $Q^2$=1.9 GeV$^2$ and $x_B$=0.36. We extract a linear combination of generalized parton distributions (GPDs) particularly sensitive to $E_q$, the least constrained GPD. A model dependent constraint on the contribution of the up and down quarks to the nucleon spin is deduced.
Deeply Virtual Compton Scattering off 4He
Joosten, Sylvester; CLAS Collaboration
2015-10-01
The European Muon Collaboration (EMC) observed the first signs of a modification of the partonic structure of the nucleon when present in a nuclear medium. The precise nature of these effects, as well as their underlying cause, is yet to be determined. The generalized parton distribution (GPD) framework provides a powerful tool to study the partonic structure of nucleons inside a nucleus. Hard exclusive leptoproduction of a real photon off a nucleon, deeply virtual Compton scattering (DVCS), is presently considered the cleanest experimental access to the GPDs, through the Compton form factors (CFFs). This is especially the case for scattering off the spin-zero helium nucleus, where only a single CFF contributes to the process. The real and imaginary parts of this CFF can be constrained through the beam-spin asymmetry (BSA). We will present the first measurements of the DVCS process off 4He using the CEBAF 6 GeV polarized electron beam and the CLAS detector at JLab. The CLAS detector was supplemented with an inner electromagnetic calorimeter for photons produced at small angles, as well as a radial time projection chamber (RTPC) to detect low-energy recoil nuclei. This setup allowed for a clean measurement of the BSA in both the coherent and incoherent channels.
Virtual compton scattering at low energy
The work described in this PhD is a study of the Virtual Compton scattering (VCS) off the proton at low energy, below pion production threshold. Our experiment has been carried out at MAMI in the collaboration with the help of two high resolution spectrometers. Experimentally, the VCS process is the electroproduction of photons off a liquid hydrogen target. First results of data analysis including radiative corrections are presented and compared with low energy theorem prediction. VCS is an extension of the Real Compton Scattering. The virtuality of the incoming photon allows us to access new observables of the nucleon internal structure which are complementarity to the elastic form factors: the generalized polarizabilities (GP). They are function of the squared invariant mass of the virtual photo. The mass limit of these observables restore the usual electric and magnetic polarizabilities. Our experiment is the first measurement of the VCS process at a virtual photon mass equals 0.33 Ge V square. The experimental development presents the analysis method. The high precision needed in the absolute cross-section measurement required an accurate estimate of radiative corrections to the VCS. This new calculation, which has been performed in the dimensional regulation scheme, composes the theoretical part of this thesis. At low q', preliminary results agree with low energy theorem prediction. At higher q', substraction of low energy theorem contribution to extract GP is discussed. (author)
Radiative corrections to pion Compton scattering
Kaiser, N
2008-01-01
We calculate the one-photon loop radiative corrections to charged pion Compton scattering, $\\pi^- \\gamma \\to \\pi^- \\gamma $. Ultraviolet and infrared divergencies are both treated in dimensional regularization. Analytical expressions for the ${\\cal O}(\\alpha)$ corrections to the invariant Compton scattering amplitudes, $A(s,u)$ and $B(s,u)$, are presented for 11 classes of contributing one-loop diagrams. Infrared finiteness of the virtual radiative corrections is achieved (in the standard way) by including soft photon radiation below an energy threshold $\\lambda$, and its relation to the experimental detection threshold is discussed. We find that the radiative corrections are maximal in backward directions, reaching e.g. -2.4% for a center-of-mass energy of $\\sqrt{s}=4m_\\pi$ and $\\lambda=5 $MeV. Furthermore, we extend our calculation of the radiative corrections by including the leading pion structure effect (at low energies) in form of its electric and magnetic polarizability difference, $\\alpha_\\pi - \\beta_...
Compton scatter correction for planner scintigraphic imaging
A major problem in nuclear medicine is the image degradation due to Compton scatter in the patient. Photons emitted by the radioactive tracer scatter in collision with electrons of the surrounding tissue. Due to the resulting loss of energy and change in direction, the scattered photons induce an object dependant background on the images. This results in a degradation of the contrast of warm and cold lesions. Although theoretically interesting, most of the techniques proposed in literature like the use of symmetrical photopeaks can not be implemented on the commonly used gamma camera due to the energy/linearity/sensitivity corrections applied in the detector. A method for a single energy isotope based on existing methods with adjustments towards daily practice and clinical situations is proposed. It is assumed that the scatter image, recorded from photons collected within a scatter window adjacent to the photo peak, is a reasonable close approximation of the true scatter component of the image reconstructed from the photo peak window. A fraction 'k' of the image using the scatter window is subtracted from the image recorded in the photo peak window to produce the compensated image. The principal matter of the method is the right value for the factor 'k', which is determined in a mathematical way and confirmed by experiments. To determine 'k', different kinds of scatter media are used and are positioned in different ways in order to simulate a clinical situation. For a secondary energy window from 100 to 124 keV below a photo peak window from 126 to 154 keV, a value of 0.7 is found. This value has been verified using both an antropomorph thyroid phantom and the Rollo contrast phantom
Compton scatter correction for planner scintigraphic imaging
Vaan Steelandt, E.; Dobbeleir, A.; Vanregemorter, J. [Algemeen Ziekenhuis Middelheim, Antwerp (Belgium). Dept. of Nuclear Medicine and Radiotherapy
1995-12-01
A major problem in nuclear medicine is the image degradation due to Compton scatter in the patient. Photons emitted by the radioactive tracer scatter in collision with electrons of the surrounding tissue. Due to the resulting loss of energy and change in direction, the scattered photons induce an object dependant background on the images. This results in a degradation of the contrast of warm and cold lesions. Although theoretically interesting, most of the techniques proposed in literature like the use of symmetrical photopeaks can not be implemented on the commonly used gamma camera due to the energy/linearity/sensitivity corrections applied in the detector. A method for a single energy isotope based on existing methods with adjustments towards daily practice and clinical situations is proposed. It is assumed that the scatter image, recorded from photons collected within a scatter window adjacent to the photo peak, is a reasonable close approximation of the true scatter component of the image reconstructed from the photo peak window. A fraction `k` of the image using the scatter window is subtracted from the image recorded in the photo peak window to produce the compensated image. The principal matter of the method is the right value for the factor `k`, which is determined in a mathematical way and confirmed by experiments. To determine `k`, different kinds of scatter media are used and are positioned in different ways in order to simulate a clinical situation. For a secondary energy window from 100 to 124 keV below a photo peak window from 126 to 154 keV, a value of 0.7 is found. This value has been verified using both an antropomorph thyroid phantom and the Rollo contrast phantom.
“Stereo Compton cameras” for the 3-D localization of radioisotopes
Takeuchi, K. [Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo (Japan); Kataoka, J., E-mail: dianthus_k@ruri.waseda.jp [Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo (Japan); Nishiyama, T.; Fujita, T.; Kishimoto, A. [Research Institute for Science and Engineering, Waseda University, 3-4-1, Ohkubo, Shinjuku, Tokyo (Japan); Ohsuka, S.; Nakamura, S.; Adachi, S.; Hirayanagi, M.; Uchiyama, T.; Ishikawa, Y.; Kato, T. [Solid State Division, Hamamatsu Photonics K. K., 1126-1, Ichino-cho, Hamamatsu, Shizuoka (Japan)
2014-11-21
The Compton camera is a viable and convenient tool used to visualize the distribution of radioactive isotopes that emit gamma rays. After the nuclear disaster in Fukushima in 2011, there is a particularly urgent need to develop “gamma cameras”, which can visualize the distribution of such radioisotopes. In response, we propose a portable Compton camera, which comprises 3-D position-sensitive GAGG scintillators coupled with thin monolithic MPPC arrays. The pulse-height ratio of two MPPC-arrays allocated at both ends of the scintillator block determines the depth of interaction (DOI), which dramatically improves the position resolution of the scintillation detectors. We report on the detailed optimization of the detector design, based on Geant4 simulation. The results indicate that detection efficiency reaches up to 0.54%, or more than 10 times that of other cameras being tested in Fukushima, along with a moderate angular resolution of 8.1° (FWHM). By applying the triangular surveying method, we also propose a new concept for the stereo measurement of gamma rays by using two Compton cameras, thus enabling the 3-D positional measurement of radioactive isotopes for the first time. From one point source simulation data, we ensured that the source position and the distance to the same could be determined typically to within 2 meters' accuracy and we also confirmed that more than two sources are clearly separated by the event selection from two point sources of simulation data. - Highlights: • A scintillator-based Compton camera is being optimized using Geant4 simulations. • Both high efficiency and moderate angular resolution can be achieved simultaneously. • We ensured a new method of sensing the 3-D position of a source through simulations. • The source position can be determined typically within 2 meters' accuracy. • More than two sources can be visualized individually via a simple event selection.
Anomalous nonlinear X-ray Compton scattering
Fuchs, Matthias; Trigo, Mariano; Chen, Jian; Ghimire, Shambhu; Shwartz, Sharon; Kozina, Michael; Jiang, Mason; Henighan, Thomas; Bray, Crystal; Ndabashimiye, Georges; Bucksbaum, Philip H.; Feng, Yiping; Herrmann, Sven; Carini, Gabriella A.; Pines, Jack; Hart, Philip; Kenney, Christopher; Guillet, Serge; Boutet, Sébastien; Williams, Garth J.; Messerschmidt, Marc; Seibert, M. Marvin; Moeller, Stefan; Hastings, Jerome B.; Reis, David A.
2015-11-01
X-ray scattering is typically used as a weak linear atomic-scale probe of matter. At high intensities, such as produced at free-electron lasers, nonlinearities can become important, and the probe may no longer be considered weak. Here we report the observation of one of the most fundamental nonlinear X-ray-matter interactions: the concerted nonlinear Compton scattering of two identical hard X-ray photons producing a single higher-energy photon. The X-ray intensity reached 4 × 1020 W cm-2, corresponding to an electric field well above the atomic unit of strength and within almost four orders of magnitude of the quantum-electrodynamic critical field. We measure a signal from solid beryllium that scales quadratically in intensity, consistent with simultaneous non-resonant two-photon scattering from nearly-free electrons. The high-energy photons show an anomalously large redshift that is incompatible with a free-electron approximation for the ground-state electron distribution, suggesting an enhanced nonlinearity for scattering at large momentum transfer.
Deeply virtual Compton scattering at Jefferson Laboratory
Biselli, Angela
2015-01-01
The generalized parton distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply virtual Compton scattering (DVCS) on a proton or neutron ($N$), $e N \\rightarrow e' N' \\gamma$, is the process more directly interpretable in terms of GPDs. The amplitudes of DVCS and Bethe-Heitler, the process where a photon is emitted by either the incident or scattered electron, can be accessed via cross-section measurements or exploiting their interference which gives rise to spin asymmetries. Spin asymmetries, cross sections and cross-section differences can be connected to different combinations of the four leading-twist GPDs (${H}$, ${E}$, ${\\tilde{H}}$, ${\\tilde{E}}$) for each quark flavors, depending on the observable and on the type of target. This paper gives an overview of recent experimental results obtained for DVCS at Jefferson Laboratory in the halls A and B. Several experiments have been done extracting DVCS observables o...
Compton scattering profile for in vivo XRF techniques.
Tartari, A; Baraldi, C; Felsteiner, J; Casnati, E
1991-05-01
The contribution from single Compton scattered photons to the background in in vivo x-ray fluorescence analysis is evaluated by taking into account the energy broadening of the scattered photons which reflects the momentum distribution of the target electrons. A general-purpose Monte Carlo evaluation of multiple scattering components, as well as accurate experimental verifications with 59.54 keV photons impinging on various targets of interest for real-life irradiation, confirm that the single Compton scattering profiles of the elements composing the biological matrix dominate the trend and amplitude of the background in the region of interest with near-backscatter configurations. Step features are likewise explained in terms of single Compton phenomenology. Other probable sources of background, such as photoelectron Bremsstrahlung and pile-up distribution, are studied both theoretically and experimentally in order to compare their amplitude and features with those of single Compton scattered photon profiles. PMID:2068224
Compton scatter imaging: A tool for historical exploration
Harding, G. [GE Security Germany GmbH, Heselstuecken 3, D-22453 Hamburg (Germany)], E-mail: Geoffrey.Harding@ge.com; Harding, E. [University of Muenster, Interdisciplinary Research Training Group ' Societal symbolism in mediaeval and early modern times' (German Research Foundation, DFG), Pferdegasse 3/D-48143 Muenster (Germany)
2010-06-15
This review discusses the principles and technological realisation of a technique, termed Compton scatter imaging (CSI), which is based on spatially resolved detection of Compton scattered X-rays. The applicational focus of this review is to objects of historical interest. Following a historical survey of CSI, a description is given of the major characteristics of Compton X-ray scatter. In particular back-scattered X-rays allow massive objects to be imaged, which would otherwise be too absorbing for the conventional transmission X-ray technique. The ComScan (an acronym for Compton scatter scanner) is a commercially available backscatter imaging system, which is discussed here in some detail. ComScan images from some artefacts of historical interest, namely a fresco, an Egyptian mummy and a mediaeval clasp are presented and their use in historical analysis is indicated. The utility of scientific and technical advance for not only exploring history, but also restoring it, is briefly discussed.
Computations of Compton scattering redistribution function in plasma
Madej, J; Majczyna, A; Należyty, M
2016-01-01
Compton scattering is the dominant opacity source in hot neutron stars, accretion disks around black holes and hot coronae. We present here a set of numerical expressions of the Compton scattering redistribution functions for unpolarized radiation, which are more exact than the widely used Kompaneets equation. This paper fulfills three goals: 1. We have organized three existing algorithms into a form ready to use in radiative transfer and model atmosphere codes. 2. We present the correct algorithm derived first by Guilbert (1981). 3. We modify the exact algorithm by Suleimanov et al. (2012) in order to use it for the scattering in a very wide spectral range from hard X- rays to radio waves. We present sample computations of the Compton scattering redistribution functions in thermal plasma at temperatures corresponding to the atmospheres of bursting neutron stars and hot intergalactic medium. Our formulae are also useful to the study Compton scattering of unpolarised microwave background radiation in hot intra...
NDE of spacecraft materials using 3D Compton backscatter x-ray imaging
Burke, E. R.; Grubsky, V.; Romanov, V.; Shoemaker, K.
2016-02-01
We present the results of testing of the NDE performance of a Compton Imaging Tomography (CIT) system for single-sided, penetrating 3D inspection. The system was recently developed by Physical Optics Corporation (POC) and delivered to NASA for testing and evaluation. The CIT technology is based on 3D structure mapping by collecting the information on density profiles in multiple object cross sections through hard x-ray Compton backscatter imaging. The individual cross sections are processed and fused together in software, generating a 3D map of the density profile of the object which can then be analyzed slice-by-slice in x, y, or z directions. The developed CIT scanner is based on a 200-kV x-ray source, flat-panel x-ray detector (FPD), and apodized x-ray imaging optics. The CIT technology is particularly well suited to the NDE of lightweight aerospace materials, such as the thermal protection system (TPS) ceramic and composite materials, micrometeoroid and orbital debris (MMOD) shielding, spacecraft pressure walls, inflatable habitat structures, composite overwrapped pressure vessels (COPVs), and aluminum honeycomb materials. The current system provides 3D localization of defects and features with field of view 20x12x8 cm3 and spatial resolution ˜2 mm. In this paper, we review several aerospace NDE applications of the CIT technology, with particular emphasis on TPS. Based on the analysis of the testing results, we provide recommendations for continued development on TPS applications that can benefit the most from the unique capabilities of this new NDE technology.
Experimental aspects of virtual Compton scattering at MAMI
Virtual Compton scattering allows us to measure for the first time the generalized polarizabilities of the proton. The experimental method to extract these new observables is shown as well as some preliminary results obtained at MAMI. (authors)
Virtual Compton scattering γ→γ'p'
The Virtual Compton scattering allows us to measure for the first time the generalized polarizabilities of the proton. The experimental method used to extract these new observables is presented as well as some preliminary results obtained at MAMI. (authors)
Validation of Compton Scattering Monte Carlo Simulation Models
Weidenspointner, Georg; Hauf, Steffen; Hoff, Gabriela; Kuster, Markus; Pia, Maria Grazia; Saracco, Paolo
2014-01-01
Several models for the Monte Carlo simulation of Compton scattering on electrons are quantitatively evaluated with respect to a large collection of experimental data retrieved from the literature. Some of these models are currently implemented in general purpose Monte Carlo systems; some have been implemented and evaluated for possible use in Monte Carlo particle transport for the first time in this study. Here we present first and preliminary results concerning total and differential Compton scattering cross sections.
Comparison between electron and neutron Compton scattering studies
Moreh Raymond; Finkelstein Yacov; Vos Maarten
2015-01-01
We compare two techniques: Electron Compton Scattering (ECS) and neutron Compton scattering (NCS) and show that using certain incident energies, both can measure the atomic kinetic energy of atoms in molecules and solids. The information obtained is related to the Doppler broadening of nuclear levels and is very useful for deducing the widths of excited levels in many nuclei in self absorption measurements. A comparison between the atomic kinetic energies measured by the two methods on the sa...
An algorithm and program for data processing from a Compton scattering imaging device
Vasiliev, V. N.; Zaytseva, K. V.
2005-07-01
The VolumeScope, a prototype 3D X-ray scanner based on Compton backscatter detection, was designed for examination of a human body electron density distribution. An algorithm and computer program for 3D image reconstruction from the VolumeScope measured data are presented. The reconstruction includes corrections for photon attenuation and multiple scatter in surrounding tissues and postprocessing digital filtering. Properties of multiple scattered photons inside the object of examination were studied by Monte Carlo technique and a geometrical efficiency of the multiple scatter detection was calculated on the base of the collimator design. The contribution of multiple scattered photons in semi-infinite water medium was from 15 to 23% of maximum detector response. The VolumeScope program is described to perform data processing and display the electron density distribution of the object as 2D grayscale images and 3D surfaces of internal structures.
Polarization observables in Virtual Compton Scattering
Doria, Luca
2007-10-15
Virtual Compton Scattering (VCS) is an important reaction for understanding nucleon structure at low energies. By studying this process, the generalized polarizabilities of the nucleon can be measured. These observables are a generalization of the already known polarizabilities and will permit theoretical models to be challenged on a new level. More specifically, there exist six generalized polarizabilities and in order to disentangle them all, a double polarization experiment must be performed. Within this work, the VCS reaction p(e,e'p){gamma} was measured at MAMI using the A1 Collaboration three spectrometer setup with Q{sup 2}=0.33 (GeV/c){sup 2}. Using the highly polarized MAMI beam and a recoil proton polarimeter, it was possible to measure both the VCS cross section and the double polarization observables. Already in 2000, the unpolarized VCS cross section was measured at MAMI. In this new experiment, we could confirm the old data and furthermore the double polarization observables were measured for the first time. The data were taken in five periods between 2005 and 2006. In this work, the data were analyzed to extract the cross section and the proton polarization. For the analysis, a maximum likelihood algorithm was developed together with the full simulation of all the analysis steps. The experiment is limited by the low statistics due mainly to the focal plane proton polarimeter efficiency. To overcome this problem, a new determination and parameterization of the carbon analyzing power was performed. The main result of the experiment is the extraction of a new combination of the generalized polarizabilities using the double polarization observables. (orig.)
Polarization observables in Virtual Compton Scattering
Virtual Compton Scattering (VCS) is an important reaction for understanding nucleon structure at low energies. By studying this process, the generalized polarizabilities of the nucleon can be measured. These observables are a generalization of the already known polarizabilities and will permit theoretical models to be challenged on a new level. More specifically, there exist six generalized polarizabilities and in order to disentangle them all, a double polarization experiment must be performed. Within this work, the VCS reaction p(e,e'p)γ was measured at MAMI using the A1 Collaboration three spectrometer setup with Q2=0.33 (GeV/c)2. Using the highly polarized MAMI beam and a recoil proton polarimeter, it was possible to measure both the VCS cross section and the double polarization observables. Already in 2000, the unpolarized VCS cross section was measured at MAMI. In this new experiment, we could confirm the old data and furthermore the double polarization observables were measured for the first time. The data were taken in five periods between 2005 and 2006. In this work, the data were analyzed to extract the cross section and the proton polarization. For the analysis, a maximum likelihood algorithm was developed together with the full simulation of all the analysis steps. The experiment is limited by the low statistics due mainly to the focal plane proton polarimeter efficiency. To overcome this problem, a new determination and parameterization of the carbon analyzing power was performed. The main result of the experiment is the extraction of a new combination of the generalized polarizabilities using the double polarization observables. (orig.)
Colour coherence in deep inelastic Compton scattering
MC simulation of Deep Inelastic Compton on proton - both QED and QCD - was performed on the basis of LUCIFER program for HERA energies. Charged hadron flow was calculated for string and independent fragmentation with different cuts on pt and x. It is shown that interjet colour coherence leads in the case of QCD Compton to the drag effects diminishing the hadron flow in the direction between quark jet and proton remnant jet. (orig.)
Colour coherence in deep inelastic Compton scattering
Lebedev, A.I.; Vazdik, J.A. (Lebedev Physical Inst., Academy of Sciences, Moscow (USSR))
1992-01-01
MC simulation of Deep Inelastic Compton on proton - both QED and QCD - was performed on the basis of LUCIFER program for HERA energies. Charged hadron flow was calculated for string and independent fragmentation with different cuts on p{sub t} and x. It is shown that interjet colour coherence leads in the case of QCD Compton to the drag effects diminishing the hadron flow in the direction between quark jet and proton remnant jet. (orig.).
Ultra-fast hybrid CPU-GPU multiple scatter simulation for 3-D PET.
Kim, Kyung Sang; Son, Young Don; Cho, Zang Hee; Ra, Jong Beom; Ye, Jong Chul
2014-01-01
Scatter correction is very important in 3-D PET reconstruction due to a large scatter contribution in measurements. Currently, one of the most popular methods is the so-called single scatter simulation (SSS), which considers single Compton scattering contributions from many randomly distributed scatter points. The SSS enables a fast calculation of scattering with a relatively high accuracy; however, the accuracy of SSS is dependent on the accuracy of tail fitting to find a correct scaling factor, which is often difficult in low photon count measurements. To overcome this drawback as well as to improve accuracy of scatter estimation by incorporating multiple scattering contribution, we propose a multiple scatter simulation (MSS) based on a simplified Monte Carlo (MC) simulation that considers photon migration and interactions due to photoelectric absorption and Compton scattering. Unlike the SSS, the MSS calculates a scaling factor by comparing simulated prompt data with the measured data in the whole volume, which enables a more robust estimation of a scaling factor. Even though the proposed MSS is based on MC, a significant acceleration of the computational time is possible by using a virtual detector array with a larger pitch by exploiting that the scatter distribution varies slowly in spatial domain. Furthermore, our MSS implementation is nicely fit to a parallel implementation using graphic processor unit (GPU). In particular, we exploit a hybrid CPU-GPU technique using the open multiprocessing and the compute unified device architecture, which results in 128.3 times faster than using a single CPU. Overall, the computational time of MSS is 9.4 s for a high-resolution research tomograph (HRRT) system. The performance of the proposed MSS is validated through actual experiments using an HRRT. PMID:24403412
Application of nondiffracting laser beam to laser compton scattering
Li, D; Aoki, M; Miyamoto, S; Amano, S; Mochizuki, T
2003-01-01
Nondiffracting laser beam - J sub 0 Bessel beam, is suggested to take the place of conventional Gaussian laser beam in a laser Compton scattering system, in order to increase the flux of scattered photons through maintaining an efficient interaction of electron beam and laser beam in a long distance. A novel cavity is proposed to produce and store the J sub 0 Bessel beam based on our present laser Compton scattering experimental setup for gamma-ray generation, and the propagation features and intensity distribution of the J sub 0 Bessel beam inside the cavity are analyzed. The flux of Compton scattering gamma-ray is estimated theoretically and the results reveal that a significant growth are accomplished with the use of J sub 0 Bessel laser beam contrasting with the use of Gaussian laser beam. (author)
Infrared phenomena in quantum electrodynamics : II. Bremsstrahlung and compton scattering
Haeringen, W. van
1960-01-01
The infrared aspects of quantum electrodynamics are discussed by treating two examples of scattering processes, bremsstrahlung and Compton scattering. As in the previous paper one uses a non-covariant diagram technique which gives very clear insight in the cancelling of infrared divergences between
Effect of spatial behavior of scatter on 3D PET
Jan, Meei-Ling; Pei, Cheng-Chih
1997-05-01
In 3D positron emission tomography (PET), all the coincidence events can be collected to increase the sensitivity of signal detection. However, the sensitivity increase results in the enlargement of scatter fraction which degrades image quality. For improving the accuracy of PET images, an effective scatter correction technique is necessary. In this paper, Monte Carlo simulations were done according to the system configuration of the animal PET design at the Institute of Nuclear Energy Research. From the simulation data we could understand what the scatter effect of our planned system will be. The convolution-subtraction method was chosen to correct for the scatter. A new approach to determine the scatter kernel function which could do better job on scatter correction will be presented.
Magnetic Compton scattering from HoFe2
The compound HoFe2 has been used to study both the nature and scope of magnetic Compton scattering investigations with circularly polarised synchrotron radiation. It has a large orbital-dominated moment on the holmium site which is antiferromagnetically coupled to the spin-dominated moment on the iron sites. Studies of the total intensity of the magnetic scattering as well as its spectral distribution at the Daresbury Synchrotron Source and the KEK Accumulation Ring have shown that, in contrast to diffraction studies, Compton scattering is uniquely sensitive to the spin moment. Detailed analysis of the magnetic Compton profile has determined the extent to which the individual moments, both spin and orbital in origin, can be deduced by combining the results with magnetisation data. (orig.)
Measurement of radiative Bhabha and quasi-real Compton scattering
Acciarri, M; Aguilar-Benítez, M; Ahlen, S P; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Ambrosi, G; Anderhub, H; Andreev, V P; Angelescu, T; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Baksay, L; Banerjee, S; Banerjee, Sw; Banicz, K; Barczyk, A; Barillère, R; Barone, L; Bartalini, P; Baschirotto, A; Basile, M; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Bhattacharya, S; Biasini, M; Biland, A; Bilei, G M; Blaising, J J; Blyth, S C; Bobbink, Gerjan J; Böck, R K; Böhm, A; Boldizsar, L; Borgia, B; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brigljevic, V; Brock, I C; Buffini, A; Buijs, A; Burger, J D; Burger, W J; Busenitz, J K; Cai, X D; Campanelli, M; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A M; Casaus, J; Castellini, G; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada-Canales, M; Cesaroni, F; Chamizo-Llatas, M; Chang, Y H; Chaturvedi, U K; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chéreau, X J; Chiefari, G; Chien, C Y; Cifarelli, Luisa; Cindolo, F; Civinini, C; Clare, I; Clare, R; Coignet, G; Colijn, A P; Colino, N; Costantini, S; Cotorobai, F; de la Cruz, B; Csilling, Akos; Dai, T S; D'Alessandro, R; De Asmundis, R; Degré, A; Deiters, K; Della Volpe, D; Denes, P; De Notaristefani, F; Diemoz, M; Van Dierendonck, D N; Di Lodovico, F; Dionisi, C; Dittmar, Michael; Dominguez, A; Doria, A; Dova, M T; Duchesneau, D; Duinker, P; Durán, I; Easo, S; El-Mamouni, H; Engler, A; Eppling, F J; Erné, F C; Ernenwein, J P; Extermann, Pierre; Fabre, M; Faccini, R; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, Marta; Ferguson, T; Ferroni, F; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, Frank; Fisher, P H; Fisk, I; Forconi, G; Fredj, L; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gau, S S; Gentile, S; Gheordanescu, N; Giagu, S; Goldfarb, S; Goldstein, J; Gong, Z F; Gougas, Andreas; Gratta, Giorgio; Grünewald, M W; van Gulik, R; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hartmann, B; Hasan, A; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hidas, P; Hirschfelder, J; Van Hoek, W C; Hofer, H; Hoorani, H; Hou, S R; Hu, G; Iashvili, I; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kasser, A; Khan, R A; Kamrad, D; Kapustinsky, J S; Karyotakis, Yu; Kaur, M; Kienzle-Focacci, M N; Kim, D; Kim, D H; Kim, J K; Kim, S C; Kinnison, W W; Kirkby, A; Kirkby, D; Kirkby, Jasper; Kiss, D; Kittel, E W; Klimentov, A; König, A C; Kopp, A; Korolko, I; Koutsenko, V F; Krämer, R W; Krenz, W; Kunin, A; Lacentre, P E; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lapoint, C; Lassila-Perini, K M; Laurikainen, P; Lavorato, A; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Lee, H J; Le Goff, J M; Leiste, R; Leonardi, E; Levchenko, P M; Li Chuan; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lu, W; Lü, Y S; Lübelsmeyer, K; Luci, C; Luckey, D; Luminari, L; Lustermann, W; Ma Wen Gan; Maity, M; Majumder, G; Malgeri, L; Malinin, A; Maña, C; Mangeol, D J J; Marchesini, P A; Marian, G; Marin, A; Martin, J P; Marzano, F; Massaro, G G G; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Von der Mey, M; Migani, D; Mihul, A; Van Mil, A J W; Milcent, H; Mirabelli, G; Mnich, J; Molnár, P; Monteleoni, B; Moore, R; Moulik, T; Mount, R; Muheim, F; Muijs, A J M; Nahn, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Niessen, T; Nippe, A; Nisati, A; Nowak, H; Oh, Yu D; Organtini, G; Ostonen, R; Palit, S; Palomares, C; Pandoulas, D; Paoletti, S; Paolucci, P; Park, H K; Park, I H; Pascale, G; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Peach, D; Pei, Y J; Pensotti, S; Perret-Gallix, D; Petersen, B; Petrak, S; Pevsner, A; Piccolo, D; Pieri, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Postema, H; Pothier, J; Produit, N; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Raja, N; Rancoita, P G; Rattaggi, M; Raven, G; Razis, P A; Ren, D; Rescigno, M; Reucroft, S; Van Rhee, T; Riemann, S; Riles, K; Robohm, A; Rodin, J; Roe, B P; Romero, L; Rosier-Lees, S; Roth, S; Rubio, Juan Antonio; Ruschmeier, D; Rykaczewski, H; Sakar, S; Salicio, J; Sánchez, E; Sanders, M P; Sarakinos, M E; Schäfer, C; Shchegelskii, V; Schmidt-Kärst, S; Schmitz, D; Scholz, N; Schopper, Herwig Franz; Schotanus, D J; Schwenke, J; Schwering, G; Sciacca, C; Sciarrino, D; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shukla, J; Shumilov, E; Shvorob, A V; Siedenburg, T; Son, D; Smith, B; Spillantini, P; Steuer, M; Stickland, D P; Stone, A; Stone, H; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Susinno, G F; Suter, H; Swain, J D; Tang, X W; Tauscher, Ludwig; Taylor, L; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Uchida, Y; Ulbricht, J; Valente, E; Vesztergombi, G; Vetlitskii, I; Viertel, Gert M; Vivargent, M; Vlachos, S; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Vorvolakos, A; Wadhwa, M; Wallraff, W; Wang, J C; Wang, X L; Wang, Z M; Weber, A; Wu, S X; Wynhoff, S; Xu, J; Xu, Z Z; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Ye, J B; Yeh, S C; You, J M; Zalite, A; Zalite, Yu; Zemp, P; Zeng, Y; Zhang, Z P; Zhou, B; Zhu, G Y; Zhu, R Y; Zichichi, Antonino; Ziegler, F; Zilizi, G
1998-01-01
We report on a study of radiative Bhabha and quasi-real Compton scattering at centre-of-mass energies between 50~{\\GeV} and 170~{\\GeV} and 20~{\\GeV} and 140~{\\GeV}, respectively, using the L3 detector at LEP. The analysis is based on data corresponding to an integrated luminosity of $232.2 \\,\\pb$. A total of 2856 radiative Bhabha and 4641 Compton scattering events are collected. Total and differential cross sections for both reactions are presented and found to be in good agreement with QED expectations. Our measurement of Compton scattering at the highest energies obtained so far is used to derive exclusion limits on the coupling $\\lambda$ for the on-shell production of an excited electron $\\e^{\\star}$ decaying into a $\\gamma\\e$ pair in the mass range $20 \\gev < m_{\\e^{\\star}} < 170 \\gev$.
Compton scattering off the deuteron at low and intermediate energies
Compton scattering off the deuteron is studied for photon energies up to about 100 MeV. This energy limit reflects the fact that only intermediate nucleon-nucleon (NN) states are considered. The NN propagator is constructed in a separable potential model, the parameters of which are fitted to describe the experimental NN scattering phase shifts. The problem of gauge invariance of the Compton amplitude is analyzed and the role of nonlocal currents is discussed. The low-energy theorem is satisfied. Our approach enables a direct calculation of both the real and imaginary part of the Compton scattering amplitude. It turns out that the strongest multipoles are dominated by the Born terms. Numerical results are compared to a previous dispersion theoretical calculation, and we find a strong disagreement between both calculations. We are led to conclude that certain assumptions made in the dispersion theoretical calculation are not justified
Rosseland and flux mean opacities for Compton scattering
Poutanen, Juri
2016-01-01
Rosseland mean opacity plays an important role in theories of stellar evolution and X-ray burst models. In the high-temperature regime, when most of the gas is completely ionized, the opacity is dominated by Compton scattering. Our aim here is to critically evaluate previous works on this subject and to compute exact Rosseland mean opacity for Compton scattering in a broad range of temperatures and electron degeneracy parameter. We use relativistic kinetic equations for Compton scattering and compute the photon mean free path as a function of photon energy by solving the corresponding integral equation in the diffusion limit. As a byproduct we also demonstrate the way to compute photon redistribution functions in case of degenerate electrons. We then compute the Rosseland mean opacity as a function of temperature and electron degeneracy. We compare our results to the previous calculations and find a significant difference in the low-temperature regime and strong degeneracy. We find useful analytical expressio...
Nonlinear single Compton scattering of an electron wave-packet
Angioi, A; Di Piazza, A
2016-01-01
In the presence of a sufficiently intense electromagnetic laser field, an electron can absorb on average a large number of photons from the laser and emit a high-energy one (nonlinear single Compton scattering). The case of nonlinear single Compton scattering by an electron with definite initial momentum has been thoroughly investigated in the literature. Here, we consider a more general initial state of the electron and use a wave-packet obtained as a superposition of Volkov wave functions. In particular, we investigate the energy spectrum of the emitted radiation at fixed observation direction and show that in typical experimental situations the sharply peaked structure of nonlinear single Compton scattering spectra of an electron with definite initial energy is almost completely washed out. Moreover, we show that at comparable uncertainties, the one in the momentum of the incoming electron has a larger impact on the photon spectra at a fixed observation direction than the one on the laser frequency, relate...
Compton Scattering from Bulk and Surface of Water
Wang, Wenjie; Kuzmenko, Ivan; Vaknin, David
2014-03-01
Elastic and Compton scattering at grazing angle X-ray incidence from water show distinct behaviors below and above the critical angle for total reflections suggesting surface restructuring of the water surface. Using X-ray synchrotron radiation in reflectivity mode, we collect the Thomson and Compton scattering signals with energy dispersive detector at various angles near the normal to surface as a function of the angle of incidence. Analysis of the ratio between the Thomson and Compton intensity above the critical angle (which mainly probes bulk water) is a constant as expected from incoherent scattering from single water molecule, whereas the signal from the surface shows strong angular dependence on the incident angle. Although we do not fully understand the phenomena, we attribute the observation to more organized water at the interface. Ames Laboratory, DOE under contract No. DE-AC02-07CH11358 and Advanced Photon Source, DOE under contract No. DE-AC02-06CH11357.
Multiple scattering Compton camera with neutron activation for material inspection
We designed a multiple scattering Compton camera (MSCC) based on a lanthanum bromide (LaBr3:Ce) scintillator to detect neutron-activated prompt gamma-rays for material inspection. The system parameters such as detector thickness and inter-detector distances were optimized on the basis of figure of merit (FOM). The FOM was maximized when the inter-detector distance and detector thickness were 18 cm and 1.5 cm, respectively. Under the optimized conditions, energy spectra and spatial images were obtained to identify various substances, and the results matched well with theoretical data. The probability of multiple Compton scattering was higher than that of conventional Compton scattering at high energies (~MeV), which proved the effectiveness of MSCC to detect prompt gamma-rays. Simulations with realistic conditions showed the feasibility of using the MSCC investigate of materials in field applications
Photon Polarization in Photonic Crystal Fibers under Compton Scattering
HAO Dong-shan; ZHANG Xiao-fu
2007-01-01
Using the quantum invariant theory and unitary transformation means, we study the influences of multi-photon nonlinear Compton scattering on the photon polarization in photonic crystal fibers(PCF). The results show that the photon polarization of the incident photon changes a lot due to scattered optical, and its general geometric phase factor, Hamiton number and evolution operator are definited both by the incident and scattered optical.
Spin and orbital magnetization loops obtained using magnetic Compton scattering
We present an application of magnetic Compton scattering (MCS) to decompose a total magnetization loop into spin and orbital magnetization contributions. A spin magnetization loop of SmAl2 was measured by recording the intensity of magnetic Compton scattering as a function of applied magnetic field. Comparing the spin magnetization loop with the total magnetization one measured by a vibrating sample magnetometer, the orbital magnetization loop was obtained. The data display an anti-coupled behavior between the spin and orbital magnetizations and confirm that the orbital part dominates the magnetization.
Compton scatter imaging: A tool for historical exploration.
Harding, G; Harding, E
2010-06-01
This review discusses the principles and technological realisation of a technique, termed Compton scatter imaging (CSI), which is based on spatially resolved detection of Compton scattered X-rays. The applicational focus of this review is to objects of historical interest. Following a historical survey of CSI, a description is given of the major characteristics of Compton X-ray scatter. In particular back-scattered X-rays allow massive objects to be imaged, which would otherwise be too absorbing for the conventional transmission X-ray technique. The ComScan (an acronym for Compton scatter scanner) is a commercially available backscatter imaging system, which is discussed here in some detail. ComScan images from some artefacts of historical interest, namely a fresco, an Egyptian mummy and a mediaeval clasp are presented and their use in historical analysis is indicated. The utility of scientific and technical advance for not only exploring history, but also restoring it, is briefly discussed. PMID:20138773
Nonlinear effects in Compton scattering at photon colliders
Galynskii, M; Levchuk, M I; Telnov, Valery I
2001-01-01
The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e-> gamma conversion the density of laser photons in the conversion region should be so high that simultaneous interaction of one electron with several laser photons is possible (nonlinear Compton effect). In this paper, a detailed consideration of energy spectra, helicities of final photons and electrons in nonlinear backward Compton scattering of circularly polarized laser photons is given. Distributions of gamma gamma luminosities with total helicities 0 and 2 are investigated. Very high intensity of laser wave leads to broadening of the energy (luminosity) spectra and shift to lower energies (invariant masses). Beside complicated exact formulae, approximate formulae for energy spectrum and polarization of backscattered photons are given for relatively small nonlinear parameter xi sup 2 (first order correction). All this is necessary for optimization of the conversion region at photo...
Nonlinear effects in Compton scattering at photon colliders
Galynsky, M V; Levchuk, M I; Telnov, V I
2001-01-01
The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e->gamma conversion the density of laser photons in the conversion region should be so high that simultaneous interaction of one electron with several laser photons is possible (nonlinear Compton effect). In this paper a detailed consideration of energy spectra, helicities of final photons and electrons in nonlinear backward Compton scattering of circularly polarized laser photons is given. Distributions of gamma-gamma luminosities with total helicities 0 and 2 are investigated. Very high intensity of laser wave leads to broadening of the energy (luminosity) spectra and shift to lower energies (invariant masses). Beside complicated exact formulae, approximate formulae for energy spectrum and polarization of backscattered photons are given for relatively small nonlinear parameter xi^2 (first order correction). All this is necessary for optimization of the conversion region at photon coll...
Unified ab initio treatment of attosecond photoionization and Compton scattering
We present a new theoretical approach to attosecond laser-assisted photo- and Compton ionization. Attosecond x-ray absorption and scattering are described by S-circumflex(1,2)-matrices, which are coherent superpositions of 'monochromatic' S-circumflex(1,2)-matrices in a laser-modified Furry representation. Besides refining the existing theory of the soft x-ray photoelectron attosecond streak camera and spectral phase interferometry (ASC and ASPI), we formulate a theory of hard x-ray photoelectron and Compton ASC and ASPI. The resulting scheme has a simple structure and leads to closed-form expressions for ionization amplitudes. We investigate Compton electron interference in the separable Coulomb-Volkov continuum with both Coulomb and laser fields treated non-perturbatively. We find that at laser-field intensities below 1013 Wcm-2 normalized Compton lines almost coincide with the lines obtained in the laser-free regime. At higher intensities, attosecond interferences survive integration over electron momenta, and feature prominently in the Compton lines themselves. We define a regime where the electron ground-state density can be measured with controllable accuracy in an attosecond time interval. The new theory provides a firm basis for extracting photo- and Compton electron phases and atomic and molecular wavefunctions from experimental data.
Kataoka, J., E-mail: kataoka.jun@waseda.jp [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Kishimoto, A.; Nishiyama, T.; Fujita, T.; Takeuchi, K.; Kato, T.; Nakamori, T. [Research Institute for Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555 (Japan); Ohsuka, S. [Central Research Laboratory, Hamamatsu Photonics K.K., 5000, Hirakuchi, Hamakita-ku, Hamamatsu, Shizuoka (Japan); Nakamura, S.; Hirayanagi, M.; Adachi, S.; Uchiyama, T.; Yamamoto, K. [Solid State Division, Hamamatsu Photonics K.K., 1126-1, Ichino-cho, Higashi-ku, Hamamatsu, Shizuoka (Japan)
2013-12-21
The release of radioactive isotopes (mainly {sup 137}Cs, {sup 134}Cs and {sup 131}I) from the crippled Fukushima Daiichi Nuclear Plant remains a serious problem in Japan. To help identify radiation hotspots and ensure effective decontamination operation, we are developing a novel Compton camera weighting only 1 kg and measuring just ∼10cm{sup 2} in size. Despite its compactness, the camera realizes a wide 180° field of vision with a sensitivity about 50 times superior to other cameras being tested in Fukushima. We expect that a hotspot producing a 5μSv/h dose at a distance of 3 m can be imaged every 10 s, with angular resolution better than 10° (FWHM). The 3D position-sensitive scintillators and thin monolithic MPPC arrays are the key technologies developed here. By measuring the pulse-height ratio of MPPC-arrays coupled at both ends of a Ce:GAGG scintillator block, the depth of interaction (DOI) is obtained for incident gamma rays as well as the usual 2D positions, with accuracy better than 2 mm. By using two identical 10 mm cubic Ce:GAGG scintillators as a scatterer and an absorber, we confirmed that the 3D configuration works well as a high-resolution gamma camera, and also works as spectrometer achieving typical energy resolution of 9.8% (FWHM) for 662 keV gamma rays. We present the current status of the prototype camera (weighting 1.5 kg and measuring 8.5×14×16 cm{sup 3} in size) being fabricated by Hamamatsu Photonics K.K. Although the camera still operates in non-DOI mode, angular resolution as high as 14° (FWHM) was achieved with an integration time of 30 s for the assumed hotspot described above. -- Highlights: •We are developing a novel Compton camera weighting only 1 kg and measuring just ∼10×10 cm{sup 2} in size. •The camera realizes a wide 180° field of vision with a sensitivity about 50 times superior to other cameras being tested in Fukushima. •The depth of interaction (DOI) is obtained for incident gamma rays as well as the usual 2
The release of radioactive isotopes (mainly 137Cs, 134Cs and 131I) from the crippled Fukushima Daiichi Nuclear Plant remains a serious problem in Japan. To help identify radiation hotspots and ensure effective decontamination operation, we are developing a novel Compton camera weighting only 1 kg and measuring just ∼10cm2 in size. Despite its compactness, the camera realizes a wide 180° field of vision with a sensitivity about 50 times superior to other cameras being tested in Fukushima. We expect that a hotspot producing a 5μSv/h dose at a distance of 3 m can be imaged every 10 s, with angular resolution better than 10° (FWHM). The 3D position-sensitive scintillators and thin monolithic MPPC arrays are the key technologies developed here. By measuring the pulse-height ratio of MPPC-arrays coupled at both ends of a Ce:GAGG scintillator block, the depth of interaction (DOI) is obtained for incident gamma rays as well as the usual 2D positions, with accuracy better than 2 mm. By using two identical 10 mm cubic Ce:GAGG scintillators as a scatterer and an absorber, we confirmed that the 3D configuration works well as a high-resolution gamma camera, and also works as spectrometer achieving typical energy resolution of 9.8% (FWHM) for 662 keV gamma rays. We present the current status of the prototype camera (weighting 1.5 kg and measuring 8.5×14×16 cm3 in size) being fabricated by Hamamatsu Photonics K.K. Although the camera still operates in non-DOI mode, angular resolution as high as 14° (FWHM) was achieved with an integration time of 30 s for the assumed hotspot described above. -- Highlights: •We are developing a novel Compton camera weighting only 1 kg and measuring just ∼10×10 cm2 in size. •The camera realizes a wide 180° field of vision with a sensitivity about 50 times superior to other cameras being tested in Fukushima. •The depth of interaction (DOI) is obtained for incident gamma rays as well as the usual 2D positions. •We present the
On the inverse Compton scattering model of radio pulsars
Qiao, G J; Liu Jian Fei; Han, J L; Zhang, B
2000-01-01
Some characteristics of the inverse Compton scattering (ICS) model are reviewed. At least the following properties of radio pulsars can be reproduced in the model: core or central emission beam, one or two hollow emission cones, different emission heights of these components, diverse pulse profiles at various frequencies, linear and circular polarization features of core and cones.
New JLab/Hall A Deeply Virtual Compton Scattering results
Defurne, Maxime [CEA, Centre de Saclay, IRFU/SPhN/LSN, F-91191 Gif-sur-Yvette, France
2015-08-01
New data points for unpolarized Deeply Virtual Compton Scattering cross sections have been extracted from the E00-110 experiment at Q^{2}=1.9 GeV^{2} effectively doubling the statistics available in the valence region. A careful study of systematic uncertainties has been performed.
Simulating Compton scattering using Monte Carlo method: COSMOC library
Adámek, K.; Bursa, Michal
Opava: Silesian University, 2014 - (Stuchlík, Z.), s. 1-10. (Publications of the Institute of Physics. 7). ISBN 9788075101266. ISSN 2336-5668. [RAGtime /14.-16./. Opava (CZ), 18.09. 2012 -22.09. 2012 ] Institutional support: RVO:67985815 Keywords : Monte Carlo * Compton scattering * C++ Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics
Study of Compton Broadening Due to Electron-Photon Scattering
Srinivasa Rao, M.
2010-06-01
Full Text Available We have investigated the effects of Compton broadening due to electron-photon scattering in hot stellar atmospheres. A purely electron-photon scattering media is assumed to have plane parallel geometry with an input radiation field localized on one side of the slab. The method is based on the discrete space theory of radiative transfer for the intensity of emitted radiation.The solution is developed to study the importance of scattering of radiation by free electrons in high temperature stellar atmospheres which produces a brodening and shift in spectral lines because of the Compton effect and the Doppler effect arising from mass and thermal motions of scattering electrons.It is noticed that the Comptonized spectrum depends on three parameters: the optical depth of the medium, the temperature of the thermal electrons and the viewing angle.We also showed that the Compton effect produces red shift and asymmetry in the line. These two effects increase as the optical depth increases. It is also noticed that the emergent specific intensities become completely asymmetric for higher optical depths.
Pion photoproduction and compton scattering at Saskatoon (SAL)
I focus on three photoproduction problems, namely the behavior of E0+ just above the π0 threshold in the proton and 3He, and near-threshold π+ production from the proton. Finally, I describe part of the Compton scattering program at SAL. (orig.)
Correction for Compton scattering in glassy-carbon diffraction patterns
In a preliminary investigation reported here, it has been found that the use of Co-Ni balanced filters not only provide better monochromatization of CuKα, but is quite suitable for determining the incoherent (Compton) scattering in two Glassy-Carbon (GC) samples
Kataoka, J.; Kishimoto, A.; Nishiyama, T.; Fujita, T.; Takeuchi, K.; Kato, T.; Nakamori, T.; Ohsuka, S.; Nakamura, S.; Hirayanagi, M.; Adachi, S.; Uchiyama, T.; Yamamoto, K.
2013-12-01
The release of radioactive isotopes (mainly 137Cs, 134Cs and 131I) from the crippled Fukushima Daiichi Nuclear Plant remains a serious problem in Japan. To help identify radiation hotspots and ensure effective decontamination operation, we are developing a novel Compton camera weighting only 1 kg and measuring just ∼10 cm2 in size. Despite its compactness, the camera realizes a wide 180° field of vision with a sensitivity about 50 times superior to other cameras being tested in Fukushima. We expect that a hotspot producing a 5 μSv/h dose at a distance of 3 m can be imaged every 10 s, with angular resolution better than 10° (FWHM). The 3D position-sensitive scintillators and thin monolithic MPPC arrays are the key technologies developed here. By measuring the pulse-height ratio of MPPC-arrays coupled at both ends of a Ce:GAGG scintillator block, the depth of interaction (DOI) is obtained for incident gamma rays as well as the usual 2D positions, with accuracy better than 2 mm. By using two identical 10 mm cubic Ce:GAGG scintillators as a scatterer and an absorber, we confirmed that the 3D configuration works well as a high-resolution gamma camera, and also works as spectrometer achieving typical energy resolution of 9.8% (FWHM) for 662 keV gamma rays. We present the current status of the prototype camera (weighting 1.5 kg and measuring 8.5×14×16 cm3 in size) being fabricated by Hamamatsu Photonics K.K. Although the camera still operates in non-DOI mode, angular resolution as high as 14° (FWHM) was achieved with an integration time of 30 s for the assumed hotspot described above.
The electromagnetic calorimeter in JLab Real Compton Scattering Experiment
Albert Shahinyan; Eugene Chudakov; A. Danagoulian; P. Degtyarenko; K. Egiyan; V. Gorbenko; J. Hines; E. Hovhannisyan; Ch. Hyde; C.W. de Jager; A. Ketikyan; V. Mamyan; R. Michaels; A.M. Nathan; V. Nelyubin; I. Rachek; M. Roedelbrom; A. Petrosyan; R. Pomatsalyuk; V. Popov; J. Segal; Yu. Shestakov; J. Templon; H. Voskanyan; B. Wojtsekhowski
2007-04-16
A hodoscope calorimeter comprising of 704 lead-glass blocks is described. The calorimeter was constructed for use in the JLab Real Compton Scattering experiment. The detector provides a measurement of the coordinates and the energy of scattered photons in the GeV energy range with resolutions of 5 mm and 6\\%/$\\sqrt{E_\\gamma \\, [GeV]}$, respectively. Design features and performance parameters during the experiment are presented.
Investigating Neutron Polarizabilities through Compton Scattering on $^3He$
Choudhury, D.; Nogga, A.; Phillips, D.R.
2007-01-01
We examine manifestations of neutron electromagnetic polarizabilities in coherent Compton scattering from the Helium-3 nucleus. We calculate $\\gamma ^3He$ elastic scattering observables using chiral perturbation theory to next-to-leading order (${\\mathcal O}(e^2 Q)$). We find that the unpolarized differential cross section can be used to measure neutron electric and magnetic polarizabilities, while two double-polarization observables are sensitive to different linear combinations of the four ...
Compton Scattering and Photo-absorption Sum Rules on Nuclei
Gorchtein, Mikhail; Hobbs, Timothy; Londergan, J. Timothy; Szczepaniak, Adam P.
2011-01-01
We revisit the photo-absorption sum rule for real Compton scattering from the proton and from nuclear targets. In analogy with the Thomas-Reiche-Kuhn sum rule appropriate at low energies, we propose a new "constituent quark model" sum rule that relates the integrated strength of hadronic resonances to the scattering amplitude on constituent quarks. We study the constituent quark model sum rule for several nuclear targets. In addition we extract the $\\alpha=0$ pole contribution for both proton...
Design of a Compton scatter based radiation tracking system
Healy, Heather
Gamma spectroscopy is one of the most common techniques used for the detection of radiologic materials. This technology is deployed in a variety of scenarios such as emergency response, monitoring, and the recovery of lost, stolen, or otherwise unaccounted radiologic material. In most practical scenarios, it is useful to know the location of a source in relation to a detector, in addition to the classic output from gamma spectrometers such as decay rate and energy peak information. In collaboration with the Remote Sensing Laboratory (RSL) at Andrews Air Force Base, a novel detector design by RSL, which utilizes a 360° detectable range in order to increase the probability of remote detection, was investigated for the possibility to recreate source location information from Compton scattering events within the detector. A recreation of this novel detector is simulated using Geant4 to determine the optimal dimensions of sodium iodide detectors that produce the most single Compton scattering events in order to facilitate source location through the back-projection of Compton scattering angles. The optimal detector dimensions are determined by maximizing the number of single Compton scatter events and minimizing the percentage of Compton events that undergo multiple successive scatters in detectors of varying thicknesses and lengths. The optimal detector thickness was chosen to be 1.88 in, and the optimal detector length was chosen to be 4 to 4.5 in. In future projects, these optimized detectors can be used to apply suggested back-projection algorithms in order to determine the feasibility and functionality of this detector design for the purpose of radiologic source location.
Generalized Parton Distributions from Deeply Virtual Compton Scattering at HERMES
Guidal, M
2009-01-01
The HERMES collaboration has recently published a set of (correlated) beam charge, beam spin and target spin relative asymmetries for the Deeply Virtual Compton Scattering process. This reaction allows in principle to access the Generalized Parton Distributions of the nucleon. We have fitted, in the QCD leading-order and leading-twist handbag approximation, but in a model independent way, this set of data and we report our results for the extracted Compton Form Factors. In particular, we are able to extract constrains on the $H$ GPD.
Generalized parton distributions from deeply virtual compton scattering at HERMES
Guidal, M. [Institut de Physique Nucleaire d' Orsay, Orsay (France); Moutarde, H. [Service de Physique Nucleaire, CEA Saclay, Gif-Sur-Yvette (France)
2009-10-15
The HERMES Collaboration has recently published a set of (correlated) beam charge, beam spin and target spin asymmetries for the Deeply Virtual Compton Scattering (DVCS) process. This reaction allows in principle to access the generalized parton distributions (GPDs) of the nucleon. We have fitted, in the QCD leading-order and leading-twist handbag approximation, but in a model-independent way, this set of data and we report our results for the extracted Compton form factors. In particular, we are able to extract constrains on the H GPD. (orig.)
Novel approach to stationary transmission scanning using Compton scattered radiation
Transmission scanning-based estimation of the attenuation map plays a crucial role in quantitative radionuclide imaging. X-ray computed tomography (CT) reconstructs directly the attenuation coefficients map from data transmitted through the object. This paper proposes an alternative route for reconstructing the object attenuation map by exploiting Compton scatter of transmitted radiation from an externally placed radionuclide source. In contrast to conventional procedures, data acquisition is realized as a series of images parameterized by the Compton scattering angle and registered on a stationary gamma camera operating without spatial displacement. Numerical simulation results using realistic voxel-based phantoms are presented to illustrate the efficiency of this new transmission scanning approach for attenuation map reconstruction. The encouraging results presented in this paper may suggest the possibility of proposing a new concept for emission/transmission imaging using scattered radiation, which has many advantages compared to conventional technologies
Gamma-ray burst polarization via Compton scattering process
Chang, Zhe; Jiang, Yunguo
2014-01-01
Synchrotron radiation and Compton scattering are widely accepted as the most likely emission mechanisms of some astrophysical phenomena, such as gamma-ray bursts (GRBs) and active galactic nuclei (AGNs). The measurement on polarization of photons provides a useful tool to distinguish different emission mechanisms and structures of the emission region. Based on the differential cross section of a polarized photon scattered by an unpolarized electron of any initial momentum, we derive analytical formula of polarization for beamed photons scattered by isotropic electrons with a power law distribution. Numerical calculations are carried out in four special cases: electrons at rest, Thomson limit, head-on collision and monochromatic electrons. It is found that the maximum polarization can be as high as $100\\%$ for low energy photons, if the electrons are at rest. Although polarization is highly suppressed due to the isotropic electrons, a maximum value of $\\sim 10\\% - 20\\%$ can still be achieved. Compton scatterin...
Timelike Compton Scattering from JLAB to RHIC and LHC energies
Pire, B; Wagner, J
2012-01-01
Timelike Compton scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass nicely complements the already successful experimental study of deeply virtual Compton scattering (DVCS). The same Generalized Parton Distributions enter both amplitudes, which offer a promissing way to access the quark and gluon nucleon structure. We review recent progress in this domain, emphasizing the fact that analyticity and factorization properties dictate the relation of the NLO corrections to TCS to those of DVCS. We also stress that data on TCS at high energy should be available soon thanks to the proposed experimental program at JLab at 12 GeV, and that, before the future high energy electron ion colliders become reality, the study of ultraperipheral collisions at the RHIC and LHC may open a window on quark and gluon GPDs at very small skewness. .
Nucleon Polarizabilities: from Compton Scattering to Hydrogen Atom
Hagelstein, Franziska; Pascalutsa, Vladimir
2015-01-01
We review the current state of knowledge of the nucleon polarizabilities and of their role in nucleon Compton scattering and in hydrogen spectrum. We discuss the basic concepts, the recent lattice QCD calculations and advances in chiral effective-field theory. On the experimental side, we review the ongoing programs aimed to measure the nucleon (scalar and spin) polarizabilities via the Compton scattering processes, with real and virtual photons. A great part of the review is devoted to the general constraints based on unitarity, causality, discrete and continuous symmetries, which result in model-independent relations involving nucleon polarizabilities. We (re-)derive a variety of such relations and discuss their empirical value. The proton polarizability effects are presently the major sources of uncertainty in the assessment of the muonic hydrogen Lamb shift and hyperfine structure. Recent calculations of these effects are reviewed here in the context of the "proton-radius puzzle". We conclude with summary...
Model independent dispersion approach to proton Compton scattering
The proton Compton scattering at low and intermediate energies is studied by means of a dispersion framework which exploits in an optimal way the (fixed momentum transfer) analyticity properties of the amplitudes in conjunction with the consequences of the (s-channel) unitarity. The mathematical background of the work consists of methods specific to boundary value problems for analytic vector-valued functions and interpolation theory. In comparison with previous related work, the external problems to be solved now are much more difficult because of the inclusion of the photoproduction input and also lead to additional computational complications. The lower bounds on the differential cross-section, obtained without any reference to subtractions and annihilation channel contributions, appear sufficiently restrictive to evidentiate rigorously some inconsistencies between results of single pion photoproduction multipole extractions and proton Compton scattering data. (author)
Precise polarization measurements via detection of compton scattered electrons
The Qweak experiment at Jefferson Lab aims to make a 4% measurement of the parity-violating asymmetry in elastic scattering at very low Q2 of a longitudinally polarized electron beam off a proton target. One of the dominant experimental systematic uncertainties in Qweak will result from determining the beam polarization. A new Compton polarimeter was installed in the fall of 2010 to provide a non-invasive and continuous monitoring of the electron beam polarization in Hall C at Jefferson Lab. The Compton-scattered electrons are detected in four planes of diamond micro-strip detectors. We have achieved the design goals of <1% statistical uncertainty per hour and expect to achieve <1% systematic uncertainty
On timelike Compton scattering at medium and high energies
Pire, B; Wagner, J
2011-01-01
We emphasize the complementarity of timelike and spacelike studies of deep exclusive processes, taking as an example the case of timelike Compton Scattering (TCS) i.e. the exclusive photoproduction of a lepton pair with large invariant mass, vs deeply virtual Compton scattering (DVCS) i.e. the exclusive leptoproduction of a real photon. Both amplitudes factorize with the same generalized parton distributions (GPDs) as their soft parts and coefficient functions which differ significantly at next to leading order in alpha_s. We also stress that data on TCS at very high energy should be available soon thanks to the study of ultraperipheral collisions at the LHC, opening a window on quark and gluon GPDs at very small skewness.
COMPACT, TUNABLE COMPTON SCATTERING GAMMA-RAY SOURCES
Hartemann, F V; Albert, F; Anderson, G G; Anderson, S G; Bayramian, A J; Betts, S M; Chu, T S; Cross, R R; Ebbers, C A; Fisher, S E; Gibson, D J; Ladran, A S; Marsh, R A; Messerly, M J; O' Neill, K L; Semenov, V A; Shverdin, M Y; Siders, C W; McNabb, D P; Barty, C J; Vlieks, A E; Jongewaard, E N; Tantawi, S G; Raubenheimer, T O
2009-08-20
Recent progress in accelerator physics and laser technology have enabled the development of a new class of gamma-ray light sources based on Compton scattering between a high-brightness, relativistic electron beam and a high intensity laser pulse produced via chirped-pulse amplification (CPA). A precision, tunable gamma-ray source driven by a compact, high-gradient X-band linac is currently under development at LLNL. High-brightness, relativistic electron bunches produced by the linac interact with a Joule-class, 10 ps laser pulse to generate tunable {gamma}-rays in the 0.5-2.5 MeV photon energy range via Compton scattering. The source will be used to excite nuclear resonance fluorescence lines in various isotopes; applications include homeland security, stockpile science and surveillance, nuclear fuel assay, and waste imaging and assay. The source design, key parameters, and current status are presented.
Comparison between electron and neutron Compton scattering studies
Moreh, Raymond; Finkelstein, Yacov; Vos, Maarten
2015-05-01
We compare two techniques: Electron Compton Scattering (ECS) and neutron Compton scattering (NCS) and show that using certain incident energies, both can measure the atomic kinetic energy of atoms in molecules and solids. The information obtained is related to the Doppler broadening of nuclear levels and is very useful for deducing the widths of excited levels in many nuclei in self absorption measurements. A comparison between the atomic kinetic energies measured by the two methods on the same samples is made. Some results are also compared with calculated atomic kinetic energies obtained using the harmonic approximation where the vibrational frequencies were taken from IR/Raman optical measurements. The advantages of the ECS method are emphasized.
Comparison between electron and neutron Compton scattering studies
Moreh Raymond
2015-01-01
Full Text Available We compare two techniques: Electron Compton Scattering (ECS and neutron Compton scattering (NCS and show that using certain incident energies, both can measure the atomic kinetic energy of atoms in molecules and solids. The information obtained is related to the Doppler broadening of nuclear levels and is very useful for deducing the widths of excited levels in many nuclei in self absorption measurements. A comparison between the atomic kinetic energies measured by the two methods on the same samples is made. Some results are also compared with calculated atomic kinetic energies obtained using the harmonic approximation where the vibrational frequencies were taken from IR/Raman optical measurements. The advantages of the ECS method are emphasized.
Timelike Compton scattering off the neutron and generalized parton distributions
Boer, M.; Guidal, M. [CNRS-IN2P3, Universite Paris-Sud, Institut de Physique Nucleaire d' Orsay, Orsay (France); Vanderhaeghen, M. [Johannes Gutenberg Universitaet, Institut fuer Kernphysik and PRISMA Cluster of Excellence, Mainz (Germany)
2016-02-15
We study the exclusive photoproduction of an electron-positron pair on a neutron target in the Jefferson Lab energy domain. The reaction consists of two processes: the Bethe-Heitler and the Timelike Compton Scattering. The latter process provides potentially access to the Generalized Parton Distributions (GPDs) of the nucleon. We calculate all the unpolarized, single- and double-spin observables of the reaction and study their sensitivities to GPDs. (orig.)
The first dedicated virtual Compton Scattering Experiment at MAMI
We measured the absolute cross sections for photon electro-production off the proton, ep → epγ, with the high resolution spectrometers at MAMI at momentum transfer q = 600 MeV/c and photon polarization ε=0.62. We covered the momentum range for the outgoing real photon q' = 33/111 MeV/c. >From the extracted Virtual Compton Scattering amplitude we deduce values for two structure functions related to the generalized polarizabilities of the proton
Overview of Deeply Virtual Compton Scattering at HERMES
Murray, Morgan
2012-01-01
Deeply Virtual Compton Scattering represents the best experimental channel through which to understand Generalised Parton Distributions. The HERMES experiment measured the most diverse set of DVCS results of any experiment; this talk discusses the most recent sets of DVCS results released by HERMES and the unique experimental conditions found at HERMES that facilitated the measurements. We also examine the various ways in which the HERMES experimental measurements are being used to constrain GPDs and how future experiments can learn from the HERMES program.
Monte Carlo simulation of virtual Compton scattering below pion threshold
This paper describes the Monte Carlo simulation developed specifically for the Virtual Compton Scattering (VCS) experiments below pion threshold that have been performed at MAMI and JLab. This simulation generates events according to the (Bethe-Heitler + Born) cross-section behaviour and takes into account all relevant resolution-deteriorating effects. It determines the 'effective' solid angle for the various experimental settings which are used for the precise determination of the photon electroproduction absolute cross-section
Magnetic-Compton-scattering study of spin moments in UFe2
Spin moments were derived from the magnetic-Compton profile of UFe2, which was measured using 59.38-keV circularly polarized synchrotron radiation from the Accumulation Ring Source at KEK, Japan. Although the net moment on the uranium site is no more than a tenth of a Bohr magneton, the individual spin and orbital moments, which are coupled antiparallel, are much larger and it is the spin moment that can be determined in magnetic-Compton scattering. The data have been analyzed in terms of the U 5f, Fe 3d and delocalized spin moments. The observed uranium-5f spin moment is less than half (i.e., B) and the diffuse spin moment more than double (i.e., >0.20μB) those predicted from theory. These values compare favorably with those deduced from neutron measurements of the total magnetization. copyright 1997 The American Physical Society
Commissioning of a dual-phase Xenon TPC and first Compton scatter results
With the MainzTPC, a small 3D position-sensitive dual-phase xenon time projection chamber (TPC), we aim to measure the xenon response for low-energy recoils (few keV) with better precision than previous experiments. Furthermore the setup allows to study the liquid xenon scintillation pulse shape. The goal is to deepen the understanding of xenon as a detection material in the low-energy regime for Dark Matter searches. Here we report on the commissioning of the MainzTPC and first measurements, including scintillation and charge signals as well as coincidence signals between the TPC and a germanium detector for the Compton scattering.
Sokhan, Daria
Measurements of Deeply Virtual Compton Scattering (DVCS) give access to Generalised Parton Distributions (GPDs) which provide a 3D image of the nucleon and carry information on the composition of its spin. Data from both proton and neutron targets is highly desirable for an extraction of all GPDs and to allow their flavour-decomposition. Although a number of measurements have been made on proton targets, data on the neutron is almost non-existent. We present preliminary results in the extraction of beam-spin asymmetry in neutron DVCS from CLAS and the proposed experimental programme with CLAS12 at Jefferson Laboratory.
Measurements of Compton Scattered Transition Radiation at High Lorentz Factors
Case, G L; Cherry, M L; Isbert, J; Mitchell, J W; Patterson, D; Case, Gary L.; Cherry, Michael L.; Isbert, Joachim; Mitchell, John W.; Patterson, Donald
2004-01-01
X-ray transition radiation can be used to measure the Lorentz factor of relativistic particles. Standard transition radiation detectors (TRDs) typically incorporate thin plastic foil radiators and gas-filled x-ray detectors, and are sensitive up to \\gamma ~ 10^4. To reach higher Lorentz factors (up to \\gamma ~ 10^5), thicker, denser radiators can be used, which consequently produce x-rays of harder energies (>100 keV). At these energies, scintillator detectors are more efficient in detecting the hard x-rays, and Compton scattering of the x-rays out of the path of the particle becomes an important effect. The Compton scattering can be utilized to separate the transition radiation from the ionization background spatially. The use of conducting metal foils is predicted to yield enhanced signals compared to standard nonconducting plastic foils of the same dimensions. We have designed and built a Compton Scatter TRD optimized for high Lorentz factors and exposed it to high energy electrons at the CERN SPS. We pres...
SPECT Compton-scattering correction by analysis of energy spectra.
Koral, K F; Wang, X Q; Rogers, W L; Clinthorne, N H; Wang, X H
1988-02-01
The hypothesis that energy spectra at individual spatial locations in single photon emission computed tomographic projection images can be analyzed to separate the Compton-scattered component from the unscattered component is tested indirectly. An axially symmetric phantom consisting of a cylinder with a sphere is imaged with either the cylinder or the sphere containing 99mTc. An iterative peak-erosion algorithm and a fitting algorithm are given and employed to analyze the acquired spectra. Adequate separation into an unscattered component and a Compton-scattered component is judged on the basis of filtered-backprojection reconstruction of corrected projections. In the reconstructions, attenuation correction is based on the known geometry and the total attenuation cross section for water. An independent test of the accuracy of separation is not made. For both algorithms, reconstructed slices for the cold-sphere, hot-surround phantom have the correct shape as confirmed by simulation results that take into account the measured dependence of system resolution on depth. For the inverse phantom, a hot sphere in a cold surround, quantitative results with the fitting algorithm are accurate but with a particular number of iterations of the erosion algorithm are less good. (A greater number of iterations would improve the 26% error with the algorithm, however.) These preliminary results encourage us to believe that a method for correcting for Compton-scattering in a wide variety of objects can be found, thus helping to achieve quantitative SPECT. PMID:3258023
Materials characterization in petroleum pipeline using Compton Scattering technique
Gouveia, M. A. G.; Lopes, R. T.; de Jesus, E. F. O.; Camerini, C. S.
2003-06-01
In this paper Compton Scattering technique is analyzed as a possible tool for the characterization of materials inside draining petroleum pipelines. The study was accomplished in laboratory scale, so the results should be analyzed to conclude if the system could be used in the field. The system used was composed of two detectors aligned by a Ce-137 source forming an angle of 90° with the detectors line (662 keV—direct beam, and 288 keV—scattered beam). The results obtained show the capability of the system for the characterization of materials like sand, paraffin and water inside pipelines.
Polarisation Transfer in Proton Compton Scattering at High Momentum Transfer
Hamilton, David
2004-12-31
The Jefferson Lab Hall A experiment E99-114 comprised a series of measurements to explore proton Compton scattering at high momentum transfer. For the first time, the polarisation transfer observables in the p (~ 0 ~ p) reaction were measured in the GeV energy range, where it is believed that quark-gluon degrees of freedom begin to dominate. The experiment utilised a circularly polarised photon beam incident on a liquid hydrogen target, with the scattered photon and recoil proton detected in a lead-glass calorimeter and a magnetic spectrometer, respectively.
Compton scattering at finite temperature: thermal field dynamics approach
Full text: Compton scattering is a classical problem of quantum electrodynamics and has been studied in its early beginnings. Perturbation theory and Feynman diagram technique enables comprehensive analysis of this problem on the basis of which famous Klein-Nishina formula is obtained [1, 2]. In this work this problem is extended to the case of finite temperature. Finite-temperature effects in Compton scattering is of practical importance for various processes in relativistic thermal plasmas in astrophysics. Recently Compton effect have been explored using closed-time path formalism with temperature corrections estimated [3]. It was found that the thermal cross section can be larger than that for zero-temperature by several orders of magnitude for the high temperature realistic in astrophysics [3]. In our work we use a main tool to account finite-temperature effects, a real-time finite-temperature quantum field theory, so-called thermofield dynamics [4, 5]. Thermofield dynamics is a canonical formalism to explore field-theoretical processes at finite temperature. It consists of two steps, doubling of Fock space and Bogolyubov transformations. Doubling leads to appearing additional degrees of freedom, called tilded operators which together with usual field operators create so-called thermal doublet. Bogolyubov transformations make field operators temperature-dependent. Using this formalism we treat Compton scattering at finite temperature via replacing in transition amplitude zero-temperature propagators by finite-temperature ones. As a result finite-temperature extension of the Klein-Nishina formula is obtained in which differential cross section is represented as a sum of zero-temperature cross section and finite-temperature correction. The obtained result could be useful in quantum electrodynamics of lasers and for relativistic thermal plasma processes in astrophysics where correct account of finite-temperature effects is important. (author)
Resonant Cyclotron Scattering and Comptonization in Neutron Star Magnetospheres
Lyutikov, M; Lyutikov, Maxim; Gavriil, Fotis P.
2006-01-01
Resonant cyclotron scattering of the surface radiation in the magnetospheres of neutron stars may considerably modify the emergent spectra and impede efforts to constraint neutron star properties. Resonant cyclotron scattering by a non-relativistic warm plasma in an inhomogeneous magnetic field has a number of unusual characteristics: (i) in the limit of high resonant optical depth, the cyclotron resonant layer is half opaque, in sharp contrast to the case of non-resonant scattering. (ii) The transmitted flux is on average Compton up-scattered by ~ $1+ 2 beta_T$, where $\\beta_T$ is the typical thermal velocity in units of the velocity of light; the reflected flux has on average the initial frequency. (iii) For both the transmitted and reflected fluxes the dispersion of intensity decreases with increasing optical depth. (iv) The emergent spectrum is appreciably non-Plankian while narrow spectral features produced at the surface may be erased. (v) Optical photons are less affected by resonant Comptonization tha...
Test of pulse shape analysis using single Compton scattering events
Abt, I; Kröninger, K; Liu, J; Liu, X; Majorovits, B
2008-01-01
Compton scattering is one of the dominant interaction processes in germanium for photons with an energy of around two MeV. If a photon scatters only once inside a germanium detector, the resulting event contains only one electron which normally deposits its energy within a mm range. Such events are similar to Ge-76 neutrinoless double beta-decay events with just two electrons in the final state. Other photon interactions like pair production or multiple scattering can result in events composed of separated energy deposits. One method to identify the multiple energy deposits is the use of timing information contained in the electrical response of a detector or a segment of a detector. The procedures developed to separate single- and multiple-site events are tested with specially selected event samples provided by an 18-fold segmented prototype germanium detector for Phase II of the GERmanium Detector Array, GERDA. The single Compton scattering, i.e. single-site, events are tagged by coincidently detecting the ...
Gamma-Ray Burst Polarization via Compton Scattering Process
Chang, Zhe; Lin, Hai-Nan; Jiang, Yunguo
2014-03-01
Synchrotron radiation and Compton scattering are widely accepted as the most likely emission mechanisms of some astrophysical phenomena, such as gamma-ray bursts (GRBs) and active galactic nuclei. The measurement of the polarization of photons provides a useful tool to distinguish different emission mechanisms and structures of the emission region. Based on the differential cross section of a polarized photon scattered by an unpolarized electron of any initial momentum, we derive an analytical formula of polarization for beamed photons scattered by isotropic electrons with a power-law distribution. Numerical calculations are carried out in four special cases: electrons at rest, Thomson limit, head-on collision, and monochromatic electrons. It is found that the maximum polarization can be as high as 100% for low energy photons, if the electrons are at rest. Although polarization is highly suppressed due to the isotropic electrons, a maximum value of ~10%-20% can still be achieved. The Compton scattering process can be used to explain the polarization of GRB 041219A and GRB 100826A.
The polarization effect of a laser in multiphoton Compton scattering
Liang, Guo-Hua; Lü, Qing-Zheng; Teng, Ai-Ping; Li, Ying-Jun
2014-05-01
The multiphoton Compton scattering in a high-intensity laser beam is studied by using the laser-dressed quantum electrodynamics (QED) method, which is a non-perturbative theory for the interaction between a plane electromagnetic field and a charged particle. In order to analyze in the real experimental condition, a Lorentz transformation for the cross section of this process is derived between the laboratory frame and the initial rest frame of electrons. The energy of the scattered photon is analyzed, as well as the cross sections for different laser intensities and polarizations and different electron velocities. The angular distribution of the emitted photon is investigated in a special velocity of the electron, in which for a fixed number of absorbed photons, the electron energy will not change after the scattering in the lab frame. We obtain the conclusion that higher laser intensities suppress few-laser-photon absorption and enhance more-laser-photon absorption. A comparison between different polarizations is also made, and we find that the linearly polarized laser is more suitable to generate nonlinear Compton scattering.
Photon Acceleration of Laser-plasma Based on Compton Scattering
HAO Dong-shan; XIE Hong-jun
2006-01-01
The one-dimensional electron density disturbance is studied by using the inelastic collision model of the relativity electron and photon group, the relativity theory, the momentum equation and the continuity equation, which is generated by a driving laser pulse and scattered laser pulse propagating through a tenuous plasma, and the electron density disturbance is closely associated with the incident laser and scattering laser. The electron plasma wave(EPW)is formed by the propagation of the electron density disturbance. Owing to the action of EPW, the increasing of the frequency of the photons in the incident laser pulses that there is a distance with the driving laser pulses is studied by using optical metric. The results show that it is possible that the photon will gain higher energy from the EPW when photon number is decreased and one-photon Compton scattering enters, the photon will be accelerated.
Densitometry and temperature measurement of combustion gas by X-ray Compton scattering
Sakurai, Hiroshi; Kawahara, Nobuyuki; Itou, Masayoshi; Tomita, Eiji; Suzuki, Kosuke; Sakurai, Yoshiharu
2016-01-01
Measurement of combustion gas by high-energy X-ray Compton scattering is reported. The intensity of Compton-scattered X-rays has shown a position dependence across the flame of the combustion gas, allowing us to estimate the temperature distribution of the combustion flame. The energy spectra of Compton-scattered X-rays have revealed a significant difference across the combustion reaction zone, which enables us to detect the combustion reaction. These results demonstrate that high-energy X-ray Compton scattering can be employed as an in situ technique to probe inside a combustion reaction. PMID:26917151
Non-thermal shielding effects on the Compton scattering power in astrophysical plasmas
Shin, Dong-Soo; Jung, Young-Dae
2015-10-01
The non-thermal shielding effects on the inverse Compton scattering are investigated in astrophysical non-thermal Lorentzian plasmas. The inverse Compton power is obtained by the modified Compton scattering cross section in Lorentzian plasmas with the blackbody photon distribution. The total Compton power is also obtained by the Lorentzan distribution of plasmas. It is found that the influence of non-thermal character of the plasma suppresses the inverse Compton power in astrophysical Lorentzian plasmas. It is also found that the non-thermal effect on the inverse Compton power decreases with an increase of the temperature. In addition, the non-thermal effect on the total Compton power with Lorentzan plasmas increases in low-temperature photons and, however, decreases in intermediate-temperature photons with increasing Debye length. The variation of the total Compton power is also discussed.
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...
Radiative corrections to real and virtual muon Compton scattering revisited
Kaiser, N. [Physik-Department T39, Technische Universitaet Muenchen, D-85747 Garching (Germany)], E-mail: nkaiser@ph.tum.de
2010-06-01
We calculate in closed analytical form the one-photon loop radiative corrections to muon Compton scattering {mu}{sup -}{gamma}{yields}{mu}{sup -}{gamma}. Ultraviolet and infrared divergences are both treated in dimensional regularization. Infrared finiteness of the (virtual) radiative corrections is achieved (in the standard way) by including soft photon radiation below an energy cut-off {lambda}. We find that the anomalous magnetic moment {alpha}/2{pi} provides only a very small portion of the full radiative corrections. Furthermore, we extend our calculation of radiative corrections to the muon-nucleus bremsstrahlung process (or virtual muon Compton scattering {mu}{sup -}{gamma}{sub 0}*{yields}{mu}{sup -}{gamma}). These results are particularly relevant for analyzing the COMPASS experiment at CERN in which muon-nucleus bremsstrahlung serves to calibrate the Primakoff scattering of high-energy pions off a heavy nucleus with the aim of measuring the pion electric and magnetic polarizabilities. We find agreement with an earlier calculation of these radiative corrections based on a different method.
Compton Scattering of Quasi-Real Virtual Photons at LEP
Achard, P; Aguilar-Benítez, M; Alcaraz, J; Alemanni, G; Allaby, James V; Aloisio, A; Alviggi, M G; Anderhub, H; Andreev, V P; Anselmo, F; Arefev, A; Azemoon, T; Aziz, T; Bagnaia, P; Bajo, A; Baksay, G; Baksay, L; Baldew, S V; Banerjee, S; Barczyk, A; Barillère, R; Bartalini, P; Basile, M; Batalova, N; Battiston, R; Bay, A; Becattini, F; Becker, U; Behner, F; Bellucci, L; Berbeco, R; Berdugo, J; Berges, P; Bertucci, B; Betev, B L; Biasini, M; Biglietti, M; Biland, A; Blaising, J J; Blyth, S C; Bobbink, G J; Böhm, A; Boldizsar, L; Borgia, B; Bottai, S; Bourilkov, D; Bourquin, Maurice; Braccini, S; Branson, J G; Brochu, F; Burger, J D; Burger, W J; Cai, X D; Capell, M; Cara Romeo, G; Carlino, G; Cartacci, A; Casaus, J; Cavallari, F; Cavallo, N; Cecchi, C; Cerrada, M; Chamizo-Llatas, M; Chang, Y H; Chemarin, M; Chen, A; Chen, G; Chen, G M; Chen, H F; Chen, H S; Chiefari, G; Cifarelli, Luisa; Cindolo, F; Clare, I; Clare, R; Coignet, G; Colino, N; Costantini, S; de la Cruz, B; Cucciarelli, S; van Dalen, J A; De Asmundis, R; Déglon, P L; Debreczeni, J; Degré, A; Dehmelt, K; Deiters, K; Della Volpe, D; Delmeire, E; Denes, P; De Notaristefani, F; De Salvo, A; Diemoz, M; Dierckxsens, M; Dionisi, C; Dittmar, M; Doria, A; Dova, M T; Duchesneau, D; Duda, M; Echenard, B; Eline, A; El-Hage, A; El-Mamouni, H; Engler, A; Eppling, F J; Extermann, P; Falagán, M A; Falciano, S; Favara, A; Fay, J; Fedin, O; Felcini, M; Ferguson, T; Fesefeldt, H S; Fiandrini, E; Field, J H; Filthaut, F; Fisher, P H; Fisher, W; Fisk, I; Forconi, G; Freudenreich, Klaus; Furetta, C; Galaktionov, Yu; Ganguli, S N; García-Abia, P; Gataullin, M; Gentile, S; Giagu, S; Gong, Z F; Grenier, G; Grimm, O; Grünewald, M W; Guida, M; Gupta, V K; Gurtu, A; Gutay, L J; Haas, D; Hatzifotiadou, D; Hebbeker, T; Hervé, A; Hirschfelder, J; Hofer, H; Hohlmann, M; Holzner, G; Hou, S R; Hu, Y; Jin, B N; Jones, L W; de Jong, P; Josa-Mutuberria, I; Kaur, M; Kienzle-Focacci, M N; Kim, J K; Kirkby, Jasper; Kittel, E W; Klimentov, A; König, A C; Kopal, M; Koutsenko, V F; Kraber, M; Krämer, R W; Krüger, A; Kunin, A; Ladrón de Guevara, P; Laktineh, I; Landi, G; Lebeau, M; Lebedev, A; Lebrun, P; Lecomte, P; Lecoq, P; Le Coultre, P; Le Goff, J M; Leiste, R; Levtchenko, M; Levchenko, P M; Li, C; Likhoded, S; Lin, C H; Lin, W T; Linde, Frank L; Lista, L; Liu, Z A; Lohmann, W; Longo, E; Lü, Y S; Luci, C; Luminari, L; Lustermann, W; Ma Wen Gan; Malgeri, L; Malinin, A; Maña, C; Mans, J; Martin, J P; Marzano, F; Mazumdar, K; McNeil, R R; Mele, S; Merola, L; Meschini, M; Metzger, W J; Mihul, A; Milcent, H; Mirabelli, G; Mnich, J; Mohanty, G B; Muanza, G S; Muijs, A J M; Musicar, B; Musy, M; Nagy, S; Natale, S; Napolitano, M; Nessi-Tedaldi, F; Newman, H; Nisati, A; Novák, T; Nowak, H; Ofierzynski, R A; Organtini, G; Pal, I; Palomares, C; Paolucci, P; Paramatti, R; Passaleva, G; Patricelli, S; Paul, T; Pauluzzi, M; Paus, C; Pauss, Felicitas; Pedace, M; Pensotti, S; Perret-Gallix, D; Petersen, B; Piccolo, D; Pierella, F; Pioppi, M; Piroué, P A; Pistolesi, E; Plyaskin, V; Pohl, M; Pozhidaev, V; Pothier, J; Prokofev, D; Prokofiev, D O; Quartieri, J; Rahal-Callot, G; Rahaman, M A; Raics, P; Raja, N; Ramelli, R; Rancoita, P G; Ranieri, R; Raspereza, A V; Razis, P; Ren, D; Rescigno, M; Reucroft, S; Riemann, S; Riles, K; Roe, B P; Romero, L; Rosca, A; Rosemann, C; Rosenbleck, C; Rosier-Lees, S; Roth, S; Rubio, J A; Ruggiero, G; Rykaczewski, H; Sakharov, A; Saremi, S; Sarkar, S; Salicio, J; Sánchez, E; Schäfer, C; Shchegelskii, V; Schopper, Herwig Franz; Schotanus, D J; Sciacca, C; Servoli, L; Shevchenko, S; Shivarov, N; Shoutko, V; Shumilov, E; Shvorob, A; Son, D; Souga, C; Spillantini, P; Steuer, M; Stickland, D P; Stoyanov, B; Strässner, A; Sudhakar, K; Sultanov, G G; Sun, L Z; Sushkov, S; Suter, H; Swain, J D; Szillási, Z; Tang, X W; Tarjan, P; Tauscher, L; Taylor, L; Tellili, B; Teyssier, D; Timmermans, C; Ting, Samuel C C; Ting, S M; Tonwar, S C; Tóth, J; Tully, C; Tung, K L; Ulbricht, J; Valente, E; Van de Walle, R T; Vásquez, R; Veszpremi, V; Vesztergombi, G; Vetlitskii, I; Vicinanza, D; Viertel, Gert M; Villa, S; Vivargent, M; Vlachos, S; Vodopyanov, I; Vogel, H; Vogt, H; Vorobev, I; Vorobyov, A A; Wadhwa, M; Wang, Q; Wang, X L; Wang, Z M; Weber, M; Wilkens, H; Wynhoff, S; Xia, L; Xu, Z Z; Yamamoto, J; Yang, B Z; Yang, C G; Yang, H J; Yang, M; Yeh, S C; Zalite, A; Zalite, Yu; Zhang, Z P; Zhao, J; Zhu, G Y; Zhu, R Y; Zhuang, H L; Zichichi, A; Zimmermann, B; Zöller, M
2005-01-01
Compton scattering of quasi-real virtual photons, gamma e+- -> gamma e+-, is studied with 0.6fb-1 of data collected by the L3 detector at the LEP e+e- collider at centre-of-mass energies root(s')=189-209GeV. About 4500 events produced by the interaction of virtual photons emitted by e+- of one beam with e-+ of the opposite beam are collected for effective centre-of-mass energies of the photon-electron and photon-positron systems in the range from root(s')= 35GeV up to root(s')=175GeV, the highest energy at which Compton scattering was ever probed. The cross sections of the gamma e+- -> gamma e+- process as a function of root(s') and of the rest-frame scattering angle are measured, combined with previous L3 measurements down to root(s')~20GeV, and found to agree with the QED expectations.
Electronic structure of the palladium hydride studied by compton scattering
Mizusaki, S; Yamaguchi, M; Hiraoka, N; Itou, M; Sakurai, Y
2003-01-01
The hydrogen-induced changes in the electronic structure of Pd have been investigated by Compton scattering experiments associated with theoretical calculations. Compton profiles (CPs) of single crystal of Pd and beta phase hydride PdH sub x (x=0.62-0.74) have been measured along the [100], [110] and [111] directions with a momentum resolution of 0.14-0.17 atomic units using 115 keV x-rays. The theoretical Compton profiles have been calculated from the wavefunctions obtained utilizing the full potential linearized augmented plane wave method within the local density approximation for Pd and stoichiometric PdH. The experimental and the theoretical results agreed well with respect to the difference in the CPs between PdH sub x and Pd, and the anisotropy in the CPs of Pd or PdH sub x. This study provides lines of evidence that upon hydride formation the lowest valance band of Pd is largely modified due to hybridization with H 1s-orbitals and the Fermi energy is raised into the sp-band. (author)
Magnetic compton profile study of orbital ordering state of 3d electrons in YTiO3
Orbital ordering state of 3d electrons in YTiO3 has been studied by magnetic Compton profile (MCP) measurement for crystallographic directions of [100] (a-axis) and [001] (c-axis). The magnetic effect of the observed MCP leads to the spin moment that is equal to the saturated magnetic moment within the estimated errors, which strongly suggests quenching of the orbital moment. Shape of the observed MCPs shows directional anisotropy between the two axes. The MCPs are calculated by using an atomic model wave function of a linear combination of two 3d-t2g orbitals, udyz ± vdzx (u2 + v2=1) for the Ti sites. The observed MCP is best reproduced by the calculated MCP with u=0.84±0.04 and v=0.54±0.04. This value of u is slightly larger than those obtained in the previous studies. (author)
Polarization Transfer in Proton Compton Scattering at High Momentum Transfer
Compton scattering from the proton was investigated at s=6.9 GeV2 and t=-4.0 GeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton
Polarization Transfer in Proton Compton Scattering at High Momentum Transfer
Hamilton, D J; Aniol, K A; Annand, J R M; Bertin, P Y; Bimbot, L; Bosted, P; Calarco, J R; Camsonne, A; Chang, G C; Chang, T H; Chen, J P; Seonho Choi; Chudakov, E; Danagulyan, A S; Degtyarenko, P; De Jager, C W; Deur, A; Dutta, D; Egiyan, K; Gao, H; Garibaldi, F; Gayou, O; Gilman, R; Glamazdin, A; Glashausser, C; Gómez, J; Hansen, J O; Hayes, D; Higinbotham, D W; Hinton, W; Horn, T; Howell, C; Hunyady, T; Hyde-Wright, C E; Jiang, X; Jones, M K; Khandaker, M; Ketikyan, A; Koubarovski, V; Krämer, K; Kumbartzki, G; Laveissière, G; Le Rose, J J; Lindgren, R A; Margaziotis, D J; Markowitz, P; McCormick, K; Meziani, Z E; Michaels, R; Moussiegt, P; Nanda, S; Nathan, A M; Nikolenko, D M; Nelyubin, V V; Norum, B E; Paschke, K; Pentchev, L; Perdrisat, C F; Piasetzky, E; Pomatsalyuk, R I; Punjabi, V A; Rachek, Igor A; Radyushkin, A V; Reitz, B; Roché, R; Roedelbronn, M; Ron, G; Sabatie, F; Saha, A; Savvinov, N; Shahinyan, A; Shestakov, Yu V; Sirca, S; Slifer, K J; Solvignon, P; Stoler, P; Tajima, S; Sulkosky, V; Todor, L; Vlahovic, B; Weinstein, L B; Wang, K; Wojtsekhowski, B; Voskanyan, H; Xiang, H; Zheng, X; Zhu, L
2004-01-01
Compton scattering from the proton was investigated at s=6.9 (GeV/c)**2 and \\t=-4.0 (GeV/c)**2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.
Magnetic Compton scattering study of UCoAl
We have performed a magnetic Compton scattering experiment across the critical magnetic field of the metamagnetic transition in UCoAl. The sign of the total spin moment is negative at 2.0 T. This indicates that the orbital moment is dominant in the field-induced ferromagnetic state. The ratio of the orbital moment to the spin moment obtained is much larger than that in a magnetic circular dichroism experiment at U M4 and M5 edges. This leads to a conclusion that Co atoms have a significant spin moment with positive sign
MICROBUNCH TEMPORAL DIAGNOSTIC BY COMPTON SCATTERING IN INTERFERING LASER BEAMS
The exact solution of the classical nonlinear equation of motion for a relativistic electron in the field of two electromagnetic (EM) waves is obtained. For the particular case of the linearly polarized standing EM wave in the planar optical cavity, the intensity of the nonlinear Compton scattering, the time of flight, and the momentum variation after the relativistic electron passes along the cavity axis are calculated in weak and strong field limits. The extent of these effects depends on the initial phase of the EM wave when the electron enters the cavity. This can be used for the production, diagnosis, and acceleration of relativistic electron (positron) microbunches
X-ray spectrometer for observation of nonlinear Compton scattering
An x-ray spectrometer, which consists of a multilayer device and a two-dimensional position sensitive detector, is designed for measurement of the x-ray energy spectrum and angular distribution from the nonlinear Compton scattering of 60 MeV electron and high power CO2 laser beams provided by a user facility at Brookhaven National Laboratory. A Prototype of the spectrometer has constructed and tested using isotropic 8 keV (Cu Kα) x-rays from a sealed x-ray tube
Compton Scattering, Pair Annihilation and Pair Production in a Plasma
Krishan, Vinod
1999-01-01
The square of the four momentum of a photon in vacuum is zero. However, in an unmagnetized plasma it is equal to the square of the plasma frequency. Further, the electron-photon coupling vertex is modified in a plasma to include the effect of the plasma medium. I calculate the cross sections of the three processes - the Compton scattering, electron-positron pair annihilation and production in a plasma. At high plasma densities, the cross sections are found to change significantly. Such high p...
Transition-radiation-Compton-scattering detector for very relativistic nuclei
Osborne, W. Z.; Mack, J. E.
1975-01-01
The paper presents the design and predicted performance of a large acceptance (2 sq m sr) transition-radiation-Compton-scattering detector system which can be used to measure energy spectra up to several thousand Gev/nucleon for nuclei with Z between 6 and 28, as well as up to 40,000 GeV/nucleon for He. The following circumstances made such a detector system practicable: (1) transition radiation output is proportional to the square of particle charge; (2) output varies at least as rapidly as the square of Lorentz factor over the range from several hundred to several thousand.
Deeply Virtual Compton Scattering at JLab Hall A
Eric Voutier
2007-04-16
The deeply virtual Compton scattering reaction has been investigated in the Hall A of the Jefferson Laboratory by measuring longitudinally polarized (e,e'gamma) cross sections, in the valence quark region, for protons and neutrons. In the proton channel, experimental results strongly support the factorization of the cross section at Q2 as low as 2 GeV2, opening the path to systematic measurements of generalized parton distributions (GPDs). In the neutron case, preliminary data show sensitivity to the angular momentum of quarks.
Deeply virtual compton scattering program with CLAS and CLAS12
Full text: The beam-spin asymmetries in the hard exclusive electroproduction of photons on the proton were measured over a wide kinematic range and with high statistical accuracy. These asymmetries result from the interference of the Bethe-Heitler process and of deeply virtual Compton scattering. Over the whole kinematic range, the azimuthal dependence of the asymmetries is compatible with expectation from leading-twist dominance. This extensive set of data can be used to constrain significantly the generalized parton distributions of the nucleon in the valence quark. Some of the recent DVCS results with CLAS will be presented together with future plan with upgraded CLAS12. (author)
Comparative evaluation of scatter correction in 3D PET using different scatter-level approximations
In 3D positron emission tomography (PET), scatter of the gamma photons is one of the most significant physical factors which degrades not only image quality but also quantification. The currently most used scatter estimation method is the analytic single scatter simulation (SSS) which usually accommodates for multiple scattering by scaling the single scatter estimation. However, it has not been clear yet how accurate this approximation is for cases where multiple scatter is significant, raising the question: 'How important is correction for multiple scattered photons, and how accurately do we need to simulate all scattered events by appropriate scaling?' This study answers these questions and evaluates the accuracy of SSS implementation in the open-source library software for tomographic image reconstruction (STIR). Different scatter orders approximations are evaluated including different levels of scattering and different scaling approaches using Monte Carlo (id est (i.e.) Sim system for emission tomography (SET)) data. SimSET simulations of a large anthropomorphic phantom were reconstructed with iterative reconstruction algorithms. Images reconstructed with 3D filtered back-projection reprojection algorithm have been compared quantitatively in order to clarify the errors due to different scatter order approximations. Quantification in regions has improved by scatter correction. For example, in the heart the ideal value was 3, whereas before scatter correction the standard uptake value (SUV) was 4.0, after single scatter correction was 3.3 and after single and double scatter correction was 3.0. After correction by scaling single scatter with tail-fit, the SUV was 3.1, whereas with total-fit it was 3.0. Similarly, for the SSS correction methodology implemented in STIR using tail-fit the heart SUV was 3.1 whereas using total-fit it was 3.0. The results demonstrate that correction for double scatter improves image contrast and therefore it is required for the
Deeply Virtual Compton Scattering off ^4He nucleus
El Alaoui, Ahmed
2010-02-01
The recently developed formalism of generalized parton distributions (GPDs) provides a theoretical tool to reveal the internal structure of the nucleon. These objects can be obtained via Deeply Virtual Compton Scattering (DVCS) processes. They contain informations on the transverse spatial position and the longitudinal momentum of quarks inside the nucleon and they also give access to the contribution of the quark orbital angular momentum to the nucleon. In contrast to many DVCS experiments using a proton target, only few experiments are devoted to study GPDs in a nuclear target which is important because it allows to address medium modification of bound nucleon GPDs compared to free nucleon GPDs. One of the goals of the new EG6 experiment at Thomas Jefferson Laboratory is to extract the real and imaginary parts of the ^4He Compton form factor (HA(xB,t)) from measurement of beam spin asymmetries by scattering a polarized 6 GeV electron beam off a ^4He pressurized gaz target. Details on the experiment will be presented here. )
Nucleon polarizabilities: From Compton scattering to hydrogen atom
Hagelstein, Franziska; Miskimen, Rory; Pascalutsa, Vladimir
2016-05-01
We review the current state of knowledge of the nucleon polarizabilities and of their role in nucleon Compton scattering and in hydrogen spectrum. We discuss the basic concepts, the recent lattice QCD calculations and advances in chiral effective-field theory. On the experimental side, we review the ongoing programs aimed to measure the nucleon (scalar and spin) polarizabilities via the Compton scattering processes, with real and virtual photons. A great part of the review is devoted to the general constraints based on unitarity, causality, discrete and continuous symmetries, which result in model-independent relations involving nucleon polarizabilities. We (re-)derive a variety of such relations and discuss their empirical value. The proton polarizability effects are presently the major sources of uncertainty in the assessment of the muonic hydrogen Lamb shift and hyperfine structure. Recent calculations of these effects are reviewed here in the context of the "proton-radius puzzle". We conclude with summary plots of the recent results and prospects for the near-future work.
Recent Deuteron Compton Scattering Results and Extracted Neutron Polarizabilities
Myers L.S.
2016-01-01
Full Text Available The COMPTON@MAX-lab collaboration has recently published a new measurement of elastic photon scattering from deuterium using tagged photons at the MAX IV Laboratory [1]. The experiment utilized the Tagged Photon Facility at MAX IV and three of the largest NaI(Tl detectors in the world. Correction terms to the cross section were determined via Monte Carlo simulations [2, 3] and were confirmed by comparisons to the well-known 12C(γ,γ12C reaction [4]. These results represent the most extensive data on deuteron Compton scattering ever measured and effectively double the world data set. In addition, the energy range overlaps previous experiments and extends nearly 20 MeV higher where the sensitivity to the polarizabilities is enhanced. As a result, we have obtained the neutron polarizabilities as αn=[11.55 ± 1.25(stat ± 0.2(BSR ± 0.8(th] × 10−4 fm3 and βn=[3.65 ∓ 1.25(stat ± 0.2(BSR ± 0.8(th] × 10−4 fm3, which represents a 30% reduction in the statistical uncertainty.
Design of a Compton camera for 3D prompt-γ imaging during ion beam therapy
We investigate, by means of Geant4 simulations, a real-time method to control the position of the Bragg peak during ion therapy, based on a Compton camera in combination with a beam tagging device (hodoscope) in order to detect the prompt gamma emitted during nuclear fragmentation. The proposed set-up consists of a stack of 2 mm thick silicon strip detectors and a LYSO absorber detector. The γ emission points are reconstructed analytically by intersecting the ion trajectories given by the beam hodoscope and the Compton cones given by the camera. The camera response to a polychromatic point source in air is analyzed with regard to both spatial resolution and detection efficiency. Various geometrical configurations of the camera have been tested. In the proposed configuration, for a typical polychromatic photon point source, the spatial resolution of the camera is about 8.3 mm FWHM and the detection efficiency 2.5x10-4 (reconstructable photons/emitted photons in 4π). Finally, the clinical applicability of our system is considered and possible starting points for further developments of a prototype are discussed.
Design of a Compton camera for 3D prompt-{gamma} imaging during ion beam therapy
Roellinghoff, F., E-mail: roelling@ipnl.in2p3.fr [Universite de Lyon, F-69622 Lyon (France); Universite Lyon 1 and CNRS/IN2P3, UMR 5822, IPNL, F-69622 Villeurbanne (France); INSA-Lyon Laboratory of Nondestructive Testing using Ionizing Radiation (CNDRI), F-69621 Villeurbanne Cedex (France); Richard, M.-H., E-mail: mrichard@ipnl.in2p3.fr [Universite de Lyon, F-69622 Lyon (France); Universite Lyon 1 and CNRS/IN2P3, UMR 5822, IPNL, F-69622 Villeurbanne (France); INSA-Lyon Laboratory of Nondestructive Testing using Ionizing Radiation (CNDRI), F-69621 Villeurbanne Cedex (France); Chevallier, M.; Constanzo, J.; Dauvergne, D. [Universite de Lyon, F-69622 Lyon (France); Universite Lyon 1 and CNRS/IN2P3, UMR 5822, IPNL, F-69622 Villeurbanne (France); Freud, N. [INSA-Lyon Laboratory of Nondestructive Testing using Ionizing Radiation (CNDRI), F-69621 Villeurbanne Cedex (France); Henriquet, P.; Le Foulher, F. [Universite de Lyon, F-69622 Lyon (France); Universite Lyon 1 and CNRS/IN2P3, UMR 5822, IPNL, F-69622 Villeurbanne (France); Letang, J.M. [INSA-Lyon Laboratory of Nondestructive Testing using Ionizing Radiation (CNDRI), F-69621 Villeurbanne Cedex (France); Montarou, G. [LPC, CNRS/IN2P3, Clermont-F. University (France); Ray, C.; Testa, E.; Testa, M. [Universite de Lyon, F-69622 Lyon (France); Universite Lyon 1 and CNRS/IN2P3, UMR 5822, IPNL, F-69622 Villeurbanne (France); Walenta, A.H. [Uni-Siegen, FB Physik, Emmy-Noether Campus, D-57068 Siegen (Germany)
2011-08-21
We investigate, by means of Geant4 simulations, a real-time method to control the position of the Bragg peak during ion therapy, based on a Compton camera in combination with a beam tagging device (hodoscope) in order to detect the prompt gamma emitted during nuclear fragmentation. The proposed set-up consists of a stack of 2 mm thick silicon strip detectors and a LYSO absorber detector. The {gamma} emission points are reconstructed analytically by intersecting the ion trajectories given by the beam hodoscope and the Compton cones given by the camera. The camera response to a polychromatic point source in air is analyzed with regard to both spatial resolution and detection efficiency. Various geometrical configurations of the camera have been tested. In the proposed configuration, for a typical polychromatic photon point source, the spatial resolution of the camera is about 8.3 mm FWHM and the detection efficiency 2.5x10{sup -4} (reconstructable photons/emitted photons in 4{pi}). Finally, the clinical applicability of our system is considered and possible starting points for further developments of a prototype are discussed.
Beam-Shape Effects in Nonlinear Compton and Thomson Scattering
Heinzl, T; Kämpfer, B
2009-01-01
We discuss intensity effects in collisions between beams of optical photons from a high-power laser and relativistic electrons. Our main focus are the modifications of the emission spectra due to realistic finite-beam geometries. By carefully analyzing the classical limit we precisely quantify the distinction between strong-field QED Compton scattering and classical Thomson scattering. A purely classical, but fully covariant, calculation of the bremsstrahlung emitted by an electron in a plane wave laser field yields radiation into harmonics, as expected. This result is generalized to pulses of finite duration and explains the appearance of line broadening and harmonic substructure as an interference phenomenon. The ensuing numerical treatment confirms that strong focussing of the laser leads to a broad continuum while higher harmonics become visible only at moderate focussing, hence lower intensity. We present a scaling law for the backscattered photon spectral density which facilitates averaging over electro...
Nuclear probe for soil water content measurements by Compton scattering
There are few types of nuclear probes that measure the soil water content. The aim of this study is to develop a new nuclear probe, optimise its geometry using the code MCNP4C and calibrate it. This nuclear probe is constituted by a 60 keV gamma radiation source, a soil sample and a plastic scintillator. A beam of radiation coming from the source reaches the sample and is scattered by Compton effect. The scintillator then detects this scattered radiation. Its optimization is made using the MCNP4C adjusting the three parameters: distance between the source and the scintillator, dimensions of soil sample and source's energy. After choosing the optimized system, small amount of water is progressively added into the soil sample until its saturation, what permits correlate counts with water content. The results showed the viability of using this method to measure soil water content. (author)
Compton scatter with polychromatic sources for lung densitometry.
Hanson, J A; Moore, W E; Figley, M M; Duke, P R
1984-01-01
A mobile lung densitometer using conventional x-ray tubes, NaI detectors, and principles of two-source, two-detector Compton scattered densitometry, is described. The device is capable of one to two per second density measurements from a 45-cm3 volume with a precision of 5%. The expected in vivo accuracy (2%-3%) is determined by using an anthropomorphic phantom with replaceable lung inserts. The unintentional detection of multiple-scattered x rays results in a small density-dependent error. This error is predictable and relatively insensitive to differences in surrounding absorbers such as the chest wall. With this device, dynamic in vivo densitometry of the lung in the clinical laboratory and intensive care unit will be possible. PMID:6503878
The nonlinear effect in relativistic Compton scattering for an intense circularly polarized laser
Luo, W.; Zhuo, H. B.; Ma, Y. Y.; Zhu, Z. C.; Fan, G. T.; Xu, W.; Song, Y. M.
2014-07-01
Compton scattering between an intense laser pulse and a relativistic electron beam offers a promising development path toward high-energy, high-brightness x- and gamma-ray sources. Increasing laser peak power to obtain intense x- and gamma rays causes nonlinear Compton scattering to occur. To predict high-order harmonic radiation properties, we upgrade a Monte Carlo laser-Compton scattering simulation code (MCLCSS) by taking into account the nonlinear effect for the relativistic Compton scattering process. The energy spectra and angular and harmonic intensity distributions of the scattered photons are investigated using nonlinear Compton scattering of an intense circularly polarized laser. It is found that the laser parameter {{a}_{0}}\\equiv e{\\rm{A}}\\;{{m}_{e}}{{c}^{-2}} plays an important role in the generation of high-order harmonic radiation. Our study also suggests that the high-energy tails of the second and higher harmonics will stray from the backscattering region.
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.
Gladkikh, P I; Karnaukhov, I M
2002-01-01
The feasibility of the development of intense X-ray sources based on Compton scattering in laser-electron storage rings is discussed. The results of the electron beam dynamics simulation involving Compton and intrabeam scattering are presented.
Deeply virtual compton scattering at 6 GeV
We propose a measurement of the Deep Virtual Compton Scattering process (DVCS) ep → epγ in Hall A at Jefferson Lab with a 6 GeV beam. We are able to explore the onset of Q2 scaling, by measuring a beam helicity asymmetry for Q2 ranging from 1.5 to 2.5 GeV2 at xB∼0.35. At this kinematics, the asymmetry is dominated by the DVCS - Bethe-Heitler (BH) interference, which is proportional to the imaginary part of the DVCS amplitude amplified by the full magnitude of the BH amplitude. The imaginary part of the DVCS amplitude is expected to scale early. Indeed, the imaginary part of the forward Compton amplitude measured in deep inelastic scattering (via the optical theorem) scales at Q2 as low as 1 GeV2. If the scaling regime is reached, we will make an 8% measurement of the skewed parton distributions (SPD) contributing to the DVCS amplitude. Also, this experiment allows us to separately estimate the size of the higher-twist effects, since they are only suppressed by an additional factor 1/Q compared to the leading-twist term, and have a different angular dependence. We use a polarized electron beam and detect the scattered electron in the HRSe, the real photon in an electromagnetic calorimeter (under construction) and the recoil proton in a shielded scintillator array (to be constructed). This allows as to determine the difference in cross-sections for electrons of opposite helicities. This observable is directly linked to the SPD's. We estimate that 25 days of beam (600 hours) are needed to achieve this goal. (authors)
Hadron Optics: Diffraction Patterns in Deeply Virtual Compton Scattering
Brodsky, S
2006-05-16
We show that the Fourier transform of the Deeply Virtual Compton Scattering (DVCS) amplitude with respect to the skewness variable {zeta} provides a unique way to visualize the light-front wavefunctions (LFWFs) of the target state in the boost-invariant longitudinal coordinate space variable ({sigma} = P{sup +}y{sup -}/2). The results are analogous to the diffractive scattering of a wave in optics in which the dependence of the amplitude on {sigma} measures the physical size of the scattering center of a one-dimensional system. If one combines this longitudinal transform with the Fourier transform of the DVCS amplitude with respect to the transverse momentum transfer {Delta}{sup {perpendicular}}, one can obtain a complete three-dimensional description of hadron optics at fixed light-front time {tau} = t + z/c. As a specific example, we utilize the quantum fluctuations of a fermion state at one loop in QED to obtain the behavior of the DVCS amplitude for electron-photon scattering. We then simulate the wavefunctions for a hadron by differentiating the above LFWFs with respect to M{sup 2} and study the corresponding DVCS amplitudes in {sigma} space.
Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation
Afanasev, Andrei; /Hampton U. /Jefferson Lab; Brodsky, Stanley J.; /SLAC; Carlson, Carl E.; /William-Mary Coll.; Mukherjee, Asmita; /Indian Inst. Tech., Mumbai
2009-03-31
We propose measurements of the deeply virtual Compton amplitude (DVCS) {gamma}* {yields} H{bar H}{gamma} in the timelike t = (p{sub H} + p{sub {bar H}}){sup 2} > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e{sup +}e{sup -} {yields} H{bar H}{gamma}. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H{bar H} hadron pairs such as {pi}{sup +}{pi}{sup -}, K{sup +}K{sup -}, and D{bar D} as well as p{bar p}. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C = - form factors. The interference between the amplitudes measures the phase of the C = + timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e{sup +} {leftrightarrow} e{sup -} asymmetry. The J = 0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.
Timelike Virtual Compton Scattering from Electron-Positron Radiative Annihilation
Andrei Afanaciev,Andrei Afanasev, Stanley J. Brodsky, Carl E. Carlson, Asmita Mukherjee
2010-02-01
We propose measurements of the deeply virtual Compton amplitude (DVCS), gamma* to H H-bar gamma, in the timelike t = (p_{H} + p_{H-bar})^2 > 0 kinematic domain which is accessible at electron-positron colliders via the radiative annihilation process e+ e- to H H-bar gamma. These processes allow the measurement of timelike deeply virtual Compton scattering for a variety of H H-bar hadron pairs such as pi+ pi-, K+ K-, and D D-bar as well as p p-bar. As in the conventional spacelike DVCS, there are interfering coherent amplitudes contributing to the timelike processes involving C= - form factors. The interference between the amplitudes measures the phase of the C=+ timelike DVCS amplitude relative to the phase of the timelike form factors and can be isolated by considering the forward-backward e+ \\leftrightarrow e- asymmetry. The J=0 fixed pole contribution which arises from the local coupling of the two photons to the quark current plays a special role. As an example we present a simple model.
Measurement of Deeply Virtual Compton Scattering at HERA
Andreev, V; Aplin, S; Asmone, A; Babaev, A; Backovic, S; Bähr, J; Baghdasaryan, A; Baranov, P; Barrelet, E; Bartel, Wulfrin; Baudrand, S; Baumgartner, S; Becker, J; Beckingham, M; Behnke, O; Behrendt, O; Belousov, A; Berger, C; Berger, N; Bizot, J C; Boenig, M O; Boudry, V; Bracinik, J; Brandt, G; Brisson, V; Brown, D P; Bruncko, Dusan; Büsser, F W; Bunyatyan, A; Buschhorn, G; Bystritskaya, L; Campbell, A J; Caron, S; Cassol-Brunner, F; Cerny, K; Chekelian, V; Contreras, J G; Coughlan, J A; Cox, B E; Cozzika, G; Cvach, J; Dainton, J B; Dau, W D; Daum, K; Delcourt, B; Demirchyan, R; de Roeck, A; Desch, Klaus; De Wolf, E A; Diaconu, C; Dodonov, V; Dubak, A; Eckerlin, G; Efremenko, V; Egli, S; Eichler, R; Eisele, F; Ellerbrock, M; Elsen, E; Erdmann, W; Essenov, S; Faulkner, P J W; Favart, L; Fedotov, A; Felst, R; Ferencei, J; Finke, L; Fleischer, M; Fleischmann, P; Fleming, Y H; Flucke, G; Fomenko, A; Foresti, I; Formánek, J; Franke, G; Frising, G; Frisson, T; Gabathuler, Erwin; Garutti, E; Gayler, J; Gerhards, R; Gerlich, C; Ghazaryan, S; Ginzburgskaya, S; Glazov, A; Glushkov, I; Görlich, L; Göttlich, M; Gogitidze, N; Gorbounov, S; Goyon, C; Grab, C; Greenshaw, T; Gregori, M; Grindhammer, G; Gwilliam, C; Haidt, D; Hajduk, L; Haller, J; Hansson, M; Heinzelmann, G; Henderson, R C W; Henschel, H; Henshaw, O; Herrera-Corral, G; Herynek, I; Heuer, R D; Hildebrandt, M; Hiller, K H; Hoffmann, D; Horisberger, R P; Hovhannisyan, A; Ibbotson, M; Ismail, M; Jacquet, M; Janauschek, L; Janssen, X; Jemanov, V; Jönsson, L B; Johnson, D P; Jung, H; Kapichine, M; Karlsson, M; Katzy, J; Keller, N; Kenyon, I R; Kiesling, C; Klein, M; Kleinwort, C; Klimkovich, T; Kluge, T; Knies, G; Knutsson, A; Korbel, V; Kostka, P; Koutouev, R; Krastev, K; Kretzschmar, J; Kropivnitskaya, A; Krüger, K; Kuckens, J; Landon, M P J; Lange, W; Lastoviicka, T; Laycock, P; Lebedev, A; Leiner, B; Lendermann, V; Levonian, S; Lindfeld, L; Lipka, K; List, B; Lobodzinska, E; Loktionova, N; López-Fernandez, R; Lubimov, V; Lucaci-Timoce, A I; Lüders, H; Lüke, D; Lux, T; Lytkin, L; Makankine, A; Malden, N; Malinovskii, E I; Mangano, S; Marage, P; Marshall, R; Martisikova, M; Martyn, H U; Maxfield, S J; Meer, D; Mehta, A; Meier, K; Meyer, A B; Meyer, H; Meyer, J; Mikocki, S; Milcewicz-Mika, I; Milstead, D; Mohamed, A; Moreau, F; Morozov, A; Morris, J V; Mozer, M U; Müller, K; Murn, P; Nankov, K; Naroska, Beate; Naumann, J; Naumann, T; Newman, P R; Niebuhr, C B; Nikiforov, A; Nikitin, D K; Nowak, G; Nozicka, M; Oganezov, R; Olivier, B; Olsson, J E; Osman, S; Ozerov, D; Pascaud, C; Patel, G D; Peez, M; Pérez, E; Perez-Astudillo, D; Perieanu, A; Petrukhin, A; Pitzl, D; Placakyte, R; Pöschl, R; Portheault, B; Povh, B; Prideaux, P; Raicevic, N; Reimer, P; Rimmer, A; Risler, C; Rizvi, E; Robmann, P; Roland, B; Roosen, R; Rostovtsev, A; Rurikova, Z; Rusakov, S V; Salvaire, F; Sankey, D P C; Sauvan, E; Schatzel, S; Scheins, J; Schilling, F P; Schmidt, S; Schmitt, S; Schmitz, C; Schoeffel, L; Schöning, A; Schröder, V; Schultz-Coulon, H C; Schwanenberger, C; Sedlak, K; Sefkow, F; Shevyakov, I; Shtarkov, L N; Sirois, Y; Sloan, T; Smirnov, P; Soloviev, Yu; South, D; Spaskov, V; Specka, A; Stella, B; Stiewe, J; Strauch, I; Straumann, U; Tchoulakov, V; Thompson, G; Thompson, P D; Tomasz, F; Traynor, D; Truöl, P; Tsakov, I; Tsipolitis, G; Tsurin, I; Turnau, J; Tzamariudaki, E; Urban, M; Usik, A; Utkin, D; Valkár, S; Valkárová, A; Vallée, C; Van Mechelen, P; Van Remortel, N; Vargas-Trevino, A; Vazdik, Ya A; Veelken, C; Vest, A; Vinokurova, S; Volchinski, V; Vujicic, B; Wacker, K; Wagner, J; Weber, G; Weber, R; Wegener, D; Werner, C; Werner, N; Wessels, M; Wessling, B; Wigmore, C; Winter, G G; Wissing, C; Wolf, R; Wünsch, E; Xella, S M; Yan, W; Yeganov, V; Zaicek, J; Zaleisak, J; Zhang, Z; Zhelezov, A; Zhokin, A; Zimmermann, J; Zohrabyan, H G; Zomer, F
2005-01-01
A measurement is presented of elastic deeply virtual Compton scattering \\gamma* p \\to \\gamma p made using e^+ p collision data corresponding to a luminosity of 46.5 pb^{-1}, taken with the H1 detector at HERA. The cross section is measured as a function of the photon virtuality, Q^2, the invariant mass of the \\gamma* p system, W, and for the first time, differentially in the squared momentum transfer at the proton vertex, t, in the kinematic range 2 < Q^2 < 80 GeV^2, 30 < W < 140 GeV and |t| < 1 GeV^2. QCD based calculations at next-to-leading order using generalized parton distributions can describe the data, as can colour dipole model predictions.
Lorentz violation and black-hole thermodynamics: Compton scattering process
A Lorentz-noninvariant modification of quantum electrodynamics (QED) is considered, which has photons described by the nonbirefringent sector of modified Maxwell theory and electrons described by the standard Dirac theory. These photons and electrons are taken to propagate and interact in a Schwarzschild spacetime background. For appropriate Lorentz-violating parameters, the photons have an effective horizon lying outside the Schwarzschild horizon. A particular type of Compton scattering event, taking place between these two horizons (in the photonic ergoregion) and ultimately decreasing the mass of the black hole, is found to have a nonzero probability. These events perhaps allow for a violation of the generalized second law of thermodynamics in the Lorentz-noninvariant theory considered.
Laser propagation and compton scattering in parabolic plasma channel
A Gaussian laser beam propagating in a parabolic plasma channel is discussed in this paper. For a weak laser, plasma density perturbation induced by interaction between the laser field and plasma is very small, the refractive index can be assumed to be constant with respect to time variable. For a parabolic plasma channel, through the static propagation equation, we obtain an analytical solution of the profile function of the Gaussian laser beam for an unmatched case and give the general condition for the matched case. As the laser intensity increases, an effect due to strong laser fields is included. We discuss how to design and select the distribution of plasma density for a certain experiment in which a plasma channel is utilized to guide a laser beam. The number of scattered photons (X-rays) generated through Compton backscattering in a plasma channel is discussed. (author)
Calculation of Nuclear Deeply Virtual Compton Scattering in HERMES Experiment
YE Hong-Xue; MAO Ya-Jun; WANG Si-Guang; SUN Bo
2009-01-01
We investigate the possibility to acquire information of nuclear generalized parton distribution (GPD) H by studying the deeply virtual Compton scattering (DVCS) off several nuclear targets at the HERMES group (Hadron-Electron Ring Accelerator Measurement of Spin). Two different models are used and developed to demonstrate the leading asymmetry amplitude AsinφLU for coherent-enriched and incoherent-enriched parts with both statistical and systematic uncertainties estimated. It is found that a clear enhancement of ratio of nuclear asymmetry AA,sinφLU to free proton asymmetry AH,sinφLU in the coherent-enriched region is expected by both models, and a decrease of the ratio in incoherent-enriched region; both give the information about nuclear modifications. It is also possible to distinguish between those two models even under the limited statistics.
Laser propagation and compton scattering in parabolic plasma channel
Dongguo, L; Yokoya, K; Hirose, T
2003-01-01
A Gaussian laser beam propagating in a parabolic plasma channel is discussed in this paper. For a weak laser, plasma density perturbation induced by interaction between the laser field and plasma is very small, the refractive index can be assumed to be constant with respect to time variable. For a parabolic plasma channel, through the static propagation equation, we obtain an analytical solution of the profile function of the Gaussian laser beam for an unmatched case and give the general condition for the matched case. As the laser intensity increases, an effect due to strong laser fields is included. We discuss how to design and select the distribution of plasma density for a certain experiment in which a plasma channel is utilized to guide a laser beam. The number of scattered photons (X-rays) generated through Compton backscattering in a plasma channel is discussed. (author)
Shielding evaluation by laser compton scattering gamma-ray
Laser Compton scattering gamma-ray beam was used for evaluation of gamma ray shield. The gamma source of a NewSUBARU Synchrotron Radiation Facility can generate the quasi-monochromatic gamma ray beam of 0.5-1.7 MeV by combining a carbon dioxide laser and a 0.5-1.0 GeV electron beam. This gamma-ray source has small divergence of 1/γ radian due to the relativistic effect, where γ is relativistic factor of electron. Small diameter test beam of gamma-ray of about 1 mm in diameter is possible to use at the 10 m from the gamma-ray source by combining the small divergence gamma-ray beam with small hole lead collimator. Test sample size used was 2 cm in diameter. Measured shield factor was compared with calculated value using known shield materials such as lead. (author)
Measurement of deeply virtual Compton scattering at HERA
Chekanov, S; Krakauer, D A; Loizides, J H; Magill, S; Musgrave, B; Repond, J; Yoshida, R; Mattingly, M C K; Antonioli, P; Bari, G; Basile, M; Bellagamba, L; Boscherini, D; Bruni, A; Bruni, G; Cara Romeo, G; Cifarelli, Luisa; Cindolo, F; Contin, A; Corradi, M; De Pasquale, S; Giusti, P; Iacobucci, G; Margotti, A; Nania, R; Palmonari, F; Pesci, A; Sartorelli, G; Zichichi, A; Aghuzumtsyan, G; Bartsch, D; Brock, I; Goers, S; Hartmann, H; Hilger, E; Irrgang, P; Jakob, H P; Kappes, A; Katz, U F; Kind, O; Meyer, U; Paul, E; Rautenberg, J; Renner, R; Stifutkin, A; Tandler, J; Voss, K C; Wang, M; Weber, A; Bailey, D S; Brook, N H; Cole, J E; Foster, B; Heath, G P; Heath, H F; Robins, S; Rodrigues, E; Scott, J; Tapper, R J; Wing, M; Capua, M; Mastroberardino, A; Schioppa, M; Susinno, G; Kim, J Y; Kim, Y K; Lee, J H; Lim, I T; Pac, M Y; Caldwell, A; Helbich, M; Liu, X; Mellado, B; Ning, Y; Paganis, S; Ren, Z; Schmidke, W B; Sciulli, F; Chwastowski, J; Eskreys, Andrzej; Figiel, J; Olkiewicz, K; Stopa, P; Zawiejski, L; Adamczyk, L; Bold, T; Grabowska-Bold, I; Kisielewska, D; Kowal, A M; Kowal, M; Kowalski, T; Przybycien, M B; Suszycki, L; Szuba, D; Szuba, J; Kotanski, A; Slominski, W; Adler, D; Bauerdick, L A T; Behrens, U; Bloch, I; Borras, K; Chiochia, V; Dannheim, D; Drews, G; Fourletova, J; Fricke, U; Geiser, A; Göttlicher, P; Gutsche, O; Haas, T; Hain, W; Hartner, G F; Hillert, S; Kahle, B; Kowalski, H; Kramberger, G; Labes, H; Lelas, D; Löhr, B; Mankel, R; Melzer-Pellmann, I A; Moritz, M; Nguyen, C N; Notz, D; Petrucci, M C; Polini, A; Raval, A; Schneekloth, U; Selonke, F; Stoesslein, U; Wessoleck, H; Wolf, G; Youngman, C; Zeuner, W; Schlenstedt, S; Barbagli, G; Gallo, E; Genta, C; Pelfer, P G; Bamberger, A; Benen, A; Coppola, N; Bell, M; Bussey, P J; Doyle, A T; Glasman, C; Hamilton, J; Hanlon, S; Lee, S W; Lupi, A; Saxon, D H; Skillicorn, I O; Gialas, I; Bodmann, B; Carli, T; Holm, U; Klimek, K; Krumnack, N; Lohrmann, E; Milite, M; Salehi, H; Stonjek, S; Wick, K; Ziegler, A; Collins-Tooth, C; Foudas, C; Goncalo, R; Long, K R; Tapper, A D; Cloth, P; Filges, D; Nagano, K; Tokushuku, K; Yamada, S; Yamazaki, Y; Barakbaev, A N; Boos, E G; Pokrovskiy, N S; Zhautykov, B O; Lim, H; Son, D; Barreiro, F; González, O; Labarga, L; Del Peso, J; Tassi, E; Terron, J; Vázquez, M; Barbi, M; Corriveau, F; Gliga, S; Lainesse, J; Padhi, S; Stairs, D G; Tsurugai, T; Antonov, A; Danilov, P; Dolgoshein, B A; Gladkov, D; Sosnovtsev, V V; Suchkov, S; Dementiev, R K; Ermolov, P F; Golubkov, Yu A; Katkov, I I; Khein, L A; Korzhav--, I A; Kuzmin, V A; Levchenko, B B; Lukina, O Yu; Proskuryakov, A S; Shcheglova, L M; Vlasov, N N; Zotkin, S A; Grijpink, S; Koffeman, E; Kooijman, P; Maddox, E; Pellegrino, A; Schagen, S; Tiecke, H G; Velthuis, J J; Wiggers, L; De Wolf, E; Br mmer, N; Bylsma, B; Durkin, L S; Ling, T Y; Cooper-Sarkar, A M; Cottrell, A; Devenish, R C E; Ferrando, J; Grzelak, G; Patel, S; Sutton, M R; Walczak, R; Bertolin, A; Brugnera, R; Carlin, R; Dal Corso, F; Dusini, S; Garfagnini, A; Limentani, S; Longhin, A; Parenti, A; Posocco, M; Stanco, L; Turcato, M; Heaphy, E A; Metlica, F; Oh, B Y; Saull, P R B; Toothacker, W S; Whitmore, J J; Iga, Y; D'Agostini, Giulio; Marini, G; Nigro, A; Cormack, C; Hart, J C; McCubbin, N A; Heusch, C A; Park, I H; Pavel, N; Abramowicz, H; Gabareen, A; Kananov, S; Kreisel, A; Levy, A; Kuze, M; Abe, T; Fusayasu, T; Kagawa, S; Kohno, T; Tawara, T; Yamashita, T; Hamatsu, R; Hirose, T; Inuzuka, M; Kitamura, S; Matsuzawa, K; Nishimura, T; Arneodo, M; Ferrero, M I; Monaco, V; Ruspa, M; Sacchi, R; Solano, A; Koop, T; Levman, G M; Martin, J F; Mirea, A; Butterworth, J M; Gwenlan, C; Hall-Wilton, R; Jones, T W; Lightwood, M S; West, B J; Ciborowski, J; Ciesielski, R; Nowak, R J; Pawlak, J M; Sztuk, J; Tymieniecka, T; Ukleja, A; Ukleja, J; Eisenberg, Y; Gladilin, L K; Hochman, D; Riveline, U; Karshon, M; Kcira, D; Lammers, S; Li, L; Reeder, D D; Savin, A A; Smith, W H; Deshpande, A A; Dhawan, S; Straub, P B; Bhadra, S; Catterall, C D; Fourletov, S; Hartner, G; Menary, S R; Soares, M; Standage, J
2003-01-01
The cross section for deeply virtual Compton scattering in the reaction ep -> e gamma p has been measured with the ZEUS detector at HERA using integrated luminosities of 95.0 pb-1 of e+p and 16.7 pb-1 of e-p collisions. Differential cross sections are presented as a function of the exchanged-photon virtuality, Q2, and the centre-of-mass energy, W, of the gamma*p system in the region 5
Polarizability sum rule across real and virtual Compton scattering processes
Pascalutsa, Vladimir
2014-01-01
We derive a sum rule relating various electromagnetic properties of a spin-1/2 particle and consider its empirical implications for the proton. Given the measured values of the proton anomalous magnetic moment, electric and magnetic charge radii, the slope of the first moment of the spin structure function $g_1$, and the recently determined proton spin polarizability $\\gamma_{E1M2}$, the sum rule yields a constraint on the low-momentum behavior of a generalized polarizability appearing in virtual Compton scattering. With the help of the presently ongoing measurements of different electromagnetic observables at the MAMI, Jefferson Lab, and HI$\\gamma$S facilities, the sum rule will provide a model-independent test of the low-energy spin structure of the nucleon.
Longitudinal target-spin asymmetries for deeply virtual Compton scattering
Seder, E; Pisano, S; Niccolai, S
2014-01-01
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6-GeV electron beam, a longitudinally polarized proton target and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for $ep\\to e'p'\\gamma$ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in $Q^2$, $x_B$, $t$ and $\\phi$, for 166 four-dimensional bins. In the framework of Generalized Parton Distributions (GPDs), at leading twist the $t$ dependence of these asymmetries provides insight on the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even GPDs.
Results on Deeply Virtual Compton Scattering at Jefferson Lab
Franck Sabatie
2006-10-02
After about 10 years of growing interest for Generalized Parton Distributions come the first results from dedicated experiments, using the golden Deeply Virtual Compton Scattering process. After a short introduction, we will explain the experimental methodology and show results of the Hall A E00-110 experiment, which aimed at measuring helicity-dependent photon electroproduction cross sections. We will emphasize how this experiment provided the first stringent tests of the scaling property of this process, allowing for the first time a model-independent extraction of a linear combination of Generalized Parton Distributions. We will also describe the Hall B E01-113 experiment which measured the photon electroproduction beam spin asymmetry over a wide kinematical range. The summary will include an outlook on the next generation of experiments which are already planned at Jefferson Lab at 6 GeV, but also after the planned 12 GeV upgrade.
Compton scattering off massive fundamental bosons of pure spin 1
Delgado-Acosta, E G; Napsuciale, M; Rodríguez, S
2013-01-01
Relativistic particles with spins $J>0$ are described by means of multicomponent wave functions which transform covariantly according to Lorentz-group representations that contain at rest the spin of interest. The symmetry group of space-time provides not one but an infinity of such representations which are equivalent for free particles but yield different electromagnetic couplings upon gauging; thus the challenge is to develop criteria which allow us to select those of them which relate to physically detectable particles. We here take the position that the unitarity of the Compton scattering cross sections in the ultrarelativistic limit, when predicted by a consistent method for a spin-$1$ description, could provide such a criterion. We analyze the properties of massive fundamental spin-$1$ bosons transforming as antisymmetric tensors of second rank, $(1,0)\\oplus(0,1)$. For this purpose, we employ the Poincar\\'e covariant projector method, which provides consistent, causal, and representation specific Lagra...
Gauge invariance and Compton scattering from relativistic composite systems
Using the Ward-Takahashi (W-T) identity and the Bethe-Salpeter (B-S) wave equation, we investigate the dynamical requirements imposed by electromagnetic gauge invariance on Compton scattering from relativistic composite system. The importance of off-shell rescattering in intermediate states, which is equivalent to final state interactions in inclusive processes, is clarified in the context of current conservation. It is shown that, if the nuclear force is nonlocal, there will be both two-photon interaction currents and rescattering contributions to terms involving one-photon interaction currents. We derive the two-body W-T identity for the two-photon interaction currents, and obtain explicit forms for the interaction current operators for three illustrative models of nuclear forces: (a) two-pion exchange forces with baryon resonances, (b) covariant separable forces, and (c) charged one-pion exchange
Measurements of deeply virtual Compton scattering from HERMES
Yu, Weilin; Airapetian, Avetik; Dueren, Michael; Perez-Benito, Roberto; Stenzel, Hasko [II. Physikalisches Institut, Justus-Liebig-Universitaet Giessen (Germany)
2009-07-01
Generalized Parton Distributions (GPDs) provide a way to access to the total angular momenta of partons and give a more complete picture of the nucleon structure than the ordinary Parton Distribution Functions (PDFs). Deeply Virtual Compton Scattering (DVCS) is the most direct exclusive process to study GPDs. Different azimuthal cross-section asymmetries of the DVCS and Bethe-Heitler (BH) interference term have been measured in the HERMES experiment. The HERMES experiment was upgraded by installing a Recoil Detector in January 2006. Data were taken until the end of the HERA running, June 2007. Exclusive DVCS measurement can be achieved first time by detecting the recoiling proton with the Recoil Detector in the HERMES experiment.
Virtual compton scattering on the proton below pion threshold
Bertin, P.Y.; VCS Collaboration
1995-12-31
This paper presents the preliminary results of an electron-proton interaction experiment carried out with the accelerator of MAMI at Mainz (Germany) for the recording of virtual compton scattering events. More than 2 10{sup 4} events were recorded in a two days run with a liquid hydrogen target. The main limitation for the counting rate comes from the limitation of the acquisition rate (100 Hz) and the single rates (10{sup 5}) in the drift chambers. The aim of this experiment is the understanding of both the low energy expansion and the generalized polarizabilities in order to compare, confirm or exclude the models of Quantum Chromodynamics used for the understanding of the nucleon. (J.S.). 3 refs., 5 figs.
Longitudinal target-spin asymmetries for deeply virtual compton scattering.
Seder, E; Biselli, A; Pisano, S; Niccolai, S; Smith, G D; Joo, K; Adhikari, K; Amaryan, M J; Anderson, M D; Anefalos Pereira, S; Avakian, H; Battaglieri, M; Bedlinskiy, I; Bono, J; Boiarinov, S; Bosted, P; Briscoe, W; Brock, J; Brooks, W K; Bültmann, S; Burkert, V D; Carman, D S; Carlin, C; Celentano, A; Chandavar, S; Charles, G; Colaneri, L; Cole, P L; Contalbrigo, M; Crabb, D; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Doughty, D; Dupre, R; El Fassi, L; Elouadrhiri, L; Eugenio, P; Fedotov, G; Fegan, S; Filippi, A; Fleming, J A; Fradi, A; Garillon, B; Garçon, M; Gevorgyan, N; Ghandilyan, Y; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hattawy, M; Hirlinger Saylor, N; Holtrop, M; Hughes, S M; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jo, H S; Joosten, S; Keith, C D; Keller, D; Khachatryan, G; Khandaker, M; Kim, A; Kim, W; Klein, A; Klein, F J; Koirala, S; Kubarovsky, V; Kuhn, S E; Lenisa, P; Livingston, K; Lu, H Y; MacGregor, I J D; Markov, N; Mayer, M; McKinnon, B; Meekins, D G; Mineeva, T; Mirazita, M; Mokeev, V; Montgomery, R; Moody, C I; Moutarde, H; Movsisyan, A; Munoz Camacho, C; Nadel-Turonski, P; Niculescu, I; Osipenko, M; Ostrovidov, A I; Paolone, M; Pappalardo, L L; Park, K; Park, S; Pasyuk, E; Peng, P; Phelps, W; Pogorelko, O; Price, J W; Prok, Y; Protopopescu, D; Puckett, A J R; Ripani, M; Rizzo, A; Rosner, G; Rossi, P; Roy, P; Sabatié, F; Salgado, C; Schott, D; Schumacher, R A; Senderovich, I; Simonyan, A; Skorodumina, I; Sokhan, D; Sparveris, N; Stepanyan, S; Stoler, P; Strakovsky, I I; Strauch, S; Sytnik, V; Taiuti, M; Tang, W; Tian, Y; Ungaro, M; Voskanyan, H; Voutier, E; Walford, N K; Watts, D P; Wei, X; Weinstein, L B; Wood, M H; Zachariou, N; Zana, L; Zhang, J; Zonta, I
2015-01-23
A measurement of the electroproduction of photons off protons in the deeply inelastic regime was performed at Jefferson Lab using a nearly 6 GeV electron beam, a longitudinally polarized proton target, and the CEBAF Large Acceptance Spectrometer. Target-spin asymmetries for ep→e^{'}p^{'}γ events, which arise from the interference of the deeply virtual Compton scattering and the Bethe-Heitler processes, were extracted over the widest kinematics in Q^{2}, x_{B}, t, and ϕ, for 166 four-dimensional bins. In the framework of generalized parton distributions, at leading twist the t dependence of these asymmetries provides insight into the spatial distribution of the axial charge of the proton, which appears to be concentrated in its center. These results also bring important and necessary constraints for the existing parametrizations of chiral-even generalized parton distributions. PMID:25658994
Calculation of Nuclear Deeply Virtual Compton Scattering in HERMES Experiment
We investigate the possibility to acquire information of nuclear generalized parton distribution (GPD) H by studying the deeply virtual Compton scattering (DVCS) of several nuclear targets at the HERMES group (Hadron–Electron Ring Accelerator Measurement of Spin). Two different models are used and developed to demonstrate the leading asymmetry amplitude ALUsinØ for coherent-enriched and incoherent-enriched parts with both statistical and systematic uncertainties estimated. It is found that a clear enhancement of ratio of nuclear asymmetry ALUA,sinø to free proton asymmetry ALUH,sinø in the coherent-enriched region is expected by both models, and a decrease of the ratio in incoherent-enriched region; both give the information about nuclear modifications. It is also possible to distinguish between those two models even under the limited statistics
Modulated 3D cross-correlation light scattering: Improving turbid sample characterization
Block, Ian D.; Scheffold, Frank
2011-01-01
Accurate characterization using static light scattering (SLS) and dynamic light scattering (DLS) methods mandates the measurement and analysis of singly-scattered light. In turbid samples, the suppression of multiple scattering is therefore required to obtain meaningful results. One powerful technique for achieving this, known as 3D cross-correlation, uses two simultaneous light scattering experiments performed at the same scattering vector on the same sample volume in order to extract only t...
Higher twist effects in deeply virtual Compton scattering
Pirnay, Bjoern Michael
2016-08-01
In this work we explore the effects of higher twist power corrections on the deeply virtual Compton scattering process. The calculation of the helicity amplitudes for all possible polarization combinations is performed within the framework of QCD operator product expansion. As a result the known accuracy of the amplitudes is improved to include the (kinematic) twist-4 contributions. For the most part the analysis focuses on spin-1/2 targets, the answers for scalar targets conveniently emerge as a byproduct. We investigate the analytical structure of these corrections and prove consistency with QCD factorization. We give an estimation of the numerical impact of the sub-leading twist contributions for proton targets with the help of a phenomenological model for the nonperturbative proton generalized parton distributions. We compare different twist approximations and relate predictions for physical observables to experiments performed by the Hall A, CLAS, HERMES, H1 and ZEUS collaborations. The estimate also includes a numerical study for planned COMPASS-II runs. Throughout the analysis special emphasis is put on the convention dependence induced by finite twist truncation of scattering amplitudes.
Compton Scattering from the Deuteron at Low Energies
Lundin, Magnus [Lund Univ. (Sweden). Dept. of Physics
2002-05-01
A series of three Compton scattering experiments on deuterium have been performed at the high-resolution tagged-photon facility MAX-lab located in Lund, Sweden. The 50 < E{sub g} < 70 MeV tagged photons were scattered from a liquid deuterium target and detected simultaneously in three (10{sup x}10{sup )} NaI detectors. The average laboratory angles investigated were 45, 125 and 135 deg. The influence of the inelastic contribution was minimized by implementing a narrow elastic fit-region in the missing energy spectra. Absolute cross sections were extracted for average photon energies of 55 and 66 MeV at each angle and for each experiment. The extracted cross sections are in good agreement with those measured at Illinois by Lucas et al. The difference between the electric and magnetic isospin-averaged polarizabilities of the nucleon inside the deuteron, was varied within the calculations of Levchuk and L'vov to best reproduce the data, holding the sum fixed at 14.6 (10{sup -4} fm{sup 3}). The result implies that the electric polarizability of the neutron is the same as that of the proton within the experimental uncertainties. The result also indicates that the magnetic polarizability of the neutron is larger than that of the proton.
Nuclear probe for soil water content measurements by Compton scattering
Two methods for measuring soil moisture were developed. They are based on incoherent and coherent Compton scattering of 60 keV gamma rays. Scattered γ ray rates by small soil samples, less than 4 cm3, were measured using a X-Ray NaI(Tl) detector. Known water amounts were introduced in these samples and count rates were measured and correlated with water contents. Results have shown the viability of using this method to measure soil water content. A second method uses cylindrical soil samples with radius of 10 cm and height of 15 cm. These samples has an axial hole with 1.2 cm of diameter and 9 cm depth where the densimeter is placed. This densimeter consists of a cylinder of five centimeter length where inside a 241Am source, a lead shield and a plastic scintillator is axially placed. This scintillator is coupled to a light guide to light to a photocathode of a photomultiplier tube. The densimeter was tested using soil samples with water contents ranges from 5 to 25%. Linear correlation between count rates and water content has shown correlation coefficient better than 0.99. (author)
Attosecond dynamics of nuclear wavepackets induced by neutron Compton scattering
For the first time, time-dependent nuclear wavepacket theory is applied to the experimental context of neutron Compton scattering (NCS). The derivation is analogous to the well-known expression of infrared laser absorption spectra (IR-LAS) in terms of autocorrelation functions of nuclear wavepackets moving on molecular potential energy surfaces in the electronic ground state. This analogy allows us to transfer the methods for nuclear wavepacket dynamics from IR-LAS to NCS. Systematic investigations for two model systems, HOD and C6D5H, demonstrate the effects of nuclear dynamics induced by NCS in the as (10-18 s) time domain on the NCS spectra. This is a consequence of the large momentum transfer from the neutron to the scattering atom and consequentially the ultrashort time for the nuclear wavepacket to travel the distance of its narrow width, followed by dissociation. This initial time evolution may be described approximately in terms of normal mode vibrations, together with additional excitations of translations and rotations which support depletion of any recurrences of the vibrational autocorrelation functions, also due to dissociation. In spite of the analogous derivation we predict some surprising, opposite trends in NCS i.e. in contrast to LAS. Thus, increasing the number of excited modes for polyatomic molecules, the resulting dynamics slow down for NCS and therefore, the spectral width narrows
Beam-shape effects in nonlinear Compton and Thomson scattering
We discuss intensity effects in collisions between beams of optical photons from a high-power laser and relativistic electrons. Our main focus is on the modifications of the emission spectra due to realistic finite-beam geometries. By carefully analyzing the classical limit we precisely quantify the distinction between strong-field QED Compton scattering and classical Thomson scattering. A purely classical, but fully covariant, calculation of the bremsstrahlung emitted by an electron in a plane-wave laser field yields radiation into harmonics, as expected. This result is generalized to pulses of finite duration and explains the appearance of line broadening and harmonic substructure as an interference phenomenon. The ensuing numerical treatment confirms that strong focusing of the laser leads to a broad continuum while higher harmonics become visible only at moderate focusing, and hence lower intensity. We present a scaling law for the backscattered photon spectral density which facilitates averaging over electron beam phase space. Finally, we propose a set of realistic parameters such that the observation of intensity-induced spectral red shift, higher harmonics, and their substructure becomes feasible.
Hadron radiation scattering on nuclei and Compton effect at small energy
A possibility of studying the Compton scattering on hadron at low energies by measuring the cross section of high-energy hadron radiation scattering on nuclei is discussed. It is shown that the method considered may be interesting not only in the study on the Compton scattering on non-stable hadrons but also in the case of proton and neutron it may be more preferable than photon direct scattering from the view point of the measured effect. An expression for #bettaπ#-scattering cross section permitting to obtain π-meson polarizability according to the experimental data on #bettaπ#-scattering is obtained
Spin and orbital magnetisation densities determined by Compton scattering of photons
Compton scattering of a circularly polarized photon beam is shown to provide direct information on orbital and spin magnetisation densities. Experiments are reported which demonstrate the feasibility of the method by correctly predicting the ratio of spin and orbital magnetisation components in iron and cobalt. A partially polarised beam of 45 keV photons from the Daresbury Synchrotron Radiation Source produces charge-magnetic interference scattering which is measured by a field-difference method. Theory shows that the interference cross section contains the Compton profile of polarised electrons modulated by a structure factor which is a weighted sum of spin and orbital magnetisations. In particular, the scattering geometry for which the structure factor vanishes yields a unique value for the ratio of the magnetisation densities. Compton scattering, being an incoherent process, provides data on total unit cell magnetisations which can be directly compared with bulk data. In this respect, Compton scattering complements magnetic neutron and photon Bragg diffraction. (author)
Narrowband inverse Compton scattering x-ray sources at high laser intensities
Seipt, D; Surzhykov, A; Fritzsche, S
2014-01-01
Narrowband x- and gamma-ray sources based on the inverse Compton scattering of laser pulses suffer from a limitation of the allowed laser intensity due to the onset of nonlinear effects that increase their bandwidth. It has been suggested that laser pulses with a suitable frequency modulation could compensate this ponderomotive broadening and reduce the bandwidth of the spectral lines, which would allow to operate narrowband Compton sources in the high-intensity regime. In this paper we, therefore, present the theory of nonlinear Compton scattering in a frequency modulated intense laser pulse. We systematically derive the optimal frequency modulation of the laser pulse from the scattering matrix element of nonlinear Compton scattering, taking into account the electron spin and recoil. We show that, for some particular scattering angle, an optimized frequency modulation completely cancels the ponderomotive broadening for all harmonics of the backscattered light. We also explore how sensitive this compensation ...
Compton scattering imaging of a working battery using synchrotron high-energy X-rays
Synchrotron-based Compton scattering imaging has visualized the interior of a battery under in situ and operando conditions. Results of studies on Compton scattering imaging using synchrotron high-energy X-rays are reported. The technique is applied to a discharging coin cell, and the intensity of Compton scattered X-rays from the inside of the cell has been measured as a function of position and time. The position–time intensity map captures the migration of lithium ions in the positive electrode and reveals the structural change due to the volume expansion of the electrode. This experiment is a critical step in developing synchrotron-based Compton scattering imaging for electrochemical cells at a product level
Constraint on Parameters of Inverse Compton Scattering Model for PSR B2319+60
H. G. Wang; M. Lv
2011-03-01
Using the multifrequency radio profiles of pulsar PSR B2319+60, two parameters of inverse Compton scattering model, the initial Lorentz factor and the factor of energy loss of relativistic particles are constrained.
Compton scattering imaging of a working battery using synchrotron high-energy X-rays
Itou, Masayoshi, E-mail: mito@spring8.or.jp [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan); Orikasa, Yuki; Gogyo, Yuma [Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Suzuki, Kosuke; Sakurai, Hiroshi [Faculty of Science and Technology, Gunma University, 1-5-1 Tenjin-cho, Kiryu, Gunma 376-8515 (Japan); Uchimoto, Yoshiharu [Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501 (Japan); Sakurai, Yoshiharu [Japan Synchrotron Radiation Research Institute, 1-1-1 Kouto, Sayo, Hyogo 679-5198 (Japan)
2015-01-01
Synchrotron-based Compton scattering imaging has visualized the interior of a battery under in situ and operando conditions. Results of studies on Compton scattering imaging using synchrotron high-energy X-rays are reported. The technique is applied to a discharging coin cell, and the intensity of Compton scattered X-rays from the inside of the cell has been measured as a function of position and time. The position–time intensity map captures the migration of lithium ions in the positive electrode and reveals the structural change due to the volume expansion of the electrode. This experiment is a critical step in developing synchrotron-based Compton scattering imaging for electrochemical cells at a product level.
Properties of Differential Scattering Section Based on Multi-photon Nonlinear Compton Effect
无
2002-01-01
Properties of damping electrons in collision with photons based on multi-photon nonlinear Compton effect are investigated. The expressions of the differential scattering section are derived. Several useful conclusions are drawn.
Compton scattering and nucleon polarisabilities in chiral EFT: Status and future
Grießhammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.
2016-05-01
We review theoretical progress and prospects for determining the nucleon's static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1-5] for details and a more thorough bibliography.
News on Compton Scattering γX → γX in Chiral EFT
Grießhammer, Harald W.; McGovern, Judith A.; Phillips, Daniel R.
2016-03-01
We review theoretical progress and prospects to understand the nucleon's static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1-5] for details and a more thorough bibliography.
Scattering and absorption differential cross sections for double photon Compton scattering
B S Sandhu; M B Saddi; B Singh; B S Ghumman
2001-10-01
The scattering and absorption differential cross sections for nonlinear QED process such as double photon Compton scattering have been measured as a function of independent ﬁnal photon energy. The incident gamma photons are of 0.662 MeV in energy as produced by an 8 Ci137Cs radioactive source and thin aluminum foils are used as scatterer. The two simultaneously emitted photons in this process are detected in coincidence using two NaI(T1) scintillation detectors and a slow-fast coincidence set-up of 30 nsec resolving time. The measured values of scattering and absorption differential cross sections agree with theory within experimental estimated error.
Wide Angle Compton Scattering within the SCET factorization Framework
Kivel Nikolay
2016-01-01
Full Text Available Existing data for the electromagnetic proton form factors and for the cross section of the wide angle Compton scattering (WACS show that the hard two-gluon exchange mechanism (collinear factorization is still not applicable in the kinematical region where Mandelstam variables s ~ −t ~ −u are about few GeV2. On the other hand these observables can be described in phenomenological models where spectator quarks are soft which assumes a large contribution due to the soft-overlap mechanism. It turns out that the simple QCD factorization picture is not complete and must also include the soft-overlap contribution which can be described as a certain matrix element in the soft collinear effective theory (SCET. Then the leading power contribution to WACS amplitude is described as a sum of the hard- and soft-spectator contributions. The existing experimental data allows one to check certain conclusions based on the assumption about dominant role of the soft-spectator mechanism.
Beam Diagnostics for Laser Undulator Based on Compton Backward Scattering
Kuroda, R
2005-01-01
A compact soft X-ray source is required in various research fields such as material and biological science. The laser undulator based on Compton backward scattering has been developed as a compact soft X-ray source for the biological observation at Waseda University. It is performed in a water window region (250eV - 500 eV) using the interaction between 1047 nm Nd:YLF laser (10ps FWHM) and about 5 MeV high quality electron beam (10ps FWHM) generated from rf gun system. The range of X-ray energy in the water window region has K-shell absorption edges of Oxygen, Carbon and Nitrogen, which mainly constitute of living body. Since the absorption coefficient of water is much smaller than the protein's coefficient in this range, a dehydration of the specimens is not necessary. To generate the soft X-ray pulse stably, the electron beam diagnostics have been developed such as the emittance measurement using double slit scan technique, the bunch length measurement using two frequency analysis technique. In this confere...
Deeply virtual Compton Scattering cross section measured with CLAS
Guegan, Baptistse [Institut de Physique Nucleaire, Orsay
2014-09-01
The Generalized Parton Distributions (GPDs) provide a new description of nucleon structure in terms of its elementary constituents, the quarks and the gluons. Including and extending the information provided by the form factors and the parton distribution functions, they describe the correlation between the transverse position and the longitudinal momentum fraction of the partons in the nucleon. Deeply Virtual Compton Scattering (DVCS), the electroproduction of a real photon on a single quark in the nucleon eN --> e'N'g, is the exclusive process most directly interpretable in terms of GPDs. A dedicated experiment to study DVCS with the CLAS detector at Jefferson Lab has been carried out using a 5.9-GeV polarized electron beam and an unpolarized hydrogen target, allowing us to collect DVCS events in the widest kinematic range ever explored in the valence region : 1.0 < Q2 < 4.6 GeV2, 0.1 < xB < 0.58 and 0.09 < -t < 2.0 GeV2. In this paper, we show preliminary results of unpolarized cross sections and of polarized cross section differences for the DVCS channel.
Theoretical description of deeply virtual Compton scattering off $^3$He
Rinaldi, Matteo
2014-01-01
Recently, coherent deeply virtual Compton scattering (DVCS) off $^3$He nuclei has been proposed to access the neutron generalized parton distributions (GPDs). In Impulse Approximation (IA) studies, it has been shown, in particular, that the sum of the two leading twist, quark helicity conserving GPDs of $^3$He, $H$ and $E$, at low momentum transfer, is dominated by the neutron contribution, so that $^3$He is very promising for the extraction of the neutron information. Nevertheless, such an extraction could be not trivial. A technique, able to take into account the nuclear effects included in the IA analysis in the extraction procedure, has been therefore developed. In this work, the IA calculation of the spin dependent GPD $\\tilde H$ of $^3$He is presented for the first time. This quantity is found to be largely dominated, at low momentum transfer, by the neutron contribution, which could be extracted using arguments similar to the ones previously proposed for the other GPDs. The known forward limit of the I...
Deeply virtual Compton scattering off longitudinally polarised protons at HERMES
This thesis details the simultaneous extraction of three polarisation-dependent asymmetries in the distribution of real photons from the ep→epγ interaction and its indistinguishable deeply virtual Compton scattering and Bethe-Heitler processes at the HERMES fixed-target experiment at Desy. The data analysed were taken using a longitudinally polarised 27.57 GeV positron beam incident on a longitudinally polarised hydrogen gas target. The extracted asymmetries include two single-spin asymmetries AUL and ALU which depend on the polarisation of the target and beam respectively, averaged over all other polarisation states. The double-spin asymmetry ALL dependent on the product of the beam and target polarisations is extracted for the first time. The asymmetry amplitudes extracted relate to combinations of Generalised Parton Distributions (GPDs), predominantly H and H. The extracted amplitudes are presented across the HERMES kinematic range alongside theoretical predictions from a GPD model based on double distributions. Large sin φ and cos(0φ) amplitudes are observed for AUL and ALL respectively, with an unexpectedly large sin(2φ) amplitude for AUL. The results for the AUL and ALL asymmetries are broadly compatible with theory predictions, and the extracted ALU amplitudes are compatible with HERMES results extracted from a significantly larger data set. It is foreseen that these results will form input to future global data-based GPD models which aim to provide a better understanding of GPDs. (orig.)
Deeply virtual Compton scattering off unpolarised deuterium at HERMES
The HERMES experiment was a forward angle spectrometer on the HERA storage ring at DESY, Hamburg, Germany. HERMES successfully increased understanding of the ''spin puzzle'', the spin structure of the nucleon, by providing high precision measurements of ΔΣ in the Quark Parton Model, the fraction of the spin carried by the current quarks. Following the link of another piece of the puzzle, the orbital angular momentum of quarks and gluons, to the Generalised Parton Distribution (GPD) theoretical framework, HERMES focused on measurements of the Deeply Virtual Compton Scattering (DVCS) process. These measurements are sensitive to GPDs, allowing further experimental constraints to be made on the components of nucleon spin. In the Winter shutdown period 2005-2006 HERMES was upgraded with a Recoil Detector in the target region. This allowed the experiment to make exclusive measurements of the DVCS process for the rst time, reducing background and increasing the resolution of various kinematic variables. The method for reconstructing particle tracks in the inhomogeneous magnetic eld is investigated here. DVCS o a deuterium target is measured with all available data prior to the installation of the Recoil Detector. A comparison is made to currently available models of spin-(1)/(2) GPDs. This analysis has been approved for publication by the HERMES collaboration. The data is further employed in an investigation of a model dependent constraint of the total angular momentum of up and down quarks in the nucleon. (orig.)
Selected HERMES results on deeply virtual compton scattering
Riedl, Caroline [DESY, Zeuthen (Germany)
2009-07-01
The HERMES experiment has collected a rich data set for the analysis of Deeply Virtual Compton Scattering (DVCS), employing different settings of the beam helicity, the beam charge, the target polarization (both longitudinal and transverse) and the target type (H, D and heavier nuclei). The azimuthal asymmetries measured for the exclusive DVCS reaction allow to access the imaginary and/or real part of certain Generalized Parton Distributions (GPDs). Those GPDs are of great theoretical interest as they embody both spatial and momentum density information of quarks and gluons. Moreover, in a certain kinematic limit, certain moments of the quark (gluon) GPDs E and H deliver the total angular momentum carried by quarks (gluons) in the nucleon. Until the year 2005, the recoiling target nucleon from the DVCS reaction was not detected by HERMES. Exclusivity was ensured indirectly by a missing-mass-technique. Data with a new Recoil Detector were taken in the last two years of HERA running. The Recoil Detector can identify the recoiling target nucleon and the particles from underlying background processes and can thus be used to directly tag exclusive events and to reject competing background channels. Selected DVCS results are shown and an outlook to results from the HERMES Recoil Detector is presented.
Neutron Polarisabilities from Deuteron Compton Scattering in \\chiEFT
Griesshammer, Harald W
2007-01-01
Chiral Effective Field Theory is for photon energies up to 200 MeV the tool to accurately determine the polarisabilities of the neutron from deuteron Compton scattering. A multipole analysis reveals that dispersive effects from an explicit Delta(1232) prove in particular indispensable to understand the data at 95 MeV measured at SAL. Simple power-counting arguments derived from nuclear phenomenology lead to the correct Thomson limit and gauge invariance. At next-to-leading order, the static scalar dipole polarisabilities are extracted as identical for proton and neutron within the error-bar of available data: \\alpha^n=11.6\\pm1.5_stat\\pm0.6_Baldin, \\beta^n=3.6\\mp1.5_stat\\pm0.6_Baldin for the neutron, in units of 10^-4 fm^3, compared to \\alpha^p=11.0\\pm1.4_stat\\pm0.4_Baldin, \\beta}^p=2.8\\mp1.4_stat\\pm0.4_Baldin for the proton in the same framework. New experiments e.g. at MAXlab (Lund) will improve the statistical error-bar.
Deeply virtual Compton scattering off unpolarised deuterium at HERMES
Hill, Gordon D.
2008-10-15
The HERMES experiment was a forward angle spectrometer on the HERA storage ring at DESY, Hamburg, Germany. HERMES successfully increased understanding of the ''spin puzzle'', the spin structure of the nucleon, by providing high precision measurements of {delta}{sigma} in the Quark Parton Model, the fraction of the spin carried by the current quarks. Following the link of another piece of the puzzle, the orbital angular momentum of quarks and gluons, to the Generalised Parton Distribution (GPD) theoretical framework, HERMES focused on measurements of the Deeply Virtual Compton Scattering (DVCS) process. These measurements are sensitive to GPDs, allowing further experimental constraints to be made on the components of nucleon spin. In the Winter shutdown period 2005-2006 HERMES was upgraded with a Recoil Detector in the target region. This allowed the experiment to make exclusive measurements of the DVCS process for the rst time, reducing background and increasing the resolution of various kinematic variables. The method for reconstructing particle tracks in the inhomogeneous magnetic eld is investigated here. DVCS o a deuterium target is measured with all available data prior to the installation of the Recoil Detector. A comparison is made to currently available models of spin-(1)/(2) GPDs. This analysis has been approved for publication by the HERMES collaboration. The data is further employed in an investigation of a model dependent constraint of the total angular momentum of up and down quarks in the nucleon. (orig.)
Preliminary observation of nonlinear effects in Compton scattering
In a new experiment at the Final Focus Test Beam at SLAC a low- emittance 46.6 GeV electron beam is brought into collision with terawatt pulses from a 1.06 μ wavelength Nd:glass laser. Peak laser intensities of 1018 W/cm2 have been achieved corresponding to a value of 0.6 for the parameter η = eE/mw0c, and to a value of 0.3 for the parameter Υ = E*/Ecrit = 2γehE/m2c3 in the case of frequency doubled laser pulses. In these circumstances an electron that crosses the center of the laser pulse has near unit interaction probability. Signals are presented for multiphoton Compton scattering in which up to 4 laser photons interact with an electron. High energy backscattered photons of GeV energy can interact within the laser focus to create electron- positron pairs; an excess of 15 positrons above a background of 14 was observed in a run of 6,000 laser shots
Second harmonic stimulated Compton scattering of laser in a plasma
An intense laser of frequency ω 0 and wavenumber k-vector0 produces longitudinal electron velocity v-vector2ω0 at (2ω0, 2k-vector0). This velocity couples a plasma wave (ω,k-vector) and a sideband electromagnetic wave (ω-2ω0, k-vektor - 2k-vector0). The density perturbation associated with the plasma wave couples with v-vector2ω0 to produce a nonlinear current driving the sideband. The magnetic field of the sideband couples with v-vector2ω0 to exert a pondero-motive force on electrons driving the plasma wave. The process can take place at any density ne up to the critical density ncr corresponding to laser frequency ω 0. At electron temperature Te ≥1 keV, the plasma wave is strongly Landau damped on electrons for ne ≤ncr/4, and the process appears as stimulated Compton scattering (SCS) producing side bands at second harmonic laser frequency shifted by the plasma frequency. At laser intensity IL ∼1017 W cm-2 at 1 μ m, the SCS instability grows on a sub pico second timescale
A system for monitoring multiple scatter during a clinical Compton scatter densitometry measurement of bone density is described. Multiple scatter from the measurement site was measured using a supplementary collimated detector positioned so that only multiply scattered photons could enter the detector. The data from the detector were used to form a multiple-scatter correction factor (mcf) to correct for the bias attributed to multiple scatter. The results of experimental and computer simulations are presented which demonstrate the relationship between the multiple-scatter reading and calculated mcf values. The influence of bone size on the values of mcf in large measurement sites, such as the femoral neck, was shown to be negligible. A simulation was used to produce a visualization of the multiple scatter in order to ascertain the optimum position of the supplementary detector. This technique was shown to be a rapid and accurate method of measuring the multiple-scatter bias and suitable for use during clinical CSD measurements. (author)
Rao, D V; Brunetti, A; Gigante, G E
2003-01-01
Total Compton, individual shell and Compton energy-absorption scattering cross-sections are evaluated in the energy region 0.005 to 10 MeV for H, C. N, O. P and Ca. Compton energy absorption cross-sections deviate numerically with available values. The cause of the numerical discrepancies are not fully understood but can be attributed to Doppler broadening of the Compton scattered photons through a given angle. (authors)
Scattering for the radial 3d cubic wave equation
Dodson, Benjamin; Lawrie, Andrew
2014-01-01
Consider the Cauchy problem for the radial cubic wave equation in 1+3 dimensions with either the focusing or defocusing sign. This problem is critical in $\\dot{H}^{\\frac{1}{2}} \\times \\dot{H}^{-\\frac{1}{2}}$ and subcritical with respect to the conserved energy. Here we prove that if the critical norm of a solution remains bounded on the maximal time-interval of existence, then the solution must in fact be global-in-time and scatter to free waves as $t \\to \\pm \\infty$.
Hamamatsu SHR74000 is a newly designed full three-dimensional (3D) whole body positron emission tomography (PET) scanner with small crystal size and large field of view (FOV). With the improvement of sensitivity, the scatter events increase significantly at the same time, especially for large objects. Monte Carlo simulations help us to understand the scatter phenomena and provide good references for scatter correction. In this paper, we introduce an effective scatter correction method based on single scatter simulation for the new PET scanner, which accounts for the full 3D scatter correction. With the results from Monte Carlo simulations, we implement a new scale method with special concentration on scatter events from outside the axial FOV and multiple scatter events. The effects of scatter correction are investigated and evaluated by phantom experiments; the results show good improvements in quantitative accuracy and contrast of the images, even for large objects. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
Magnetic Compton scattering using the elliptical multipole wiggler at sector 11-ID-B
Magnetic Compton scattering has been used to measure the momentum distribution of magnetic electrons in several materials. The polarization and frequency tunability of the elliptical multipole wiggler (EMW) makes it an ideal source for magnetic Compton scattering experiments. We performed the measurements using 50, 100 and 150 keV photons simultaneously. The EMW was operated at Ky=14 (Ec=32 keV) and Kx between 0.6 and 1.03. The degree of circular polarization was about 80% or higher. The sample was mounted between the poles of an electromagnet in a field of 0.8 T. The majority of Compton scattering measurements were performed by switching the magnet polarity. Tests using an iron foil target gave a similar magnetic Compton profile by either switching the magnetic field or the photon helicity. A 9-element Ge solid state detector array was used for detection
Deeply virtual Compton scattering off longitudinally polarised protons at HERMES
Mahon, David Francis
2010-06-15
This thesis details the simultaneous extraction of three polarisation-dependent asymmetries in the distribution of real photons from the ep{yields}ep{gamma} interaction and its indistinguishable deeply virtual Compton scattering and Bethe-Heitler processes at the HERMES fixed-target experiment at Desy. The data analysed were taken using a longitudinally polarised 27.57 GeV positron beam incident on a longitudinally polarised hydrogen gas target. The extracted asymmetries include two single-spin asymmetries A{sub UL} and A{sub LU} which depend on the polarisation of the target and beam respectively, averaged over all other polarisation states. The double-spin asymmetry A{sub LL} dependent on the product of the beam and target polarisations is extracted for the first time. The asymmetry amplitudes extracted relate to combinations of Generalised Parton Distributions (GPDs), predominantly H and H. The extracted amplitudes are presented across the HERMES kinematic range alongside theoretical predictions from a GPD model based on double distributions. Large sin {phi} and cos(0{phi}) amplitudes are observed for A{sub UL} and A{sub LL} respectively, with an unexpectedly large sin(2{phi}) amplitude for A{sub UL}. The results for the A{sub UL} and A{sub LL} asymmetries are broadly compatible with theory predictions, and the extracted A{sub LU} amplitudes are compatible with HERMES results extracted from a significantly larger data set. It is foreseen that these results will form input to future global data-based GPD models which aim to provide a better understanding of GPDs. (orig.)
Comparative evaluation of scatter correction techniques in 3D positron emission tomography
Zaidi, H
2000-01-01
Much research and development has been concentrated on the scatter compensation required for quantitative 3D PET. Increasingly sophisticated scatter correction procedures are under investigation, particularly those based on accurate scatter models, and iterative reconstruction-based scatter compensation approaches. The main difference among the correction methods is the way in which the scatter component in the selected energy window is estimated. Monte Carlo methods give further insight and might in themselves offer a possible correction procedure. Methods: Five scatter correction methods are compared in this paper where applicable. The dual-energy window (DEW) technique, the convolution-subtraction (CVS) method, two variants of the Monte Carlo-based scatter correction technique (MCBSC1 and MCBSC2) and our newly developed statistical reconstruction-based scatter correction (SRBSC) method. These scatter correction techniques are evaluated using Monte Carlo simulation studies, experimental phantom measurements...
High-Power Laser Pulse Recirculation for Inverse Compton Scattering-Produced Gamma-Rays
Jovanovic, I; Shverdin, M; Gibson, D; Brown, C
2007-04-17
Inverse Compton scattering of high-power laser pulses on relativistic electron bunches represents an attractive method for high-brightness, quasi-monoenergetic {gamma}-ray production. The efficiency of {gamma}-ray generation via inverse Compton scattering is severely constrained by the small Thomson scattering cross section. Furthermore, repetition rates of high-energy short-pulse lasers are poorly matched with those available from electron accelerators, resulting in low repetition rates for generated {gamma}-rays. Laser recirculation has been proposed as a method to address those limitations, but has been limited to only small pulse energies and peak powers. Here we propose and experimentally demonstrate an alternative method for laser pulse recirculation that is uniquely capable of recirculating short pulses with energies exceeding 1 J. Inverse Compton scattering of recirculated Joule-level laser pulses has a potential to produce unprecedented peak and average {gamma}-ray brightness in the next generation of sources.
Influence of Heat-radiating on Multi-photon Compton Scattering High-energy Electron
HAO Dong-shan; WANG Xin-min
2007-01-01
Using the model of the inverse Compton scattering between high-energy electrons and heat-radiation photons, the influence of heat-radiating photons on multi-photon Compton scattering high-energy electrons is studied . The results show that the energy loss, power loss, light resistance and light pressure of the high-energy electron formed by heat radiating are all proportional to the temperature T4 of the vacuum cavity of the electron,the Lorentz factor γ2 of the high-energy electrons, the scattering section of the electron and the number of photons acting at the same time with high-energy electrons. A good method for lessening the energy loss of the high-energy electron by using the one-photon Compton scattering between high-energy electrons and heat radiation photons is proposed.
Form factor description of the non-collinear Compton scattering tensor
Lu, W
1997-01-01
We present a parameterization of the non-collinear (virtual) Compton scattering tensor in terms of form factors, in which the Lorentz tensor associated with each form factor possesses manifest electromagnetic gauge invariance. The main finding is that in a well-defined form factor expansion of the scattering tensor, the form factors are either symmetric or antisymmetric under the exchange of two Mandelstam variables, $s$ and $u$. Our decomposition can be used to organize complicated higher-order and higher-twist contributions in the study of the virtual Compton scattering off the proton. Such procedures are illustrated by use of the virtual Compton scattering off the lepton. In passing, we note the general symmetry constraints on Ji's off-diagonal parton distributions and Rudyushkin's non-forward distribution amplitudes with two variables.
A pedagogic model for Deeply Virtual Compton Scattering with quark-hadron duality
Close, Francis Edwin; Close, Frank E; Zhao, Qiang
2002-01-01
We show how quark-hadron duality can emerge for the valence spin averaged structure functions, and for the non-forward distributions of Deeply Virtual Compton Scattering. Novel factorisations of the non-forward amplitudes are proposed. Some implications for large angle scattering and deviations from the quark counting rules are illustrated.
On the Origin of the Intensity Deficit in Neutron Compton Scattering
Reiter, G. F.; Platzman, P. M.
2004-01-01
Neutron Compton Scattering measurements in a variety of materials have shown a relative deficit in the total signal from hydrogen compared to deuterium and heavier ions. We show here that a breakdown in the Born-Oppenheimer approximation in the final states of the scattering process leads to such a deficit, and may be responsible for the effect.
Sensitivity Analysis of the Scattering-Based SARBM3D Despeckling Algorithm.
Di Simone, Alessio
2016-01-01
Synthetic Aperture Radar (SAR) imagery greatly suffers from multiplicative speckle noise, typical of coherent image acquisition sensors, such as SAR systems. Therefore, a proper and accurate despeckling preprocessing step is almost mandatory to aid the interpretation and processing of SAR data by human users and computer algorithms, respectively. Very recently, a scattering-oriented version of the popular SAR Block-Matching 3D (SARBM3D) despeckling filter, named Scattering-Based (SB)-SARBM3D, was proposed. The new filter is based on the a priori knowledge of the local topography of the scene. In this paper, an experimental sensitivity analysis of the above-mentioned despeckling algorithm is carried out, and the main results are shown and discussed. In particular, the role of both electromagnetic and geometrical parameters of the surface and the impact of its scattering behavior are investigated. Furthermore, a comprehensive sensitivity analysis of the SB-SARBM3D filter against the Digital Elevation Model (DEM) resolution and the SAR image-DEM coregistration step is also provided. The sensitivity analysis shows a significant robustness of the algorithm against most of the surface parameters, while the DEM resolution plays a key role in the despeckling process. Furthermore, the SB-SARBM3D algorithm outperforms the original SARBM3D in the presence of the most realistic scattering behaviors of the surface. An actual scenario is also presented to assess the DEM role in real-life conditions. PMID:27347971
Electronic structure of lanthanum sesquioxide: A Compton scattering study
Sharma, Sonu [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India); Sahariya, Jagrati [Department of Physics, Manipal University Jaipur, Jaipur 303007, Rajasthan (India); Arora, Gunjan [Department of Physics, Geetanjali Institute of Technical Studies, Udaipur 313022, Rajasthan (India); Ahuja, B.L., E-mail: blahuja@yahoo.com [Department of Physics, M.L. Sukhadia University, Udaipur 313001, Rajasthan (India)
2014-10-01
We present the first-ever experimental and theoretical momentum densities of La{sub 2}O{sub 3}. The Compton line shape is measured using a 20 Ci {sup 137}Cs Compton spectrometer at an intermediate resolution with full width at half maximum of 0.34 a.u. The experimental Compton profile is compared with the theoretical electron momentum densities computed using linear combination of atomic orbitals (LCAO) method with density functional theory (DFT). It is seen that the generalized gradient approximation (GGA) within DFT reconciles better with the experiment than other DFT based approximations, validating the GGA approximation for rare-earth sesquioxides. The energy bands and density of states computed using LCAO calculations show its wide band gap nature which is in tune with the available reflectivity and photo-absorption data. In addition, Mulliken's population and charge density are also computed and discussed.
Electronic structure of lanthanum sesquioxide: A Compton scattering study
We present the first-ever experimental and theoretical momentum densities of La2O3. The Compton line shape is measured using a 20 Ci 137Cs Compton spectrometer at an intermediate resolution with full width at half maximum of 0.34 a.u. The experimental Compton profile is compared with the theoretical electron momentum densities computed using linear combination of atomic orbitals (LCAO) method with density functional theory (DFT). It is seen that the generalized gradient approximation (GGA) within DFT reconciles better with the experiment than other DFT based approximations, validating the GGA approximation for rare-earth sesquioxides. The energy bands and density of states computed using LCAO calculations show its wide band gap nature which is in tune with the available reflectivity and photo-absorption data. In addition, Mulliken's population and charge density are also computed and discussed
Electronic structure of lanthanum sesquioxide: A Compton scattering study
Sharma, Sonu; Sahariya, Jagrati; Arora, Gunjan; Ahuja, B. L.
2014-10-01
We present the first-ever experimental and theoretical momentum densities of La2O3. The Compton line shape is measured using a 20 Ci 137Cs Compton spectrometer at an intermediate resolution with full width at half maximum of 0.34 a.u. The experimental Compton profile is compared with the theoretical electron momentum densities computed using linear combination of atomic orbitals (LCAO) method with density functional theory (DFT). It is seen that the generalized gradient approximation (GGA) within DFT reconciles better with the experiment than other DFT based approximations, validating the GGA approximation for rare-earth sesquioxides. The energy bands and density of states computed using LCAO calculations show its wide band gap nature which is in tune with the available reflectivity and photo-absorption data. In addition, Mulliken's population and charge density are also computed and discussed.
Xu, Wenjiang; Wickersham, A J; Wu, Yue; He, Fan; Ma, Lin
2015-03-20
This work reports the measurements of 3D flame topography using tomographic chemiluminescence and its validation by direct comparison against planar Mie scattering measurements. Tomographic measurements of the 3D topography of various well-controlled laboratory flames were performed using projections measured by seven cameras, and a simultaneous Mie scattering measurement was performed to measure a 2D cross section of the 3D flame topography. The tomographic measurements were based on chemiluminescence emissions from the flame, and the Mie scattering measurements were based on micrometer-size oil droplets seeded into the flow. The flame topography derived from the 3D tomographic and the Mie scattering measurement was then directly compared. The results show that the flame topography obtained from tomographic chemiluminescence and the Mie measurement agreed qualitatively (i.e., both methods yielded the same profile of the flame fronts), but a quantitative difference on the order of millimeters was observed between these two methods. These results are expected to be useful for understanding the capabilities and limitations of the 3D tomographic and Mie scattering techniques in combustion diagnostics. PMID:25968497
Spin density in Gd studied by magnetic Compton scattering
The spin-dependent momentum density of single-crystal ferromagnetic gadolinium was probed by the magnetic Compton profile technique. Comparison with electronic structure calculations indicate that the local spin-density approximation is adequate for describing the magnetic Compton profiles. Furthermore, the linear combination of muffin-tin orbitals prescription compared favourably with a full-potential method. We find that testing theory against the experimental density of states is problematic. Our calculations also indicate that the spin density is sensitive to the treatment of the 5p electrons. (author)
3D LTE spectral line formation with scattering in red giant stars
Hayek, W; Collet, R; Nordlund, Å
2011-01-01
We investigate the effects of coherent isotropic continuum scattering on the formation of spectral lines in local thermodynamic equilibrium (LTE) using 3D hydrodynamical and 1D hydrostatic model atmospheres of red giant stars. Continuum flux levels, spectral line profiles and curves of growth for different species are compared with calculations that treat scattering as absorption. Photons may escape from deeper, hotter layers through scattering, resulting in significantly higher continuum flux levels beneath a wavelength of 5000 A. The magnitude of the effect is determined by the importance of scattering opacity with respect to absorption opacity; we observe the largest changes in continuum flux at the shortest wavelengths and lowest metallicities; intergranular lanes of 3D models are more strongly affected than granules. Continuum scattering acts to increase the profile depth of LTE lines: continua gain more brightness than line cores due to their larger thermalization depth in hotter layers. We thus observe...
Dynamic scattering theory for dark-field electron holography of 3D strain fields
Lubk, Axel; Javon, Elsa; Cherkashin, Nikolay; Reboh, Shay; Gatel, Christophe; HYTCH, Martin
2014-01-01
Abstract: Dark-held electron holography maps strain in crystal lattices into reconstructed phases over large fields of view. Here we investigate the details of the lattice strain-reconstructed phase relationship by applying dynamic scattering theory both analytically and numerically. We develop efficient analytic linear projection rules for 3D strain fields, facilitating a straight-forward calculation of reconstructed phases from 3D strained materials. They are used in the following to quanti...
X-ray scattering in the elastic regime as source for 3D imaging reconstruction technique
Kocifaj, Miroslav; Mego, Michal
2015-11-01
X-ray beams propagate across a target object before they are projected onto a regularly spaced array of detectors to produce a routine X-ray image. A 3D attenuation coefficient distribution is obtained by tomographic reconstruction where scattering is usually regarded as a source of parasitic signals which increase the level of electromagnetic noise that is difficult to eliminate. However, the elastically scattered radiation could be a valuable source of information, because it can provide a 3D topology of electron densities and thus contribute significantly to the optical characterization of the scanned object. The scattering and attenuation data form a complementary base for concurrent retrieval of both electron density and attenuation coefficient distributions. In this paper we developed the 3D reconstruction method that combines both data inputs and produces better image resolution compared to traditional technology.
Compton scattering as a probe for materials investigation
S. Mohammadi
2009-01-01
This article investigates into the feasibility of using gamma radiation Compton backscatter spectra as a means of material characterization, with the view to developing a portable, hand held probe for investigative purposes such as searching for illicit substances hidden in wall or car door cavities.
Compton scattering as a probe for materials investigation
S Mohammadi
2009-09-01
Full Text Available This article investigates into the feasibility of using gamma radiation Compton backscatter spectra as a means of material characterization, with the view to developing a portable, hand held probe for investigative purposes such as searching for illicit substances hidden in wall or car door cavities.
A Compton scattering technique to determine wood density and locating defects in it
A Compton scattering technique is presented to determine density and void location in the given wooden samples. The technique uses a well collimated gamma ray beam from 137Cs along with the NaI(Tl) scintillation detector. First, a linear relationship is established between Compton scattered intensity and known density of chemical compounds, and then density of the wood is determined from this linear relation. In another experiment, the ability of penetration of gamma rays is explored to detect voids in wooden (low Z) sample. The sudden reduction in the Compton scattered intensities agrees well with the position and size of voids in the wooden sample. It is concluded that wood density and the voids of size ∼ 4 mm and more can be detected easily by this method
Inexpensive Mie scattering experiment for the classroom manufactured by 3D printing
Scholz, Christian; Sack, Achim; Heckel, Michael; Pöschel, Thorsten
2016-09-01
Scattering experiments are fundamental for structure analysis of matter on molecular, atomic and sub-atomic length scales. In contrast, it is not standard to demonstrate optical scattering experiments on the undergraduate level beyond simple diffraction gratings. We present an inexpensive Mie scattering setup manufactured with 3D printing and open hardware. The experiment can be used to determine the particle size in dilute monodisperse colloidal suspensions with surprisingly high accuracy and is, thus, suitable to demonstrate relations between scattering measurements and microscopic properties of particles within undergraduate lab course projects.
The limitations of resonant Compton scattering as a gamma-ray burst model
Brainerd, J. J.
1992-01-01
Resonant Compton upscattering is commended as a mechanism that produces a hard gamma-ray spectrum while suppressing X-rays. This model, however, has severe physical and observational limitations. Effective X-ray suppression places a lower limit on the electron density; above this limit X-rays scatter multiple times, so the single-scattering approximation of this mechanism is invalid. Multiple scattering produces a spectrum that is much harder than the single-scattering spectrum. As the Thomson optical depth of a power-law electron beam approaches unity, photon spawning commences at a high rate and physically invalidates the underlying electron distribution. The Compton upscattering model is therefore only valid over a narrow range of electron densities. An observational consequence of this model is the absence of the third cyclotron resonance. Resonant scattering produces gamma-rays that propagate nearly along the magnetic field. The resonant cross section of the third harmonic, which is strongly angle dependent, falls below the Compton continuum for these gamma rays. The observation of a third cyclotron resonance in a gamma-ray burst spectrum would eliminate resonant Compton scattering as a gamma-ray burst process.
Compton Scattering X-Ray Sources Driven by Laser Wakefield Acceleration
Hartemann, F V; Gibson, D J; Brown, W J; Rousse, A; Phuoc, K T; Pukhov, A
2005-10-19
Recent laser wakefield acceleration experiments have demonstrated the generation of femtosecond, nano-Coulomb, low emittance, nearly monokinetic relativistic electron bunches of sufficient quality to produce bright, tunable, ultrafast x-rays via Compton scattering. Design parameters for a proof-of-concept experiment are presented using a three-dimensional Compton scattering code and a laser-plasma interaction particle-in-cell code modeling the wakefield acceleration process; x-ray fluxes exceeding 10{sup 22} s{sup -1} are predicted, with a peak brightness > 10{sup 20} photons/(mm{sup 2} x mrad{sup 2} x s x 0.1% bandwidth).
A magnetic Compton scattering study of Ga rich Co-Ni-Ga ferromagnetic shape memory alloys
The temperature dependent spin momentum densities of Co1.8NiGa1.2 and Co2Ni0.76Ga1.24 alloys have been measured using the magnetic Compton scattering technique. The individual contributions of constituents in the formation of the total spin moment are also calculated using Compton line shape analysis. The magnetic Compton data when compared with the magnetization data obtained using a vibrating sample magnetometer show a negligible orbital contribution. The spin moments deduced from the experimental Compton data are compared with the theoretical results obtained from the full potential linearized augmented plane wave method and are found to be in good agreement. The origin of the magnetism in both alloys is also described in terms of the eg and t2g contributions of Ni and Co. (paper)
On the line-shape analysis of Compton profiles and its application to neutron scattering
Romanelli, G.; Krzystyniak, M.
2016-05-01
Analytical properties of Compton profiles are used in order to simplify the analysis of neutron Compton scattering experiments. In particular, the possibility to fit the difference of Compton profiles is discussed as a way to greatly decrease the level of complexity of the data treatment, making the analysis easier, faster and more robust. In the context of the novel method proposed, two mathematical models describing the shapes of differenced Compton profiles are discussed: the simple Gaussian approximation for harmonic and isotropic local potential, and an analytical Gauss-Hermite expansion for an anharmonic or anisotropic potential. The method is applied to data collected by VESUVIO spectrometer at ISIS neutron and muon pulsed source (UK) on Copper and Aluminium samples at ambient and low temperatures.
Electronic properties and Compton scattering studies of monoclinic tungsten dioxide
Heda, N. L.; Ahuja, Ushma
2015-01-01
We present the first ever Compton profile measurement of WO2 using a 20 Ci 137Cs γ-ray source. The experimental data have been used to test different approximations of density functional theory in linear combination of atomic orbitals (LCAO) scheme. It is found that theoretical Compton profile deduced using generalized gradient approximation (GGA) gives a better agreement than local density approximation and second order GGA. The computed energy bands, density of states and Mulliken's populations (MP) data confirm a metal-like behavior of WO2. The electronic properties calculated using LCAO approach are also compared with those obtained using full potential linearized augmented plane wave method. The nature of bonding in WO2 is also compared with isoelectronic WX2 (X=S, Se) compounds in terms of equal-valence-electron-density profiles and MP data, which suggest an increase in ionic character in the order WSe2→WS2→WO2.
Electronic properties and Compton scattering studies of monoclinic tungsten dioxide
We present the first ever Compton profile measurement of WO2 using a 20 Ci 137Cs γ-ray source. The experimental data have been used to test different approximations of density functional theory in linear combination of atomic orbitals (LCAO) scheme. It is found that theoretical Compton profile deduced using generalized gradient approximation (GGA) gives a better agreement than local density approximation and second order GGA. The computed energy bands, density of states and Mulliken's populations (MP) data confirm a metal-like behavior of WO2. The electronic properties calculated using LCAO approach are also compared with those obtained using full potential linearized augmented plane wave method. The nature of bonding in WO2 is also compared with isoelectronic WX2 (X=S, Se) compounds in terms of equal-valence-electron-density profiles and MP data, which suggest an increase in ionic character in the order WSe2→WS2→WO2. - Highlights: • Presented first-ever Compton profile (CP) measurements on WO2. • Analyzed CP data in terms of LCAO–DFT calculations. • Discussed energy band, DOS and Mulliken's population. • Discussed equally scaled CPs and bonding of isoelectronic WO2, WS2 and WSe2. • Reported metallic character and Fermi surface topology of WO2
Cross-sections for total and Compton scattering of circularly polarized photons by magnetic materials are presented. The expressions include scattering from both the spin and orbital magnetization densities, together with inelasticity corrections. (author)
Narrowband inverse Compton scattering x-ray sources at high laser intensities
Seipt, D.; Rykovanov, S. G.; Surzhykov, A.; Fritzsche, S.
2015-03-01
Narrowband x- and γ -ray sources based on the inverse Compton scattering of laser pulses suffer from a limitation of the allowed laser intensity due to the onset of nonlinear effects that increase their bandwidth. It has been suggested that laser pulses with a suitable frequency modulation could compensate this ponderomotive broadening and reduce the bandwidth of the spectral lines, which would allow one to operate narrowband Compton sources in the high-intensity regime. In this paper we therefore present the theory of nonlinear Compton scattering in a frequency-modulated intense laser pulse. We systematically derive the optimal frequency modulation of the laser pulse from the scattering matrix element of nonlinear Compton scattering, taking into account the electron spin and recoil. We show that, for some particular scattering angle, an optimized frequency modulation completely cancels the ponderomotive broadening for all harmonics of the backscattered light. We also explore how sensitively this compensation depends on the electron-beam energy spread and emittance, as well as the laser focusing.
Hayek, W; Carlsson, M; Trampedach, R; Collet, R; Gudiksen, B V; Hansteen, V H; Leenaarts, J
2010-01-01
We present the implementation of a radiative transfer solver with coherent scattering in the new BIFROST code for radiative magneto-hydrodynamical (MHD) simulations of stellar surface convection. The code is fully parallelized using MPI domain decomposition, which allows for large grid sizes and improved resolution of hydrodynamical structures. We apply the code to simulate the surface granulation in a solar-type star, ignoring magnetic fields, and investigate the importance of coherent scattering for the atmospheric structure. A scattering term is added to the radiative transfer equation, requiring an iterative computation of the radiation field. We use a short-characteristics-based Gauss-Seidel acceleration scheme to compute radiative flux divergences for the energy equation. The effects of coherent scattering are tested by comparing the temperature stratification of three 3D time-dependent hydrodynamical atmosphere models of a solar-type star: without scattering, with continuum scattering only, and with bo...
Evaluation of simulation-based scatter correction for 3-D PET cardiac imaging
Quantitative imaging of the human thorax poses one of the most difficult challenges for three-dimensional (3-D) (septaless) positron emission tomography (PET), due to the strong attenuation of the annihilation radiation and the large contribution of scattered photons to the data. In [18F] fluorodeoxyglucose (FDG) studies of the heart with the patient's arms in the field of view, the contribution of scattered events can exceed 50% of the total detected coincidences. Accurate correction for this scatter component is necessary for meaningful quantitative image analysis and tracer kinetic modeling. For this reason, the authors have implemented a single-scatter simulation technique for scatter correction in positron volume imaging. In this paper they describe this algorithm and present scatter correction results from human and chest phantom studies
Jeffrey, Natasha
2011-01-01
This paper aims to study the polarization of hard X-ray (HXR) sources in the solar atmosphere, including Compton backscattering of photons in the photosphere (the albedo effect) and the spatial distribution of polarization across the source. HXR photon polarization and spectra produced via electron-ion bremsstrahlung are calculated from electron distributions typical for solar flares. Compton scattering and photoelectric absorption are then modelled using Monte Carlo simulations of photon transport in the photosphere. Polarization maps across HXR sources (primary and albedo components) for each of the modelled electron distributions are calculated at various source locations from the solar centre to the limb. We show that Compton scattering produces a distinct polarization variation across the albedo patch at peak albedo energies of 20-50 keV for all anisotropies modelled. The results show that there are distinct spatial polarization changes in both the radial and perpendicular to radial directions across the...
Theory Viewpoint on Extracting Nucleon Polarisabilities in Low-Energy Compton Scattering
Griesshammer, Harald W; McGovern, Judith A; Pascalutsa, Vladimir; Pasquini, Barbara; Phillips, Daniel R
2014-01-01
During the workshop "Compton Scattering off Protons and Light Nuclei: pinning down the nucleon polarisabilities" (ECT*, Trento, Italy, 29 July -- 2 August 2013, http://www.ectstar.eu/node/98), recent developments had been reviewed in experimental and theoretical studies of real and virtual Compton scattering, static and generalized dipole scalar and spin polarisabilities of nucleons, as well as related phenomena in physics of muonic atoms. A vivid topic at the workshop was pathways towards the most precise extraction of the static polarisabilities from low-energy Compton cattering---including pertinent theoretical uncertainties. Being asked by our experimental colleagues, we prepared during the workshop a short letter with conclusions of the discussion, emphasising future prospects.
Improved surface-enhanced Raman scattering on arrays of gold quasi-3D nanoholes
Yue, Weisheng
2012-10-04
Arrays of gold quasi-3D nanoholes were proposed and fabricated as substrates for surface-enhanced Raman scattering (SERS). By detecting rhodamine 6G (R6G) molecules, the gold quasi-3D nanoholes demonstrated an SERS intensity that was 25-62 times higher than that of two-dimensional nanoholes with the same geometrical shapes and periodicities. The larger SERS enhancement of the quasi-3D nanoholes is attributed to the enhanced electromagnetic field on the top-layer nanohole, the bottom nanodiscs and the field coupling between the two layers. In addition, the investigation of the shape dependence of the SERS on the quasi-3D nanoholes demonstrated that the quadratic, circular, triangular and rhombic holes exhibited different SERS properties. Numerical simulations of the electromagnetic properties on the nanostructures were performed with CST Microwave Studio, and the results agree with the experimental observations. © 2012 IOP Publishing Ltd.
A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor
A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is done by means of the Klein-Nishina formula, but the multiple scattering is accounted for by making use of a dose buildup factor. An asset of the present model is the possibility of generating a complete two-dimensional (2D) PSF that can be used for 3D SPECT reconstruction by means of iterative algorithms. The proposed model is convenient in those situations where more exact techniques are not economical. For the proposed model's testing purpose calculations (for the point source in a nonuniform scattering object for parallel beam collimator geometry), the multiple-order scatter PSF generated by means of the proposed model matched well with those using Monte Carlo (MC) simulations. Discrepancies are observed only at the exponential tails mostly due to the high statistic uncertainty of MC simulations in this area, but not because of the inappropriateness of the model
A 3D point-kernel multiple scatter model for parallel-beam SPECT based on a gamma-ray buildup factor
Marinkovic, Predrag; Ilic, Radovan; Spaic, Rajko
2007-09-01
A three-dimensional (3D) point-kernel multiple scatter model for point spread function (PSF) determination in parallel-beam single-photon emission computed tomography (SPECT), based on a dose gamma-ray buildup factor, is proposed. This model embraces nonuniform attenuation in a voxelized object of imaging (patient body) and multiple scattering that is treated as in the point-kernel integration gamma-ray shielding problems. First-order Compton scattering is done by means of the Klein-Nishina formula, but the multiple scattering is accounted for by making use of a dose buildup factor. An asset of the present model is the possibility of generating a complete two-dimensional (2D) PSF that can be used for 3D SPECT reconstruction by means of iterative algorithms. The proposed model is convenient in those situations where more exact techniques are not economical. For the proposed model's testing purpose calculations (for the point source in a nonuniform scattering object for parallel beam collimator geometry), the multiple-order scatter PSF generated by means of the proposed model matched well with those using Monte Carlo (MC) simulations. Discrepancies are observed only at the exponential tails mostly due to the high statistic uncertainty of MC simulations in this area, but not because of the inappropriateness of the model.
Yoshida, Eiji, E-mail: rush@nirs.go.jp; Tashima, Hideaki; Yamaya, Taiga
2014-11-01
In a conventional PET scanner, coincidence events are measured with a limited energy window for detection of photoelectric events in order to reject Compton scatter events that occur in a patient, but Compton scatter events caused in detector crystals are also rejected. Scatter events within the patient causes scatter coincidences, but inter crystal scattering (ICS) events have useful information for determining an activity distribution. Some researchers have reported the feasibility of PET scanners based on a Compton camera for tracing ICS into the detector. However, these scanners require expensive semiconductor detectors for high-energy resolution. In the Anger-type block detector, single photons interacting with multiple detectors can be obtained for each interacting position and complete information can be gotten just as for photoelectric events in the single detector. ICS events in the single detector have been used to get coincidence, but single photons interacting with multiple detectors have not been used to get coincidence. In this work, we evaluated effect of sensitivity improvement using Compton kinetics in several types of DOI-PET scanners. The proposed method promises to improve the sensitivity using coincidence events of single photons interacting with multiple detectors, which are identified as the first interaction (FI). FI estimation accuracy can be improved to determine FI validity from the correlation between Compton scatter angles calculated on the coincidence line-of-response. We simulated an animal PET scanner consisting of 42 detectors. Each detector block consists of three types of scintillator crystals (LSO, GSO and GAGG). After the simulation, coincidence events are added as information for several depth-of-interaction (DOI) resolutions. From the simulation results, we concluded the proposed method promises to improve the sensitivity considerably when effective atomic number of a scintillator is low. Also, we showed that FI estimate
In a conventional PET scanner, coincidence events are measured with a limited energy window for detection of photoelectric events in order to reject Compton scatter events that occur in a patient, but Compton scatter events caused in detector crystals are also rejected. Scatter events within the patient causes scatter coincidences, but inter crystal scattering (ICS) events have useful information for determining an activity distribution. Some researchers have reported the feasibility of PET scanners based on a Compton camera for tracing ICS into the detector. However, these scanners require expensive semiconductor detectors for high-energy resolution. In the Anger-type block detector, single photons interacting with multiple detectors can be obtained for each interacting position and complete information can be gotten just as for photoelectric events in the single detector. ICS events in the single detector have been used to get coincidence, but single photons interacting with multiple detectors have not been used to get coincidence. In this work, we evaluated effect of sensitivity improvement using Compton kinetics in several types of DOI-PET scanners. The proposed method promises to improve the sensitivity using coincidence events of single photons interacting with multiple detectors, which are identified as the first interaction (FI). FI estimation accuracy can be improved to determine FI validity from the correlation between Compton scatter angles calculated on the coincidence line-of-response. We simulated an animal PET scanner consisting of 42 detectors. Each detector block consists of three types of scintillator crystals (LSO, GSO and GAGG). After the simulation, coincidence events are added as information for several depth-of-interaction (DOI) resolutions. From the simulation results, we concluded the proposed method promises to improve the sensitivity considerably when effective atomic number of a scintillator is low. Also, we showed that FI estimate
Angular correlations in double ionization of Helium by high-energy Compton scattering
Kaliman, Z. [Department of Physics, Faculty of Arts and Sciences, Omladinska 14, Rijeka (Croatia)], E-mail: kaliman@ffri.hr; Pisk, K.; Suric, T. [Rudjer Boskovic Institute, P.O. Box 180, Zagreb (Croatia)
2007-09-21
We present theoretical results for double differential cross section d{sup 2}{sigma}/d{omega}{sub 1}d{omega}{sub 2} in the process of double ionization of Helium by high-energy Compton scattering. We discuss the energy and angular dependence of the cross section, as well as the relative importance of shake and final state interaction mechanisms.
Reggeometry of deeply virtual compton scattering and exclusive diffractive vector meson production
We extend a simple Pomerons pole amplitude by t and Q2 , Mν, dependencies inspired by geometrical ideas. The experimentally transition from soft to hard dynamics is realized by the introduction of two Po meron poles with different Q2, Mν - dependent residue. A unified description of deeply virtual Compton scattering as well as the elastic electroproduction of all vector meson is suggested
Compton scattering from the free and bound proton above {pi}-threshold
Wissmann, F.; Achenbach, P.; Ahrens, J.; Arends, H.-J.; Beck, R.; Bilger, R.; Camen, M.; Capitani, G.P.; Caselotti, G.; Galler, G.; Grabmayr, P.; Haerter, F.; Hehl, T.; Heid, E.; Hejny, V.; Jahn, O.; Jennewein, P.; Kondratjev, R.; Kossert, K.; Kotulla, M.; Krusche, B.; Kuhr, V.; Lang, M.; Leukel, R.; Levchuk, M.I.; Lisin, V.; L' vov, A.I.; Massone, A.M.; Metag, V.; Natter, A.; Novotny, R.; Olmos de Leon, V.; Ottonello, P.; Peise, J.; Polonski, A.; Preobrashenskij, I.; Proff, S.; Rambo, F.; Robbiano, A.; Rosenkranz, D.; Sanzone, M.; Schilling, E.; Schmidt, A.; Schumacher, M.; Seitz, B.; Siodlaczek, U.; Smend, F.; Stroeher, H.; Vorwerk, H.; Walcher, Th.; Weiss, J.; Wolf, M.; Wolf, S.; Zapadtka, F
2000-01-31
The differential cross sections for Compton scattering from the proton have been measured at MAMI with three different detector setups. There is a good agreement among all the results. The theoretical calculation based on dispersion relations shows that there is no drastic change necessary in the parameters of this approach.
Designing scheme of a γ-ray ICT system using compton back-scattering
The designing scheme of a γ ray ICT system by using Compton back-scattering is put forward. The technical norms, detector system, γ radioactive source, mechanical scanning equipment, and data acquisition and image reconstruction principle of this ICT are described
Constraints on the virtual nucleon Compton scattering in a new dispersive formalism
Caprini, Irinel
2016-01-01
The dispersive representation of the virtual Compton forward scattering amplitude has been recently reexamined in connection with the evaluation of the Cottingham formula for the proton-neutron electromagnetic mass difference. The most difficult part of the analysis is related to one of the invariant amplitudes, denoted as $T_1(\
The Bell's inequality has been experimentally tested using angular correlation of Compton-scattered photons from annihilation of positrons emitted from 22Na source. The result shows a better agreement with the quantum mechanics predictions rather than with the Bell's inequality
News on Compton Scattering γX → γX in Chiral EFT
Grießhammer Harald W.
2016-01-01
Full Text Available We review theoretical progress and prospects to understand the nucleon’s static dipole polarisabilities from Compton scattering on few-nucleon targets, including new values; see Refs. [1–5] for details and a more thorough bibliography.