Nucleon Electromagnetic Form Factors
Energy Technology Data Exchange (ETDEWEB)
Kees de Jager
2004-08-01
Although nucleons account for nearly all the visible mass in the universe, they have a complicated structure that is still incompletely understood. The first indication that nucleons have an internal structure, was the measurement of the proton magnetic moment by Frisch and Stern (1933) which revealed a large deviation from the value expected for a point-like Dirac particle. The investigation of the spatial structure of the nucleon, resulting in the first quantitative measurement of the proton charge radius, was initiated by the HEPL (Stanford) experiments in the 1950s, for which Hofstadter was awarded the 1961 Nobel prize. The first indication of a non-zero neutron charge distribution was obtained by scattering thermal neutrons off atomic electrons. The recent revival of its experimental study through the operational implementation of novel instrumentation has instigated a strong theoretical interest. Nucleon electro-magnetic form factors (EMFFs) are optimally studied through the exchange of a virtual photon, in elastic electron-nucleon scattering. The momentum transferred to the nucleon by the virtual photon can be selected to probe different scales of the nucleon, from integral properties such as the charge radius to scaling properties of its internal constituents. Polarization instrumentation, polarized beams and targets, and the measurement of the polarization of the recoiling nucleon have been essential in the accurate separation of the charge and magnetic form factors and in studies of the elusive neutron charge form factor.
Nucleon Electromagnetic Form Factors
Energy Technology Data Exchange (ETDEWEB)
Marc Vanderhaeghen; Charles Perdrisat; Vina Punjabi
2007-10-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has greatly improved by performing double polarization experiments, in comparison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at JLab, MAMI, and MIT-Bates. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed, including the recent progress in the determination of the valence quark generalized parton distributions of the nucleon, as well as the steady rate of improvements made in the lattice QCD calculations.
Maas, F. E.; Paschke, K. D.
2017-07-01
A broad program measuring parity-violation in electron-nuclear scattering has now provided a large set of precision data on the weak-neutral-current form-factors of the proton. Under comparison with well-measured electromagnetic nucleon form-factors, these measurements reveal the role of the strange quark sea on the low-energy interactions of the proton through the strange-quark-flavor vector form-factors. This review will describe the experimental program and the implications of the global data for the strange-quark vector form-factors. We present here a new fit to the world data.
Strange chiral nucleon form factors
Hemmert, T R; Meißner, Ulf G; Hemmert, Thomas R.; Kubis, Bastian; Meissner, Ulf-G.
1999-01-01
We investigate the strange electric and magnetic form factors of the nucleon in the framework of heavy baryon chiral perturbation theory to third order in the chiral expansion. All counterterms can be fixed from data. In particular, the two unknown singlet couplings can be deduced from the parity-violating electron scattering experiments performed by the SAMPLE and the HAPPEX collaborations. Within the given uncertainties, our analysis leads to a small and positive electric strangeness radius, $ = (0.05 \\pm 0.16) fm^2$. We also deduce the consequences for the upcoming MAMI A4 experiment.
Electromagnetic Form Factors of the Nucleon
Bijker, R
1997-01-01
We reanalyze the world data on the electromagnetic form factors of the nucleon. The calculations are performed in the framework of an algebraic model of the nucleon combined with vector meson dominance.
Charge-symmetry-breaking nucleon form factors
Kubis, Bastian
2009-01-01
A quantitative understanding of charge-symmetry breaking is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors. We review the theoretical understanding of the charge-symmetry-breaking form factors, both for single nucleons and for Helium-4.
Calculation of Nucleon Electromagnetic Form Factors
Renner, D B; Dolgov, D S; Eicker, N; Lippert, T; Negele, J W; Pochinsky, A V; Schilling, K; Lippert, Th.
2002-01-01
The fomalism is developed to express nucleon matrix elements of the electromagnetic current in terms of form factors consistent with the translational, rotational, and parity symmetries of a cubic lattice. We calculate the number of these form factors and show how appropriate linear combinations approach the continuum limit.
Axial Nucleon form factors from lattice QCD
Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, M
2010-01-01
We present results on the nucleon axial form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length $L=2.1$ fm and $L=2.8$ fm. Cut-off effects are investigated using three different values of the lattice spacings, namely $a=0.089$ fm, $a=0.070$ fm and $a=0.056$ fm. The nucleon axial charge is obtained in the continuum limit and chirally extrapolated to the physical pion mass enabling comparison with experiment.
Nucleon Form Factors - A Jefferson Lab Perspective
Energy Technology Data Exchange (ETDEWEB)
John Arrington, Kees de Jager, Charles F. Perdrisat
2011-06-01
The charge and magnetization distributions of the proton and neutron are encoded in their elastic electromagnetic form factors, which can be measured in elastic electron--nucleon scattering. By measuring the form factors, we probe the spatial distribution of the proton charge and magnetization, providing the most direct connection to the spatial distribution of quarks inside the proton. For decades, the form factors were probed through measurements of unpolarized elastic electron scattering, but by the 1980s, progress slowed dramatically due to the intrinsic limitations of the unpolarized measurements. Early measurements at several laboratories demonstrated the feasibility and power of measurements using polarization degrees of freedom to probe the spatial structure of the nucleon. A program of polarization measurements at Jefferson Lab led to a renaissance in the field of study, and significant new insight into the structure of matter.
The Form Factors of the Nucleons
Energy Technology Data Exchange (ETDEWEB)
Perdrisat, Charles F. [William and Mary College, JLAB
2013-11-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double-polarization experiments, in comparison with with pre-vious unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high- precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model in- dependently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed u and d quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius "crisis" will also be discussed.
The form factors of the nucleons
Perdrisat, C. F.
2013-11-01
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double-polarization experiments, in comparison with with previous unpolarized cross section data. Here we will review the experimental data base in view of the new results for the proton and the neutron, obtained at MIT-Bates, JLab and MAMI. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed. In particular, the possibility that the proton is non-spherical in its ground state, and that the transverse charge density are model independently defined in the infinite momentum frame. Likewise, flavor decomposition of the nucleon form factors into dressed u and d quark form factors, may give information about the quark-diquark structure of the nucleon. The current proton radius "crisis" will also be discussed.
Nucleon electromagnetic form factors with Wilson fermions
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-10-15
The nucleon electromagnetic form factors continue to be of major interest for experimentalists and phenomenologists alike. They provide important insights into the structure of nuclear matter. For a range of interesting momenta they can be calculated on the lattice. The limiting factor continues to be the value of the pion mass. We present the latest results of the QCDSF collaboration using gauge configurations with two dynamical, non-perturbatively improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Chiral extrapolation of nucleon magnetic form factors
Energy Technology Data Exchange (ETDEWEB)
P. Wang; D. Leinweber; A. W. Thomas; R.Young
2007-04-01
The extrapolation of nucleon magnetic form factors calculated within lattice QCD is investigated within a framework based upon heavy baryon chiral effective-field theory. All one-loop graphs are considered at arbitrary momentum transfer and all octet and decuplet baryons are included in the intermediate states. Finite range regularization is applied to improve the convergence in the quark-mass expansion. At each value of the momentum transfer (Q{sup 2}), a separate extrapolation to the physical pion mass is carried out as a function of m{sub {pi}} alone. Because of the large values of Q{sup 2} involved, the role of the pion form factor in the standard pion-loop integrals is also investigated. The resulting values of the form factors at the physical pion mass are compared with experimental data as a function of Q{sup 2} and demonstrate the utility and accuracy of the chiral extrapolation methods presented herein.
Nucleon and Elastic and Transition Form Factors
Segovia, Jorge; Cloët, Ian C.; Roberts, Craig D.; Schmidt, Sebastian M.
2014-12-01
We present a unified study of nucleon and elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector vector contact-interaction. The comparison emphasises that experiments are sensitive to the momentum dependence of the running couplings and masses in the strong interaction sector of the Standard Model and highlights that the key to describing hadron properties is a veracious expression of dynamical chiral symmetry breaking in the bound-state problem. Amongst the results we describe, the following are of particular interest: possesses a zero at Q 2 = 9.5 GeV2; any change in the interaction which shifts a zero in the proton ratio to larger Q 2 relocates a zero in to smaller Q 2; there is likely a value of momentum transfer above which ; and the presence of strong diquark correlations within the nucleon is sufficient to understand empirical extractions of the flavour-separated form factors. Regarding the -baryon, we find that, inter alia: the electric monopole form factor exhibits a zero; the electric quadrupole form factor is negative, large in magnitude, and sensitive to the nature and strength of correlations in the Faddeev amplitude; and the magnetic octupole form factor is negative so long as rest-frame P- and D-wave correlations are included. In connection with the transition, the momentum-dependence of the magnetic transition form factor, , matches that of once the momentum transfer is high enough to pierce the meson-cloud; and the electric quadrupole ratio is a keen measure of diquark and orbital angular momentum correlations, the zero in which is obscured by meson-cloud effects on the domain currently accessible to experiment. Importantly, within each framework, identical propagators and vertices are sufficient to describe all properties discussed herein. Our
Gravitational form factors and nucleon spin structure
Teryaev, O. V.
2016-10-01
Nucleon scattering by the classical gravitational field is described by the gravitational (energy-momentum tensor) form factors (GFFs), which also control the partition of nucleon spin between the total angular momenta of quarks and gluons. The equivalence principle (EP) for spin dynamics results in the identically zero anomalous gravitomagnetic moment, which is the straightforward analog of its electromagnetic counterpart. The extended EP (ExEP) describes its (approximate) validity separately for quarks and gluons and, in turn, results in equal partition of the momentum and total angular momentum. It is violated in quantum electrodynamics and perturbative quantum chromodynamics (QCD), but may be restored in nonperturbative QCD because of confinement and spontaneous chiral symmetry breaking, which is supported by models and lattice QCD calculations. It may, in principle, be checked by extracting the generalized parton distributions from hard exclusive processes. The EP for spin-1 hadrons is also manifested in inclusive processes (deep inelastic scattering and the Drell-Yan process) in sum rules for tensor structure functions and parton distributions. The ExEP may originate in either gravity-proof confinement or in the closeness of the GFF to its asymptotic values in relation to the mediocrity principle. The GFFs in time-like regions reveal some similarity between inflation and annihilation.
The structure of the nucleon: Elastic electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Punjabi, V. [Norfolk State University, Norfolk, VA (United States); Perdrisat, C.F.; Carlson, C.E. [The College of William and Mary, Williamsburg, VA (United States); Jones, M.K. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Brash, E.J. [Thomas Jefferson National Accelerator Facility, Newport News, VA (United States); Christopher Newport University, Newport News, VA (United States)
2015-07-15
Precise proton and neutron form factor measurements at Jefferson Lab, using spin observables, have recently made a significant contribution to the unraveling of the internal structure of the nucleon. Accurate experimental measurements of the nucleon form factors are a test-bed for understanding how the nucleon's static properties and dynamical behavior emerge from QCD, the theory of the strong interactions between quarks. There has been enormous theoretical progress, since the publication of the Jefferson Lab proton form factor ratio data, aiming at reevaluating the picture of the nucleon. We will review the experimental and theoretical developments in this field and discuss the outlook for the future. (orig.)
Flavour decomposition of electromagnetic transition form factors of nucleon resonances
Segovia, Jorge
2016-01-01
In Poincar\\'e-covariant continuum treatments of the three valence-quark bound-state problem, the force behind dynamical chiral symmetry breaking also generates nonpointlike, interacting diquark correlations in the nucleon and its resonances. We detail the impact of these correlations on the nucleon's elastic and nucleon-to-Roper transition electromagnetic form factors, providing flavour-separation versions that can be tested at modern facilities.
Progress in the Calculation of Nucleon Transition form Factors
Eichmann, Gernot
2016-10-01
We give a brief account of the Dyson-Schwinger and Faddeev-equation approach and its application to nucleon resonances and their transition form factors. We compare the three-body with the quark-diquark approach and present a quark-diquark calculation for the low-lying nucleon resonances including scalar, axialvector, pseudoscalar and vector diquarks. We also discuss the timelike structure of transition form factors and highlight the advantages of form factors over helicity amplitudes.
Progress in the calculation of nucleon transition form factors
Eichmann, Gernot
2016-01-01
We give a brief account of the Dyson-Schwinger and Faddeev-equation approach and its application to nucleon resonances and their transition form factors. We compare the three-body with the quark-diquark approach and present a quark-diquark calculation for the low-lying nucleon resonances including scalar, axialvector, pseudoscalar and vector diquarks. We also discuss the timelike structure of transition form factors and highlight the advantages of form factors over helicity amplitudes.
Nucleon form factors program with SBS at JLAB
Energy Technology Data Exchange (ETDEWEB)
Wojtsekhowski, Bogdan B. [JLAB
2014-12-01
The physics of the nucleon form factors is the basic part of the Jefferson Laboratory program. We review the achievements of the 6-GeV era and the program with the 12- GeV beam with the SBS spectrometer in Hall A, with a focus on the nucleon ground state properties.
Dissecting nucleon transition electromagnetic form factors
Segovia, Jorge
2016-01-01
In Poincar\\'e-covariant continuum treatments of the three valence-quark bound-state problem, the force behind dynamical chiral symmetry breaking also generates nonpointlike, interacting diquark correlations in the nucleon and its resonances. We detail the impact of these correlations on the electromagnetically-induced nucleon-$\\Delta$ and nucleon-Roper transitions, providing a flavour-separation of the latter and associated predictions that can be tested at modern facilities.
Low energy analysis of the nucleon electromagnetic form factors
Kubis, B; Kubis, Bastian; Meissner, Ulf-G.
2001-01-01
We analyze the electromagnetic form factors of the nucleon to fourth order in relativistic baryon chiral perturbation theory. We employ the recently proposed infrared regularization scheme and show that the convergence of the chiral expansion is improved as compared to the heavy fermion approach. We also discuss the inclusion of vector mesons and obtain an accurate description of all four nucleon form factors for momentum transfer squared up to Q^2 \\simeq 0.4 GeV^2.
Nucleon Form Factors in the Space- and Timelike Regions
Hammer, H W
2001-01-01
Dispersion relations provide a powerful tool to describe the electromagnetic form factors of the nucleon both in the spacelike and timelike regions with constraints from unitarity and perturbative QCD. We give a brief introduction into dispersion theory for nucleon form factors and present results from a recent form factor analysis. Particular emphasis is given to the form factors in the timelike region. Furthermore, some recent results for the spacelike form factors at low momentum transfer from a ChPT calculation by Kubis and Meissner are discussed.
Isospin mixing in the nucleon and 4He and the nucleon strange electric form factor
Viviani, M; Kievsky, A; Kubis, B; Lewis, R; Marcucci, L E; Rosati, S; Schiavilla, R
2007-01-01
In order to isolate the contribution of the nucleon strange electric form factor to the parity-violating asymmetry measured in 4He(\\vec e,e')4He experiments, it is crucial to have a reliable estimate of the magnitude of isospin-symmetry-breaking (ISB) corrections in both the nucleon and 4He. We examine this issue in the present letter. Isospin admixtures in the nucleon are determined in chiral perturbation theory, while those in 4He are derived from nuclear interactions, including explicit ISB terms. A careful analysis of the model dependence in the resulting predictions for the nucleon and nuclear ISB contributions to the asymmetry is carried out. We conclude that, at the low momentum transfers of interest in recent measurements reported by the HAPPEX collaboration at Jefferson Lab, these contributions are of comparable magnitude to those associated with strangeness components in the nucleon electric form factor.
Dispersion-theoretical analysis of the nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Belushkin, M.
2007-09-29
The structure of the proton and the neutron is of fundamental importance for the study of the strong interaction dynamics over a wide range of momentum transfers. The nucleon form factors encode information on the internal structure of the nucleon as probed by the electromagnetic interaction, and, to a certain extent, reflect the charge and magnetisation distributions within the proton and the neutron. In this thesis we report on our investigation of the electromagnetic form factors of the proton and the neutron with dispersion relation techniques, including known experimental input on the {pi}{pi}, K anti K and the {rho}{pi} continua and perturbative QCD constraints. We include new experimental data on the pion form factor and the nucleon form factors in our simultaneous analysis of all four form factors in both the space- and the timelike regions for all momentum transfers, and perform Monte- Carlo sampling in order to obtain theoretical uncertainty bands. Finally, we discuss the implications of our results on the pion cloud of the nucleon, the nucleon radii and the Okubo-Zweig-Iizuka rule, and present our results of a model-independent approach to estimating two-photon effects in elastic electron-proton scattering. (orig.)
Dispersion-theoretical analysis of the nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Belushkin, M.
2007-09-29
The structure of the proton and the neutron is of fundamental importance for the study of the strong interaction dynamics over a wide range of momentum transfers. The nucleon form factors encode information on the internal structure of the nucleon as probed by the electromagnetic interaction, and, to a certain extent, reflect the charge and magnetisation distributions within the proton and the neutron. In this thesis we report on our investigation of the electromagnetic form factors of the proton and the neutron with dispersion relation techniques, including known experimental input on the {pi}{pi}, K anti K and the {rho}{pi} continua and perturbative QCD constraints. We include new experimental data on the pion form factor and the nucleon form factors in our simultaneous analysis of all four form factors in both the space- and the timelike regions for all momentum transfers, and perform Monte- Carlo sampling in order to obtain theoretical uncertainty bands. Finally, we discuss the implications of our results on the pion cloud of the nucleon, the nucleon radii and the Okubo-Zweig-Iizuka rule, and present our results of a model-independent approach to estimating two-photon effects in elastic electron-proton scattering. (orig.)
Form factors in an algebraic model of the nucleon
Bijker, R
1995-01-01
We study the electromagnetic form factors of the nucleon in a collective model of baryons. In an algebraic approach to hadron structure, we derive closed expressions for both elastic and transition form factors, and consequently for the helicity amplitudes that can be measured in electro- and photoproduction.
Electromagnetic Transition form Factor of Nucleon Resonances
Sato, Toru
2016-10-01
A dynamical coupled channel model for electron and neutrino induced meson production reactions is developed. The model is an extension of our previous reaction model to describe reactions at finite Q^2. The electromagnetic transition form factors of the first (3/2^+,3/2) and (3/2^-,1/2) resonances extracted from partial wave amplitude are discussed.
Dispersive analysis of the scalar form factor of the nucleon
Hoferichter, M; Kubis, B; Meißner, U -G
2012-01-01
Based on the recently proposed Roy-Steiner equations for pion-nucleon scattering, we derive a system of coupled integral equations for the pi pi --> N-bar N and K-bar K --> N-bar N S-waves. These equations take the form of a two-channel Muskhelishvili-Omnes problem, whose solution in the presence of a finite matching point is discussed. We use these results to update the dispersive analysis of the scalar form factor of the nucleon fully including K-bar K intermediate states. In particular, we determine the correction Delta_sigma=sigma(2M_pi^2)-sigma_{pi N}, which is needed for the extraction of the pion-nucleon sigma term from pi N scattering, as a function of pion-nucleon subthreshold parameters and the pi N coupling constant.
Skyrme-Model $\\pi NN$ Form Factor and Nucleon-Nucleon Interaction
Holzwarth, G
1997-01-01
We apply the strong $\\pi NN$ form factor, which emerges from the Skyrme model, in the two-nucleon system using a one-boson-exchange (OBE) model for the nucleon-nucleon (NN) interaction. Deuteron properties and phase parameters of NN scattering are reproduced well. In contrast to the form factor of monopole shape that is traditionally used in OBE models, the Skyrme form factor leaves low momentum transfers essentially unaffected while it suppresses the high-momentum region strongly. It turns out that this behavior is very appropriate for models of the NN interaction and makes possible to use a soft pion form factor in the NN system. As a consequence, the $\\pi N$ and the $NN$ systems can be described using the same soft $\\pi NN$ form factor, which is impossible with the monopole.
Survey of nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Perdrisat, Charles F. [William and Mary College; Punjabi, Vina A. [Norfolk State U.
2011-09-20
There has been much activity in the measurement of the elastic electromagnetic proton and neutron form factors in the last decade, and the quality of the data has been greatly improved by performing double polarization experiments, in compar- ison with previous unpolarized data. Here we review the experimental data base in view of the new results for the proton, and neutron, obtained at MIT-Bates, MAMI, and JLab. The rapid evolution of phenomenological models triggered by these high-precision experiments will be discussed.
Nucleon form factors and O(a) Improvement
Capitani, S; Horsley, R; Klaus, B; Oelrich, H; Perlt, H; Petters, D; Pleiter, D; Rakow, P E L; Schierholz, G; Schiller, A; Stephenson, P W
1999-01-01
Nucleon form factors have been extensively studied both experimentally and theoretically for many years. We report here on new results of a high statistics quenched lattice QCD calculation of vector and axial-vector nucleon form factors at low momentum transfer within the Symanzik improvement programme. The simulations are performed at three kappa and three beta values allowing first an extrapolation to the chiral limit and then an extrapolation in the lattice spacing to the continuum limit. The computations are all fully non-perturbative. A comparison with experimental results is made.
Excited state systematics in extracting nucleon electromagnetic form factors
Capitani, Stefano; von Hippel, Georg; Jäger, Benjamin; Knippschild, Bastian; Meyer, Harvey B; Rae, Thomas D; Wittig, Hartmut
2012-01-01
We present updated preliminary results for the nucleon electromagnetic form factors for non-perturbatively $\\mathcal{O}(a)$ improved Wilson fermions in $N_f=2$ QCD measured on the CLS ensembles. The use of the summed operator insertion method allows us to suppress the influence of excited states in our measurements. A study of the effect that excited state contaminations have on the $Q^2$ dependence of the extracted nucleon form factors may then be made through comparisons of the summation method to standard plateau fits, as well as to excited state fits.
Nucleon form factors with dynamical twisted mass fermions
Alexandrou, C; Brinet, M; Carbonell, J; Drach, V; Harraud, P A; Korzec, T; Koutsou, G
2008-01-01
The electromagnetic and axial form factors of the nucleon are evaluated in twisted mass QCD with two degenerate flavors of light, dynamical quarks. The axial charge g_A, magnetic moment and the Dirac and Pauli radii are determined for pion masses in the range 300 MeV to 500 MeV.
Electromagnetic form factors in a collective model of the nucleon
Bijker, R; Leviatan, A
1995-01-01
We study the electromagnetic form factors of the nucleon in a collective model of baryons. Using the algebraic approach to hadron structure, we derive closed expressions for both elastic and transition form factors, and consequently for the helicity amplitudes that can be measured in electro- and photoproduction. Effects of spin-flavor symmetry breaking and of swelling of hadrons with increasing excitation energy are considered.
Electromagnetic form factors in a collective model of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Bijker, R.; Iachello, F.; Leviatan, A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 (Mexico)]|[Distrito Federale (Mexico)]|[Center for Theoretical Physics, Sloane Laboratory, Yale University, New Haven, Connecticut 06520-8120 (United States)]|[Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
1996-10-01
We study the electromagnetic form factors of the nucleon in a collective model of baryons. Using the algebraic approach to hadron structure, we derive closed expressions for both elastic and transition form factors, and consequently for the helicity amplitudes that can be measured in electro- and photoproduction. Effects of spin-flavor symmetry breaking and of swelling of hadrons with increasing excitation energy are considered. {copyright} {ital 1996 The American Physical Society.}
Form factors and other measures of strangeness in the nucleon
Energy Technology Data Exchange (ETDEWEB)
Diehl, M. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Feldmann, T. [Siegen Univ. (Germany). Theoretische Physik I; Kroll, P. [Bergische Univ., Wuppertal (Germany). Fachbereich Physik
2007-11-15
We discuss the phenomenology of strange-quark dynamics in the nucleon, based on experimental and theoretical results for electroweak form factors and for parton densities. In particular, we construct a model for the generalized parton distribution that relates the asymmetry s(x)- anti s(x) between the longitudinal momentum distributions of strange quarks and antiquarks with the form factor F{sup s}{sub 1}(t), which describes the distribution of strangeness in transverse position space. (orig.)
Nucleon electromagnetic form factors in twisted mass lattice QCD
Alexandrou, C; Carbonell, J; Constantinou, M; Harraud, P A; Guichon, P; Jansen, K; Korzec, T; Papinutto, M
2011-01-01
We present results on the nucleon electromagnetic form factors within lattice QCD using two flavors of degenerate twisted mass fermions. Volume effects are examined using simulations at two volumes of spatial length L=2.1 fm and L=2.8 fm. Cut-off effects are investigated using three different values of the lattice spacings, namely a=0.089 fm, a=0.070 and a=0.056 fm. The nucleon magnetic moment, Dirac and Pauli radii are obtained in the continuum limit and chirally extrapolated to the physical pion mass allowing for a comparison with experiment.
Nucleon form factors with Nf=2 dynamical twisted mass fermions
Alexandrou, C; Koutsou, G; Baron, R; Guichon, P; Brinet, M; Carbonell, J; Harraud, P -A; Jansen, K
2009-01-01
We present results on the electromagnetic and axial nucleon form factors using two degenerate flavors of twisted mass fermions on lattices of spatial size 2.1 fm and 2.7 fm and a lattice spacing of about 0.09 fm. We consider pion masses in the range of 260-470 MeV. We chirally extrapolate results on the nucleon axial ch arge, the isovector Dirac and Pauli root mean squared radii and magnetic moment to the physical point and co mpare to experiment.
Nucleon form factors in the canonically quantized Skyrme model
Energy Technology Data Exchange (ETDEWEB)
Acus, A.; Norvaisas, E. [Lithuanian Academy of Sciences, Vilnius (Lithuania). Inst. of Theoretical Physics and Astronomy; Riska, D.O. [Helsinki Univ. (Finland). Dept. of Physics; Helsinki Univ. (Finland). Helsinki Inst. of Physics
2001-08-01
The explicit expressions for the electric, magnetic, axial and induced pseudoscalar form factors of the nucleons are derived in the ab initio quantized Skyrme model. The canonical quantization procedure ensures the existence of stable soliton solutions with good quantum numbers. The form factors are derived for representations of arbitrary dimension of the SU(2) group. After fixing the two parameters of the model, f{sub {pi}} and e, by the empirical mass and electric mean square radius of the proton, the calculated electric and magnetic form factors are fairly close to the empirical ones, whereas the the axial and induced pseudoscalar form factors fall off too slowly with momentum transfer. (orig.)
Nucleon form factors in the canonically quantized Skyrme model
Acus, A; Riska, D O
2001-01-01
The explicit expressions for the electric, magnetic, axial and induced pseudoscalar form factors of the nucleons are derived in the {\\it ab initio} quantized Skyrme model. The canonical quantization procedure ensures the existence of stable soliton solutions with good quantum numbers. The form factors are derived for representations of arbitrary dimension of the SU(2) group. After fixing the two parameters of the model, $f_\\pi$ and $e$, by the empirical mass and electric mean square radius of the proton, the calculated electric and magnetic form factors are fairly close to the empirical ones, whereas the the axial and induced pseudoscalar form factors fall off too slowly with momentum transfer.
Dispersion Relation for the Nucleon Electromagnetic Form Factors
Furuichi, Susumu; Watanbe, Keiji
2010-01-01
Elastic electromagnetic form factors of nucleons are investigated both for the time-like and the space-like momentums by using the unsubtracted dispersion relation with QCD constraints. It is shown that the calculated form factors reproduce the experimental data reasonably well; they agree with recent experimental data for the neutron magnetic form factors for the space-like data obtained by the CLAS collaboration and are compatible with the ratio of the electric and magnetic form factors for the time-like momentum obtained by the BABAR collaboration.
Possible diquark signatures in the elastic nucleon form factors
Cates, Gordon
2013-10-01
There has been considerable interest in the elastic nucleon form factors ever since the discovery that the proton form-factor ratio, GEp /GMp , decreases nearly linearly above roughly Q2 = 1 GeV2 . More recent measurements of the neutron form-factor ratio, GEn /GMn , up to 3 . 4 GeV2 have made it possible to constrain calculations using both proton and neutron data in the Q2 regime where the interesting behavior of the proton was first observed. Calculations based on QCD's Dyson-Schwinger equations, as well as certain relativistic constituent quark models, suggest that the observed behavior is related to the importance of diquark degrees of freedom. To understand this connection, it is particularly useful to consider the flavor-separated form factors, which can be extracted by combining proton and neutron data, and assuming charge symmetry. Distinctly different behavior is seen for the u - and d - quarks. The behaviors of the different quark flavors and the connection to diquarks can also be understood using naive scaling arguments, although this approach has yet to be made more rigorous. This talk will discuss how measurements of the nucleon form factors at high Q2 provides a rich opportunity to better understand the structure of the nucleon.
Nucleon form factors, generalized parton distributions and quark angular momentum
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Kroll, Peter [Bergische Univ., Wuppertal (Germany). Fachbereich Physik; Regensburg Univ. (Germany). Institut fuer Theoretische Physik
2013-02-15
We extract the individual contributions from u and d quarks to the Dirac and Pauli form factors of the proton, after a critical examination of the available measurements of electromagnetic nucleon form factors. From this data we determine generalized parton distributions for valence quarks, assuming a particular form for their functional dependence. The result allows us to study various aspects of nucleon structure in the valence region. In particular, we evaluate Ji's sum rule and estimate the total angular momentum carried by valence quarks at the scale {mu}=2 GeV to be J{sup u}{sub v}=0.230{sup +0.009}{sub -0.024} and J{sup d}{sub v}=-0.004{sup +0.010}{sub -0.016}.
Isospin violation in the vector form factors of the nucleon
Kubis, B; Kubis, Bastian; Lewis, Randy
2006-01-01
A quantitative understanding of isospin violation is an increasingly important ingredient for the extraction of the nucleon's strange vector form factors from experimental data. We calculate the isospin violating electric and magnetic form factors in chiral perturbation theory to leading and next-to-leading order respectively, and we extract the low-energy constants from resonance saturation. Uncertainties are dominated largely by limitations in the current knowledge of some vector meson couplings. The resulting bounds on isospin violation are sufficiently precise to be of value to on-going experimental studies of the strange form factors.
Flavor Analysis of Nucleon, Δ , and Hyperon Electromagnetic Form Factors
Rohrmoser, Martin; Choi, Ki-Seok; Plessas, Willibald
2017-03-01
By the analysis of the world data base of elastic electron scattering on the proton and the neutron (for the latter, in fact, on ^2H and ^3He) important experimental insights have recently been gained into the flavor compositions of nucleon electromagnetic form factors. We report on testing the Graz Goldstone-boson-exchange relativistic constituent-quark model in comparison to the flavor contents in low-energy nucleons, as revealed from electron-scattering phenomenology. It is found that a satisfactory agreement is achieved between theory and experiment for momentum transfers up to Q^2˜ 4 GeV^2, relying on three-quark configurations only. Analogous studies have been extended to the Δ and the hyperon electromagnetic form factors. For them we here show only some sample results in comparison to data from lattice quantum chromodynamics.
Flavor decomposition of the nucleon electromagnetic form factors
Qattan, I A
2012-01-01
Background: The spatial distribution of charge and magnetization in the proton and neutron are encoded in the nucleon electromagnetic form factors. The form factors are all approximated by a simple dipole function, normalized to the charge or magnetic moment of the nucleon. The differences between the proton and neutron form factors and the deviation of GEn from zero are sensitive to the difference between up- and down-quark contributions to the form factors. Methods: We combine recent measurements of the neutron form factors with updated extractions of the proton form factors, accounting for two-photon exchange corrections and including an estimate of the uncertainties for all of the form factors to obtain a complete set of measurements up to Q^2 approximately 4 (GeV/c)^2. We use this to extract the up- and down-quark contributions which we compare to recent fits and calculations. Results: We find a large differences between the up- and down-quark contributions to G_E and G_M, implying significant flavor dep...
Axial form factor of the nucleon at large momentum transfers
Anikin, I V; Offen, N
2016-01-01
Motivated by the emerging possibilities to study threshold pion electroproduction at large momentum transfers at Jefferson Laboratory following the 12 GeV upgrade, we provide a short theory summary and an estimate of the nucleon axial form factor for large virtualities in the $Q^2 = 1-10~\\text{GeV}^2$ range using next-to-leading order light-cone sum rules.
Exploring strange nucleon form factors on the lattice
Babich, Ronald; Clark, Michael A; Fleming, George T; Osborn, James C; Rebbi, Claudio; Schaich, David
2010-01-01
We discuss techniques for evaluating sea quark contributions to hadronic form factors on the lattice and apply these to an exploratory calculation of the strange electromagnetic, axial, and scalar form factors of the nucleon. We employ the Wilson gauge and fermion actions on an anisotropic 24^3 x 64 lattice, probing a range of momentum transfer with Q^2 _0. We discuss the unique systematic uncertainties affecting the latter quantity relative to the continuum, as well as prospects for improving future determinations with Wilson-like fermions.
Nucleon axial form factors from two-flavour Lattice QCD
Junnarkar, P M; Djukanovic, D; von Hippel, G; Hua, J; Jäger, B; Meyer, H B; Rae, T D; Wittig, H
2014-01-01
We present preliminary results on the axial form factor $G_A(Q^2)$ and the induced pseudoscalar form factor $G_P(Q^2)$ of the nucleon. A systematic analysis of the excited-state contributions to form factors is performed on the CLS ensemble `N6' with $m_\\pi = 340 \\ \\text{MeV}$ and lattice spacing $a \\sim 0.05 \\ \\text{fm}$. The relevant three-point functions were computed with source-sink separations ranging from $t_s \\sim 0.6 \\ \\text{fm}$ to $t_s \\sim \\ 1.4 \\ \\text{fm}$. We observe that the form factors suffer from non-trivial excited-state contributions at the source-sink separations available to us. It is noted that naive plateau fits underestimate the excited-state contributions and that the method of summed operator insertions correctly accounts for these effects.
Nucleon electromagnetic form factors from the covariant Faddeev equation
Eichmann, G.
2011-07-01
We compute the electromagnetic form factors of the nucleon in the Poincaré-covariant Faddeev framework based on the Dyson-Schwinger equations of QCD. The general expression for a baryon’s electromagnetic current in terms of three interacting dressed quarks is derived. Upon employing a rainbow-ladder gluon-exchange kernel for the quark-quark interaction, the nucleon’s Faddeev amplitude and electromagnetic form factors are computed without any further truncations or model assumptions. The form-factor results show clear evidence of missing pion-cloud effects below a photon momentum transfer of ˜2GeV2 and in the chiral region, whereas they agree well with experimental data at higher photon momenta. Thus, the approach reflects the properties of the nucleon’s quark core.
Nucleon form factors on the lattice with light dynamical fermions
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Technische Univ. Muenchen, Garching (Germany). Inst. fuer Theoretische Physik T39; Horsley, R. [Edinburgh Univ. (GB). School of Physics] (and others)
2007-09-15
The electromagnetic form factors provide important insight into the internal structure of the nucleon and continue to be of major interest for experiment and phenomenology. For an intermediate range of momenta the form factors can be calculated on the lattice. However, the reliability of the results is limited by systematic errors mostly due to the required extrapolation to physical quark masses. Chiral effective field theories predict a rather strong quark mass dependence in a range which was yet inaccessible for lattice simulations. We give an update on recent results from the QCDSF collaboration using gauge configurations with dynamical N{sub f}=2, non-perturbatively O(a)-improved Wilson fermions at pion masses as low as 350 MeV. (orig.)
Nucleon electromagnetic form factors in two-flavour QCD
Capitani, S; Djukanovic, D; von Hippel, G; Hua, J; Knippschild, B Jäger B; Meyer, H B; Rae, T D; Wittig, H
2015-01-01
We present results for the nucleon electromagnetic form factors, including the momentum transfer dependence and derived quantities (charge radii and magnetic moment). The analysis is performed using O(a) improved Wilson fermions in Nf=2 QCD measured on the CLS ensembles. Particular focus is placed on a systematic evaluation of the influence of excited states in three-point correlation functions, which lead to a biased evaluation, if not accounted for correctly. We argue that the use of summed operator insertions and fit ans\\"atze including excited states allow us to suppress and control this effect. We employ a novel method to perform joint chiral and continuum extrapolations, by fitting the form factors directly to the expressions of covariant baryonic chiral effective field theory. The final results for the charge radii and magnetic moment from our lattice calculations include, for the first time, a full error budget. We find that our estimates are compatible with experimental results within their overall u...
Nucleon Structure and Hyperon Form Factors from Lattice QCD.
Energy Technology Data Exchange (ETDEWEB)
Lin,H.W.
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point. to be 1.23(5), consistent with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(2G), consistent with the Adelaide-JLab Collaboration's result. The hyperon {Sigma} and {Xi} axial coupling constants are also performed for the first time in a lattice calculation, g{sub {Sigma}{Sigma}} = 0.441(14) and g{sub {Xi}{Xi}} = -0.277(11).
Nucleon Structure and hyperon form factors from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Lin, Huey-Wen
2007-06-11
In this work, I report the latest lattice QCD calculations of nucleon and hyperon structure from chiral fermions in 2+1-flavor dynamical simulations. All calculations are done with a chirally symmetric fermion action, domain-wall fermions, for valence quarks. I begin with the latest lattice results on the nucleon structure, focusing on results from RBC/UKQCD using 2+1-flavor chiral fermion actions. We find the chiral-extrapolated axial coupling constant at physical pion mass point to be 1.23(5), consistant with experimental value. The renormalization constants for the structure functions are obtained from RI/MOM-scheme non-perturbative renormalization. We find first moments of the polarized and unpolarized nucleon structure functions at zero transfer momentum to be 0.133(13) and 0.203(23) respectively, using continuum chiral extrapolation. These are consistent with the experimental values, unlike previous calculations which have been 50% larger. We also have a prediction for the transversity, which we find to be 0.56(4). The twist-3 matrix element is consistent with zero which agrees with the prediction of the Wandzura-Wilczek relation. In the second half of this work, I report an indirect dynamical estimation of the strangeness proton magnetic moments using mixed actions. With the analysis of hyperon form factors and using charge symmetry, the strangeness of proton is found to be -0.066(26), consistent with the Adelaide-JLab Collaboration's result. The hyperon Sigma and Xi axial coupling constants are also performed for the first time in a lattice calculation, g_SigmaSigma = 0.441(14) and g_XiXi = -0.277(11).
Axial form factor of the nucleon in the perturbative chiral quark model
Khosonthongkee, K; Faessler, Amand; Gutsche, T; Lyubovitskij, V E; Pumsa-ard, K; Yan, Y
2004-01-01
We apply the perturbative chiral quark model (PCQM) at one loop to analyze the axial form factor of the nucleon. This chiral quark model is based on an effective Lagrangian, where baryons are described by relativistic valence quarks and a perturbative cloud of Goldstone bosons as dictated by chiral symmetry. We apply the formalism to obtain analytical expressions for the axial form factor of the nucleon, which is given in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core).
Bound Nucleon Form Factors, Quark-Hadron Duality, and Nuclear EMC Effect
Tsushima, K; Melnitchouk, W; Saitô, K; Thomas, A W
2003-01-01
We discuss the electromagnetic form factors, axial form factors, and structure functions of a bound nucleon in the quark-meson coupling (QMC) model. Free space nucleon form factors are calculated using the improved cloudy bag model (ICBM). After describing finite nuclei and nuclear matter in the quark-based QMC model, we compute the in-medium modification of the bound nucleon form factors in the same framework. Finally, limits on the medium modification of the bound nucleon $F_2$ structure function are obtained using the calculated in-medium electromagnetic form factors and local quark-hadron duality.
Institute of Scientific and Technical Information of China (English)
MA Wei-Xing; DONG Yu-Bing; ZHOU Li-Juan
2002-01-01
Based on the [SUSF(6) O(3)]sym SUc(3) quark model, we study transverse transition form factors fromthe nucleon to nucleonic excitation states △(1232), N* (1535), and N* (1680). The transition form factors GT(Q2) arecalculated with a realistic and relativistic electromagnetic interaction. Therefore, a fit to experimental data examinesto what extent the constituent quark model is workable. The comparison between theoretical results and experimentaldata shows that the constituent quark model cannot provide a successful description of the transitions.
Bonner Prize: The Elastic Form Factors of the Nucleon
Perdrisat, Charles F.
2017-01-01
A series of experiments initiated in 1998 at the then new Continuous Electron Beam Accelerator, or CEBAF in Newport News Virginia, resulted in unexpected results, changing significantly our understanding of the structure of the proton. These experiments used a relatively new technique to obtain the ratio of the two form factors of the proton, namely polarization. An intense beam of highly polarized electrons with energy up to 6 GeV was made to interact elastically with un-polarized protons in a hydrogen target. The polarization of the recoiling protons, with energies up to 5 GeV, was measured from a second interaction in a polarimeter consisting of blocs of graphite or CH2 and tracking wire chambers. The scattered electrons were detected in an electromagnetic lead-glass calorimeter, to select elastically scattered events. After a short introduction describing the path which brought me from the University of Geneva to the College of William and Mary in 1966, I will introduce the subject of elastic electron scattering, describe some of the apparatus required for such experiments, and show the results which were unexpected at the time. These results demonstrated unequivocally that the two form factors required to describe elastic ep scattering, electric GE and magnetic GM in the Born approximation, had a drastically different dependence upon the four-momentum squared q2 = q2 -ω2 with q the momentum, and ω the energy transferred in the reaction. The finding, in flagrant disagreement with the data available at the time, which had been obtained dominantly from cross section measurements of the type first used by Nobel Prize R. Hofstadter 60 years ago, have led to a reexamination of the information provided by form factors on the structure of the nucleon, in particular its quark-gluon content. The conclusion will then be a brief outline of several theoretical considerations to put the results in a proper perspective.
Effect of the bound nucleon form factors on charged-current neutrino-nucleus scattering
Tsushima, K; Saitô, K; Kim, Hungchong
2003-01-01
We study the effect of bound nucleon form factors on charged-current neutrino-nucleus scattering. The bound nucleon form factors associated with the vector and axial-vector currents are calculated in the quark-meson coupling model. We compute the inclusive $^{12}$C($nu_mu,mu^-$)$X$ differential and total cross sections, which have been measured by the LSND collaboration at Los Alamos, using a relativistic Fermi gas model with the calculated bound nucleon form factors. It is shown that the bound nucleon form factors reduce the total cross section by about 8% relative to that calculated with the free nucleon form factors, where most of the conventional calculations overestimate the total cross section data by about 30% to 100%.
Constructing Nucleon Operators on a Lattice for Form Factors with High Momentum Transfer
Energy Technology Data Exchange (ETDEWEB)
Syritsyn, Sergey [Stony Brook Univ., NY (United States); Gambhir, Arjun S. [College of William and Mary, Williamsburg, VA (United States); Musch, Bernhard U. [Univ. of Regensburg (Germany); Orginos, Konstantinos [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
We present preliminary results of computing nucleon form factor at high momentum transfer using the 'boosted' or 'momentum' smearing. We use gauge configurations generated with N f = 2 + 1dynamical Wilson-clover fermions and study the connected as well as disconnected contributions to the nucleon form factors. Our initial results indicate that boosted smearing helps to improve the signal for nucleon correlators at high momentum. However, we also find evidence for large excited state contributions, which will likely require variational analysis to isolate the boosted nucleon ground state.
Nucleon generalized form factors and sigma term from lattice QCD near the physical quark mass
Bali, G S; Gläßle, B; Göckeler, M; Najjar, J; Rödl, R; Schäfer, A; Schiel, R; Söldner, W; Sternbeck, A; Wein, P
2013-01-01
We present new N_f=2 data for the nucleon generalized form factors, varying volume, lattice spacing and pion mass, down to 150 MeV. We also give an update of our direct calculation of the nucleon sigma term for a range of pion mass values including the lightest one.
Electromagnetic Form Factors of the Nucleon and Compton Scattering
Energy Technology Data Exchange (ETDEWEB)
Charles Hyde-Wright; Cornelis De Jager
2004-12-01
We review the experimental and theoretical status of elastic electron scattering and elastic low-energy photon scattering (with both real and virtual photons) from the nucleon. As a consequence of new experimental facilities and new theoretical insights, these subjects are advancing with unprecedented precision. These reactions provide many important insights into the spatial distributions and correlations of quarks in the nucleon.
von Hippel, G M; Djukanovic, D; Hua, J; Jäger, B; Junnarkar, P; Meyer, H B; Rae, T D; Wittig, H
2014-01-01
We study the ability of a variety of fitting techniques to extract the ground state matrix elements of the vector current from ratios of nucleon three- and two-point functions that contain contaminations from excited states. Extending our high-statistics study of nucleon form factors, we are able to demonstrate that the treatment of excited-state contributions in conjunction with approaching the physical pion mass has a significant impact on the $Q^2$-dependence of the form factors.
Nucleon shape and electromagnetic form factors in the chiral constituent quark model
Dahiya, Harleen
2010-01-01
The electromagnetic form factors are the most fundamental quantities to describe the internal structure of the nucleon and the shape of a spatially extended particle is determined by its intrinsic quadrupole moment which can be related to the charge radii. We have calculated the electromagnetic form factors, nucleon charge radii and the intrinsic quadrupole moment of the nucleon in the framework of chiral constituent quark model. The results obtained are comparable to the latest experimental studies and also show improvement over some theoretical interpretations.
Nucleon Charges, Form-factors and Neutron EDM
Gupta, Rajan; Cirigliano, Vincenzo; Lin, Huey-Wen; Yoon, Boram
2016-01-01
We present an update of our analysis of statistical and systematic errors in the calculation of iso-vector scalar, axial and tensor charges of the nucleon. The calculations are done using $N_f=2+1+1$ flavor HISQ ensembles generated by the MILC Collaboration at three values of the lattice spacing ($a=0.12,\\ 0.09,$ and $0.06$ fm) and three values of the quark mass ($M_\\pi \\approx 310,\\ 220$ and $130$ MeV); and clover fermions for calculating the correlation functions, i.e., we use a clover-on-HISQ lattice formulation. The all-mode-averaging method allows us to increase the statistics by a factor of eight for the same computational cost leading to a better understanding of and control over excited state contamination. Our current results, after extrapolation to the continuum limit and physical pion mass are $g_A^{u-d} = 1.21(3)$, $g_T^{u-d} = 1.005(59)$ and $g_S^{u-d} = 0.95(12) $. Further checks of control over all systematic errors, especially in $g_A^{u-d}$, are still being performed. Using results for the fl...
Calculation of the Nucleon Axial Form Factor Using Staggered Lattice QCD
Meyer, Aaron S; Kronfeld, Andreas S; Li, Ruizi; Simone, James N
2016-01-01
The nucleon axial form factor is a dominant contribution to errors in neutrino oscillation studies. Lattice QCD calculations can help control theory errors by providing first-principles information on nucleon form factors. In these proceedings, we present preliminary results on a blinded calculation of $g_A$ and the axial form factor using HISQ staggered baryons with 2+1+1 flavors of sea quarks. Calculations are done using physical light quark masses and are absolutely normalized. We discuss fitting form factor data with the model-independent $z$ expansion parametrization.
Aznauryan, I G
2012-01-01
We utilize a light-front relativistic quark model (LF RQM) to predict the 3q core contribution to the electroexcitation amplitudes for the Delta(1232)P33, N(1440)P11, N(1520)D13, and N(1535)S11 up to Q2= 12GeV2. The parameters of the model have been specified via description of the nucleon electromagnetic form factors in the approach that combines 3q and pion-cloud contributions in the LF dynamics.
Electromagnetic form factors of the nucleon. Experiments at MAMI
Energy Technology Data Exchange (ETDEWEB)
Ostrick, M. [Universitaet Bonn, Physikalisches Institut, Bonn (Germany)
2006-05-15
Elastic form factors are of fundamental importance for the understanding of microscopic spatial structures. In case of the proton and the neutron, charge and magnetic form factors can be studied in elastic electron scattering. Techniques to accelerate polarised continuous electron beams, the availability of polarised targets as well as modern concepts and instrumentation for coincidence experiments and recoil polarimetry had an enormous impact on these measurements. The developments and experiments at the Mainz Microtron MAMI will be discussed in a general context. (orig.)
Nucleon electromagnetic form factors using lattice simulations at the physical point
Alexandrou, C.; Constantinou, M.; Hadjiyiannakou, K.; Jansen, K.; Kallidonis, Ch.; Koutsou, G.; Vaquero Aviles-Casco, A.
2017-08-01
We present results for the nucleon electromagnetic form factors using an ensemble of maximally twisted mass clover-improved fermions with pion mass of about 130 MeV. We use multiple sink-source separations and three analysis methods to probe ground-state dominance. We evaluate both the connected and disconnected contributions to the nucleon matrix elements. We find that the disconnected quark loop contributions to the isoscalar matrix elements are small, giving an upper bound of up to 2% of the connected and smaller than its statistical error. We present results for the isovector and isoscalar electric and magnetic Sachs form factors and the corresponding proton and neutron form factors. By fitting the momentum dependence of the form factors to a dipole form or to the z expansion, we extract the nucleon electric and magnetic radii, as well as the magnetic moment. We compare our results to experiment as well as to other recent lattice QCD calculations.
Radiative corrections in nucleon time-like form factors measurements
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, Jacques [Universite de Paris-Sud, Institut de Physique Nucleaire, Orsay Cedex (France); Ong, Saro [Universite de Paris-Sud, Institut de Physique Nucleaire, Orsay Cedex (France); Universite de Picardie Jules Verne, Amiens (France)
2013-02-15
The completely general radiative corrections to lowest order, including the final- and initial-state radiations, are studied in proton-antiproton annihilation into an electron-positron pair. Numerical estimates have been made in a realistic configuration of the PANDA detector at FAIR for the proton time-like form factors measurements. (orig.)
Sufian, Raza Sabbir; de Téramond, Guy F.; Brodsky, Stanley J.; Deur, Alexandre; Dosch, Hans Günter
2017-01-01
We present a comprehensive analysis of the spacelike nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front (LF) holographic QCD (LFHQCD) We show that the inclusion of the higher Fock components |q q q q q ¯ ⟩ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD results for the proton and neutron form factors at any momentum transfer range, including asymptotic predictions, and show that our results agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30% in the proton and about 40% in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The free parameters needed to describe the experimental nucleon form factors are very few: two parameters for the probabilities of higher Fock states for the spin-flip form factor and a phenomenological parameter r , required to account for possible SU(6) spin-flavor symmetry breaking effects in the neutron, whereas the Pauli form factors are normalized to the experimental values of the anomalous magnetic moments. The covariant spin structure for the Dirac and Pauli nucleon form factors prescribed by AdS5 semiclassical gravity incorporates the correct twist scaling behavior from hard scattering and also leads to vector dominance at low energy.
Nucleon and gamma N -> Delta lattice form factors in a constituent quark model
Ramalho, G
2008-01-01
A covariant quark model, based both on the spectator formalism and on Vector Meson Dominance, and previously calibrated by the physical data, is here extended to the unphysical region of the lattice data by means of one single extra adjustable parameter - the constituent quark mass in the chiral limit. We calculated the Nucleon (N) and the Gamma N -> Delta form factors in the universe of values for that parameter described by quenched lattice QCD. A qualitative description of the Nucleon and Gamma N -> Delta form factors lattice data is achieved for light pion masses.
A Diquark-Quark Model with Its Use in Nucleon Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2005-01-01
The nucleon electromagnetic form factors are investigated within a simple diquark-quark model using the light-front formalism. In this model, baryon is described as a bound state of one quark and one clustering diquark.The calculational results are compared with the experimental ones. We also regard the quarks in a baryon as pointlike constituent quarks.
Nucleon electromagnetic form factors in a relativistic quark model with chiral symmetry
Energy Technology Data Exchange (ETDEWEB)
Barik, N.; Das, M.
1987-05-01
The nucleon electromagnetic form factors are computed in an independent quark model based on the Dirac equation. Corrections for centre-of-mass motion and pion-cloud effects are incorporated. Results for static quantities are in reasonable agreement with the experimental data.
Axial Nucleon to Delta transition form factors on 2+1 flavor hybrid lattices
Alexandrou, C; Leontiou, Th; Negele, J W; Tsapalis, A; 10.1103/PhysRevD.80.099901
2009-01-01
We correct the values of the dominant nucleon to Delta axial transition form factors CA_5 and CA_6 published in C. Alexandrou et.al., Phys. Rev. D 76,094511 (2007). The analysis error affects only the values obtained when using the hybrid action in the low Q^2 regime bringing them into agreement with those obtained with Wilson fermions.
The electric dipole form factor of the nucleon in chiral perturbation theory to subleading order
Mereghetti, E; de Vries, Jordy; Hockings, W.H.; Maekawa, C.M.; van Kolck, U
2011-01-01
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD ¯ term and from the quark color-electric dipole moments is calculated in chiral perturbation theory to sub-leading order. This is the lowest order in which the isoscalar EDFF receives a calculable, non-analytic contribution
The nucleon electric dipole form factor from dimension-six time-reversal violation
de Vries, J.; Mereghetti, E.; Timmermans, R. G. E.; van Kolck, U.
2011-01-01
We calculate the electric dipole form factor of the nucleon that arises as a low-energy manifestation of time-reversal violation in quark-gluon interactions of effective dimension 6: the quark electric and chromoelectric dipole moments, and the gluon chromoelectric dipole moment. We use the framewor
The Pion-Cloud Contribution to the Electromagnetic Nucleon Form Factors
Directory of Open Access Journals (Sweden)
Kupelwieser Daniel
2016-01-01
Full Text Available We study the electromagnetic structure of the nucleon within a hybrid constituent-quark model that comprises, in addition to the 3q valence component, also a 3q+π non-valence component. To this aim we employ a Poincaré-invariant multichannel formulation based on the point-form of relativistic quantum mechanics. With a simple 3-quark wave function for the bare nucleon, i.e. the 3q-component, we obtain reasonable results for the nucleon form factors and predict the meson-cloud contribution to be significant only below Q2 ≲ 0:5 GeV2 amounting to about 10% for Q2 → 0, in accordance with the findings of other authors.
Nucleon-to-Delta axial transition form factors in relativistic baryon chiral perturbation theory
Geng, L S; Alvarez-Ruso, L; Vacas, M J Vicente
2008-01-01
We report a theoretical study of the axial Nucleon to Delta(1232) ($N\\to\\Delta$) transition form factors up to one-loop order in relativistic baryon chiral perturbation theory. We adopt a formalism in which the $\\Delta$ couplings obey the spin-3/2 gauge symmetry and, therefore, decouple the unphysical spin-1/2 fields. We compare the results with phenomenological form factors obtained from neutrino bubble chamber data and in quark models.
A Perturbative QCD Analysis of the Nucleon's Pauli Form Factor F_2(Q^2)
Belitsky, A V; Yuan, F; Belitsky, Andrei V.; Ji, Xiangdong; Yuan, Feng
2003-01-01
We perform a perturbative QCD analysis of the nucleon's Pauli form factor $F_2(Q^2)$ in the asymptotically large $Q^2$ limit. We find that the leading contribution to $F_2(Q^2)$ goes like $1/Q^6$, consistent with the well-known folklore. Its coefficient is expressed in terms of an overlap integral involving the leading and subleading light-cone wave functions of the nucleon, the latter describing the quark state with one unit of orbital angular momentum. We estimate the numerical size of the coefficient and comment on the contribution from the end-point region.
Lattice calculation of electric dipole moments and form factors of the nucleon
Abramczyk, M.; Aoki, S.; Blum, T.; Izubuchi, T.; Ohki, H.; Syritsyn, S.
2017-07-01
We analyze commonly used expressions for computing the nucleon electric dipole form factors (EDFF) F3 and moments (EDM) on a lattice and find that they lead to spurious contributions from the Pauli form factor F2 due to inadequate definition of these form factors when parity mixing of lattice nucleon fields is involved. Using chirally symmetric domain wall fermions, we calculate the proton and the neutron EDFF induced by the C P -violating quark chromo-EDM interaction using the corrected expression. In addition, we calculate the electric dipole moment of the neutron using a background electric field that respects time translation invariance and boundary conditions, and we find that it decidedly agrees with the new formula but not the old formula for F3. Finally, we analyze some selected lattice results for the nucleon EDM and observe that after the correction is applied, they either agree with zero or are substantially reduced in magnitude, thus reconciling their difference from phenomenological estimates of the nucleon EDM.
Lattice calculation of electric dipole moments and form factors of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Abramczyk, M.; Aoki, S.; Blum, T.; Izubuchi, T.; Ohki, H.; Syritsyn, S.
2017-07-01
We analyze commonly used expressions for computing the nucleon electric dipole form factors (EDFF) $F_3$ and moments (EDM) on a lattice and find that they lead to spurious contributions from the Pauli form factor $F_2$ due to inadequate definition of these form factors when parity mixing of lattice nucleon fields is involved. Using chirally symmetric domain wall fermions, we calculate the proton and the neutron EDFF induced by the CP-violating quark chromo-EDM interaction using the corrected expression. In addition, we calculate the electric dipole moment of the neutron using background electric field that respects time translation invariance and boundary conditions, and find that it decidedly agrees with the new formula but not the old formula for $F_3$. Finally, we analyze some selected lattice results for the nucleon EDM and observe that after the correction is applied, they either agree with zero or are substantially reduced in magnitude, thus reconciling their difference from phenomenological estimates of the nucleon EDM.
de Teramond, Guy F
2016-01-01
The superconformal algebraic approach to hadronic physics is used to construct a semiclassical effective theory for nucleons which incorporates essential nonperturbative dynamical features, such as the emergence of a confining scale and the Regge resonance spectrum. Relativistic bound-state equations for nucleons follow from the extension of superconformal quantum mechanics to the light front and its holographic embedding in a higher dimensional gravity theory. Superconformal algebra has been used elsewhere to describe the connections between the light mesons and baryons, but in the present context it relates the fermion positive and negative chirality states and uniquely determines the confinement potential of nucleons. The holographic mapping of multi-quark bound states also leads to a light-front cluster decomposition of form factors for an arbitrary number of constituents. The remarkable analytical structure which follows incorporates the correct scaling behavior at high photon virtualities and also vecto...
de Téramond, Guy F.
2016-10-01
The superconformal algebraic approach to hadronic physics is used to construct a semiclassical effective theory for nucleons which incorporates essential nonperturbative dynamical features, such as the emergence of a confining scale and the Regge resonance spectrum. Relativistic bound-state equations for nucleons follow from the extension of superconformal quantum mechanics to the light front and its holographic embedding in a higher dimensional gravity theory. Superconformal algebra has been used elsewhere to describe the connections between the light mesons and baryons, but in the present context it relates the fermion positive and negative chirality states and uniquely determines the confinement potential of nucleons. The holographic mapping of multi-quark bound states also leads to a light-front cluster decomposition of form factors for an arbitrary number of constituents. The remarkable analytical structure which follows incorporates the correct scaling behavior at high photon virtualities and also vector dominance at low energies.
Improved dispersive analysis of the scalar form factor of the nucleon
Hoferichter, Martin; Kubis, Bastian; ner, Ulf-G Meiß
2012-01-01
We present a coupled system of integral equations for the pi pi --> Nbar N and Kbar K --> Nbar N S-waves derived from Roy-Steiner equations for pion-nucleon scattering. We discuss the solution of the corresponding two-channel Muskhelishvili-Omnes problem and apply the results to a dispersive analysis of the scalar form factor of the nucleon fully including Kbar K intermediate states. In particular, we determine the corrections Delta_sigma and Delta_D, which are needed for the extraction of the pion-nucleon sigma term from pi N scattering, and show that the difference Delta_D - Delta_sigma=(-1.8 +/- 0.2) MeV is insensitive to the input pi N parameters.
De Sanctis, M; Santopinto, E; Vassallo, A
2015-01-01
We briefly describe our relativistic quark-diquark model, developed within the framework of point form dynamics, which is the relativistic extension of the interacting quark-diquark model. In order to do that we have to show the main properties and quantum numbers of the effective degree of freedom of constituent diquark. Our results for the nonstrange baryon spectrum and for the nucleon electromagnetic form factors are discussed.
Extraction of the isovector magnetic form factor of the nucleon at zero momentum
Alexandrou, Constantia; Koutsou, Giannis; Ottnad, Konstantin; Petschlies, Marcus
2014-01-01
The extraction of the magnetic form factor of the nucleon at zero momentum transfer is usually performed by adopting a parametrization for its momentum dependence and fitting the results obtained at finite momenta. We present position space methods that rely on taking the derivative of relevant correlators to extract directly the magnetic form factor at zero momentum without the need to assume a functional form for its momentum dependence. These methods are explored on one ensemble using $N_f=2+1+1$ Wilson twisted mass fermions.
On the pi pi continuum in the nucleon form factors and the proton radius puzzle
Hoferichter, M; de Elvira, J Ruiz; Hammer, H -W; Meißner, U -G
2016-01-01
We present an improved determination of the $\\pi\\pi$ continuum contribution to the isovector spectral functions of the nucleon electromagnetic form factors. Our analysis includes the most up-to-date results for the $\\pi\\pi\\to\\bar N N$ partial waves extracted from Roy-Steiner equations, consistent input for the pion vector form factor, and a thorough discussion of isospin-violating effects and uncertainty estimates. As an application, we consider the $\\pi\\pi$ contribution to the isovector electric and magnetic radii by means of sum rules, which, in combination with the accurately known neutron electric radius, are found to slightly prefer a small proton charge radius.
On the ππ continuum in the nucleon form factors and the proton radius puzzle
Hoferichter, M.; Kubis, B.; Ruiz de Elvira, J.; Hammer, H.-W.; Meißner, U.-G.
2016-11-01
We present an improved determination of the ππ continuum contribution to the isovector spectral functions of the nucleon electromagnetic form factors. Our analysis includes the most up-to-date results for the ππ→bar{N} N partial waves extracted from Roy-Steiner equations, consistent input for the pion vector form factor, and a thorough discussion of isospin-violating effects and uncertainty estimates. As an application, we consider the ππ contribution to the isovector electric and magnetic radii by means of sum rules, which, in combination with the accurately known neutron electric radius, are found to slightly prefer a small proton charge radius.
Kubis, B
2001-01-01
We analyze the electromagnetic form factors of the nucleon to fourth order in relativistic baryon chiral perturbation theory. We employ the recently proposed infrared regularization scheme and show that the convergence of the chiral expansion is improved as compared to the heavy-fermion approach. We also discuss the inclusion of vector mesons and obtain an accurate description of all four-nucleon form factors for momentum transfer squared up to Q sup 2 approx =0.4 GeV sup 2.
Scalar and vector form factors of the in-medium nucleon
Saitô, K
2003-01-01
Using the quark-meson coupling model, we calculate the form factors at sigma- and omega-nucleon strong-interaction vertices in nuclear matter. The Peierls-Yoccoz projection technique is used to take account of center of mass and recoil corrections. We also apply the Lorentz contraction to the internal quark wave function. The form factors are reduced by the nuclear medium relative to those in vacuum. At normal nuclear matter density and Q^2 = 1 GeV^2, the reduction rate in the scalar form factor is about 15%, which is almost identical to that in the vector one. We parameterize the ratios of the form factors in symmetric nuclear matter to those in vacuum as a function of nuclear density and momentum transfer.
Nucleon momentum distributions and elastic electron scattering form factors for some 1p-shell nuclei
Indian Academy of Sciences (India)
A K Hamoudi; M A Hasan; A R Ridha
2012-05-01
The nucleon momentum distributions (NMD) and elastic electron scattering form factors of the ground state for 1p-shell nuclei with = (such as 6Li, 10B, 12C and 14N nuclei) have been calculated in the framework of the coherent density ﬂuctuation model (CDFM) and expressed in terms of the weight function $|f(x)|^2$. The weight function has been expressed in terms of nucleon density distribution (NDD) of the nuclei and determined from the theory and the experiment. The feature of the long-tail behaviour at high-momentum region of the NMDs has been obtained by both the theoretical and experimental weight functions. The experimental form factors $F(q)$ of all the considered nuclei are very well reproduced by the present calculations for all values of momentum transfer . It is found that the contributions of the quadrupole form factors $F_{C2}(q)$ in 10B and 14N nuclei, which are described by the undeformed p-shell model, are essential for obtaining a remarkable agreement between the theoretical and experimental form factors.
Strangeness Vector and Axial-Vector Form Factors of the Nucleon
Directory of Open Access Journals (Sweden)
Pate Stephen
2014-03-01
Full Text Available A revised global fit of electroweak ep and vp elastic scattering data has been performed, with the goal of determining the strange quark contribution to the vector and axial-vector form factors of the nucleon in the momentum-transfer range 0 < Q2 < 1 GeV2. The two vector (electric and magnetic form factors GsE(Q2 and GsM(Q2 are strongly constrained by ep elastic scattering data, while the major source of information on the axial-vector form factor GsA(Q2 is vp scattering data. Combining the two kinds of data into a single global fit makes possible additional precision in the determination of these form factors, and provides a unique way to determine the strange quark contribution to the nucleon spin, ΔS , independently of leptonic deep-inelastic scattering. The fit makes use of data from the BNL-E734, SAMPLE, HAPPEx, G0, and PVA4 experiments; we will also compare the result of the fit with recent data from MiniBooNE, and anticipate how this fit can be improved when new data from MicroBooNE become available.
Overview of high-Q2 nucleon form factor program with Super BigBite Spectrometer in JLab's Hall A
Puckett, Andrew; Jefferson Lab Hall A; Super BigBite Spectrometer Collaboration
2017-01-01
The elastic electromagnetic form factors (EMFFs) of the nucleon describe the impact-parameter-space distributions of electric charge and magnetization in the nucleon in the infinite momentum frame. The form factors are among the simplest and most fundamental measurable dynamical quantities describing the nucleon's structure. Precision measurements of the nucleon form factors provide stringent benchmarks testing the most sophisticated theoretical models of the nucleon, as well as ab initio calculations in lattice QCD and continuum non-perturbative QCD calculations based on the Dyson-Schwinger equations. Measurements at momentum transfers Q in the few-GeV range probe the theoretically challenging region of transition between the non-perturbative and perturbative regimes of QCD. The recent upgrade of the Continuous Electron Beam Accelerator Facility (CEBAF) to a maximum electron beam energy of 11 GeV will facilitate the measurement of the nucleon helicity-conserving (F1) and helicity-flip (F2) form factors of both proton and neutron to Q2 > 10 GeV2, In this talk, I will present an overview of the Super BigBite Spectrometer, currently under construction in CEBAF's experimental Hall A, and its physics program of high-Q2 nucleon EMFF measurements. Supported by US DOE award DE-SC0014230.
Excited state systematics in extracting nucleon electromagnetic form factors from the lattice
Energy Technology Data Exchange (ETDEWEB)
Rae, Thomas; Hippel, Georg von; Knippschild, Bastian [PRISMA Cluster of Excellence and Institut fuer Kernphysik, University of Mainz (Germany); Capitani, Stefano; Wittig, Hartmut; Jaeger, Benjamin; Meyer, Harvey; Della Morte, Michele [PRISMA Cluster of Excellence and Institut fuer Kernphysik, University of Mainz (Germany); Helmholtz Institute Mainz, University of Mainz (Germany)
2013-07-01
We present recent results for the nucleon electromagnetic form factors using lattice QCD. This includes the determination of the charge radii. The standard approach is to extract the form factors via a plateau fit to the lattice data using a 'large-enough' time separation between the operators at the source and sink. To check that this removes excited state contaminations to an acceptable level, we employ two further extraction methods: a fit that explicitly accounts for the contamination; and the use of a summed operator insertion, which suppresses the contamination. A comparison of the methods allows for the study of systematic effects related to excited state contributions entering in the q{sup 2} dependence of the form factors. We employ the CLS ensembles using non-perturbatively O(a) improved Wilson fermions in N{sub f}=2 QCD.
New large-$N_c$ relations for the electromagnetic nucleon-to-$\\Delta$ form factors
Energy Technology Data Exchange (ETDEWEB)
Vladimir Pascalutsa; Marc Vanderhaeghen
2007-12-01
We establish relations which express the three $N\\to \\Delta$ transition form factors in terms of the nucleon form factors. These relations are based on the known large-$N_c$ relation between the $N\\to \\De$ electric quadrupole moment and the neutron charge radius, and a newly derived large-$N_c$ relation between the electric quadrupole ($E2$) and Coulomb quadrupole ($C2$) transitions. Namely, in the large-$N_c$ limit we find $C2=E2$. We show that these relations provide predictions for the $N\\to\\Delta$ electromagnetic form factors which are found to be in very good agreement with experiment for moderate momentum transfers. They also provide constraints for the $N \\to \\Delta$ GPDs.
Nucleon form factors and couplings with $N_\\mathrm{f} = 2 + 1$ Wilson fermions
Djukanovic, Dalibor; von Hippel, Georg; Junnarkar, Parikshit; Meyer, Harvey B; Wittig, Hartmut
2016-01-01
We present updated results on the nucleon electromagnetic form factors and axial coupling calculated using CLS ensembles with $N_\\mathrm{f}=2+1$ dynamical flavours of Wilson fermions. The measurements are performed on large, fine lattices with a pseudoscalar mass reaching down to 200 MeV. The truncated-solver method is employed to reduce the variance of the measurements. Estimation of the matrix elements is challenging due to large contamination from excited states and further investigation is necessary to bring these effects under control.
Error reduction technique using covariant approximation and application to nucleon form factor
Blum, Thomas; Shintani, Eigo
2012-01-01
We demonstrate the new class of variance reduction techniques for hadron propagator and nucleon isovector form factor in the realistic lattice of $N_f=2+1$ domain-wall fermion. All-mode averaging (AMA) is one of the powerful tools to reduce the statistical noise effectively for wider varieties of observables compared to existing techniques such as low-mode averaging (LMA). We adopt this technique to hadron two-point functions and three-point functions, and compare with LMA and traditional source-shift method in the same ensembles. We observe AMA is much more cost effective in reducing statistical error for these observables.
Electron-Positron to Nucleon-Antinucleon Pair at Threshold and Proton Form Factor
Yan, Y; Kobdaj, C; Suebka, P
2009-01-01
The reactions of electron-positron to nucleon-antinucleon pair at energy threshold are studied in a non-perturbative quark model. The puzzling experimental result that the ratio of the cross section of electron-positron to proton-antiproton to the one of electron-positron to neutron-antineutron is smaller than 1 can be understood in the framework of the phenomenological nonrelativistic quark model and the theoretical predictions for the time-like proton form factor at energy threshold are well consistent with the experimental data. The work suggests that the two-step process, in which the primary quark-antiquark pair forms first a vector meson which in turn decays into a hadron pair, is dominant over the one-step process in which the primary quark-antiquark pair is directly dressed by additional quark-antiquark pairs to form a hadron pair. The experimental data on the reactions of electron-positron to nucleon-antinucleon strongly suggest the reported vector meson omega(1930) to be a 2D-wave particle, while th...
High-precision calculation of the strange nucleon electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Green, Jeremy [Johannes Gutenberg Univ., Mainz (Germany); Meinel, Stefan [Univ. of Arizona, Tucson, AZ (United States); Brookhaven National Lab. (BNL), Upton, NY (United States); Engelhardt, Michael G. [New Mexico State Univ., Las Cruces, NM (United States); Krieg, Stefan [Bergische Univ., Wuppertal (Germany); Julich Supercomputing Centre, Julich (Germany); Laeuchli, Jesse [College of William and Mary, Williamsburg, VA (United States); Negele, John W. [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Orginos, Kostas [College of William and Mary, Williamsburg, VA (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Pochinsky, Andrew [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States); Syritsyn, Sergey [Brookhaven National Lab. (BNL), Upton, NY (United States)
2015-08-26
We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors G^{s}_{E} and G^{s}_{M} in the kinematic range 0 ≤ Q^{2} ≤ 1.2GeV^{2}. For the first time, both G^{s}_{E} and G^{s}_{M} are shown to be nonzero with high significance. This work uses closer-to-physical lattice parameters than previous calculations, and achieves an unprecented statistical precision by implementing a recently proposed variance reduction technique called hierarchical probing. We perform model-independent fits of the form factor shapes using the z-expansion and determine the strange electric and magnetic radii and magnetic moment. As a result, we compare our results to parity-violating electron-proton scattering data and to other theoretical studies.
Pinto, Sérgio Alexandre; Gross, Franz
2009-01-01
We present the first calculations of the electromagnetic form factors of $^3$He and $^3$H within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a non-relativistic framework, such as "Z-graphs", but omits other two and three-body currents. We compare our results to non-relativistic calculations augmented by relativistic corrections of ${\\cal O}(v/c)^2$.
Energy Technology Data Exchange (ETDEWEB)
Pinto, Sérgio Alexandre; Stadler, Alfred; Gross, Franz
2009-05-01
We present the first calculations of the electromagnetic form factors of ^{3}He and ^{3}H within the framework of the Covariant Spectator Theory (CST). This first exploratory study concentrates on the sensitivity of the form factors to the strength of the scalar meson-nucleon off-shell coupling, known from previous studies to have a strong influence on the three-body binding energy. Results presented here were obtained using the complete impulse approximation (CIA), which includes contributions of relativistic origin that appear as two-body corrections in a non-relativistic framework, such as "Z-graphs," but omits other two and three-body currents. Finally, we compare our results to non-relativistic calculations augmented by relativistic corrections of O(v/c)^{2}.
Energy Technology Data Exchange (ETDEWEB)
Peters, Gerhard
2008-05-15
In this work the leading-twist next-to-leading order (NLO) correction to the light-cone sum rules prediction for the electromagnetic form factors of the nucleon are calculated. Here the Ioffe nucleon interpolation current is used and it is worked in the M{sub N}=0 approximation, with M{sub N} being the mass of the nucleon. In this approximation, only the Pauli form factor F{sub 2} receives a correction and the calculated correction is quite sizable. The numerical results for the proton form factors show the improved agreement with the experimental data. Furthermore the problems encountered when going away from M{sub N}=0 approximation at NLO, as well as, gauge invariance of the perturbative results are discussed. This work presents the first step towards the NLO accuracy in the light-cone sum rules for baryon form factors. (orig.)
Silva, A; Urbano, D; Göke, K; Silva, Antonio; Kim, Hyun-CHul; Urbano, Diana; Goeke, Klaus
2005-01-01
We investigate three different axial-vector form factors of the nucleon, $G_A^{0}$, $G_A^3$, $G_A^8$, within the framework of the SU(3) chiral quark-soliton model, emphasizing their strangeness content. We take into account the rotational $1/N_c$ and linear strange quark ($m_s$) contributions using the symmetry-conserving SU(3) quantization and assuming isospin symmetry. The strange axial-vector form factor is also obtained and they all are discussed in the context of the parity-violating scattering of polarized electrons off the nucleon and its relevance to the strange vector form factors.
SU(6) breaking effects in the nucleon elastic electromagnetic form factors
Cardarelli, F; Cardarelli, Fabio; Simula, Silvano
2000-01-01
The effects of SU(6) breaking on the nucleon elastic form factors are investigated within the constituent quark model formulated on the light-front. It is shown that the kinematical SU(6) breaking caused by the Melosh rotations of the quark spins as well as the dynamical SU(6) breaking due to the mixed-symmetry component generated in the nucleon wave function by the spin-dependent terms of the quark-quark interaction, can affect both GEn(Q**2) and GMp(Q**2)/GMn(Q**2). The calculated GEn(Q**2) is found to be qualitatively consistent with existing data. while the calculations of GM(Q**2) based on the plus component of the current are found to be plagued by spurious effects related to the loss of the rotational covariance in the light-front formalism. These unwanted effects can be avoided by considering the transverse y-component of the current. In this way our light-front predictions are found to be consistent with the data on both GEn(Q**2) and GMp(Q**2)/GMn(Q**2). Finally, it is shown that a suppression of th...
Sufian, Raza Sabbir; Brodsky, Stanley J; Deur, Alexandre; Dosch, Hans Günter
2016-01-01
We present a comprehensive analysis of the nucleon electromagnetic form factors and their flavor decomposition within the framework of light-front holographic QCD. We show that the inclusion of the higher Fock components $|qqqq\\bar{q}>$ has a significant effect on the spin-flip elastic Pauli form factor and almost zero effect on the spin-conserving Dirac form factor. We present light-front holographic QCD predictions of proton and neutron form factors in the momentum transfer range of $0\\leq Q^2 \\leq 20\\, \\text{GeV}^2$ and show that these predictions agree with the available experimental data with high accuracy. In order to correctly describe the Pauli form factor we need an admixture of a five quark state of about 30$\\%$ in the proton and about 40$\\%$ in the neutron. We also extract the nucleon charge and magnetic radii and perform a flavor decomposition of the nucleon electromagnetic form factors. The number of free parameters needed to describe the experimental nucleon form factors in the space-like domain...
Nucleon form factors and moments of parton distributions in twisted mass lattice QCD
Alexandrou, C; Carbonell, J; Constantinou, M; Guichon, P; Harraud, P A; Jansen, K; Kallidonis, C; Korzec, T; Papinutto, M
2012-01-01
We present results on the electroweak form factors and on the lower moments of parton distributions of the nucleon, within lattice QCD using two dynamical flavors of degenerate twisted mass fermions. Results are obtained on lattices with three different values of the lattice spacings, namely a=0.089 fm, a=0.070 fm and a=0.056 fm, allowing the investigation of cut-off effects. The volume dependence is examined by comparing results on two lattices of spatial length L=2.1 fm and L=2.8 fm. The simulations span pion masses in the range of 260-470 MeV. Our results are renormalized non-perturbatively and the values are given in the MS-scheme at a scale mu=2 GeV.
Silva, Antonio; Kim, Hyun-Chul
2013-01-01
We investigate the flavor decomposition of the electromagnetic form factors of the nucleon, based on the chiral quark-soliton model with symmetry-conserving quantization. We consider the rotational 1/N_c and linear strange-quark mass (m_s) corrections. To extend the results to higher momentum transfer, we take into account the kinematical relativistic effects. We discuss the results of the flavor-decomposed electromagnetic form factors in comparison with the recent experimental data. In order to see the effects of the strange quark, we compare the SU(3) results with those of SU(2). We finally discuss the transverse charge densities for both unpolarized and polarized nucleons.
Nucleon form factors and static properties of baryons in a quark model
Energy Technology Data Exchange (ETDEWEB)
Barik, N. (Department of Physics, Utkal University, Bhubaneswar 751004, Orissa, India (IN) ); Jena, S.N. (Department of Physics, Berhampur University, Berhampur 760007, Orissa, India (IN)); Rath, D.P. (Department of Physics, Aska Science College, Aska 761110, Orissa, India (IN))
1990-03-01
The nucleon electromagnetic form factors {ital G}{sub {ital E}}{sup {ital p}}(q{sup 2}), {ital G}{sub {ital M}}{sup {ital p}}(q{sup 2}), {ital G}{sub {ital M}}{sup {ital n}}(q{sup 2}), and the axial-vector form factor {ital G}{sub {ital A}}(q{sup 2}) are calculated in a simple independent-quark model based on the Dirac equation with a logarithmic confining potential of the form {ital V}{prime}({ital r})=(1+{gamma}{sup 0})a ln({ital r}/{ital b}). The respective rms radii associated with {ital G}{sub {ital E}}{sup {ital p}}(q{sup 2}) and {ital G}{sub {ital A}}(q{sup 2}) come out as ({l angle}{ital r}{sup 2}{r angle}{sub E}{sup P}){sup 1/2}=0.938 fm and {l angle}{ital r}{sub {ital A}}{sup 2}{r angle}{sup 1/2}=0.953 fm. The magnetic moments, charge radii, and axial-vector coupling-constant ratios for octet baryons are also calculated with the appropriate center-of-mass correction. The results so obtained are quite comparable to experimental data.
Energy Technology Data Exchange (ETDEWEB)
N. Suzuki, T. Sato, T.-S. H. Lee
2010-10-01
We explain the application of a recently developed analytic continuation method to extract the electromagnetic transition form factors for the nucleon resonances ($N^*$) within a dynamical coupled-channel model of meson-baryon reactions.Illustrative results of the obtained $N^*\\rightarrow \\gamma N$ transition form factors, defined at the resonance pole positions on the complex energy plane, for the well isolated $P_{33}$ and $D_{13}$, and the complicated $P_{11}$ resonances are presented. A formula has been developed to give an unified representation of the effects due to the first two $P_{11}$ poles, which are near the $\\pi\\Delta$ threshold, but are on different Riemann sheets. We also find that a simple formula, with its parameters determined in the Laurent expansions of $\\pi N \\rightarrow \\pi N$ and $\\gamma N \\rightarrow\\pi N$ amplitudes, can reproduce to a very large extent the exact solutions of the considered model at energies near the real parts of the extracted resonance positions. We indicate the differences between our results and those extracted from the approaches using the Breit-Wigner parametrization of resonant amplitudes to fit the data.
The electric dipole form factor of the nucleon in chiral perturbation theory to sub-leading order
Mereghetti, E.; de Vries, J.; Hockings, W. H.; Maekawa, C. M.; van Kolck, U.
2011-01-01
The electric dipole form factor (EDFF) of the nucleon stemming from the QCD (theta) over bar term and from the quark color-electric dipole moments is calculated in chiral perturbation theory to sub-leading order. This is the lowest order in which the isoscalar EDFF receives a calculable, non-analyti
Nucleon form factors in an independent-quark model based on Dirac equation with power-law potential
Energy Technology Data Exchange (ETDEWEB)
Barik, N.; Das, M.
1986-01-01
The nucleon electromagnetic form factors G/sub E//sup p/(qS) and G/sub M//sup p/(qS) and the axial-vector form factor G/sub A/(qS) are investigated in a simple model of relativistic quarks confined by a vector-scalar mixed potential U/sub q/(r) = (1+el)(a/sup nu+1/r/sup / +V0) without taking into account the center-of-mass correction and the pion-cloud effects. The respective rms radii associated with G/sub E//sup p/(qS) and G/sub A/(qS) come out as
Energy Technology Data Exchange (ETDEWEB)
Barik, N.; Dash, B.K.
1986-10-01
Nucleon charge and magnetic form factors G/sub E//sub ,//sub M//sup p//sup ,//sup n/(q/sup 2/) have been presented in a quark model with an equally mixed scalar and vector potential in harmonic form taking the pionic contributions into account. The static properties such as the magnetic moment, charge radius, and axial-vector coupling constant in the neutron-..beta..-decay process are shown to be in excellent agreement with the corresponding experimental values. The role of the finite extension of the quark-pion vertex in determining the charge radius and magnetic moment due to the pion cloud surrounding the nucleons has been studied.
Parity-Violating Electron Scattering from 4He and the Strange Electric Form Factor of the Nucleon
Airapetian, A; Akopov, Z; Amarian, M; Ammosov, V V; Andrus, A; Aschenauer, E C; Augustyniak, W; Avakian, R; Avetisian, A; Avetissian, E; Bailey, P; Balin, D; Baturin, V; Beckmann, M; Belostotskii, S; Bernreuther, S; Bianchi, N; Blok, H P; Böttcher, Helmut B; Borisov, A; Borysenko, A; Bouwhuis, M; Brack, J; Brüll, A; Bryzgalov, V; Capitani, G P; Chen, T; Chiang, H C; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; De Leo, R; Demey, M; De Nardo, L; De Sanctis, E; Devitsin, E G; Di Nezza, P; Dreschler, J; Düren, M; Ehrenfried, M; Elalaoui-Moulay, A; Elbakian, G; Ellinghaus, F; Elschenbroich, U; Fabbri, R; Fantoni, A; Feshchenko, A; Felawka, L; Fox, B; Frullani, S; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Garutti, E; Gaskell, D; Gavrilov, G; Karibian, V; Graw, G; Grebenyuk, O; Greeniaus, L G; Gregor, I M; Hafidi, K; Hartig, M; Hasch, D; Heesbeen, D; Henoch, M; Hertenberger, R; Hesselink, W H A; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, H E; Jgoun, A; Kaiser, R; Kinney, E; Kiselev, A; Kopytin, M; Korotkov, V; Kozlov, V; Krauss, B; Krivokhizhin, V G; Lagamba, L; Lapikas, L; Laziev, A; Lenisa, P; Liebing, P; Linden-Levy, L A; Lipka, K; Lorenzon, W; Lü, H; Lü, J; Lu, S; Ma, B Q; Maiheu, B; Makins, N C R; Mao, Y; Marianski, B; Marukyan, H; Masoli, F; Mexner, V; Meyners, N; Miklukho, O; Miller, C A; Miyachi, Y; Muccifora, V; Nagaitsev, A; Nappi, E; Naryshkin, Yu; Nass, A; Negodaev, M; Nowak, Wolf-Dieter; Oganessyan, K; Ohsuga, H; Pickert, N; Potashov, S Yu; Potterveld, D H; Raithel, M; Reggiani, D; Reimer, P E; Reischl, A; Reolon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanjiev, I; Savin, I; Schäfer, A; Schill, C; Schnell, G; Schüler, K P; Seele, J; Seidl, R; Seitz, B; Shanidze, R; Shearer, C; Shibata, T A; Shutov, V; Simani, M C; Sinram, K; Stancari, M; Statera, M; Steffens, E; Steijger, J J M; Stenzel, H; Stewart, J; Stinzing, F; Stösslein, U; Tait, P; Tanaka, H; Taroian, S P; Tchuiko, B; Terkulov, A R; Tkabladze, A; Trzcinski, A; Tytgat, M; Vandenbroucke, A; Van der Nat, P B; van der Steenhoven, G; Vetterli, M C; Vikhrov, V; Vincter, M G; Vogel, C; Vogt, M; Volmer, J; Weiskopf, C; Wendland, J; Wilbert, J; Ye, Y; Ye, Z; Yen, S; Zihlmann, B; Zupranski, P; Aniol, K A; Armstrong, D S; Averett, T; Benaoum, H; Bertin, P Y; Burtin, E; Cahoon, J; Cates, G D; Chang, C C; Chao Yu Chiu; Chen, J P; Seonho Choi; Chudakov, E; Craver, B; Cusanno, F; Decowski, P; Deepa, D; Ferdi, C; Feuerbach, R J; Finn, J M; Fuoti, K; Gilman, R; Glamazdin, A; Gorbenko, V; Grames, J M; Hansknecht, J; Higinbotham, D W; Holmes, R; Holmstrom, T; Humensky, T B; Ibrahim, H; De Jager, C W; Jiang, X; Kaufman, L J; Kelleher, A; Kolarkar, A; Kowalski, S; Kumar, K S; Lambert, D; La Violette, P; Le Rose, J; Lhuillier, D; Liyanage, N; Margaziotis, D J; Mazouz, M; McCormick, K; Meekins, D G; Meziani, Z E; Michaels, R; Moffit, B; Monaghan, P; Munoz-Camacho, C; Nanda, S; Nelyubin, V V; Neyret, D; Paschke, K D; Poelker, M; Pomatsalyuk, R I; Qiang, Y; Reitz, B; Roche, J; Saha, A; Singh, J; Snyder, R; Souder, P A; Subedi, R; Suleiman, R; Sulkosky, V; Tobias, W A; Urciuoli, G M; Vacheret, A; Voutier, E; Wang, K; Wilson, R; Wojtsekhowski, B; Zheng, X
2006-01-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from ^4He at an average scattering angle = 5.7 degrees and a four-momentum transfer Q^2 = 0.091 GeV^2. From these data, for the first time, the strange electric form factor of the nucleon G^s_E can be isolated. The measured asymmetry of A_PV = (6.72 +/- 0.84 (stat) +/- 0.21 (syst) parts per million yields a value of G^s_E = -0.038 +/- 0.042 (stat) +/- 0.010 (syst), consistent with zero.
Duda, G; Kemper, A; Duda, Gintaras; Gondolo, Paolo; Kemper, Ann
2006-01-01
Theoretical calculations of neutralino cross sections with various nuclei are of great interest to direct dark matter searches such as CDMS, EDELWEISS, ZEPLIN, and other experiments. These cross sections and direct detection rates are generally computed with standard, one or two parameter model-dependent nuclear form factors, which may not exactly mirror the actual form factor for the particular nucleus in question. As is well known, elastic electron scattering can allow for very precise determinations of nuclear form factors and hence nuclear charge densities for spherical or near-spherical nuclei. We use charge densities derived from elastic electron scattering data to calculate model independent form factors for various target nuclei important in dark matter searches, such as Si, Ge, S, Ca and others. We have found that for nuclear recoils in the range of 1-100 keV significant differences in cross sections and rates exist when the model independent form factors are used. DarkSUSY, a publicly-available adva...
Bianconi, Andrea; Tomasi-Gustafsson, Egle
2017-01-01
As is well known, spacelike proton form factors expressed in the Breit frame may be interpreted as the Fourier transform of static space distributions of electric charge and current. In particular, the electric form factor is simply the Fourier transform of the charge distribution F (q ) =∫ei q ⃗.r ⃗ρ (r ) d3r . We do not have an intuitive interpretation of the same level of simplicity for the proton timelike form factor appearing in the reactions e+e-↔p ¯p . However, one may suggest that, in the center-of-mass frame, where qμxμ=q t , a timelike electric form factor is the Fourier transform F (q ) =∫ei q tR (t ) d t of a function R (t ) expressing how the electric properties of the forming (or annihilating) proton-antiproton pair evolve in time. Here we analyze in depth this idea and show that the functions ρ (r ) and R (t ) can be formally written as the time and space integrals of a unique correlation function depending on both time and space coordinates.
Bianconi, Andrea
2016-01-01
As well known, spacelike proton form factors expressed in the Breit frame may be interpreted as the Fourier transform of static space distributions of electric charge and current. In particular, the electric form factor is simply the Fourier transform of the charge distribution $F(q)=\\int e^{i\\vec q \\cdot \\vec r} \\rho(r)d^3r$. We don't have an intuitive interpretation of the same level of simplicity for the proton timelike form factor appearing in the reactions $e^+e^-\\leftrightarrow \\bar{p}p$. However, one may suggest that in the center of mass (CM) frame, where $q_\\mu x^\\mu =qt$, a timelike electric form factor is the Fourier transform $F(q) =\\int e^{iqt} R(t)dt$ of a function $R(t)$ expressing how the electric properties of the forming (or annihilating) proton-antiproton pair evolve in time. Here we analyze in depth this idea, show that the functions $\\rho(r)$ and $R(t)$ can be formally written as the time and space integrals of a unique correlation function depending on both time and space coordinates.
Energy Technology Data Exchange (ETDEWEB)
Schaub, John [New Mexico State Univ., Las Cruces, NM (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2010-07-01
We studied the strange contributions to the elastic vector and axial form factors of the nucleon using all available elastic electroweak scattering data. Specifically, we combine elastic nu-p and nubar-p scattering cross-section data from the Brookhaven E734 experiment with elastic ep and quasi-elastic ed and e-^{4}He scattering parity-violating asymmetry data from the SAMPLE, HAPPEx, PVA4 and G0 experiments. We not only determined these form factors at individual values of momentum-transfer (Q^{2}), as other groups have done recently, but also fit the Q^{2}-dependence of these form factors using simple functional forms. I present an overview of the G^{0} backward-angle experiment as well as the results of these fits using existing data, along with some expectations of how we can improve our knowledge of these form factors if the MicroBooNE collaboration completes their experiment.
Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2004-01-01
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativistic constituent quark model. However its calculation results of GnE agree poorly with the new experimental data. The electromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculation results have good agreement with the new experimental data of GnE after considering the contribution of the quark structure term. This treatment seems to be able to improve the fit to experimental data of Gep/GMp, /Q2F2p/kpF1p,and Gen/GMn as well.
Contribution of Quark Structure Term in Nucleon Electric and Magnetic Form Factors
Institute of Scientific and Technical Information of China (English)
WANGHong-Min; ZHANGBen-Ai
2004-01-01
The constituent quarks in the nucleon have always been considered as a point-like particle in the relativisticconstituent quark model. However its calculation results of GEn agree poorly with the new experimental data. Theelectromagnetic structure of light front constituent quarks is considered in this paper. We find that the calculationresults have good agreement with the new experimental data of GEn after considering the contribution of the quarkstructure term. This treatment seems to be able to improve the fit to experimental data of GEp/GMp,√Q2F2p/kpF1p,and GEn/GMn as well.
Energy Technology Data Exchange (ETDEWEB)
Aniol, Konrad; Armstrong, David; Averett, Todd; Benaoum, Hachemi; Bertin, Pierre; Burtin, Etienne; Cahoon, Jason; Cates, Gordon; Chang, C; Chao, Yu-Chiu; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Craver, Brandon; Cusanno, Francesco; Decowski, Piotr; Deepa, Deepa; Ferdi, Catherine; Feuerbach, Robert; Finn, John; Frullani, Salvatore; Fuoti, Kirsten; Garibaldi, Franco; Gilman, Ronald; Glamazdin, Oleksandr; Gorbenko, V; Grames, Joseph; Hansknecht, John; Higinbotham, Douglas; Holmes, Richard; Holmstrom, Timothy; Humensky, Thomas; Ibrahim, Hassan; Jager, Cornelis De; Jiang, Xiaodong; Kaufman, Lisa; Kelleher, Aidan; Kolarkar, Ameya; Kowalski, Stanley; Kumar, Krishna; Lambert, Daniel; Laviolette, Peter; LeRose, John; Lhuillier, David; Liyanage, Nilanga; Margaziotis, Demetrius; Mazouz, Malek; McCormick, Kathy; Meekins, David; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Monaghan, Peter; Camacho, Carlos Munoz; Nanda, Sirish; Nelyubin, Vladimir; Neyret, Damien; Paschke, Kent; Poelker, Benard; Pomatsalyuk, Roman; Qiang, Yi; Reitz, Bodo; Roche, Julie; Saha, Arunava; Singh, Jaideep; Snyder, Ryan; Souder, Paul; Subedi, Ramesh; Suleiman, Riad; Sulkosky, Vincent; Tobias, William; Urciuoli, Guido; Vacheret, Antonin; Voutier, Eric; Wang, Kebin; Wilson, R; Wojtsekhowski, Bogdan; Zheng, Xiaochao
2005-06-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from {sup 4}He at an average scattering angle {theta}{sub lab} = 5.7 degrees and a four-momentum transfer Q{sup 2} = 0.091 GeV{sup 2}. From these data, for the first time, the strange electric form factor of the nucleon G{sub E}{sup s} can be isolated. The measured asymmetry of A{sub PV} = 6.72 {+-} 0.84 (stat) {+-} 0.21 (syst) parts per million yields a value of G{sub E}{sup s} = -0.038 {+-} 0.042 (stat) {+-} 0.010 (syst), consistent with zero.
Energy Technology Data Exchange (ETDEWEB)
Jardillier, Johann [Lab. de Physique Corpusculaire, Clermont-Ferrand-2 Univ., 63 - Aubiere (France)
1999-09-21
In the quark model, the proton is described as a system of three quarks UUD. However, recent experiments (CERN, SLAC) have shown that the strange quarks may contribute in a significant way to the mass and the spin of the proton. The HAPPEX experiment gives one further knowledge about the question of the role the strange quarks play inside the proton. It measures parity violating asymmetry in the scattering of polarized electrons from a proton because the latter is sensitive to the contribution of the strange quarks to the electromagnetic form factors of the nucleon. The observed asymmetry is in the order of a few ppm (part per million). The main difficulty of the experiment is to identify, to estimate and to minimize, as much as possible, all the systematic effects which could give rise to false asymmetries. This thesis discusses the principle of the HAPPEX experiment, its implementation at the Jefferson Lab (JLab), the processing and the analysis of the data, the systematic errors, and finally presents the result of the first data taking (1999) and its present interpretation. The HAPPEX experiment has measured, at Q{sup 2} = 0.5 (GeV/c){sup 2}, a strange quarks contribution of (1.0 {+-} 2.3)% to the electromagnetic form factors of the nucleon. The statistics and the systematic effects (measure of the electron beam polarization and knowledge of the neutron electric form factor) contribute equally to the error. (author)
Clean measurements of the nucleon axial-vector and free-neutron magnetic form factors
Energy Technology Data Exchange (ETDEWEB)
Deur, Alexandre P. [JLAB
2013-11-01
We discuss the feasibility of a weak charged current experiment using a low energy electron beam. A first goal is to measure the Q^2 dependence of the axial-vector form factor g_a(Q^2). It can be measured model-independently and as robustly as for electromagnetic form factors from typical electron scattering experiments, in contrast to the methods used so far to measure g_a(Q^2). If g_a(Q^2) follows a dipole form, the axial mass can be extracted with a better accuracy than the world data altogether. The most important detection equipment would be a segmented neutron detector with good momentum and angular resolution that is symmetric about the beam direction, and covers a moderate angular range. A high intensity beam (100 uA) is necessary. Beam polarization is highly desirable as it provides a clean measurement of the backgrounds. Beam energies between 70 and 110 MeV are ideal. This range would provide a Q^2 mapping of g_a between 0.01
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C. [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Physics; Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Constantinou, M.; Kallidonis, C. [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Physics; Dinter, S.; Drach, V. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Jansen, K. [Univ. of Cyprus, Nicosia (Cyprus). Dept. of Physics; Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC; Koutsou, G. [Cyprus Institute, Nicosia (Cyprus). Computation-based Science and Technology Research Center; Collaboration: European Twisted Mass Collaboration
2013-04-15
We present results on the axial and the electromagnetic form factors of the nucleon, as well as, on the first moments of the nucleon generalized parton distributions using maximally twisted mass fermions. We analyze two N{sub f}=2+1+1 ensembles having pion masses of 210 MeV and 354 MeV at two values of the lattice spacing. The lattice scale is determined using the nucleon mass computed on a total of 18 N{sub f}=2+1+1 ensembles generated at three values of the lattice spacing, a. The renormalization constants are evaluated non-perturbatively with a perturbative subtraction of O(a''2)-terms. The moments of the generalized parton distributions are given in the MS scheme at a scale of {mu}=2 GeV. We compare with recent results obtained using different discretization schemes. The implications on the spin content of the nucleon are also discussed.
Determination of the Axial Nucleon Form Factor from the MiniBooNE Data
Energy Technology Data Exchange (ETDEWEB)
Butkevich, A. V. [Moscow, INR; Perevalov, D. [Fermilab
2014-03-26
Both neutrino and antineutrino charged-current quasi-elastic scattering on a carbon target are studied to investigate the nuclear effect on the determination of the axial form factor F_A(Q^2). A method for extraction of F_A(Q^2) from the flux-integrated $d\\sigma/dQ^2$ cross section of (anti)neutrino scattering on nuclei is presented. Data from the MiniBooNE experiment are analyzed in the relativistic distorted-wave impulse approximation, Fermi gas model, and in the Fermi gas model with enhancements in the transverse cross section. We found that the values of the axial form factor, extracted in the impulse approximation and predicted by the dipole approximation with the axial mass M_A~1.37 GeV are in good agreement. On the other hand, the Q^2-dependence of F_A extracted in the approach with the transverse enhancement is found to differ significantly from the dipole approximation.
A high-statistics study of the nucleon EM form factors, axial charge and quark momentum fraction
Jäger, B; Capitani, S; Della Morte, M; Djukanovic, D; von Hippel, G; Knippschild, B; Meyer, H B; Wittig, H
2013-01-01
We present updated results for the nucleon axial charge and electromagnetic (EM) form factors, which include a significant increase in statistics for all ensembles (up to 4000 measurements), as well as the addition of ensembles with pion masses down to $m_\\pi\\sim195$ MeV. We also present results for the average quark momentum fraction. The new data allows us to perform a thorough study of the systematic effects encountered in the lattice extraction. We concentrate on systematic effects due to excited-state contaminations for each of the quantities, which we check using several different time separations between the operators at the source and sink through a comparison of plateau fits and the summed operator insertion method (which provides a mechanism to suppress the excited-state contamination). We confirm our earlier finding that a reliable extraction of the axial charge must be based on a method which eliminates excited-state contaminations. Similar conclusions apply to our EM form factor calculations . Th...
Göke, K; Ossmann, J; Schweitzer, P; Silva, A; Urbano, D
2007-01-01
The nucleon form factors of the energy-momentum tensor are studied in the large-Nc limit in the framework of the chiral quark-soliton model for model parameters that simulate physical situations in which pions are heavy. This allows for a direct comparison to lattice QCD results.
Precision Measurements of the Nucleon Strange Form Factors at Q^2 ~0.1 GeV^2
Acha, A; Armstrong, D S; Arrington, J; Averett, T; Bailey, S L; Barber, J; Beck, A; Benaoum, H; Benesch, J; Bertin, P Y; Bosted, P; Butaru, F; Burtin, E; Cates, G D; Chao Yu Chiu; Chen, J P; Chudakov, E; Cisbani, E; Craver, B; Cusanno, F; De Leo, R; Decowski, P; Deur, A; Feuerbach, R J; Finn, J M; Frullani, S; Fuchs, S A; Fuoti, K; Gilman, R; Glesener, L E; Grimm, K; Grames, J M; Hansen, J O; Hansknecht, J; Higinbotham, D W; Holmes, R; Holmstrom, T; Ibrahim, H; De Jager, C W; Jiang, X; Katich, J; Kaufman, L J; Kelleher, A; King, P M; Kolarkar, A; Kowalski, S; Kuchina, E; Kumar, K S; Lagamba, L; La Violette, P; Le Rose, J; Lindgren, R A; Lhuillier, D; Liyanage, N; Margaziotis, D J; Markowitz, P; Meekins, D G; Meziani, Z E; Michaels, R; Moffit, B; Nanda, S; Nelyubin, V V; Otis, K; Paschke, K D; Phillips, S K; Poelker, M; Pomatsalyuk, R I; Potokar, M; Prok, Y; Puckett, A; Qian, Y; Qiang, Y; Reitz, B; Roche, J; Saha, A; Sawatzky, B; Singh, J; Slifer, K J; Sirca, S; Snyder, R; Solvignon, P; Souder, P A; Stutzman, M L; Subedi, R; Suleiman, R; Sulkosky, V; Tobias, W A; Ulmer, P E; Urciuoli, G M; Wang, K; Whitbeck, A; Wilson, R; Wojtsekhowski, B; Yao, H; Ye, Y; Zhan, X; Zheng, X; Zhou, S; Ziskin, V
2006-01-01
We report new measurements of the parity-violating asymmetry A_PV in elastic scattering of 3 GeV electrons off hydrogen and 4He targets with ~0.6 degrees. The 4He result is A_PV = (+6.40 +/- 0.23 (stat) +/- 0.12 (syst)) x10^-6. The hydrogen result is A_PV = (-1.58 +/- 0.12 (stat) +/- 0.04 (syst)) x10^-6. These results significantly improve constraints on the electric and magnetic strange form factors G_E^s and G_M^s. We extract G_E^s = 0.002 +/- 0.014 +/- 0.007 at = 0.077 GeV^2, and G_E^s + 0.09 G_M^s = 0.007 +/- 0.011 +/- 0.006 at = 0.109 GeV^2, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.
Precision Measurements of the Nucleon Strange Form Factors at Q^2 ~ 0.1GeV^2
Energy Technology Data Exchange (ETDEWEB)
Armando Acha Quimper; Konrad Aniol; David Armstrong; John Arrington; Todd Averett; Stephanie Bailey; James Barber; Arie Beck; Hachemi Benaoum; Jay Benesch; Pierre Bertin; Peter Bosted; Florentin Butaru; Etienne Burtin; Gordon Cates; Yu-Chiu Chao; Jian-Ping Chen; Eugene Chudakov; Evaristo Cisbani; Brandon Craver; Francesco Cusanno; Raffaele De Leo; Piotr Decowski; Alexandre Deur; Robert Feuerbach; John Finn; Salvatore Frullani; Sabine Fuchs; Kirsten Fuoti; Ronald Gilman; Lindsay Glesener; Klaus Grimm; Joseph Grames; Jens-ole Hansen; John Hansknecht; Douglas Higinbotham; Richard Holmes; Timothy Holmstrom; Hassan Ibrahim; Cornelis De Jager; Xiaodong Jiang; Joseph Katich; Lisa Kaufman; Aidan Kelleher; Paul King; Ameya Kolarkar; Stanley Kowalski; Elena Kuchina; Krishna Kumar; Luigi Lagamba; Peter Laviolette; John LeRose; Richard Lindgren; David Lhuillier; Nilanga Liyanage; Demetrius Margaziotis; Pete Markowitz; David Meekins; Zein-Eddine Meziani; Robert Michaels; Bryan Moffit; Sirish Nanda; Vladimir Nelyubin; Keith Otis; Kent Paschke; Sasha Philips; Benard Poelker; Roman Pomatsalyuk; Milan Potokar; Yelena Prok; Andrew Puckett; Y. Qian; Yi Qiang; Bodo Reitz; Julie Roche; Arunava Saha; Bradley Sawatzky; Jaideep Singh; Karl Slifer; Simon Sirca; Ryan Snyder; Patricia Solvignon; Paul Souder; Marcy Stutzman; Ramesh Subedi; Riad Suleiman; Vincent Sulkosky; William Tobias; Paul Ulmer; Guido Urciuoli; Kebin Wang; Richard Wilson; Bogdan Wojtsekhowski; Huan Yao; Yunxiu Ye; Xiaohui Zhan; Xiaochao Zheng; Shi-Lin Zhu; Vitaliy Ziskin
2006-09-11
We report new measurements of the parity-violating asymmetry A{sub PV} in elastic scattering of 3 GeV electrons off hydrogen and {sup 4}He targets with ({theta}{sub lab}) {approx} 6.0{sup o}. The {sup 4}He result is A{sub PV} = (+6.40 {+-} 0.23 (stat) {+-} 0.12 (syst)) x 10{sup -6}. The hydrogen result is A{sub PV} = (-1.58 {+-} 0.12 (stat) {+-} 0.04 (syst)) x 10{sup -6}. These results significantly improve constraints on the electric and magnetic strange form factors G{sub E}{sup s} and G{sub M}{sup s}. We extract G{sub E}{sup s} = 0.002 {+-} 0.014 {+-} 0.007 at (Q{sup 2}) = 0.077 GeV{sup 2}, and G{sub E}{sup s} + 0.09 G{sub M}{sup s} = 0.007 {+-} 0.011 {+-} 0.006 at (Q{sup 2}) = 0.109 GeV{sup 2}, providing new limits on the role of strange quarks in the nucleon charge and magnetization distributions.
Energy Technology Data Exchange (ETDEWEB)
Miceli, Tia [New Mexico State U.; Papavassiliou, Vassili [New Mexico State U.; Pate, Stephen [New Mexico State U.; Woodruff, Katherine [New Mexico State U.
2015-11-01
The MicroBooNE neutrino experiment at Fermilab is constructing a liquid-argon time-projection chamber for the Booster Neutrino Beam to study neutrino oscillations and interactions with nucleons and nuclei, starting in 2014. We describe the experiment and focus on its unique abilities to measure cross sections at low values of $Q^2$. In particular, the neutral-current elastic scattering cross section is especially interesting, as it is sensitive to the contribution of the strange sea quark spin to the angular-momentum of the nucleon, $\\Delta s$. Implications for dark-matter searches are discussed.
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, Jacques; Ong, Saro [Universite de Paris-Sud, Institut de Physique Nucleaire d' Orsay (UMR 8608), IN2P3-CNRS, Orsay Cedex (France)
2015-10-15
We study the strong energy dependence of the proton electromagnetic form factors in the time-like region, taking into account the one-pion-exchange final-state interaction in a covariant way. This effect is quantified in terms of the corrected Dirac F{sub 1} and Pauli F{sub 2} form factors and in the commonly used electric G{sub E} and magnetic G{sub M} ones. Our results on the ratio G{sub E} /G{sub M} depend only on the values of two free parameters and allow significant comparisons with the BaBar data. (orig.)
Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2
Airapetian, A; Akopov, Z; Amarian, M; Ammosov, V V; Andrus, A; Aschenauer, E C; Augustyniak, W; Avakian, R; Avetisian, A; Avetissian, E; Bailey, P; Balin, D; Baturin, V; Beckmann, M; Belostotskii, S; Bernreuther, S; Bianchi, N; Blok, H P; Böttcher, Helmut B; Borisov, A; Borysenko, A; Bouwhuis, M; Brack, J; Brüll, A; Bryzgalov, V; Capitani, G P; Chen, T; Chiang, H C; Ciullo, G; Contalbrigo, M; Dalpiaz, P F; De Leo, R; Demey, M; De Nardo, L; De Sanctis, E; Devitsin, E G; Di Nezza, P; Dreschler, J; Düren, M; Ehrenfried, M; Elalaoui-Moulay, A; Elbakian, G; Ellinghaus, F; Elschenbroich, U; Fabbri, R; Fantoni, A; Feshchenko, A; Felawka, L; Fox, B; Frullani, S; Gapienko, G; Gapienko, V; Garibaldi, F; Garrow, K; Garutti, E; Gaskell, D; Gavrilov, G; Karibian, V; Graw, G; Grebenyuk, O; Greeniaus, L G; Gregor, I M; Hafidi, K; Hartig, M; Hasch, D; Heesbeen, D; Henoch, M; Hertenberger, R; Hesselink, W H A; Hillenbrand, A; Hoek, M; Holler, Y; Hommez, B; Iarygin, G; Ivanilov, A; Izotov, A; Jackson, H E; Jgoun, A; Kaiser, R; Kinney, E; Kiselev, A; Kopytin, M; Korotkov, V; Kozlov, V; Krauss, B; Krivokhizhin, V G; Lagamba, L; Lapikas, L; Laziev, A; Lenisa, P; Liebing, P; Linden-Levy, L A; Lipka, K; Lorenzon, W; Lü, H; Lü, J; Lu, S; Ma, B Q; Maiheu, B; Makins, N C R; Mao, Y; Marianski, B; Marukyan, H; Masoli, F; Mexner, V; Meyners, N; Miklukho, O; Miller, C A; Miyachi, Y; Muccifora, V; Nagaitsev, A; Nappi, E; Naryshkin, Yu; Nass, A; Negodaev, M; Nowak, Wolf-Dieter; Oganessyan, K; Ohsuga, H; Pickert, N; Potashov, S Yu; Potterveld, D H; Raithel, M; Reggiani, D; Reimer, P E; Reischl, A; Reolon, A R; Riedl, C; Rith, K; Rosner, G; Rostomyan, A; Rubacek, L; Rubin, J; Ryckbosch, D; Salomatin, Y; Sanjiev, I; Savin, I; Schäfer, A; Schill, C; Schnell, G; Schüler, K P; Seele, J; Seidl, R; Seitz, B; Shanidze, R; Shearer, C; Shibata, T A; Shutov, V; Simani, M C; Sinram, K; Stancari, M; Statera, M; Steffens, E; Steijger, J J M; Stenzel, H; Stewart, J; Stinzing, F; Stösslein, U; Tait, P; Tanaka, H; Taroian, S P; Tchuiko, B; Terkulov, A R; Tkabladze, A; Trzcinski, A; Tytgat, M; Vandenbroucke, A; Van der Nat, P B; van der Steenhoven, G; Vetterli, M C; Vikhrov, V; Vincter, M G; Vogel, C; Vogt, M; Volmer, J; Weiskopf, C; Wendland, J; Wilbert, J; Ye, Y; Ye, Z; Yen, S; Zihlmann, B; Zupranski, P; Aniol, K A; Armstrong, D S; Averett, T; Benaoum, H; Bertin, P Y; Burtin, E; Cahoon, J; Cates, G D; Chang, C C; Chao Yu Chiu; Chen, J P; Seonho Choi; Chudakov, E; Craver, B; Cusanno, F; Decowski, P; Deepa, D; Ferdi, C; Feuerbach, R J; Finn, J M; Fuoti, K; Gilman, R; Glamazdin, A; Gorbenko, V; Grames, J M; Hansknecht, J; Higinbotham, D W; Holmes, R; Holmstrom, T; Humensky, T B; Ibrahim, H; De Jager, C W; Jiang, X; Kaufman, L J; Kelleher, A; Kolarkar, A; Kowalski, S; Kumar, K S; Lambert, D; La Violette, P; Le Rose, J; Lhuillier, D; Liyanage, N; Margaziotis, D J; Mazouz, M; McCormick, K; Meekins, D G; Meziani, Z E; Michaels, R; Moffit, B; Monaghan, P; Munoz-Camacho, C; Nanda, S; Nelyubin, V V; Neyret, D; Paschke, K D; Poelker, M; Pomatsalyuk, R I; Qiang, Y; Reitz, B; Roche, J; Saha, A; Singh, J; Snyder, R; Souder, P A; Subedi, R; Suleiman, R; Sulkosky, V; Tobias, W A; Urciuoli, G M; Vacheret, A; Voutier, E; Wang, K; Wilson, R; Wojtsekhowski, B; Zheng, X
2006-01-01
We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle = 6.0 degrees, with the result A_PV = -1.14 +/- 0.24 (stat) +/- 0.06 (syst) parts per million. From this we extract, at Q^2 = 0.099 GeV^2, the strange form factor combination G_E^s + 0.080 G_M^s = 0.030 +/- 0.025 (stat) +/- 0.006 (syst) +/- 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. The measurement significantly improves existing constraints on G_E^s and G_M^s at Q^2 ~0.1 GeV^2. A consistent picture emerges from all measurements at this Q^2. A combined fit shows that G_E^s is consistent with zero while G_M^s prefers positive values though G_E^s=G_M^s=0 is compatible with the data at 95% C.L.
Nucleon Resonance Transition Form factors
Energy Technology Data Exchange (ETDEWEB)
Burkert, Volker D. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Mokeev, Viktor I. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Aznauryan, Inna G. [Yerevan Physics Inst. (YerPhI) (Armenia)
2016-08-01
We discuss recent results from CLAS on electromagnetic resonance transition amplitudes and their dependence on the distance scale (Q2). From the comparison of these results with most advanced theoretical calculations within QCD-based approaches there is clear evidence that meson-baryon contributions are present and important at large distances, i.e. small Q2, and that quark core contributions dominate the short distance behavior.
Okołowicz, J.; Lam, Y. H.; Płoszajczak, M.; Macchiavelli, A. O.; Smirnova, N. A.
2016-06-01
There is a considerable interest in understanding the dependence of one-nucleon removal cross sections on the asymmetry of the neutron Sn and proton Sp separation energies, following a large amount of experimental data and theoretical analyses in a framework of sudden and eikonal approximations of the reaction dynamics. These theoretical calculations involve both the single-particle cross section and the shell-model description of the projectile initial state and final states of the reaction residues. The configuration mixing in shell-model description of nuclear states depends on the proximity of one-nucleon decay threshold but does it depend sensitively on Sn -Sp? To answer this question, we use the shell model embedded in the continuum to investigate the dependence of one-nucleon spectroscopic factors on the asymmetry of Sn and Sp for mirror nuclei 24Si, 24Ne and 28S, 28Mg and for a series of neon isotopes (20 ≤ A ≤ 28).
Kondratyuk, S
2000-01-01
Pion-loop corrections for Compton scattering are calculated in a novel approach based on the use of dispersion relations in a formalism obeying unitarity. The basic framework is presented, including an application to Compton scattering. In the approach the effects of the non-pole contribution arising from pion dressing are expressed in terms of (half-off-shell) form factors and the nucleon self-energy. These quantities are constructed through the application of dispersion integrals to the pole contribution of loop diagrams, the same as those included in the calculation of the amplitudes through a K-matrix formalism. The prescription of minimal substitution is used to restore gauge invariance. The resulting relativistic-covariant model combines constraints from unitarity, causality, and crossing symmetry.
Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2
Maas, F E; Aulenbacher, K; Baunack, S; Capozza, L; Diefenbach, J; Grimm, K; Imai, Y; Hammel, T; Von Harrach, D; Kabuss, E M; Kothe, R; Lee, J H; Lorente, A; Ginja, A L; Nungesser, L; Schilling, E P; Stephan, G; Weinrich, C; Altarev, I S; Arvieux, J; Collin, B; Frascaria, R; Guidal, M; Kunne, Ronald Alexander; Marchand, D; Morlet, M; Ong, S; Van de Wiele, J; Kowalski, S; Plaster, B; Suleiman, R; Taylor, S
2004-01-01
We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a $Q^2$ of 0.230 (GeV/c)^2 and a scattering angle of \\theta_e = 30^o - 40^o. Using a large acceptance fast PbF_2 calorimeter with a solid angle of \\Delta\\Omega = 0.62 sr the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A_{phys} =(-5.44 +- 0.54_{stat} +- 0.27_{\\rm sys}) 10^{-6}. The Standard Model expectation assuming no strangeness contributions to the vector form factors is $A_0=(-6.30 +- 0.43) 10^{-6}$. The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G^s_E + 0.225 G^s_M = 0.039 +- 0.034 or F^s_1 + 0.130 F^s_2 = 0.032 +- 0.028.
Constraints on the Nucleon Strange Form Factors at Q{sup 2} {approx} 0.1 GeV{sup 2}
Energy Technology Data Exchange (ETDEWEB)
K.A. Aniol; D.S. Armstrong; T. Averett; H. Benaoum; P.Y. Bertin; E. Burtin; J. Cahoon; G.D. Cates; C.C. Chang; Y.-C. Chao; J.-P. Chen; Seonho Choi; E. Chudakov; B. Craver; F. Cusanno; Piotr Decowski; D. Deepa; C. FERDI; R.J. Feuerbach; J.M. Finn; S. Frullani; K. Fuoti; F. Garibaldi; R. Gilman; A. Glamazdin; V. Gorbenko; J.M. Grames; J. Hansknecht; D.W. Higinbotham; R. Holmes; T. Holmstrom; T.B. Humensky; H. Ibrahim; C.W. de Jager; X. Jiang; L.J. Kaufman; A. Kelleher; A. Kolarkar; S. Kowalski; K.S. Kumar; D. Lambert; P. LaViolette; J. LeRose; D. Lhuillier; N. Liyanage; M. Mazouz; K. McCormick; D.G. Meekins; Z.-E. Meziani; R. Michaels; B. Moffit; P. Monaghan; C. Munoz-Camacho; S. Nanda; V. Nelyubin; D. Neyret; K.D. Paschke; M. Poelker; R. Pomatsalyuk; Y. Qiang; B. Reitz; J. Roche; A. Saha; J. Singh; R. Snyder; P.A. Souder; R. Subedi; R. Suleiman; V. Sulkosky; W.A. Tobias; G.M. Urciuoli; A. Vacheret; E. Voutier; K. Wang; R. Wilson; B. Wojtsekhowski; X. Zheng
2005-06-01
We report the most precise measurement to date of a parity-violating asymmetry in elastic electron-proton scattering. The measurement was carried out with a beam energy of 3.03 GeV and a scattering angle <{theta}{sub lab}> = 6.0 degrees, with the result A{sub PV} = -1.14 {+-} 0.24 (stat) {+-} 0.06 (syst) parts per million. From this we extract, at Q{sup 2} = 0.099 GeV{sup 2}, the strange form factor combination G{sub E}{sup s} + 0.080 G{sub M}{sup s} = 0.030 {+-} 0.025 (stat) {+-} 0.006 (syst) {+-} 0.012 (FF) where the first two errors are experimental and the last error is due to the uncertainty in the neutron electromagnetic form factor. The measurement significantly improves existing constraints on G{sub E}{sup s} and G{sub M}{sup s} at Q{sup 2} {approx}0.1 GeV{sup 2}. A consistent picture emerges from all measurements at this Q{sup 2}. A combined fit shows that G{sub E}{sup s} is consistent with zero while G{sub M}{sup s} prefers positive values though G{sub E}{sup s} = G{sub M}{sup s} = 0 is compatible with the data at 95% C.L.
Evidence for Strange Quark Contributions to the Nucleon's Form Factors at $Q^2$ = 0.108 (GeV/c)$^2$
Maas, F E; Baunack, S; Capozza, L; Diefenbach, J; Gl"aser, B; Hammel, T; Von Harrach, D; Imai, Y; Kabuss, E M; Kothe, R; Lee, J H; Lorente, A; Schilling, E P; Schwaab, D; Sikora, M; Stephan, G; Weber, G; Weinrich, C; Altarev, I S; Arvieux, J; El-Yakoubi, M; Frascaria, R; Kunne, Ronald Alexander; Morlet, M; Ong, S; Van de Wiele, J; Kowalski, S; Plaster, B; Suleiman, R; Taylor, S
2004-01-01
We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of $Q^2$ = \\Qsquare (GeV/c)$^2$ and at a forward electron scattering angle of 30$^\\circ < \\theta_e < 40^\\circ$. The measured asymmetry is $A_{LR}(\\vec{e}p)$ = (\\Aphys $\\pm$ \\Deltastat$_{stat}$ $\\pm$ \\Deltasyst$_{syst}$) $\\times$ 10$^{-6}$. The expectation from the Standard Model assuming no strangeness contribution to the vector current is A$_0$ = (\\Azero $\\pm$ \\DeltaAzero) $\\times$ 10$^{-6}$. We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher $Q^2$. We have extracted the strangeness contribution to the electromagnetic form factors from our data to be $G_E^s$ + \\FakGMs $G_M^s$ = \\GEsGMs $\\pm $ \\DeltaGEsGMs at $Q^2$ = \\Qsquare (GeV/c)$^2$. As in our previous measurement at higher momentum transfer for $G_E^s$ + 0.230 $G_M^s$, we again find t...
Okołowicz, J; Płoszajczak, M; Macchiavelli, A O; Smirnova, N A
2015-01-01
There is a considerable interest in understanding the dependence of one-nucleon removal cross sections on the asymmetry of the neutron $S_n$ and proton $S_p$ separation energies, following a large amount of experimental data and theoretical analyses in a framework of sudden and eikonal approximations of the reaction dynamics. These theoretical calculations involve both the single-particle cross section and the shell-model description of the projectile initial state and final states of the reaction residues. The configuration mixing in shell-model description of nuclear states depends on the proximity of one-nucleon decay threshold but does it depend sensitively on $S_n - S_p$? To answer this question, we use the shell model embedded in the continuum to investigate the dependence of one-nucleon spectroscopic factors on the asymmetry of $S_n$ and $S_p$ for mirror nuclei $^{24}$Si, $^{24}$Ne and $^{28}$S, $^{28}$Mg and for a series of neon isotopes ($20 \\leq A \\leq 28$).
Chiral analysis of baryon form factors
Energy Technology Data Exchange (ETDEWEB)
Gail, T.A.
2007-11-08
This work presents an extensive theoretical investigation of the structure of the nucleon within the standard model of elementary particle physics. In particular, the long range contributions to a number of various form factors parametrizing the interactions of the nucleon with an electromagnetic probe are calculated. The theoretical framework for those calculations is chiral perturbation theory, the exact low energy limit of Quantum Chromo Dynamics, which describes such long range contributions in terms of a pion-cloud. In this theory, a nonrelativistic leading one loop order calculation of the form factors parametrizing the vector transition of a nucleon to its lowest lying resonance, the {delta}, a covariant calculation of the isovector and isoscalar vector form factors of the nucleon at next to leading one loop order and a covariant calculation of the isoscalar and isovector generalized vector form factors of the nucleon at leading one loop order are performed. In order to perform consistent loop calculations in the covariant formulation of chiral perturbation theory an appropriate renormalization scheme is defined in this work. All theoretical predictions are compared to phenomenology and results from lattice QCD simulations. These comparisons allow for a determination of the low energy constants of the theory. Furthermore, the possibility of chiral extrapolation, i.e. the extrapolation of lattice data from simulations at large pion masses down to the small physical pion mass is studied in detail. Statistical as well as systematic uncertainties are estimated for all results throughout this work. (orig.)
Neutrinos and nucleon structure
Sehgal, L M
1979-01-01
The study of neutrino interactions in matter is yielding a wealth of information on the form factors and structure functions of the nucleon. These data allow tests of models of nucleon structure and of dynamical theories of quarks and gluons. The author attempts a critical appraisal of recent facts and their impact on our theoretical understanding. (35 refs).
Magnetic form factors of the trinucleons
Energy Technology Data Exchange (ETDEWEB)
Schiavilla, R; Pandharipande, V R; Riska, Dan-Olof
1989-11-01
The magnetic form factors of ^{3}H and ^{3}He are calculated with the Monte Carlo method from variational ground-state wave functions obtained for the Argonne and Urbana two- and three-nucleon interactions. The electromagnetic current operator contains one- and two-body terms that are constructed so as to satisfy the continuity equation with the two-nucleon potential in the Hamiltonian. The results obtained with the Argonne two-nucleon interaction are in overall agreement with the empirical values. It appears that the remaining theoretical uncertainty, in the calculation of these form factors from a given interaction model, is dominated by that in the electromagnetic form factors of the nucleon. It is found that the isovector magnetic form factors are rather sensitive to the details of the isospin-dependent tensor force, and they are much better reproduced with the Argonne than the Urbana potential. The isoscalar magnetic form factors appear to be sensitive to the spin-orbit interactions, and are better reproduced with the Urbana potential. The Argonne potential has a stronger τ1∙τ2 tensor force, while the Urbana one has a shorter-range spin-orbit interaction.
From form factors to generalized parton distributions
Energy Technology Data Exchange (ETDEWEB)
Diehl, Markus
2013-06-15
I present an extraction of generalized parton distributions from selected data on the electromagnetic nucleon form factors. The extracted distributions can in particular be used to quantify the contribution to the proton spin from the total angular momentum carried by valence quarks, as well as their transverse spatial distribution inside the proton.
Electromagnetic form factors of baryons in an algebraic approach
Energy Technology Data Exchange (ETDEWEB)
Bijker, R. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, 04510 Mexico D.F. (Mexico); Leviatan, A. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel)
1999-07-01
We present a simultaneous analysis of elastic and transition form factors of the nucleon. The calculations are performed in the framework of an algebraic model of baryons. Effects of meson cloud couplings are considered. (Author)
Electromagnetic form factors of baryons in an algebraic approach
Bijker, R
1999-01-01
We present a simultaneous analysis of elastic and transition form factors of the nucleon. The calculations are performed in the framework of an algebraic model of baryons. Effects of meson cloud couplings are considered.
Electromagnetic form factors of the baryon octet in the perturbative chiral quark model
Cheedket, S; Gutsche, T; Faessler, A; Pumsa-ard, K; Yan, Y; Gutsche, Th.; Faessler, Amand
2002-01-01
We apply the perturbative chiral quark model at one loop to analyze the electromagnetic form factors of the baryon octet. The analytic expressions for baryon form factors, which are given in terms of fundamental parameters of low-energy pion-nucleon physics(weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor), and the numerical results for baryon magnetic moments, charge and magnetic radii are presented. Our results are in good agreement with experimental data.
The Neutron Electric Form Factor To The Four-momentum Factor Squared = 1.45 (gev/c) 2
Plaster, B R
2004-01-01
The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q2, the square of the four-momentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon. Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measure...
Nuclear tests for the strange charge from factor of the nucleon
Bernabéu, J.; Bilenky, S. M.; Segura, J.; Singh, S. K.
1992-05-01
It is shown that the measurements of elastic and inelastic scattering of neutrinos and parity-violating asymmetry of longitudinally polarized electrons on spin-isospin zero nuclei would yield model independent information about the strangeness charge form factor. Nunerical estimates of the contribution of this form factor are presented for 4He, 12C and 16O nuclei in impulse approximation using strangeness vector from factors of the nucleon recently suggested in the literature. A general relation between the P-odd asymmetry in electron scattering and the cross sections of neutrino and unpolarized electron scattering on spin zero nuclei is obtained. On leave of academic pursuit from Aligarh Muslim University, Aligarh 202 001, India.
Baryon transition form factors at the pole
Tiator, L.; Döring, M.; Workman, R. L.; Hadžimehmedović, M.; Osmanović, H.; Omerović, R.; Stahov, J.; Švarc, A.
2016-12-01
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the GM, GE, and GC form factors for the Δ (1232 ) resonance excitation at the Breit-Wigner resonance and pole positions up to Q2=5 GeV2 . We also explore the E /M and S /M ratios as functions of Q2. For pole and residue extraction, we apply the Laurent + Pietarinen method.
Baryon transition form factors at the pole
Tiator, L; Workman, R L; Hadžimehmedović, M; Osmanović, H; Omerović, R; Stahov, J; Švarc, A
2016-01-01
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_M$, $G_E$, and $G_C$ form factors for the $\\Delta(1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^2=5$ GeV$^2$. We also explore the $E/M$ and $S/M$ ratios as functions of $Q^2$. For pole and residue extraction, we apply the Laurent + Pietarinen method.
Baryon transition form factors at the pole
Energy Technology Data Exchange (ETDEWEB)
Tiator, L.; Döring, M.; Workman, R. L.; Hadžimehmedović, M.; Osmanović, H.; Omerović, R.; Stahov, J.; Švarc, A.
2016-12-01
Electromagnetic resonance properties are uniquely defined at the pole and do not depend on the separation of the resonance from background or the decay channel. Photon-nucleon branching ratios are nowadays often quoted at the pole, and we generalize the considerations to the case of virtual photons. We derive and compare relations for nucleon to baryon transition form factors both for the Breit-Wigner and the pole positions. Using the MAID2007 and SAID SM08 partial wave analyses of pion electroproduction data, we compare the $G_M$, $G_E$, and $G_C$ form factors for the $\\Delta(1232)$ resonance excitation at the Breit-Wigner resonance and pole positions up to $Q^2=5$ GeV$^2$. We also explore the $E/M$ and $S/M$ ratios as functions of $Q^2$. For pole and residue extraction, we apply the Laurent + Pietarinen method.
Elastic form factors at higher CEBAF energies
Energy Technology Data Exchange (ETDEWEB)
Petratos, G.G. [Kent State Univ., OH (United States)
1994-04-01
The prospects for elastic scattering from few body systems with higher beam energies at CEBAF is presented. The deuteron and{sup 3}He elastic structure functions A(Q{sup 2}) can be measured at sufficiently high momentum transfers to study the transition between the conventional meson-nucleon and the constituent quark-gluon descriptions. Possible improvements in the proton magnetic form factor data are also presented.
Energy Technology Data Exchange (ETDEWEB)
Frederic D. R. Bonnet; Robert G. Edwards; George T. Fleming; Randal Lewis; David Richards
2003-07-22
We have started a program to compute the electromagnetic form factors of mesons. We discuss the techniques used to compute the pion form factor and present preliminary results computed with domain wall valence fermions on MILC asqtad lattices, as well as Wilson fermions on quenched lattices. These methods can easily be extended to rho-to-gamma-pi transition form factors.
Göke, K; Silva, A; Urbano, D; Goeke, Klaus; Kim, Hyun-Chul; Silva, Antonio; Urbano, Diana
2006-01-01
We summarize the results of the chiral quark-soliton model ($\\chi$QSM) concerning basically all form factors necessary to interpret the present data of the parity violating electron scattering experiments SAMPLE, HAPPEX, A4 and G0. The results particularly focus on the recently measured asymmetries and the detailed data for various combinations of $G_{M}^{s}$, $G_{E}^{s}$, $\\tilde{G}_{A}^{p}$ and $\\tilde{G}_{A}^{n}$ at $Q^2=0.1$ GeV$^2$. The calculations yield positive strange magnetic and electric form factors and a negative axial vector one, all being rather small. The results are very close to the combined experimental world data from parity violating electron scattering and elastic $\
Electromagnetic proton form factors: perspectives for PANDA
Directory of Open Access Journals (Sweden)
Tomasi-Gustafsson Egle
2014-03-01
Full Text Available The PANDA collaboration studies fundamental aspects of the strong interaction in the transition region between non-perturbative and perturbative QCD, investigating charmonium spectroscopy, hybrids and glueballs, hypernuclei, light and heavy meson production with antiproton beams. In this contribution we focus on leptonic final channels which give access to nucleon electromagnetic form factors. The expected precision on the electric and magnetic form factors of the proton in the time-like region and the radiative corrections to be applied to the data are discussed.
Electromagnetic Excitation of Nucleon Resonances
Tiator, L; Kamalov, S S; Vanderhaeghen, M
2011-01-01
Recent progress on the extraction of electromagnetic properties of nucleon resonance excitation through pion photo- and electroproduction is reviewed. Cross section data measured at MAMI, ELSA, and CEBAF are analyzed and compared to the analysis of other groups. On this basis, we derive longitudinal and transverse transition form factors for most of the four-star nucleon resonances. Furthermore, we discuss how the transition form factors can be used to obtain empirical transverse charge densities. Contour plots of the thus derived densities are shown for the Delta, Roper, S11, and D13 nucleon resonances.
Kubis, B; Meißner, Ulf G; Mei{\\ss}ner, Ulf-G.
1999-01-01
We calculate the form factors of the baryon octet in the framework of heavy baryon chiral perturbation theory. The calculated charge radius of the show that kaon loop effects can play a significant role in the neutron electric form factor. Furthermore. we derive generalized Caldi-Pagels relations between various charge radii which are free of chiral loop effects.
Test of weak and strong factorization in nucleus-nucleuscollisions atseveral hundred MeV/nucleon
Energy Technology Data Exchange (ETDEWEB)
La Tessa, Chiara; Sihver, Lembit; Zeitlin, Cary; Miller, Jack; Guetersloh, Stephen; Heilbronn, Lawrence; Mancusi, Davide; Iwata,Yoshiuki; Murakami, Takeshi
2006-06-21
Total and partial charge-changing cross sections have been measured for argon projectiles at 400 MeV/nucleon in carbon, aluminum, copper, tin and lead targets; cross sections for hydrogen were also obtained, using a polyethylene target. The validity of weak and strong factorization properties has been investigated for partial charge-changing cross sections; preliminary cross section values obtained for carbon, neon and silicon at 290 and 400 MeV/nucleon and iron at 400 MeV/nucleon, in carbon, aluminum, copper, tin and lead targets have been also used for testing these properties. Two different analysis methods were applied and both indicated that these properties are valid, without any significant difference between weak and strong factorization. The factorization parameters have then been calculated and analyzed in order to find some systematic behavior useful for modeling purposes.
Vector and Axial Form Factors Applied to Neutrino Quasielastic Scattering
Budd, H; Arrington, J
2005-01-01
We calculate the quasielastic cross sections for neutrino scattering on nucleons using up to date fits to the nucleon elastic electromagnetic form factors GEp, GEn, GMp, GMn, and weak form factors. We show the extraction of Fa for neutrino experiments. We show how well \\minerva, a new approved experiment at FNAL, can measure Fa. We show the that Fa has a different contribution to the anti-neutrino cross section, and how the anti-neutrino data can be used to check Fa extracted from neutrino scattering.
Consistent off-shell pi NN vertex and nucleon self-energy
Kondratyuk, S; Scholten, O
1999-01-01
We present a consistent calculation of half-off-shell form factors in the pion-nucleon vertex and the nucleon self-energy. Numerical results are presented. Near the on-shell point the pion-nucleon vertex is dominated by the pseudovector coupling, while at large nucleon invariant masses we find a siz
Consistent off-shell πNN vertex and nucleon self-energy
Kondratyuk, S.; Scholten, O.
1999-01-01
We present a consistent calculation of half-off-shell form factors in the pion-nucleon vertex and the nucleon self-energy. Numerical results are presented. Near the on-shell point the pion-nucleon vertex is dominated by the pseudovector coupling, while at large nucleon invariant masses we find a siz
A pure S-wave covariant model for the nucleon
Gross, F; Peña, M T; Gross, Franz
2006-01-01
Using the manifestly covariant spectator theory, and modeling the nucleon as a system of three constituent quarks with their own electromagnetic structure, we show that all four nucleon electromagnetic form factors can be very well described by a manifestly covariant nucleon wave function with zero orbital angular momentum.
The Charge Form Factors of the Three- and Four-Body Nuclei
Energy Technology Data Exchange (ETDEWEB)
R. Schiavilla; V.R. Pandharipande; D.O. Riska
1990-01-01
The charge form factors of 3H, 3He, and 4He are calculated using the Monte Carlo method and variational ground-state wave functions obtained for the Argonne two-nucleon and Urbana-VII three-nucleon interactions. The model for the charge density operator contains the two-body exchange contributions of longest range. With some spread due to the uncertainty in the electromagnetic form factors of the nucleon the calculated charge form factors are in good agreement with the empirical values over the whole experimentally covered range of momentum transfer.
Triton Electric Form Factor at Low-Energies
Sadeghi, H
2009-01-01
Making use of the Effective Field Theory(EFT) expansion recently developed by the authors, we compute the charge form factor of triton up to next-to-next-to-leading order (N$^2$LO). The three-nucleon forces(3NF) is required for renormalization of the three-nucleon system and it effects are predicted for process and is qualitatively supported by available experimental data. We also show that, by including higher order corrections, the calculated charge form factor and charge radius of $^3$H are in satisfactory agreement with the experimental data and the realistic Argonne $v_{18}$ two-nucleon and Urbana IX potential models calculations. This method makes possible a high precision few-body calculations in nuclear physics. Our result converges order by order in low energy expansion and also cut-off independent.
On the nucleon–nucleon scattering phase shifts through supersymmetry and factorization
Indian Academy of Sciences (India)
U Laha; J Bhoi
2013-12-01
By exploiting the supersymmetry-inspired factorization method through a judicious use of deuteron ground state wave function, higher partial wave nucleon–nucleon potentials, both energy independent and energy dependent, are generated. We adopt the phase function method to deal with the scattering phase shifts and demonstrate the usefulness of our constructed potentials by means of model calculation.
Amo Sanchez, del P.; Raven, H.G.; Snoek, H.; BaBar, Collaboration
2011-01-01
eta((')) transition form factors in the momentum-transfer range from 4 to 40 GeV(2). The analysis is based on 469 fb(-1) of integrated luminosity collected at PEP-II with the BABAR detector at e(+)e(-) center-of-mass energies near 10.6 GeV.
Proton and kaon timelike form factors from BABAR
Serednyakov, S I
2015-01-01
The latest BABAR results on the proton and kaon timelike form factors (FF) are presented. The special emphasize is made on comparison of the spacelike and timelike FFs and the rise of the proton FF near threshold. The behavior of the cross section of e+e- annihilation into hadrons near the nucleon-antinucleon threshold is discussed.
Further comment on pion electroproduction and the axial form factor
Bernard, V; Meißner, Ulf G; Mei{\\ss}ner, Ulf-G.
2001-01-01
We show that a recent claim (H.Haberzettl, Phys. Rev. Lett. 85 (2000) 3576) that one cannot extract the nucleon weak axial form factor G_A (t) from charged pion threshold electroproduction is incorrect. Thus previous calculations remain valid and threshold charged pion electroproduction experiments can indeed be used to determine G_A (t), and they should certainly be pursued.
The neutron electric form factor to Q² = 1.45 (GeV/c)²
Energy Technology Data Exchange (ETDEWEB)
Bradley Plaster
2004-02-01
The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q2, the square of the four-momentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon. Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measurements of this fundamental quantity. Following a general overview of the experimental and theoretical status of the nucleon form factors, a detailed description of an experiment designed to extract the neutron electric form factor from measurements of the neutron's recoil polarization in quasielastic 2H(e, e')1H scattering is presented. The experiment described here employed the Thomas Jefferson National Accelerator Facility's longitudinally polarized electron beam, a magnetic spectrometer for detection of the scattered electron, and a neutron polarimeter designed specifically for this experiment. Measurements were conducted at three Q2 values of 0.45, 1.13, and 1.45 (GeV/c)2, and the final results extracted from an analysis of the data acquired in this experiment are reported and compared with recent theoretical predictions for the nucleon form factors.
The neutron electric form factor to Q² = 1.45 (GeV/c)²
Energy Technology Data Exchange (ETDEWEB)
Plaster, Bradley [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2004-02-01
The nucleon elastic electromagnetic form factors are fundamental quantities needed for an understanding of nucleon and nuclear electromagnetic structure. The evolution of the Sachs electric and magnetic form factors with Q^{2}, the square of the four-momentum transfer, is related to the distribution of charge and magnetization within the nucleon. High precision measurements of the nucleon form factors are essential for stringent tests of our current theoretical understanding of confinement within the nucleon. Measurements of the neutron form factors, in particular, those of the neutron electric form factor, have been notoriously difficult due to the lack of a free neutron target and the vanishing integral charge of the neutron. Indeed, a precise measurement of the neutron electric form factor has eluded experimentalists for decades; however, with the advent of high duty-factor polarized electron beam facilities, experiments employing polarization degrees of freedom have finally yielded the first precise measurements of this fundamental quantity. Following a general overview of the experimental and theoretical status of the nucleon form factors, a detailed description of an experiment designed to extract the neutron electric form factor from measurements of the neutron's recoil polarization in quasielastic 2H(e, e')1H scattering is presented. The experiment described here employed the Thomas Jefferson National Accelerator Facility's longitudinally polarized electron beam, a magnetic spectrometer for detection of the scattered electron, and a neutron polarimeter designed specifically for this experiment. Measurements were conducted at three Q^{2} values of 0.45, 1.13, and 1.45 (GeV/c)^{2}, and the final results extracted from an analysis of the data acquired in this experiment are reported and compared with recent theoretical predictions for the nucleon form factors.
Energy Technology Data Exchange (ETDEWEB)
Ryong Ji, C.; Pang, A.; Szczepaniak, A. [North Carolina State Univ., Raleigh, NC (United States)
1994-04-01
It is pointed out that the correct criterion to define the legal PQCD contribution to the exclusive processes in the lightcone perturbative expansion should be based on the large off-shellness of the lightcone energy in the intermediate states. In the lightcone perturbative QCD calculation of the pion form factor, the authors find that the legal PQCD contribution defined by the lightcone energy cut saturates in the smaller Q{sup 2} region compared to that defined by the gluon four-momentum square cut. This is due to the contribution by the highly off-energy-shell gluons in the end point regions of the phase space, indicating that the gluon four-momentum-square cut may have cut too much to define the legal PQCD.
The Proton Form Factor Ratio Measurements at Jefferson Lab
Energy Technology Data Exchange (ETDEWEB)
Punjabi, Vina A. [Norfolk State University, Norfolk, VA (United States); Perdrisat, Charles F. [William and Mary College, Williamsburg, VA (United States)
2014-03-01
The ratio of the proton form factors, G{sub Ep}/G{sub Mp}, has been measured from Q{sup 2} of 0.5 GeV{sup 2} to 8.5 GeV{sup 2}, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The discovery that the proton form factor ratio measured in these experiments decreases approximately linearly with four-momentum transfer, Q{sup 2}, for values above ~1 GeV{sup 2}, is one of the most significant results to come out of JLab. These results have had a large impact on progress in hadronic physics; and have required a significant rethinking of nucleon structure. The increasingly common use of the double-polarization technique to measure the nucleon form factors, in the last 15 years, has resulted in a dramatic improvement of the quality of all four nucleon electromagnetic form factors, G{sub Ep}, G{sub Mp}, G{sub En} and G{sub Mn}. There is an approved experiment at JLab, GEP(V), to continue the ratio measurements to 12 GeV{sup 2}. A dedicated experimental setup, the Super Bigbite Spectrometer (SBS), will be built for this purpose. It will be equipped with a focal plane polarimeter to measure the polarization of the recoil protons. The scattered electrons will be detected in an electromagnetic calorimeter. In this presentation, I will review the status of the proton elastic electromagnetic form factors and discuss a number of theoretical approaches to describe nucleon form factors.
Longitudinal vector form factors in weak decays of nuclei
Simkovic, F; Krivoruchenko, M I
2015-01-01
The longitudinal form factors of the weak vector current of particles with spin $ J = 1/2 $ and isospin $ I = 1/2 $ are determined by the mass difference and the charge radii of members of the isotopic doublets. The most promising reactions to measure these form factors are the reactions with large momentum transfers involving the spin-1/2 isotopic doublets with a maximum mass splitting. Numerical estimates of longitudinal form factors are given for nucleons and eight nuclear spin-1/2 isotopic doublets.
Light-cone sum rule approach for Baryon form factors
Offen, Nils
2016-01-01
We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.
Light-Cone Sum Rule Approach for Baryon Form Factors
Offen, Nils
2016-10-01
We present the state-of-the-art of the light-cone sum rule approach to Baryon form factors. The essence of this approach is that soft Feynman contributions are calculated in terms of small transverse distance quantities using dispersion relations and duality. The form factors are thus expressed in terms of nucleon wave functions at small transverse separations, called distribution amplitudes, without any additional parameters. The distribution amplitudes, therefore, can be extracted from the comparison with the experimental data on form factors and compared to the results of lattice QCD simulations.
The Proton Form Factor Ratio Measurements at Jefferson Lab
Punjabi, Vina
2014-01-01
The ratio of the proton form factors, GEp/GMp, has been measured from Q2 of 0.5 GeV2 to 8.5 GeV2, at the Jefferson Laboratory, using the polarization transfer method. This ratio is extracted directly from the measured ratio of the transverse and longitudinal polarization components of the recoiling proton in elastic electron-proton scattering. The discovery that the proton form factor ratio measured in these experiments decreases approximately linearly with four-momentum transfer, Q2, for values above ? 1 GeV2, is one of the most significant results to come out of JLab. These results have had a large impact on progress in hadronic physics; and have required a significant rethinking of nucleon structure. The increasingly common use of the double-polarization technique to measure the nucleon form factors, in the last 15 years, has resulted in a dramatic improvement of the quality of all four nucleon electromagnetic form factors, GEp, GMp, GEn and GMn. There is an approved experiment at JLab, GEP(V), to continue...
Determination of Transverse Charge Density from Kaon Form Factor Data
Mejia-Ott, Johann; Horn, Tanja; Pegg, Ian; Mecholski, Nicholas; Carmignotto, Marco; Ali, Salina
2016-09-01
At the level of nucleons making up atomic nuclei, among subatomic particles made up of quarks, K-mesons or kaons represent the most simple hadronic system including the heavier strange quark, having a relatively elementary bound state of a quark and an anti-quark as its valence structure. Its electromagnetic structure is then parametrized by a single, dimensionless quantity known as the form factor, the two-dimensional Fourier transform of which yields the quantity of transverse charge density. Transverse charge density, in turn, provides a needed framework for the interpretation of form factors in terms of physical charge and magnetization, both with respect to the propagation of a fast-moving nucleon. To this is added the value of strange quarks in ultimately presenting a universal, process-independent description of nucleons, further augmenting the importance of studying the kaon's internal structure. The pressing character of such research questions directs the present paper, describing the first extraction of transverse charge density from electromagnetic kaon form factor data. The extraction is notably extended to form factor data at recently acquired higher energy levels, whose evaluation could permit more complete phenomenological models for kaon behavior to be proposed. This work was supported in part by NSF Grant PHY-1306227.
Elastic and Transition Form Factors in DSEs
Segovia, Jorge
2016-01-01
A symmetry preserving framework for the study of continuum Quantum Chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking (DCSB), and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector$\\,\\otimes\\,$vector contact-interaction.
Elastic and Transition Form Factors in DSEs
Segovia, Jorge
2016-06-01
A symmetry preserving framework for the study of continuum quantum chromodynamics (QCD) is obtained from a truncated solution of the QCD equations of motion or QCD's Dyson-Schwinger equations (DSEs). A nonperturbative solution of the DSEs enables the study of, e.g., hadrons as composites of dressed-quarks and dressed-gluons, the phenomena of confinement and dynamical chiral symmetry breaking, and therefrom an articulation of any connection between them. It is within this context that we present a unified study of Nucleon, Delta and Roper elastic and transition form factors, and compare predictions made using a framework built upon a Faddeev equation kernel and interaction vertices that possess QCD-like momentum dependence with results obtained using a symmetry-preserving treatment of a vector ⊗ vector contact-interaction.
Dirac and Pauli form factors from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Collins, S.; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Mainz Univ. (Germany). Inst. fuer Kernphysik; Regensburg Univ. (DE). Inst. fuer Theoretische Physik] (and others)
2011-06-15
We present a comprehensive analysis of the electromagnetic form factors of the nucleon from a lattice simulation with two flavors of dynamical O(a)-improved Wilson fermions. A key feature of our calculation is that we make use of an extensive ensemble of lattice gauge field configurations with four different lattice spacings, multiple volumes, and pion masses down to m{sub {pi}}{proportional_to}180 MeV. We find that by employing Kelly-inspired parametrizations for the Q{sup 2}-dependence of the form factors, we are able to obtain stable fits over our complete ensemble. Dirac and Pauli radii and the anomalous magnetic moments of the nucleon are extracted and results at light quark masses provide evidence for chiral non-analytic behavior in these fundamental observables. (orig.)
Nucleon wave function from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Warkentin, Nikolaus
2008-04-15
In this work we develop a systematic approach to calculate moments of leading-twist and next-to-leading twist baryon distribution amplitudes within lattice QCD. Using two flavours of dynamical clover fermions we determine low moments of nucleon distribution amplitudes as well as constants relevant for proton decay calculations in grand unified theories. The deviations of the leading-twist nucleon distribution amplitude from its asymptotic form, which we obtain, are less pronounced than sometimes claimed in the literature. The results are applied within the light cone sum rule approach to calculate nucleon form factors that are compared with recent experimental data. (orig.)
Electromagnetic couplings in a collective model of the nucleon
Bijker, R
1995-01-01
We study the electromagnetic properties of the nucleon and its excitations in a collective model. In the ensuing algebraic treatment all results for helicity amplitudes and form factors can be derived in closed form in the limit of a large model space. We discuss nucleon form factors and transverse electromagnetic couplings in photo- and electroproduction, including transition form factors that can be measured at new electron facilities.
Quasielastic production of polarized hyperons in antineutrino--nucleon reactions
Akbar, F; Athar, M Sajjad; Singh, S K
2016-01-01
We have studied the longitudinal and perpendicular polarizations of final hyperon($\\Lambda$,$\\Sigma$) produced in the antineutrino induced quasielastic charged current reactions on nucleon targets. The nucleon-hyperon transition form factors are determined from the experimental data on quasielastic $(\\Delta S =0)$ charged current (anti)neutrino--nucleon scattering and the semileptonic decay of neutron and hyperons assuming G--invariance, T--invariance and SU(3) symmetry. The vector transition form factors are obtained in terms of nucleon electromagnetic form factors for which various parameterizations available in literature have been used. A dipole parameterization for the axial vector form factor and the pseudoscalar transition form factor derived in terms of axial vector form factor assuming PCAC and GT relation extended to strangeness sector have been used in numerical evaluations. The flux averaged cross section and polarization observables corresponding to CERN Gargamelle experiment have been calculated...
Energy Technology Data Exchange (ETDEWEB)
Schroers, W. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (Germany). John von Neumann-Inst. fuer Computing NIC
2007-01-15
This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, J{sub q}, the nucleon-{delta} transition form factors, and the nucleon axial coupling, g{sub A}. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out. (orig.)
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2
Puckett, A J R; Jones, M K; Luo, W; Meziane, M; Pentchev, L; Perdrisat, C F; Punjabi, V; Wesselmann, F R; Ahmidouch, A; Albayrak, I; Aniol, K A; Arrington, J; Asaturyan, A; Baghdasaryan, H; Benmokhtar, F; Bertozzi, W; Bimbot, L; Bosted, P; Boeglin, W; Butuceanu, C; Carter, P; Chernenko, S; Christy, E; Commisso, M; Cornejo, J C; Covrig, S; Danagoulian, S; Daniel, A; Davidenko, A; Day, D; Dhamija, S; Dutta, D; Ent, R; Frullani, S; Fenker, H; Frlez, E; Garibaldi, F; Gaskell, D; Gilad, S; Gilman, R; Goncharenko, Y; Hafidi, K; Hamilton, D; Higinbotham, D W; Hinton, W; Horn, T; Hu, B; Huang, J; Huber, G M; Jensen, E; Keppel, C; Khandaker, M; King, P; Kirillov, D; Kohl, M; Kravtsov, V; Kumbartzki, G; Li, Y; Mamyan, V; Margaziotis, D J; Marsh, A; Matulenko, Y; Maxwell, J; Mbianda, G; Meekins, D; Melnik, Y; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Moffit, B; Moreno, O; Mulholland, J; Narayan, A; Nedev, S; Nuruzzaman,; Piasetzky, E; Pierce, W; Piskunov, N M; Prok, Y; Ransome, R D; Razin, D S; Reimer, P; Reinhold, J; Rondon, O; Shabestari, M; Shahinyan, A; Shestermanov, K; Sirca, S; Sitnik, I; Smykov, L; Smith, G; Solovyev, L; Solvignon, P; Subedi, R; Tomasi-Gustafsson, E; Vasiliev, A; Veilleux, M; Wojtsekhowski, B B; Wood, S; Ye, Z; Zanevsky, Y; Zhang, X; Zhang, Y; Zheng, X; Zhu, L
2010-01-01
Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the non-perturbative regime.
Proton Form Factors Measurements in the Time-Like Region
Energy Technology Data Exchange (ETDEWEB)
Anulli, F.; /Frascati
2007-10-22
I present an overview of the measurement of the proton form factors in the time-like region. BABAR has recently measured with great accuracy the e{sup +}e{sup -} {yields} p{bar p} reaction from production threshold up to an energy of {approx} 4.5 GeV, finding evidence for a ratio of the electric to magnetic form factor greater than unity, contrary to expectation. In agreement with previous measurements, BABAR confirmed the steep rise of the magnetic form factor close to the p{bar p} mass threshold, suggesting the possible presence of an under-threshold N{bar N} vector state. These and other open questions related to the nucleon form factors both in the time-like and space-like region, wait for more data with different experimental techniques to be possibly solved.
Hadronic Form Factors in Asymptotically Free Field Theories
Gross, D. J.; Treiman, S. B.
1974-01-01
The breakdown of Bjorken scaling in asymptotically free gauge theories of the strong interactions is explored for its implications on the large q{sup 2} behavior of nucleon form factors. Duality arguments of Bloom and Gilman suggest a connection between the form factors and the threshold properties of the deep inelastic structure functions. The latter are addressed directly in an analysis of asymptotically free theories; and through the duality connection we are then led to statements about the form factors. For very large q{sup 2} the form factors are predicted to fall faster than any inverse power of q{sup 2}. For the more modest range of q{sup 2} reached in existing experiments the agreement with data is fairly good, though this may well be fortuitous. Extrapolations beyond this range are presented.
Kaon photoproduction with form factors in a gauge-invariant approach
Haberzettl, H; Mart, T; Feuster, T
1998-01-01
The general gauge-invariant photoproduction formalism given by Haberzettl is applied to kaon photoproduction off the nucleon at the tree level, with form factors describing composite nucleons. We demonstrate that, in contrast to Ohta's gauge-invariance prescription, this formalism allows electric current contributions to be multiplied by a form factor, i.e., they do not need to be treated like bare currents. Numerical results show that Haberzettl's gauge procedure, when compared to Ohta's, leads to much improved $\\chi^2$ values. Moreover, predictions for the new Bonn SAPHIR data for $p(\\gamma,K^+)\\Lambda$ are given.
TRASYS form factor matrix normalization
Tsuyuki, Glenn T.
1992-01-01
A method has been developed for adjusting a TRASYS enclosure form factor matrix to unity. This approach is not limited to closed geometries, and in fact, it is primarily intended for use with open geometries. The purpose of this approach is to prevent optimistic form factors to space. In this method, nodal form factor sums are calculated within 0.05 of unity using TRASYS, although deviations as large as 0.10 may be acceptable, and then, a process is employed to distribute the difference amongst the nodes. A specific example has been analyzed with this method, and a comparison was performed with a standard approach for calculating radiation conductors. In this comparison, hot and cold case temperatures were determined. Exterior nodes exhibited temperature differences as large as 7 C and 3 C for the hot and cold cases, respectively when compared with the standard approach, while interior nodes demonstrated temperature differences from 0 C to 5 C. These results indicate that temperature predictions can be artificially biased if the form factor computation error is lumped into the individual form factors to space.
$K_{13}$ transition form factors
Chueng Ryong Ji
2001-01-01
The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the meson bound state amplitudes and the dressed quark-W vertex in a manifestly covariant calculation of the K/sub l3/ transition form factors and decay width in the impulse approximation. With model gluon parameters previously fixed by the chiral condensate, the pion mass and decay constant, and the kaon mass, our results for the K/sub l3/ form factors and the kaon semileptonic decay width are in good agreement with the experimental data. (37 refs).
Institute of Scientific and Technical Information of China (English)
李志宏; 郭冰; 李云居; 苏俊; 李二涛; 白希祥; 王友宝; 曾晟; 王宝祥; 颜胜权; 李志常; 刘建成; 连钢; 金孙均; 刘鑫; 柳卫平
2012-01-01
The radiative capture reaction plays an important role in nuclear astrophysics. We have indirectly measured the astrophysical S(E) factors for some proton capture reactions and reaction rates for several neutron capture reactions with one nucleon transfer reactions at HI-13 tandem accelerator in recent years. Some of them are compiled into IAEA EXFOR database and JINA REACLIB project, and used in the network calculations of Big Bang nucleosynthesis and type-I X-ray bursts.
Energy Technology Data Exchange (ETDEWEB)
Rimal, Dipak [Florida Intl Univ., Miami, FL (United States)
2014-05-01
The electromagnetic form factors are the most fundamental observables that encode information about the internal structure of the nucleon. This dissertation explored dependence of R on kinematic variables such as squared four-momentum transfer (Q^{2}) and the virtual photon polarization parameter (ε).
Form factors and transverse charge and magnetization densities in the hard-wall AdS/QCD model
Mondal, Chandan
2016-01-01
We present a study of the flavor form factors in the framework of a hard-wall AdS/QCD model and compare with the available experimental data. We obtain the flavor form factors by decomposing the Dirac and Pauli form factors for the nucleons using the charge and isospin symmetry. Further, we present a detailed study of the flavor structures of the charge and anomalous magnetization densities in the transverse plane. Both the unpolarized and the transversely polarized nucleons are considered here. We compare the AdS/QCD results with two standard phenomenological parametrizations.
Meson-cloud effects in the electromagnetic nucleon structure
Kupelwieser, Daniel
2013-01-01
We study how the electromagnetic structure of the nucleon is influenced by a pion cloud. To this aim we make use of a constituent-quark model with instantaneous confinement and a pion that couples directly to the quarks. To derive the invariant 1- photon-exchange electron-nucleon scattering amplitude we employ a Poincar\\'e- invariant coupled-channel formulation which is based on the point-form of relativistic quantum mechanics. We argue that the electromagnetic nucleon current extracted from this amplitude can be reexpressed in terms of pure hadronic degrees of freedom with the quark substructure of the pion and the nucleon being encoded in electromagnetic and strong vertex form factors. These are form factors of bare particles, i.e. eigenstates of the pure confinement problem. First numerical results for (bare) photon-nucleon and pion-nucleon form factors, which are the basic ingredients of the further calculation, are given for a simple 3-quark wave function of the nucleon.
Baryon Form Factors at Threshold
Energy Technology Data Exchange (ETDEWEB)
Baldini Ferroli, Rinaldo [Museo Storico della Fisica e Centro Studi e Ricerche ' E. Fermi' , Rome (Italy); INFN, Laboratori Nazionali di Frascati, Frascati (Italy); Pacetti, Simone [INFN and Dipartimento di Fisica, Universita di Perugia, Perugia (Italy)
2012-04-15
An extensive study of the e{sup +}e{sup -}{yields}pp{sup Macron }BABAR cross section data is presented. Two unexpected outcomes have been found: the modulus of the proton form factor is normalized to one at threshold, i.e.: |G{sup p}(4M{sub p}{sup 2})|=1, as a pointlike fermion, and the resummation factor in the Sommerfeld formula is not needed. Other e{sup +}e{sup -} {yields} baryon-antibaryon cross sections show a similar behavior near threshold.
Nucleon-nucleon collision profile and cross section fluctuations
Rybczynski, Maciej
2013-01-01
The nucleon-nucleon collision profile, being the basic entity of the wounded nucleon model, is usually adopted in the form of hard sphere or the Gaussian shape. We suggest that the cross section fluctuations given by the gamma distribution leads to the profile function which smoothly ranges between the both limiting forms. Examples demonstrating sensitivity of profile function on cross section fluctuations are discussed.
Valence quark contributions for the gamma N -> P11(1440) form factors
Ramalho, G
2010-01-01
Using a covariant spectator quark model we estimate valence quark contributions to the F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The present model requires no extra parameters except for those already fixed by the previous studies for the nucleon. Our results are consistent with the experimental data in the high Q2 region, and those from lattice QCD. We also estimate the meson cloud contributions, focusing on the low Q2 region, where they are expected to be dominant.
Form Factors and Strong Couplings of Heavy Baryons from QCD Light-Cone Sum Rules
Khodjamirian, A; Mannel, Th; Wang, Y -M
2011-01-01
We derive QCD light-cone sum rules for the hadronic matrix elements of the heavy baryon transitions to nucleon. In the correlation functions the $\\Lambda_c,\\Sigma_c$ and $\\Lambda_b$ -baryons are interpolated by three-quark currents and the nucleon distribution amplitudes are used. To eliminate the contributions of negative parity heavy baryons, we combine the sum rules obtained from different kinematical structures. The results are then less sensitive to the choice of the interpolating current. We predict the $\\Lambda_{b}\\to p$ form factor and calculate the widths of the $\\Lambda_{b}\\to p\\ell\
Octet baryon electromagnetic form factors in a relativistic quark model
Ramalho, G
2011-01-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
Octet Baryon Electromagnetic Form Factors in a Relativistic Quark Model
Energy Technology Data Exchange (ETDEWEB)
Gilberto Ramalho, Kazuo Tsushima
2011-09-01
We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. As for the pion cloud contributions, we parameterize them in a covariant, phenomenological manner, combined with SU(3) symmetry. We also discuss the impact of the pion cloud effects on the octet baryon electromagnetic form factors and their radii.
Recoil polarization measurements of the proton electromagnetic form factor ratio to Q2 = 8.5 GeV2.
Puckett, A J R; Brash, E J; Jones, M K; Luo, W; Meziane, M; Pentchev, L; Perdrisat, C F; Punjabi, V; Wesselmann, F R; Ahmidouch, A; Albayrak, I; Aniol, K A; Arrington, J; Asaturyan, A; Baghdasaryan, H; Benmokhtar, F; Bertozzi, W; Bimbot, L; Bosted, P; Boeglin, W; Butuceanu, C; Carter, P; Chernenko, S; Christy, E; Commisso, M; Cornejo, J C; Covrig, S; Danagoulian, S; Daniel, A; Davidenko, A; Day, D; Dhamija, S; Dutta, D; Ent, R; Frullani, S; Fenker, H; Frlez, E; Garibaldi, F; Gaskell, D; Gilad, S; Gilman, R; Goncharenko, Y; Hafidi, K; Hamilton, D; Higinbotham, D W; Hinton, W; Horn, T; Hu, B; Huang, J; Huber, G M; Jensen, E; Keppel, C; Khandaker, M; King, P; Kirillov, D; Kohl, M; Kravtsov, V; Kumbartzki, G; Li, Y; Mamyan, V; Margaziotis, D J; Marsh, A; Matulenko, Y; Maxwell, J; Mbianda, G; Meekins, D; Melnik, Y; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Moffit, B; Moreno, O; Mulholland, J; Narayan, A; Nedev, S; Nuruzzaman; Piasetzky, E; Pierce, W; Piskunov, N M; Prok, Y; Ransome, R D; Razin, D S; Reimer, P; Reinhold, J; Rondon, O; Shabestari, M; Shahinyan, A; Shestermanov, K; Sirca, S; Sitnik, I; Smykov, L; Smith, G; Solovyev, L; Solvignon, P; Subedi, R; Tomasi-Gustafsson, E; Vasiliev, A; Veilleux, M; Wojtsekhowski, B B; Wood, S; Ye, Z; Zanevsky, Y; Zhang, X; Zhang, Y; Zheng, X; Zhu, L
2010-06-18
Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon's quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which G(E)(p) is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime.
Electromagnetic form factors of the Delta in a S-wave approach
Ramalho, G
2008-01-01
Without any further adjusting of parameters, a relativistic constituent quark model, successful in the description of the data for the nucleon elastic form factors and the dominant contribution to the nucleon to $\\Delta$ electromagnetic transition, is used here to predict the dominant electromagnetic form factors of the $\\Delta$ baryon. The model considered is based on a simple $\\Delta$ wave function corresponding to a quark-diquark system in an S-state. The results for E0 and M1 are consistent both with experimental results and lattice calculations. The remaining form factors M1 and E2 are negligible for small $Q^2$, as expected, given the symmetric structure considered for the $\\Delta$.
Future Perspectives on Baryon Form Factor Measurements with BES III
Schönning, Karin; Li, Cui
2017-03-01
The electromagnetic structure of hadrons, parameterised in terms of electromagnetic form factors, EMFF's, provide a key to the strong interaction. Nucleon EMFF's have been studied rigorously for more than 60 years but the new techniques and larger data samples available at modern facilities have given rise to a renewed interest for the field. Recently, the access to hyperon structure by hyperon time-like EMFF provides an additional dimension. The BEijing Spectrometer (BES III) at the Beijing Electron Positron Collider (BEPC-II) in China is the only running experiment where time-like baryon EMFF's can be studied in the e+e- → BB̅ reaction. The BES III detector is an excellent tool for baryon form factor measurements thanks to its near 4π coverage, precise tracking, PID and calorimetry. All hyperons in the SU(3) spin 1/2 octet and spin 3/2 decuplet are energetically accessible within the BEPC-II energy range. Recent data on proton and Λ hyperon form factors will be presented. Furthermore, a world-leading data sample was collected in 2014-2015 for precision measurements of baryon form factors. In particular, the data will enable a measurement of the relative phase between the electric and the magnetic form factors for Λ and Λc+ and hyperons. The modulus of the phase can be extracted from the hyperon polarisation, which in turn is experimentally accessible via the weak, parity violating decay. Furthermore, from the spin correlation between the outgoing hyperon and antihyperon, the sign of the phase can be extracted. This means that the time-like form factors can be completely determined for the first time. The methods will be outlined and the prospects of the BES III form factor measurements will be given. We will also present a planned upgrade of the BES III detector which is expected to improve future form factor measurements.
Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to Q^2 = 8.5 GeV^2
Energy Technology Data Exchange (ETDEWEB)
Puckett, A J.R.; Jones, M K; Luo, W; Meziane, M; Pentchev, L; Perdrisat, C F; Punjabi, V; Wesselmann, F R; Ahmidouch, A; Albayrak, I; Aniol, K A; Arrington, J; Asaturyan, A; Baghdasaryan, H; Benmokhtar, F; Bertozzi, W; Bimbot, L; Bosted, P; Boeglin, W; Butuceanu, C; Carter, P; Chernenko, S; Christy, E; Commisso, M; Cornejo, J C; Covrig, S; Danagoulian, S; Daniel, A; Davidenko, A; Day, D; Dhamija, S; Dutta, D; Ent, R; Frullani, S; Fenker, H; Frlez, E; Garibaldi, F; Gaskell, D; Gilad, S; Gilman, R; Goncharenko, Y; Hafidi, K; Hamilton, D; Higinbotham, D W; Hinton, W; Horn, T; Hu, B; Huang, J; Huber, G M; Jensen, E; Keppel, C; Khandaker, M; King, P; Kirillov, D; Kohl, M; Kravtsov, V; Kumbartzki, G; Li, Y; Mamyan, V; Margaziotis, D J; Marsh, A; Matulenko, Y; Maxwell, J; Mbianda, G; Meekins, D; Melnik, Y; Miller, J; Mkrtchyan, A; Mkrtchyan, H; Moffit, B; Moreno, O; Mulholland, J; Narayan, A; Nedev, S; Nuruzzaman,; Piasetzky, E; Pierce, W; Piskunov, N M; Prok, Y; Ransome, R D; Razin, D S; Reimer, P; Reinhold, J; Rondon, O; Shabestari, M; Shahinyan, A; Shestermanov, K; Sirca, S; Sitnik, I; Smykov, L; Smith, G; Solovyev, L; Solvingnon, P; Subedi, R; Tomasi-Gustafsson, E; Vasiliev, A; Veilleux, M; Wojtsekhowski, B B; Wood, S; Ye, Z; Zanevsky, Y; Zhang, X; Zhang, Y; Zheng, X
2010-06-01
Among the most fundamental observables of nucleon structure, electromagnetic form factors are a crucial benchmark for modern calculations describing the strong interaction dynamics of the nucleon’s quark constituents; indeed, recent proton data have attracted intense theoretical interest. In this Letter, we report new measurements of the proton electromagnetic form factor ratio using the recoil polarization method, at momentum transfers Q2=5.2, 6.7, and 8.5 GeV2. By extending the range of Q2 for which GEp is accurately determined by more than 50%, these measurements will provide significant constraints on models of nucleon structure in the nonperturbative regime.
Gauge-invariant meson photoproduction with extended nucleons
Haberzettl, H; Mart, T; Feuster, T
1998-01-01
The general gauge-invariant photoproduction formalism given by Haberzettl is applied to kaon photoproduction off the nucleon at the tree level, with form factors describing composite nucleons. Numerical results show that this gauge-invariance procedure, when compared to Ohta's, leads to a much improved description of experimental data. Predictions for the new Bonn SAPHIR data for $p(\\gamma,K^+)\\Lambda$ are given.
$\\chi$EFT studies of few-nucleon systems: a status report
Energy Technology Data Exchange (ETDEWEB)
Schiavilla, Rocco [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States)
2016-06-01
A status report on $\\chi$EFT studies of few-nucleon electroweak structure and dynamics is provided, including electromagnetic elastic form factors of few-nucleon systems, the $pp$ weak fusion and muon weak captures on deuteron and $^3$He, and a number of parity-violating processes induced by hadronic weak interactions.
Manifestation of Symmetry Properties of Nucleon Structure in Strong and Electromagnetic Processes
Tomasi-Gustafsson, Egle; Rekalo, Michail P.
2004-04-01
In this contribution we present a specific application of a result obtained by Franco Iachello (in collaboration with R. Bijker and A. Leviatan), which concerns the inelastic electromagnetic form factors on the nucleons. In particular we show examples where symmetries inherent to the structure of the nucleon resonances can manifest in complicated processes of the strong interaction.
Lattice calculation of composite dark matter form factors
Appelquist, T; Buchoff, M I; Cheng, M; Cohen, S D; Fleming, G T; Kiskis, J; Lin, M F; Neil, E T; Osborn, J C; Rebbi, C; Schaich, D; Schroeder, C; Syritsyn, S N; Voronov, G; Vranas, P; Wasem, J
2013-01-01
Composite dark matter candidates, which can arise from new strongly-coupled sectors, are well-motivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweak-neutral dark-matter baryons for a three-color, QCD-like theory with Nf = 2 and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal Nf dependence in these quantities. We generate mass-dependent cross-sections for dark matter-nucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.
Ideas of four-fermion operators in electromagnetic form factor calculations
Directory of Open Access Journals (Sweden)
Ji Chueng-Ryong
2014-06-01
Full Text Available Four-fermion operators have been utilized in the past to link the quark-exchange processes in the interaction of hadrons with the effective meson-exchange amplitudes. In this presentation, we apply the similar idea of Fierz rearrangement to the electromagnetic processes and focus on the electromagnetic form factors of nucleon and electron. We explain the motivation of using four-fermion operators and discuss the advantage of this method in computing electromagnetic processes.
Alvioli, Massimiliano; Morita, Hiko
2016-01-01
The two-nucleon momentum distributions have been calculated for nuclei up to A=40 and various values of the relative and center-of-mass momenta and angle between them. For complex nuclei a parameter-free linked-cluster expansion, based upon a realistic local two-nucleon interaction of the Argonne family and variational wave function featuring central, tensor, spin and iso-spin correlations, has been used. The obtained results show that: 1) independently of the mass number A, at values of the relative momentum k_rel> 2 fm^{-1} the proton-neutron momentum distributions for back-to-back (BB) nucleons (K_cm=0) exhibit the factorization property n_A^{pn}(k_rel,K_cm=0)=C_A^{pn} n_D(k_rel) n_{cm}^{pn}(K_cm=0), where n_D is the deuteron momentum distribution, n_{cm}^{pn}(K_{cm}=0) the momentum distribution of the c.m. motion of the pair and C_A^{pn} the nuclear contact measuring the number of BB pn pairs with deuteron-like momenta; 2) the values of the proton-neutron nuclear contact C_A^{pn} are obtained in a model-i...
Energy Technology Data Exchange (ETDEWEB)
Bratt, Jonathan; Engelhardt, Michael; Haegler, Philipp; Huey-Wen, Lin; Lin, Meifeng; Meyer, Harvey; Musch, Bernhard; Negele, John; Orginos, Konstantinos; Pochinsky, Andrew; Procura, Massimiliano; Richards, David; Schroers, Wolfram; Syritsyn, Sergey
2010-11-01
We present high statistics results for the structure of the nucleon from a mixed-action calculation using 2+1 flavors of asqtad sea and domain wall valence fermions. We perform extrapolations of our data based on different chiral effective field theory schemes and compare our results with available information from phenomenology. We discuss vector and axial form factors of the nucleon, moments of generalized parton distributions, including moments of forward parton distributions, and implications for the decomposition of the nucleon spin.
Energy Technology Data Exchange (ETDEWEB)
Rekalo, M.P.; Tomasi-Gustafsson, E.
1996-12-31
We analyze the properties of the inclusive d + p-reactions, with particular interest in the domain of nucleonic resonances excitation. The calculated cross section and polarization observables show that it is possible to disentangle the different reaction mechanisms ({omega}-,{sigma}-, n- exchange) and bring new information about the electromagnetic form factors of the deuteron as well as of the nucleonic resonances excitation. Existing data on the tensor analyzing power are in agreement with the predictions based on the {omega}-exchange model. (authors). 18 refs.
Alvioli, M.; Ciofi degli Atti, C.; Morita, H.
2016-10-01
Background: The two-nucleon momentum distributions of nucleons N1 and N2 in a nucleus A , nAN1N2(krel,Kc .m .) , is a relevant quantity that determines the probability of finding two nucleons with relative momentum krel and center-of-mass (c.m.) momentum Kc .m .; at high values of the relative momentum and, at the same time, low values of the c.m. momentum, nAN1N2(krel,Kc .m .) provides information on the short-range structure of nuclei. Purpose: Our purpose is to calculate the momentum distributions of proton-neutron and proton-proton pairs in 3He, 4He, 12C, 16O, and 40Ca, in correspondence to various values of krel and Kc .m .. Methods: The momentum distributions for A >4 nuclei are calculated as a function of the relative, krel, and center-of-mass, Kc.m., momenta and relative angle Θ , within a linked cluster many-body expansion approach, based upon realistic local two-nucleon interaction of the Argonne family and variational wave functions featuring central, tensor, and spin-isospin correlations. Results: Independently of the mass number A , at values of the relative momentum krel≳1.5 -2 fm-1 the momentum distributions exhibit the property of factorization, nAN1N2(krel,Kc .m .) ≃nrelN1N2(krel) nc.m . N1N2(Kc .m .) ; in particular, for p n back-to-back pairs one has nAp n(krel,Kc .m .=0 ) ≃CAp nnD(krel) nc.m . p n(Kc .m .=0 ) , where nD is the deuteron momentum distribution, nc.m . p n(Kc .m .=0 ) the c.m. motion momentum distribution of the pair, and CAp n the p n nuclear contact measuring the number of back-to-back p n pairs with deuteron-like momenta (kp≃-kn,Kc .m .=0 ). Conclusions: The values of the p n nuclear contact are extracted from the general properties of the two-nucleon momentum distributions corresponding to Kc .m .=0 . The Kc .m .-integrated p n momentum distributions exhibit the property nAp n(krel) ≃CAp nnD(krel) but only at very high values of krel, ≳3.5 -4 fm-1. The theoretical ratio of the p p /p n momentum distributions of 4He
Strange Quark Contribution to the Nucleon - (Dissertation)
Darnell, Dean
2008-01-01
The strangeness contribution to the electric and magnetic properties of the nucleon has been under investigation experimentally for many years. Lattice Quantum Chromodynamics (LQCD) gives theoretical predictions of these measurements by implementing the continuum gauge theory on a discrete, mathematical Euclidean space-time lattice which provides a cutoff removing the ultra-violet divergences. In this dissertation we will discuss effective methods using LQCD that will lead to a better determination of the strangeness contribution to the nucleon properties. Strangeness calculations are demanding technically and computationally. Sophisticated techniques are required to carry them to completion. In this thesis, new theoretical and computational methods for this calculation such as twisted mass fermions, perturbative subtraction, and General Minimal Residual (GMRES) techniques which have proven useful in the determination of these form factors will be investigated. Numerical results of the scalar form factor usin...
Soliton form factors from lattice simulations
Rajantie, Arttu
2010-01-01
The form factor provides a convenient way to describe properties of topological solitons in the full quantum theory, when semiclassical concepts are not applicable. It is demonstrated that the form factor can be calculated numerically using lattice Monte Carlo simulations. The approach is very general and can be applied to essentially any type of soliton. The technique is illustrated by calculating the kink form factor near the critical point in 1+1-dimensional scalar field theory. As expected from universality arguments, the result agrees with the exactly calculable scaling form factor of the two-dimensional Ising model.
Axial form factors of the octet baryons in a covariant quark model
Ramalho, G
2015-01-01
We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q^2. In our model the axial form factors G_A(Q^2) (axial-vector form factor) and G_P(Q^2) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g_A^q(Q^2), and the induced pseudoscalar form factor g_P^q(Q^2). The baryon wave functions are composed of a dominant S-state and a P-state mixture for the relative angular momentum of the quarks. First, we study in detail the nucleon case. We assume that the quark axial-vector form factor g_A^q(Q^2) has the same function form as that of the quark electromagnetic isovector form factor. The remaining parameters of the model, the P-state mixture and the Q^2-dependence of g_P^q(Q^2), are determined by a f...
neutrino induced threshold production of two pions and N^*(1440) electroweak form factors
Hernández, E; Singh, S K; Valverde, M; Vicente-Vacas, M J
2007-01-01
We study the threshold production of two pions induced by neutrinos in nucleon targets. The contribution of nucleon, pion and contact terms are calculated using a chiral Lagrangian. The contribution of the Roper resonance, neglected in earlier studies, has also been taken into account. The numerical results for the cross sections are presented and compared with the available experimental data. It has been found that in the two pion channels with $\\pi^+\\pi^-$ and $\\pi^0\\pi^0$ in the final state, the contribution of the $N^*(1440)$ is quite important and could be used to determine the $N^*(1440)$ electroweak transition form factors if experimental data with better statistics become available in the future.
Lattice study of the N-P11 transition form factors
Energy Technology Data Exchange (ETDEWEB)
Lin, Huey-Wen; Cohen, Saul; Edwards, Robert; Richards, David
2008-12-01
Experiments at Jefferson Laboratory, MIT-Bates, LEGS, Mainz, Bonn, GRAAL, and Spring-8 offer new opportunities to understand in detail how nucleon resonance ($N^*$) properties emerge from the nonperturbative aspects of QCD. Preliminary data from CLAS collaboration, which cover a large range of photon virtuality $Q^2$ show interesting behavior with respect to $Q^2$ dependence: in the region $Q^2 \\le 1.5 \\mbox{ GeV}^2$, both the transverse amplitude, $A_{1/2}(Q^2)$, and the longitudinal amplitude, $S_{1/2}(Q^2)$, decrease rapidly. In this work, we attempt to use first-principles lattice QCD (for the first time) to provide a model-independent study of the Roper-nucleon transition form factor.
First Lattice Study of the $N$-$P_{11}(1440)$ Transition Form Factors
Lin, Huey-Wen; Edwards, Robert G; Richards, David G
2008-01-01
Experiments at Jefferson Laboratory, MIT-Bates, LEGS, Mainz, Bonn, GRAAL, and Spring-8 offer new opportunities to understand in detail how nucleon resonance ($N^*$) properties emerge from the nonperturbative aspects of QCD. Preliminary data from CLAS collaboration, which cover a large range of photon virtuality $Q^2$ show interesting behavior with respect to $Q^2$ dependence: in the region $Q^2 \\le 1.5 {GeV}^2$, both the transverse amplitude, $A_{1/2}(Q^2)$, and the longitudinal amplitude, $S_{1/2}(Q^2)$, decrease rapidly. In this work, we attempt to use first-principles lattice QCD (for the first time) to provide a model-independent study of the Roper-nucleon transition form factor.
Form Factors in radiative pion decay
Mateu, V
2007-01-01
We perform an analysis of the form factors that rule the structure-dependent amplitude in the radiative pion decay. The resonance contributions to pion -> e nu_e gamma decays are computed through the proper construction of the vector and axial-vector form factors by setting the QCD driven asymptotic properties of the three-point Green functions VVP and VAP, and by demanding the smoothing of the form factors at high transfer of momentum. A comparison between theoretical and experimental determinations of the form factors is also carried out. We also consider and evaluate the role played by a non-standard tensor form factor. We conclude that, at present and due to the hadronic incertitudes, the search for New Physics in this process is not feasible.
New Precision Limit on the Strange Vector Form Factors of the Proton
Ahmed, Z; Aniol, K A; Armstrong, D S; Arrington, J; Baturin, P; Bellini, V; Benesch, J; Beminiwattha, R; Benmokhtar, F; Canan, M; Camsonne, A; Cates, G D; Chen, J -P; Chudakov, E; Cisbani, E; Dalton, M M; de Jager, C W; De Leo, R; Deconinck, W; Decowski, P; Deng, X; Deur, A; Dutta, C; Franklin, G B; Friend, M; Frullani, S; Garibaldi, F; Giusa, A; Glamazdin, A; Golge, S; Grimm, K; Hansen, O; Higinbotham, D W; Holmes, R; Holmstrom, T; Huang, J; Huang, M; Hyde, C E; Jen, C M; Jin, G; Jones, D; Kang, H; King, P; Kowalski, S; Kumar, K S; Lee, J H; LeRose, J J; Liyanage, N; Long, E; McNulty, D; Margaziotis, D; Meddi, F; Meekins, D G; Mercado, L; Meziani, Z -E; Michaels, R; Munoz-Camacho, C; Mihovilovic, M; Muangma, N; Myers, K E; Nanda, S; Narayan, A; Nelyubin, V; Nuruzzaman,; Oh, Y; Pan, K; Parno, D; Paschke, K D; Phillips, S K; Qian, X; Qiang, Y; Quinn, B; Rakhman, A; Reimer, P E; Rider, K; Riordan, S; Roche, J; Rubin, J; Russo, G; Saenboonruang, K; Saha, A; Sawatzky, B; Silwal, R; Sirca, S; Souder, P A; Sperduto, M; Subedi, R; Suleiman, R; Sulkosky, V; Sutera, C M; Tobias, W A; Urciuoli, G M; Waidyawansa, B; Wang, D; Wexler, J; Wilson, R; Wojtsekhowski, B; Zhan, X; Yan, X; Yao, H; Ye, L; Zhao, B; Zheng, X
2011-01-01
The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624 GeV and beam energy E =3.48 GeV to be A_PV = -23.80 +/- 0.78 (stat) +/- 0.36 (syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G_E^s + 0.517 G_M^s = 0.003 +/- 0.010 (stat) +/- 0.004 (syst) +/- 0.009 (ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.
Pion production in nucleon-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Afnan, I.R.
1982-01-01
A model describing pion production in proton-proton interactions is presented. The model includes both single nucleon and two nucleon mechanisms. A system of equations representing the reaction is derived and results calculated using these equations are presented.
Electroexcitation of nucleon resonances
Aznauryan, I G
2011-01-01
We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV2 for the Delta(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13}, respectively. These results have been confronted with calculations based on lattice QCD, large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the Delta(1232) indicate large pion-cloud contributions at low Q2 and don't show any sign of approaching the pQCD regime for Q2 0.5 GeV2, confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented.
Separation energy dependence of hole form factors
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, J.; Langevin-Joliot, H. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Vdovin, A. [Joint Inst. for Nuclear Research, Dubna (Russian Federation). Bogoliubov Lab. of Theoretical Physics
1996-04-01
Form factors of fragmented hole states are studied within the quasiparticle-phonon model, using the inhomogeneous equation method. A systematic investigation of form factors is performed for neutron and proton hole states in the valence and first inner shells of {sup 208}Pb. Average characteristics are introduced for groups of levels, namely the mean form factors, summed source terms and correction potentials, and their behaviour is presented. The role of the relative values of the interaction radius parameter and binding well radius is discussed in details. (K.A.). 21 refs.; Submitted to Elsevier Science.
Weak $\\eta$ production off the nucleon
Alam, M Rafi; Athar, M Sajjad; Vacas, M J Vicente
2013-01-01
The weak $\\eta$-meson production off the nucleon induced by (anti)neutrinos is studied at low and intermediate energies, the range of interest for several ongoing and future neutrino experiments. We consider Born diagrams and the excitation of $N^\\ast (1535)S_{11}$ and $N^\\ast(1650)S_{11}$ resonances. The vector part of the N-$S_{11}$ transition form factors has been obtained from the MAID helicity amplitudes while the poorly known axial part is constrained with the help of the partial conservation of the axial current (PCAC) and assuming the pion-pole dominance of the pseudoscalar form factor.
Weak η production off the nucleon
Energy Technology Data Exchange (ETDEWEB)
Alam, M. Rafi; Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Alvarez-Ruso, L.; Vacas, M. J. Vicente [Departamento de Física Teórica and Instituto de Física Corpuscular, Centro Mixto Universidad de Valencia-CSIC, E-46071 Valencia (Spain)
2015-05-15
The weak η-meson production off the nucleon induced by (anti)neutrinos is studied at low and intermediate energies, the range of interest for several ongoing and future neutrino experiments. We consider Born diagrams and the excitation of N{sup *} (1535)S{sub 11} and N{sup *} (1650)S{sub 11} resonances. The vector part of the N-S{sub 11} transition form factors has been obtained from the MAID helicity amplitudes while the poorly known axial part is constrained with the help of the partial conservation of the axial current (PCAC) and assuming the pion-pole dominance of the pseudoscalar form factor.
Monte Carlo simulation of finite mass nucleons interacting via a neutral, scalar boson field
Szybisz, L.; Zabolitzky, J. G.
1987-03-01
A recently proposed Monte Carlo method to solve the Schrödinger equation when expressed in Fock space is applied to the hamiltonian which describes the interaction of nucleons via a neutral, scalar boson field. The fact that a nucleon has finite mass is taken into account and a gaussian cut-off for the nucleon form factor is adopted. The problem is solved for systems with A = 1 and 2 sources (nucleons) in the three-dimensional continuous space. From the results for A = 1 a bare nucleon mass, mB c2 = 962.58 ± 0.06 MeV, is obtained. This value is used to determine the binding energy for an A = 2 system by means of this new algorithm. The result, B(2) = 2.14 ± 0.50 MeV, is consistent with the value corresponding to the static potential approximation.
Monte Carlo simulation of finite mass nucleons interacting via a neutral, scalar boson field
Energy Technology Data Exchange (ETDEWEB)
Szybisz, L.; Zabolitzky, J.G.
1987-03-23
A recently proposed Monte Carlo method to solve the Schroedinger equation when expressed in Fock space is applied to the hamiltonian which describes the interaction of nucleons via a neutral, scalar boson field. The fact that a nucleon has finite mass is taken into account and a gaussian cut-off for the nucleon form factor is adopted. The problem is solved for systems with A=1 and 2 sources (nucleons) in the three-dimensional continuous space. From the results for A=1 a bare nucleon mass, m/sub B/c/sup 2/=962.58+-0.06 MeV, is obtained. This value is used to determine the binding energy for an A=2 system by means of this new algorithm. The result, B(2)=2.14+-0.50 MeV, is consistent with the value corresponding to the static potential approximation.
The effects of density-dependent form factors for (e, e'p) reaction in quasi-elastic region
Energy Technology Data Exchange (ETDEWEB)
Kim, K.S. [Korea Aerospace University, School of Liberal Arts and Science, Goyang (Korea, Republic of); Cheoun, Myung-Ki [Soongsil University, Department of Physics, Seoul (Korea, Republic of); Kim, Hungchong [Kookmin University, Department of General Education, Seoul (Korea, Republic of); So, W.Y. [Kangwon National University at Dogye, Department of Radiological Science, Samcheok (Korea, Republic of)
2016-04-15
Within the framework of a relativistic single particle model, the effects of density-dependent electromagnetic form factors on the exclusive (e, e'p) reaction are investigated in the quasi-elastic region. The density-dependent electromagnetic form factors are generated from a quark-meson coupling model and used to calculate the cross sections in two different densities, either at the normal density of ρ{sub 0} ∝ 0.15 fm{sup -3} or at the lower density, 0.5ρ{sub 0}. Then these cross sections are analyzed in the two different kinematics: One is that the momentum of the outgoing nucleon is along the momentum transfer. The other is that the angle between the momentum of the outgoing nucleon and the momentum transfer is varied at fixed magnitude of the momentum of the outgoing nucleon. Our theoretical differential reduced cross sections are compared with the NIKHEF data for the {sup 208}Pb(e, e'p) reaction, which is related to the probability that a bound nucleon from a given orbit can be knocked-out of the nucleus. The effects of the density-dependent form factors increase the differential cross sections for both knocked-out proton and neutron by an amount of a few percent. Moreover they are shown to be almost the same within only a few percent, i.e., nearly independent of the shell location of knockout nucleons. These results are quite consistent with the characteristics of double magic nuclei which have relatively sharp smearing in the density distribution. (orig.)
Pseudoscalar meson form factors and decays
Dorokhov, A E
2011-01-01
In this communication we discuss few topics related with modern experimental data on the physics of light pseudoscalar mesons. It includes the contribution of the pseudoscalar mesons to the muon anomalous magnetic moment (AMM), $g-2$, the rare decays of light pseudoscalar mesons to lepton pair, the transition form factors of pseudoscalar mesons at large momentum transfer, the pion transversity form factor. Measuring the muon anomalous magnetic moment $g-2$ and the rare decays of light pseudoscalar mesons into lepton pair $P\\rightarrow l^{+}l^{-} $ serve as important test of the standard model. To reduce the theoretical uncertainty in the standard model predictions the data on the transition form factors of light pseudoscalar mesons play significant role. Recently new data on behavior of these form factors at large momentum transfer was supplied by the BABAR collaboration. Within the nonlocal chiral quark model it shown how to describe these data and how the meson distribution amplitude evolves as a function o...
Separation energy dependence of hole form factors
Energy Technology Data Exchange (ETDEWEB)
Van de Wiele, J. [Institut de Physique Nucleaire, 91 - Orsay (France); Vdovin, A. [Bogoliubov Laboratory of Theoretical Physics, Joint Institute for Nuclear Research, 141980 Dubna (Russian Federation); Langevin-Joliot, H. [Institut de Physique Nucleaire, 91 - Orsay (France)
1996-08-05
Form factors of fragmented hole states are studied within the quasiparticle-phonon model, using the inhomogeneous equation method. The validity of this method is successfully checked by comparison with coupled equation solutions in schematic vibrational model cases. A systematic investigation of form factors is performed for neutron and proton hole states in the valence and first inner shells of {sup 208}Pb. Large fluctuations of form factor radii are observed for individual levels superimposed on a general increase with separation energy. Average characteristics are introduced for groups of levels, namely the mean form factors, summed source terms and correction potentials, and their behaviour is presented. The role of the relative values of the interaction radius parameter and binding well radius is discussed in detail. (orig.).
Make Projects Small Form Factor PCs
Wessels, Duane
2006-01-01
Shoebox sized and smaller, small-form-factor PCs can pack as much computing muscle as a full-sized desktop computer. They consumer less power, have few or no moving parts, and are very quiet. Whether you plan to use one as a standalone PC or want to embed it in your next hacking project, a small-form-factor PC can be a lot of fun to build. Make Projects: Small Form Factor PCs is the only book available that shows you how to build small-form-factor PCs -- from kits and from scratch -- that are more interesting and more personalized than what a full-sized PC can give you. Included in the book
A relativistic quark–diquark model for the nucleon
Indian Academy of Sciences (India)
Cristian Leonardo Gutierrez; Maurizio De Sanctis
2009-02-01
We developed a constituent quark–diquark model for the nucleon and its resonances using a harmonic oscillator potential for the interaction. The effects due to relativistic kinetic energy correction are studied. Finally, charge form factor of the model is calculated and compared with experimental data.
Nucleon Structure in Lattice QCD using twisted mass fermions
Alexandrou, C; Korzec, T; Carbonell, J; Harraud, P A; Papinutto, M; Guichon, P; Jansen, K
2010-01-01
We present results on the nucleon form factors and moments of generalized parton distributions obtained within the twisted mass formulation of lattice QCD. We include a discussion of lattice artifacts by examining results at different volumes and lattice spacings. We compare our results with those obtained using different discretization schemes and to experiment.
An Algebraic Approach to Form Factors
Niedermaier, M. R.
1994-01-01
An associative $*$-algebra is introduced (containing a $TTR$-algebra as a subalgebra) that implements the form factor axioms, and hence indirectly the Wightman axioms, in the following sense: Each $T$-invariant linear functional over the algebra automatically satisfies all the form factor axioms. It is argued that this answers the question (posed in the functional Bethe ansatz) how to select the dynamically correct representations of the $TTR$-algebra. Applied to the case of integrable QFTs w...
Empirical transverse charge densities in the nucleon and the nucleon-to-Delta transition
Energy Technology Data Exchange (ETDEWEB)
Carl Carlson; Marc Vanderhaeghen
2008-01-01
Using only the current empirical information on the nucleon electromagnetic form factors we map out the transverse charge density in proton and neutron as viewed from a light front moving towards a transversely polarized nucleon. These charge densities are characterized by a dipole pattern, in addition to the monopole field corresponding with the unpolarized density. Furthermore, we use the latest empirical information on the $N \\to \\Delta$ transition form factors to map out the transition charge density which induces the $N \\to \\Delta$ excitation. This transition charge density in a transversely polarized $N$ and $\\Delta$ contains both monopole, dipole and quadrupole patterns, the latter corresponding with a deformation of the hadron's charge distribution.
Nucleon-nucleon theory and phenomenology
Energy Technology Data Exchange (ETDEWEB)
Signell, P.
1981-03-01
This project involves five inter-related subprojects: (1) derivation of the intermediate range nucleon-nucleon interaction using a new method that utilizes much shorter and simpler analytic continuation through the unphysical region that lies between the ..pi..N and ..pi pi.. physical regions of the N anti N ..-->.. ..pi pi.. amplitude (with significantly improved accuracy for the nucleon-nucleon interaction); (2) construction of a short range phenomenological potential that, with the theoretical part mentioned above, gives a precise fit to the nucleon-nucleon data and is parameterized for easy use in nucleon calculations; (3) phase shift analyses of the world data below 400 MeV, especially the large amount of very precise data below 20 MeV and the new data near 55 MeV that have never been analyzed properly; (4) the introduction of a K-matrix formulation of the Optimal Polynomial Expansion in order to accelerate convergence of the partial wave series at LAMPF energies; and (5) setting up of a cooperatively evaluated permanent nucleon-nucleon data bank in the 0-1200 MeV range that can be used by all nucleon-nucleon reseachers.
Comparing Some Nucleon-Nucleon Potentials
Naghdi, M
2013-01-01
The aim is to compare a few Nucleon-Nucleon (NN) potentials especially Reid68, Reid68-Day, Reid93, UrbanaV14, ArgonneV18, Nijmegen 93, Nijmegen I, Nijmegen II. Although these potentials have some likenesses and are almost phenomenological, they include in general different structures and its own characteristics. The potentials are constructed in a manner that fit the NN scattering data or phase shifts and are compared in this way. A high-quality scale of a potential is that it fits the data with $\\chi^{2}/N_{data} \\approx 1$, describes well deuteron properties or gives satisfactory results in nuclear structure calculations. However, these scales have some failures. Here, we first compare many potentials by confronting with data. Then, we try to compare the potential forms by considering the potential structures directly and therefore regarding their substantial basis somehow. On the other hand, since the potentials are written in different schema, it is necessary to write the potentials in a unique schema to ...
Asymptotics of Heavy-Meson Form Factors
Grozin, A.G.; Grozin, Andrey G.; Neubert, Matthias
1997-01-01
Using methods developed for hard exclusive QCD processes, we calculate the asymptotic behaviour of heavy-meson form factors at large recoil. It is determined by the leading- and subleading-twist meson wave functions. For $1\\ll |v\\cdot v'|\\ll m_Q/\\Lambda$, the form factors are dominated by the Isgur--Wise function, which is determined by the interference between the wave functions of leading and subleading twist. At $|v\\cdot v'|\\gg m_Q/\\Lambda$, they are dominated by two functions arising at order $1/m_Q$ in the heavy-quark expansion, which are determined by the leading-twist wave function alone. The sum of these contributions describes the form factors in the whole region $|v\\cdot v'|\\gg 1$. As a consequence, there is an exact zero in the form factor for the scattering of longitudinally polarized $B^*$ mesons at some value $v\\cdot v'\\sim m_b/\\Lambda$, and an approximate zero in the form factor of $B$ mesons in the timelike region ($v\\cdot v'\\sim -m_b/\\Lambda$). We obtain the evolution equations and sum rules ...
Electromagnetic matrix elements for negative parity nucleons
Owen, Benjamin; Leinweber, Derek; Mahbub, Selim; Menadue, Benjamin
2014-01-01
Here we present preliminary results for the evaluation of the electromagnetic form factors for the lowest-lying negative-parity, spin-$\\frac{1}{2}$ nucleons, namely the $S_{11}(1535)$ and $S_{11}(1650)$, through the use of the variational method. We find that the characteristics of the electric form factor, $G_{E}$, are similar between these states, however significant differences are observed between the quark-sector contributions to the magnetic form factor, $G_{M}$. Within simple constituent quark models, these states are understood to be admixtures of $s=\\frac{1}{2}$ and $s=\\frac{3}{2}$ states coupled to orbital angular momentum $\\ell = 1$. Our results reveal a qualitative difference in the manner in which the singly-represented quark sector contributes to these baryon magnetic form factors.
Parity-violating Electron Deuteron Scattering and the Proton's Neutral Weak Axial Vector Form Factor
Ito, T M; Averett, T; Barkhuff, D; Batigne, G; Beck, D H; Beise, E J; Blake, A; Breuer, H; Carr, R; Clasie, B; Covrig, S D; Danagulyan, A S; Dodson, G; Dow, K; Dutta, D; Farkhondeh, M; Filippone, B W; Franklin, W; Furget, C; Gao, H; Gao, J; Gustafsson, K K; Hannelius, L; Hasty, R; Hawthorne-Allen, A M; Herda, M C; Jones, C E; King, P; Korsch, W; Kowalski, S; Kox, S; Krämer, K; Lee, P; Liu, J; Martin, J W; McKeown, R D; Müller, B; Pitt, M L; Plaster, B; Quéméner, G; Real, J S; Ritter, J; Roche, J; Savu, V; Schiavilla, R; Seely, J; Spayde, D T; Suleiman, R; Taylor, S; Tieulent, R; Tipton, B; Tsentalovich, E; Wells, S P; Yang, B; Yuan, J; Yun, J; Zwart, T
2004-01-01
We report on a new measurement of the parity-violating asymmetry in quasielastic electron scattering from the deuteron at backward angles at Q2= 0.038 (GeV/c)2. This quantity provides a determination of the neutral weak axial vector form factor of the nucleon, which can potentially receive large electroweak corrections. The measured asymmetry A=-3.51 +/- 0.57(stat) +/- 0.58(sys)ppm is consistent with theoretical predictions. We also report on updated results of the previous experiment at Q2=0.091 (GeV/c)2, which are also consistent with theoretical predictions.
JLab Measurement of the $^4$He Charge Form Factor at Large Momentum Transfers
Camsonne, A; Olson, M; Sparveris, N; Acha, A; Allada, K; Anderson, B D; Arrington, J; Baldwin, A; Chen, J -P; Choi, S; Chudakov, E; Cisbani, E; Craver, B; Decowski, P; Dutta, C; Folts, E; Frullani, S; Garibaldi, F; Gilman, R; Gomez, J; Hahn, B; Hansen, J -O; Higinbotham, D; Holmstrom, T; Huang, J; Iodice, M; Jiang, X; Kelleher, A; Khrosinkova, E; Kievsky, A; Kuchina, E; Kumbartzki, G; Lee, B; LeRose, J J; Lindgren, R A; Lott, G; Lu, H; Marcucci, L E; Margaziotis, D J; Markowitz, P; Marrone, S; Meekins, D; Meziani, Z -E; Michaels, R; Moffit, B; Norum, B; Petratos, G G; Puckett, A; Qian, X; Rondon, O; Saha, A; Sawatzky, B; Segal, J; Shabestari, M; Shahinyan, A; Solvignon, P; Subedi, R R; Suleiman, R; Sulkosky, V; Urciuoli, G M; Viviani, M; Wang, Y; Wojtsekhowski, B B; Yan, X; Yao, H; Zhang, W -M; Zheng, X; Zhu, L
2013-01-01
The charge form factor of $^$4He has been extracted in the range 29 fm$^{-2}$ $\\le Q^2 \\le 77$ fm$^{-2}$ from elastic electron scattering, detecting $^4$He nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility of Jefferson Lab. The results are in qualitative agreement with realistic meson-nucleon theoretical calculations. The data have uncovered a second diffraction minimum, which was predicted in the $Q^2$ range of this experiment, and rule out conclusively long-standing predictions of dimensional scaling of high-energy amplitudes using quark counting.
How important is the three-nucleon force\\?
Saito, T.-Y.; Afnan, I. R.
1994-12-01
By calculating the contribution of the π-π three-body force to the three-nucleon binding energy in terms of the πN amplitude using perturbation theory, we are able to determine the contribution of the different πN partial waves to the three-nucleon force. The division of the πN amplitude into a pole and nonpole gives a unique procedure for the determination of the πNN form factor in the model. The total contribution of the three-body force to the binding energy of the triton is found to be very small.
How important is the three-nucleon force
Energy Technology Data Exchange (ETDEWEB)
Saito, T.; Afnan, I.R. (School of Physical Sciences, The Flinders University of South Australia, Bedford Park, SA 5042 (Australia))
1994-12-01
By calculating the contribution of the [pi]-[pi] three-body force to the three-nucleon binding energy in terms of the [pi][ital N] amplitude using perturbation theory, we are able to determine the contribution of the different [pi][ital N] partial waves to the three-nucleon force. The division of the [pi][ital N] amplitude into a pole and nonpole gives a unique procedure for the determination of the [pi][ital NN] form factor in the model. The total contribution of the three-body force to the binding energy of the triton is found to be very small.
Form factors for semileptonic D decays
Palmer, Teresa
2013-01-01
We study the form factors for semileptonic decays of $D$-mesons. That is, we consider the matrix element of the weak left-handed quark current for the transitions $D \\rightarrow P$ and $D \\rightarrow V$, where $P$ and $V$ are light pseudoscalar or vector mesons, respectively. Our motivation to perform the present study of these form factors are future calculations of non-leptonic decay amplitudes. We consider the form factors within a class of chiral quark models. Especially, we study how the Large Energy Effective Theory (LEET) limit works for $D$-meson decays. Compared to previous work we also introduce light vector mesons $V = \\rho, K^*,...$ within chiral quark models. In order to determine some of the parameters in our model, we use existing data and results based on some other methods like lattice calculations, light-cone sum rules, and heavy-light chiral perturbation theory. We also obtain some predictions within our framework.
Pion production off the nucleon
Alam, M Rafi; Chauhan, Shikha; Singh, S K
2016-01-01
We have studied charged current neutrino/antineutrino induced weak pion production from nucleon. For the present study, contributions from $\\Delta(1232)$-resonant term, non-resonant background terms as well as contribution from higher resonances viz. $P_{11}$(1440), $D_{13}$(1520), $S_{11}$(1535), $S_{11}$(1650) and $P_{13}$(1720) are taken. To write the hadronic current for the non-resonant background terms, a microscopic approach based on SU(2) non-linear sigma model has been used. The vector form factors for the resonances are obtained from the helicity amplitudes provided by MAID. Axial coupling in the case of $\\Delta(1232)$ resonance is obtained by fitting the ANL and BNL $\
Nucleon Resonances in Kaon Photoproduction
Bennhold, C; Waluyo, A; Haberzettl, H; Penner, G; Feuster, T; Mosel, U
1999-01-01
Nucleon resonances are investigated through the electromagnetic production of K-mesons. We study the kaon photoproduction process at tree-level and compare to a recently developed unitary K-matrix approach. Employing hadronic form factors along with the proper gauge prescription yields suppression of the Born terms and leads a resonance dominated process for both K-Lambda and K-Sigma photoproduction. Using new SAPHIR data we find the K+-Lambda photoproduction to be dominated by the S11(1650) at threshold, with additional contributions from the P11(1710) and P13(1720) states. The K-Sigma channel couples to a cluster of Delta resonances around W = 1900 MeV. We briefly discuss some tantalizing evidence for a missing D13 resonance around 1900 MeV with a strong branching ratio into KLambda channel.
Color-kinematic duality for form factors
Energy Technology Data Exchange (ETDEWEB)
Boels, Rutger H.; Kniehl, Bernd A.; Tarasov, Oleg V.; Yang, Gang [Hamburg Univ. (Germany). 2. Inst. fuer Theoretische Physik
2012-12-15
Recently a powerful duality between color and kinematics has been proposed for integrands of scattering amplitudes in quite general gauge theories. In this paper the duality proposal is extended to the more general class of gauge theory observables formed by form factors. After a discussion of the general setup the existence of the duality is verified in two and three loop examples in four dimensional maximally supersymmetric Yang-Mills theory which involve the stress energy tensor multiplet. In these cases the duality reproduces known results in a particularly transparent and uniform way. As a non-trivial application we obtain a very simple form of the integrand of the four-loop two-point (Sudakov) form factor which passes a large set of unitarity cut checks.
Form factors for $B \\to \\pi l\
Riazuddin, M; Gilani, A H S; Gilani, Amjad H S
2000-01-01
The form factors for the $B-->\\pi$ transition are evaluated in the entire momentum transfer range by using the constraints obtained in the framework combining the heavy quark expansion and chiral symmetry for light quarks and the quark model. In particular, we calculate the valence quark contributions and show that it together with the equal time commutator contribution simulate a B-meson pole q^2-dependence of form factors in addition to the usual vector meson B^{*}-pole diagram for $B --> \\pi l\
$K_{l3}$ transition form factors
Ji, C R; Ji, Chueng-Ryong; Maris, Pieter
2001-01-01
The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the meson bound state amplitudes and the dressed quark-W vertex in a manifestly covariant calculation of the K_{l3} transition form factors and decay width in impulse approximation. With model gluon parameters previously fixed by the chiral condensate, the pion mass and decay constant, and the kaon mass, our results for the K_{l3} form factors and the kaon semileptonic decay width are in good agreement with the experimental data.
Wilson Loop Form Factors: A New Duality
Chicherin, Dmitry; Heslop, Paul; Korchemsky, Gregory P.; Sokatchev, Emery
2016-01-01
We find a new duality for form factors of lightlike Wilson loops in planar $\\mathcal N=4$ super-Yang-Mills theory. The duality maps a form factor involving an $n$-sided lightlike polygonal super-Wilson loop together with $m$ external on-shell states, to the same type of object but with the edges of the Wilson loop and the external states swapping roles. This relation can essentially be seen graphically in Lorentz harmonic chiral (LHC) superspace where it is equivalent to planar graph duality....
Hyperfine splitting in hydrogen with form factors
Daza, F Garcia; Nowakowski, M
2010-01-01
Proton structure corrections to the hyperfine splittings in hydrogen are evaluated using the Breit potential with electromagnetic form factors. In contrast to other methods, several new features emerge: the Breit potential with $q^2$-dependent form factors is just an extension of the standard Breit equation which gives the hyperfine Hamiltonian. Order $\\alpha^5$ corrections are obtained from a one-photon exchange amplitude and time-independent perturbation theory. Structure corrections to $D_{21} = 8 E^{2S}_{hfs} - E^{1S}_{hfs}$ start at order $\\alpha^6$. QED corrections are comparable to structure corrections which must be evaluated ab initio.
Electroexcitation of nucleon resonances
Energy Technology Data Exchange (ETDEWEB)
Inna Aznauryan, Volker D. Burkert
2012-01-01
We review recent progress in the investigation of the electroexcitation of nucleon resonances, both in experiment and in theory. The most accurate results have been obtained for the electroexcitation amplitudes of the four lowest excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV2 for the Delta(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13, respectively. These results have been confronted with calculations based on lattice QCD, large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The amplitudes for the Delta(1232) indicate large pion-cloud contributions at low Q2 and don't show any sign of approaching the pQCD regime for Q2<7 GeV2. Measured for the first time, the electroexcitation amplitudes of the Roper resonance, N(1440)P11, provide strong evidence for this state as a predominantly radial excitation of a three-quark (3q) ground state, with additional non-3-quark contributions needed to describe the low Q2 behavior of the amplitudes. The longitudinal transition amplitude for the N(1535)S11 was determined and has become a challenge for quark models. Explanations may require large meson-cloud contributions or alternative representations of this state. The N(1520)D13 clearly shows the rapid changeover from helicity-3/2 dominance at the real photon point to helicity-1/2 dominance at Q2 > 0.5 GeV2, confirming a long-standing prediction of the constituent quark model. The interpretation of the moments of resonance transition form factors in terms of transition transverse charge distributions in infinite momentum frame is presented.
Baryon form factors in chiral perturbation theory
Kubis, B; Kubis, Bastian; Meissner, Ulf-G.
2001-01-01
We analyze the electromagnetic form factors of the ground state baryon octet to fourth order in relativistic baryon chiral perturbation theory. Predictions for the \\Sigma^- charge radius and the \\Lambda-\\Sigma^0 transition moment are found to be in excellent agreement with the available experimental information. Furthermore, the convergence behavior of the hyperon charge radii is shown to be more than satisfactory.
Electromagnetic Form Factor of Charged Scalar Meson
Institute of Scientific and Technical Information of China (English)
LI Heng-Mei; CHEN Ning; WANG Zhi-Gang; WAN Shao-Long
2007-01-01
Wavefunctions and the electromagnetic form factor of charged scalar mesons are studied with the vector-vectortype flat-bottom potential model under the framework of the spinor spinor Bethe Salpeter equation. The obtained results are in agreement with other theories.
Transition Form Factors: A Unique Opportunity to Connect Non-Perturbative Strong Interactions to QCD
Energy Technology Data Exchange (ETDEWEB)
Gothe, Ralf W. [University of South Carolina, Columbia, SC (United States)
2014-01-01
Meson-photoproduction measurements and their reaction-amplitude analyses can establish more sensitively, and in some cases in an almost model-independent way, nucleon excitations and non-resonant reaction amplitudes. However, to investigate the strong interaction from explored — where meson-cloud degrees of freedom contribute substantially to the baryon structure — to still unexplored distance scales — where quark degrees of freedom dominate and the transition from dressed to current quarks occurs — we depend on experiments that allow us to measure observables that are probing this evolving non-perturbative QCD regime over its full range. Elastic and transition form factors are uniquely suited to trace this evolution by measuring elastic electron scattering and exclusive single-meson and double-pion electroproduction cross sections off the nucleon. These exclusive measurements will be extended to higher momentum transfers with the energy-upgraded CEBAF beam at JLab to study the quark degrees of freedom, where their strong interaction is responsible for the ground and excited nucleon state formations. After establishing unprecedented high-precision data, the imminent next challenge is a high-quality analysis to extract these relevant electrocoupling parameters for various resonances that then can be compared to state-of-the-art models and QCD-based calculations. Recent results will demonstrate the status of the analysis and of their theoretical descriptions, and an experimental and theoretical outlook will highlight what shall and may be achieved in the new era of the 12-GeV upgraded transition form factor program.
Study of nucleon-nucleon and hyperon-nucleon interaction
Energy Technology Data Exchange (ETDEWEB)
Shimizu, Kiyotaka [Department of Physics, Sophia University, Tokyo (Japan); Takeuchi, Sachiko [Japan College of Social Work, Kiyose (Japan); Buchmann, A.J. [Institute for Theoretical Physics, University of Tuebinge (Germany)
2000-04-01
In this paper we review recent investigations of nucleon-nucleon and hyperon-nucleon interactions employing a non-relativistic quark cluster model. We concentrate mainly on the short and medium-range behavior of the baryon-baryon interaction based on the one-gluon and meson exchange potentials. The chiral quark model based on pion and sigma exchange between quarks is also discussed. We also review a study of the deuteron and its electromagnetic properties in a quark model with exchange currents. (author)
Nucleon-Nucleon Scattering in a Three Dimensional Approach
Fachruddin, I; Glöckle, W; Elster, Ch.
2000-01-01
The nucleon-nucleon (NN) t-matrix is calculated directly as function of two vector momenta for different realistic NN potentials. To facilitate this a formalism is developed for solving the two-nucleon Lippmann-Schwinger equation in momentum space without employing a partial wave decomposition. The total spin is treated in a helicity representation. Two different realistic NN interactions, one defined in momentum space and one in coordinate space, are presented in a form suited for this formulation. The angular and momentum dependence of the full amplitude is studied and displayed. A partial wave decomposition of the full amplitude it carried out to compare the presented results with the well known phase shifts provided by those interactions.
Pion and Kaon Electromagnetic Form Factors
Bijnens, J; Bijnens, Johan; Talavera, Pere
2002-01-01
We study the electromagnetic form factor of the pion and kaons at low-energies with the use of Chiral Perturbation Theory. The analysis is performed within the three flavour framework and at next-to-next-to-leading order. We explain carefully all the relevant consistency checks on the expressions, present full analytical results for the pion form factor and describe all the assumptions in the analysis. From the phenomenological point of view we make use of our expression and the available data to obtain the charge radius of the pion obtaining $_V^\\pi=(0.452+-0.013) fm^2$, as well as the low-energy constant $L_9^r(m_\\rho)= (5.93+-0.43)10^{-3}$. We also obtain experimental values for 3 combinations of order $p^6$ constants.
CALCULATION OF KAON ELECTROMAGNETIC FORM FACTOR
Institute of Scientific and Technical Information of China (English)
WANG ZHI-GANG; WAN SHAO-LONG; WANG KE-LIN
2001-01-01
The kaon meson electromagnetic form factor is calculated in the framework of coupled Schwinger-Dyson and Bethe-Salpeter formulation in simplified impulse approximation (dressed vertex) with modified fiat-bottom potential,which is a combination of the flat-bottom potential taking into consideration the infrared and ultraviolet asymptotic behaviours of the effective quark-gluon coupling. All the numerical results give a good fit to experimental values.
On form factors and Macdonald polynomials
Lashkevich, Michael
2013-01-01
We are developing the algebraic construction for form factors of local operators in the sinh-Gordon theory proposed in [B.Feigin, M.Lashkeivch, 2008]. We show that the operators corresponding to the null vectors in this construction are given by the degenerate Macdonald polynomials with rectangular partitions and the parameters $t=-q$ on the unit circle. We obtain an integral representation for the null vectors and discuss its simple applications.
Towards a four-loop form factor
Boels, Rutger; Yang, Gang
2016-01-01
The four-loop, two-point form factor contains the first non-planar correction to the lightlike cusp anomalous dimension. This anomalous dimension is a universal function which appears in many applications. Its planar part in N = 4 SYM is known, in principle, exactly from AdS/CFT and integrability while its non-planar part has been conjectured to vanish. The integrand of the form factor of the stress-tensor multiplet in N = 4 SYM including the non-planar part was obtained in previous work. We parametrise the difficulty of integrating this integrand. We have obtained a basis of master integrals for all integrals in the four-loop, two-point class in two ways. First, we computed an IBP reduction of the integrand of the N = 4 form factor using massive computer algebra (Reduze). Second, we computed a list of master integrals based on methods of the Mint package, suitably extended using Macaulay2 / Singular. The master integrals obtained in both ways are consistent with some minor exceptions. The second method indic...
Higgs form factors in Associated Production
Isidori, Gino; CERN
2014-01-01
We further develop a form factor formalism characterizing anomalous interactions of the Higgs-like boson (h) to massive electroweak vector bosons (V) and generic bilinear fermion states (F). Employing this approach, we examine the sensitivity of pp -> F ->Vh associated production to physics beyond the Standard Model, and compare it to the corresponding sensitivity of h -> V F decays. We discuss how determining the Vh invariant-mass distribution in associated production at LHC is a key ingredient for model-independent determinations of h V F interactions. We also provide a general discussion about the power counting of the form factor's momentum dependence in a generic effective field theory approach, analyzing in particular how effective theories based on a linear and non-linear realization of the SU(2)_L x U(1)_Y gauge symmetry map into the form factor formalism. We point out how measurements of the differential spectra characterizing h -> V F decays and pp -> F -> Vh associated production could be the leadi...
New large-Nc relations among the nucleon and nucleon-to-Delta GPDs
Energy Technology Data Exchange (ETDEWEB)
Marc Vanderhaeghen; Vladimir Pascalutsa
2006-11-15
We establish relations which express the generalized parton distributions (GPDs) describing the N {yields} {Delta} transition in terms of the nucleon GPDs. These relations are based on the known large-N{sub c} relation between the N {yields} {Delta} electric quadrupole moment and the neutron charge radius, and a newly derived large-N{sub c} relation between the electric quadrupole (E2) and Coulomb quadrupole (C2) transitions. Namely, in the large-N{sub c} limit we find C2=E2. The resulting relations among the nucleon and N {yields} {Delta} GPDs provide predictions for the N {yields} {Delta} electromagnetic form factors which are found to be in very good agreement with experiment for moderate momentum transfers.
Khetarpal, P; Aznauryan, I G; Kubarovsky, V; Adhikari, K P; Adikaram, D; Aghasyan, M; Amaryan, M J; Anderson, M D; Pereira, S Anefalos; Anghinolfi, M; Avakian, H; Baghdasaryan, H; Ball, J; Baltzell, N A; Battaglieri, M; Batourine, V; Bedlinskiy, I; Biselli, A S; Bono, J; Boiarinov, S; Briscoe, W J; Brooks, W K; Burkert, V D; Carman, D S; Celentano, A; Charles, G; Cole, P L; Contalbrigo, M; Crede, V; D'Angelo, A; Dashyan, N; De Vita, R; De Sanctis, E; Deur, A; Djalali, C; Doughty, D; Dugger, M; Dupre, R; Egiyan, H; Alaoui, A El; Fassi, L El; Eugenio, P; Fedotov, G; Fegan, S; Fersch, R; Fleming, J A; Fradi, A; Gabrielyan, M Y; Garçon, M; Gevorgyan, N; Gilfoyle, G P; Giovanetti, K L; Girod, F X; Goetz, J T; Gohn, W; Golovatch, E; Gothe, R W; Griffioen, K A; Guegan, B; Guidal, M; Guo, L; Hafidi, K; Hakobyan, H; Hanretty, C; Harrison, N; Hicks, K; Ho, D; Holtrop, M; Hyde, C E; Ilieva, Y; Ireland, D G; Ishkhanov, B S; Isupov, E L; Jo, H S; Joo, K; Keller, D; Khandaker, M; Kim, A; Kim, W; Klein, F J; Koirala, S; Kubarovsky, A; Kuleshov, S V; Kvaltine, N D; Lewis, S; Livingston, K; Lu, H Y; MacGregor, I J D; Mao, Y; Martinez, D; Mayer, M; McKinnon, B; Meyer, C A; Mineeva, T; Mirazita, M; Mokeev, V; Montgomery, R A; Moutarde, H; Munevar, E; Camacho, C Munoz; Nadel-Turonski, P; Nasseripour, R; Niccolai, S; Niculescu, G; Niculescu, I; Osipenko, M; Ostrovidov, A I; Pappalardo, L L; Paremuzyan, R; Park, K; Park, S; Pasyuk, E; Phelps, E; Phillips, J J; Pisano, S; Pogorelko, O; Pozdniakov, S; Price, J W; Procureur, S; Protopopescu, D; Puckett, A J R; Raue, B A; Ricco, G; Rimal, D; Ripani, M; Rosner, G; Rossi, P; Sabatié, F; Saini, M S; Salgado, C; Saylor, N A; Schott, D; Schumacher, R A; Seder, E; Seraydaryan, H; Sharabian, Y G; Smith, G D; Sober, D I; Sokhan, D; Stepanyan, S S; Stepanyan, S; Strakovsky, I I; Strauch, S; Taiuti, M; Tang, W; Taylor, C E; Tkachenko, S; Ungaro, M; Vernarsky, B; Voskanyan, H; Voutier, E; Walford, N K; Weinstein, L B; Weygand, D P; Wood, M H; Zachariou, N; Zhang, J; Zhao, Z W; Zonta, I
2012-01-01
We report the measurement of near threshold neutral pion electroproduction cross sections and the extraction of the associated structure functions on the proton in the kinematic range $Q^2$ from 2 to 4.5 GeV$^2$ and $W$ from 1.08 to 1.16 GeV. These measurements allow us to access the dominant pion-nucleon s-wave multipoles $E_{0+}$ and $S_{0+}$ in the near-threshold region. In the light-cone sum-rule framework (LCSR), these multipoles are related to the generalized form factors $G_1^{\\pi^0 p}(Q^2)$ and $G_2^{\\pi^0 p}(Q^2)$. The data are compared to these generalized form factors and the results for $G_1^{\\pi^0 p}(Q^2)$ are found to be in good agreement with the LCSR predictions, but the level of agreement with $G_2^{\\pi^0 p}(Q^2)$ is poor.
Proton Form Factors And Related Processes in BaBar by ISR
Energy Technology Data Exchange (ETDEWEB)
Ferroli, R.B.; /Enrico Fermi Ctr., Rome /INFN, Rome
2007-02-12
BaBar has measured with unprecedented accuracy e{sup +}e{sup -} {yields} p{bar p} from the threshold up to Q{sub p{bar p}}{sup 2} {approx} 20 GeV{sup 2}/c{sup 4}, finding out an unexpected cross section, with plateaux and drops. In particular it is well established a sharp drop near threshold, where evidence for structures in multihadronic channels has also been found. Other unexpected and spectacular features of the Nucleon form factors are reminded, the behavior of space-like G{sub E}{sup p}/G{sub M}{sup p} and the neutron time-like form factors.
The one-pion-exchange potential in the three-body model of nucleon-nucleon scattering
Garcilazo, Humberto
1981-02-01
We derive the one-pion-exchange potential in the three-body model of nucleon-nucleon scattering in which the nucleon is treated as a bound state of a pion and a nucleon, and show that it has the same form as the usual Yukawa OPEP derived from field theory, except that its range is energy dependent and it becomes complex above the pion-production threshold.
Neutron electric form factor via recoil polarimetry
Energy Technology Data Exchange (ETDEWEB)
Madey, Richard; Semenov, Andrei; Taylor, Simon; Aghalaryan, Aram; Crouse, Erick; MacLachlan, Glen; Plaster, Bradley; Tajima, Shigeyuki; Tireman, William; Yan, Chenyu; Ahmidouch, Abdellah; Anderson, Brian; Asaturyan, Razmik; Baker, O; Baldwin, Alan; Breuer, Herbert; Carlini, Roger; Christy, Michael; Churchwell, Steve; Cole, Leon; Danagoulian, Samuel; Day, Donal; Elaasar, Mostafa; Ent, Rolf; Farkhondeh, Manouchehr; Fenker, Howard; Finn, John; Gan, Liping; Garrow, Kenneth; Gueye, Paul; Howell, Calvin; Hu, Bitao; Jones, Mark; Kelly, James; Keppel, Cynthia; Khandaker, Mahbubul; Kim, Wooyoung; Kowalski, Stanley; Lung, Allison; Mack, David; Manley, D; Markowitz, Pete; Mitchell, Joseph; Mkrtchyan, Hamlet; Opper, Allena; Perdrisat, Charles; Punjabi, Vina; Raue, Brian; Reichelt, Tilmann; Reinhold, Joerg; Roche, Julie; Sato, Yoshinori; Seo, Wonick; Simicevic, Neven; Smith, Gregory; Stepanyan, Samuel; Tadevosyan, Vardan; Tang, Liguang; Ulmer, Paul; Vulcan, William; Watson, John; Wells, Steven; Wesselmann, Frank; Wood, Stephen; Yan, Chen; Yang, Seunghoon; Yuan, Lulin; Zhang, Wei-Ming; Zhu, Hong Guo; Zhu, Xiaofeng
2003-05-01
The ratio of the electric to the magnetic form factor of the neutron, G_En/G_Mn, was measured via recoil polarimetry from the quasielastic d({pol-e},e'{pol-n)p reaction at three values of Q^2 [viz., 0.45, 1.15 and 1.47 (GeV/c)^2] in Hall C of the Thomas Jefferson National Accelerator Facility. Preliminary data indicate that G_En follows the Galster parameterization up to Q^2 = 1.15 (GeV/c)^2 and appears to rise above the Galster parameterization at Q^2 = 1.47 (GeV/c)^2.
TCP transcription factors: architectures of plant form.
Manassero, Nora G Uberti; Viola, Ivana L; Welchen, Elina; Gonzalez, Daniel H
2013-04-01
After its initial definition in 1999, the TCP family of transcription factors has become the focus of a multiplicity of studies related with plant development at the cellular, organ, and tissue levels. Evidence has accumulated indicating that TCP transcription factors are the main regulators of plant form and architecture and constitute a tool through which evolution shapes plant diversity. The TCP transcription factors act in a multiplicity of pathways related with cell proliferation and hormone responses. In recent years, the molecular pathways of TCP protein action and biochemical studies on their mode of interaction with DNA have begun to shed light on their mechanism of action. However, the available information is fragmented and a unifying view of TCP protein action is lacking, as well as detailed structural studies of the TCP-DNA complex. Also important, the possible role of TCP proteins as integrators of plant developmental responses to the environment has deserved little attention. In this review, we summarize the current knowledge about the structure and functions of TCP transcription factors and analyze future perspectives for the study of the role of these proteins and their use to modify plant development.
Measurements of hadron form factors at BESIII
Morales, Cristina Morales
2016-05-01
BEPCII is a symmetric e+e--collider located in Beijing running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure hadron form factors both from direct e+e--annihilation and from initial state radiation processes. In this paper, results on e+e- → p p ¯ based on data collected by BESIII in 2011 and 2012 are presented. We also present preliminary results on e+e- → Λ Λ ¯ based on the same data samples at 4 center-of-mass energies. BESIII results obtained from e+e- → π+π- using the initial state radiation technique at the center-of-mass energy of 3.773 GeV are also summarized. Finally, expectations on the measurement of baryon electromagnetic form factors from the BESIII high luminosity energy scan in 2015 and from initial state radiation processes at different center-of-mass energies are also explained.
Measurements of Hadron Form Factors at BESIII
Morales, Cristina Morales
2016-01-01
BEPCII is a symmetric $e^+e^-$-collider located in Beijing running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure hadron form factors both from direct $e^+e^-$-annihilation and from initial state radiation processes. In this paper, results on $e^+e^-\\rightarrow p\\bar{p}$ based on data collected by BESIII in 2011 and 2012 are presented. We also present preliminary results on $e^+e^-\\rightarrow \\Lambda \\bar{\\Lambda}$ based on the same data samples at 4 center-of-mass energies. BESIII results obtained from $e^+e^-\\rightarrow \\pi^+\\pi^-$ using the initial state radiation technique at the center-of-mass energy of 3.773 GeV are also summarized. Finally, expectations on the measurement of baryon electromagnetic form factors from the BESIII high luminosity energy scan in 2015 and from initial state radiation processes at different center-of-mass energies are also reported.
Holography, chiral Lagrangian and form factor relations
Zuo, Fen
2013-01-01
We perform a detailed study of mesonic properties in a class of holographic models of QCD, which is described by the Yang-Mills plus Chern-Simons action. By decomposing the 5 dimensional gauge field into resonances and integrating out the massive ones, we reproduce the Chiral Perturbative Theory Lagrangian up to ${\\cal O}(p^6)$ and obtain all the relevant low energy constants (LECs). The numerical predictions of the LECs show minor model dependence, and agree reasonably with the determinations from other approaches. Interestingly, various model-independent relations appear among them. Some of these relations are found to be the large-distance limits of universal relations between form factors of the anomalous and even-parity sectors of QCD.
Form Factors of Few-Body Systems: Point Form Versus Front Form
Gómez-Rocha, Maria; Schweiger, Wolfgang
2011-01-01
We present a relativistic point-form approach for the calculation of electroweak form factors of few-body bound states that leads to results which resemble those obtained within the covariant light-front formalism of Carbonell et al. Our starting points are the physical processes in which such form factors are measured, i.e. electron scattering off the bound state, or the semileptonic weak decay of the bound state. These processes are treated by means of a coupled-channel framework for a Bakamjian-Thomas type mass operator. A current with the correct covariance properties is then derived from the pertinent leading-order electroweak scattering or decay amplitude. As it turns out, the electromagnetic current is affected by unphysical contributions which can be traced back to wrong cluster properties inherent in the Bakamjian-Thomas construction. These spurious contributions, however, can be separated uniquely, as in the covariant light-front approach. In this way we end up with form factors which agree with tho...
Nucleon structure from 2+1-flavor dynamical DWF ensembles
Abramczyk, Michael; Lytle, Andrew; Ohta, Shigemi
2016-01-01
Nucleon isovector vector- and axialvector-current form factors, the renormalized isovector transversity and scalar charge, and the bare quark momentum and helicity moments of isovector structure functions are reported with improved statistics from two recent RBC+UKQCD 2+1-flavor dynamical domain-wall fermions ensembles: Iwasaki\\(\\times\\)DSDR gauge \\(32^3\\times64\\) at inverse lattice spacing of 1.38 GeV and pion mass of 249 and 172 MeV.
Two photon exchange in elastic electron-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Peter Blunden; Wolodymyr Melnitchouk; John Tjon
2005-06-01
A detailed study of two-photon exchange in unpolarized and polarized elastic electron-nucleon scattering is presented, taking particular account of nucleon finite size effects. Contributions from nucleon elastic intermediate states are found to have a strong angular dependence, which leads to a partial resolution of the discrepancy between the Rosenbluth and polarization transfer measurements of the proton electric to magnetic form factor ratio. The two-photon exchange contribution to the longitudinal polarization transfer ratio P{sub L} is small, whereas the contribution to the transverse polarization transfer ratio P{sub T} is enhanced at backward angles by several percent, increasing with Q{sup 2}. This gives rise to a several percent enhancement of the polarization transfer ratio P{sub T}/P{sub l} at large Q{sup 2} and backward angles. We compare the two-photon exchange effects with data on the ratio of e{sup +p} to e{sup -p} cross sections, which is predicted to be enhanced at backward angles. Finally, we evaluate the corrections to the form factors of the neutron, and estimate the elastic intermediate state contribution to the {sup 3}He form factors.
A Covariant model for the nucleon and the $\\Delta$
Ramalho, G; Gross, Franz
2008-01-01
The covariant spectator formalism is used to model the nucleon and the $\\Delta$(1232) as a system of three constituent quarks with their own electromagnetic structure. The definition of the ``fixed-axis'' polarization states for the diquark emitted from the initial state vertex and absorbed into the final state vertex is discussed. The helicity sum over those states is evaluated and seen to be covariant. Using this approach, all four electromagnetic form factors of the nucleon, together with the {\\it magnetic} form factor, $G_M^*$, for the $\\gamma N \\to \\Delta$ transition, can be described using manifestly covariant nucleon and $\\Delta$ wave functions with {\\it zero} orbital angular momentum $L$, but a successful description of $G_M^*$ near $Q^2=0$ requires the addition of a pion cloud term not included in the class of valence quark models considered here. We also show that the pure $S$-wave model gives electric, $G_E^*$, and coulomb, $G^*_C$, transition form factors that are identically zero, showing that th...
Electric form factors of the octet baryons from lattice QCD and chiral extrapolation
Energy Technology Data Exchange (ETDEWEB)
Shanahan, P.E.; Thomas, A.W.; Young, R.D.; Zanotti, J.M. [Adelaide Univ., SA (Australia). ARC Centre of Excellence in Particle Physics at the Terascale and CSSM; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics and Astronomy; Nakamura, Y. [RIKEN Advanced Institute for Computational Science, Kobe, Hyogo (Japan); Pleiter, D. [Forschungszentrum Juelich (Germany). JSC; Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Rakow, P.E.L. [Liverpool Univ. (United Kingdom). Theoretical Physics Div.; Schierholz, G. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany); Stueben, H. [Hamburg Univ. (Germany). Regionales Rechenzentrum; Collaboration: CSSM and QCDSF/UKQCD Collaborations
2014-03-15
We apply a formalism inspired by heavy baryon chiral perturbation theory with finite-range regularization to dynamical 2+1-flavor CSSM/QCDSF/UKQCD Collaboration lattice QCD simulation results for the electric form factors of the octet baryons. The electric form factor of each octet baryon is extrapolated to the physical pseudoscalar masses, after finite-volume corrections have been applied, at six fixed values of Q{sup 2} in the range 0.2-1.3 GeV{sup 2}. The extrapolated lattice results accurately reproduce the experimental form factors of the nucleon at the physical point, indicating that omitted disconnected quark loop contributions are small. Furthermore, using the results of a recent lattice study of the magnetic form factors, we determine the ratio μ{sub p}G{sub E}{sup p}/G{sub M}{sup p}. This quantity decreases with Q{sup 2} in a way qualitatively consistent with recent experimental results.
Pion transition form factor in k_T factorization
Li, Hsiang-nan
2009-01-01
It has been pointed out that the recent BaBar data on the pi gamma^* -> gamma transition form factor F_{pi gamma}(Q^2) at low (high) momentum transfer squared Q^2 indicate an asymptotic (flat) pion distribution amplitude. These seemingly contradictory observations can be reconciled in the k_T factorization theorem: the increase of the measured Q^2F_{pi gamma}(Q^2) for Q^2 > 10 GeV^2 is explained by convoluting a k_T dependent hard kernel with a flat pion distribution amplitude, k_T being a parton transverse momentum. The low Q^2 data are accommodated by including the resummation of alpha_s ln^2x, x being a parton momentum fraction, which provides a stronger suppression at the endpoints of x. The next-to-leading-order correction to the pion transition form factor is found to be less than 20% in the considered range of Q^2.
Pion transition form factor in k{sub T} factorization
Energy Technology Data Exchange (ETDEWEB)
Li, Hsiang-nan [Academica Sinica, Taipei, Taiwan (China). Inst. of Physics; Tsing-Hua Univ., Hsinchu, Taiwan (China). Dept. of Phyiscs; National Cheng-Kung Univ., Tainan, Taiwan (China). Dept. of Physics; National Cheng-Chi Univ, Taipei, Taiwan (China). Inst. of Applied Physics; Mishima, Satoshi [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2009-07-15
It has been pointed out that the recent BaBar data on the {pi}{gamma}{sup *} {yields} {gamma} transition form factor F{sub {pi}}{sub {gamma}}(Q{sup 2}) at low (high) momentum transfer squared Q{sup 2} indicate an asymptotic (flat) pion distribution amplitude. These seemingly contradictory observations can be reconciled in the k{sub T} factorization theorem: the increase of the measured Q{sup 2}FF{sub {pi}}{sub {gamma}}(Q{sup 2}) for Q{sup 2} > 10 GeV{sup 2} is explained by convoluting a k{sub T} dependent hard kernel with a flat pion distribution amplitude, k{sub T} being a parton transverse momentum. The low Q{sup 2} data are accommodated by including the resummation of {alpha}{sub s} ln{sup 2}x, x being a parton momentum fraction, which provides a stronger suppression at the endpoints of x. The next-to-leading-order correction to the pion transition form factor is found to be less than 20% in the considered range of Q{sup 2}. (orig.)
Close, Frank
1995-01-01
This talk summarises the discussions during the conference on the spin structure of the nucleon held at Erice; July 1995. The summary focuses on where we have come, where we are now, and the emerging questions that direct where we go next in the quest to understand the nucleon spin.
Nucleon distribution amplitudes from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Horsley, R. [Edinburgh Univ. (United Kingdom). School of Physics; Kaltenbrunner, T. [Deutsches Elektronen-Synchrotron (DESY), Zeuthen (DE). John von Neumann-Inst. fuer Computing NIC] (and others)
2008-04-15
We calculate low moments of the leading-twist and next-to-leading twist nucleon distribution amplitudes on the lattice using two flavors of clover fermions. The results are presented in the MS scheme at a scale of 2 GeV and can be immediately applied in phenomenological studies. We find that the deviation of the leading-twist nucleon distribution amplitude from its asymptotic form is less pronounced than sometimes claimed in the literature. (orig.)
Flavor asymmetry of the nucleon
Bijker, R
2008-01-01
The flavor asymmetry of the nucleon sea is discussed in an unquenched quark model for baryons in which the effects of quark-antiquark pairs (u anti-u, d anti-d and s anti-s) are taken into account in an explicit form. The inclusion of q anti-q pairs leads automatically to an excess of anti-d over anti-u quarks in the proton, in agreement with experimental data.
The nucleon wave function in light-front dynamics
Karmanov, V A
1998-01-01
The general spin structure of the relativistic nucleon wave function in the $3q$-model is found. It contains 16 spin components, in contrast to 8 ones known previously, since in a many-body system the parity conservation does not reduce the number of the components. The explicitly covariant form of the wave function automatically takes into account the relativistic spin rotations, without introducing any Melosh rotation matrices. It also reduces the calculations to the standard routine of the Dirac matrices and of the trace techniques. In examples of the proton magnetic moment and of the axial nucleon form factor, with a particular wave function, we reproduce the results of the standard approach. Calculations beyond the standard assumptions give different results.
Proton Form Factor Measurements at Jefferson Lab
Energy Technology Data Exchange (ETDEWEB)
Charles Perdrisat; Vina Punjabi
2004-09-27
In two experiments at Jefferson Lab in Hall A, the first one in 1998 and the second in 2000, the ratio of the electromagnetic form factors of the proton was obtained by measuring P{sub t} and P{sub ell}, the transverse and longitudinal recoil proton polarization components, respectively, in {rvec e}p {yields} e{rvec p}; the ratio G{sub E{sub p}}/G{sub M{sub p}} is proportional to P{sub t}/P{sub {ell}}. Simultaneous measurement of P{sub t} and P{sub {ell}} provides good control of the systematic uncertainty. The first measurement of G{sub E{sub p}}/G{sub M{sub p}} ratio was made to Q{sup 2} = 3.5 GeV{sup 2} and the second measurement to Q{sup 2} = 5.6 GeV{sup 2}. The results from these two experiments indicate that the ratio scales like 1/Q{sup 2}, in stark contrast with cross section data analyzed by the Rosenbluth separation method which gives a constant value for this ratio. The incompatibility of the recoil polarization results with most of the Rosenbluth separation results appears now well established above Q{sup 2} of about 3 GeV{sup 2}. The consensus at the present time is that the interference of the two-photon exchange with the Born term, which had been deemed negligible until recently, might explain the discrepancy between the results of the two techniques; the possibility that the discrepancy is due to incomplete radiative correction has also been recently discussed.
JLab Measurement of the ^{4}He Charge Form Factor at Large Momentum Transfers
Energy Technology Data Exchange (ETDEWEB)
Camsonne, Alexandre; Katramatou, A. T.; Olson, M.; Sparveris, Nikolaos; Acha, Armando; Allada, Kalyan; Anderson, Bryon; Arrington, John; Baldwin, Alan; Chen, Jian-Ping; Choi, Seonho; Chudakov, Eugene; Cisbani, Evaristo; Craver, Brandon; Decowski, Piotr; Dutta, Chiranjib; Folts, Edward; Frullani, Salvatore; Garibaldi, Franco; Gilman, Ronald; Gomez, Javier; Hahn, Brian; Hansen, Jens-Ole; Higinbotham, Douglas; Holmstrom, Timothy; Huang, Jian; Iodice, Mauro; Kelleher, Aidan; Khrosinkova, Elena; Kievsky, A.; Kuchina, Elena; Kumbartzki, Gerfried; Lee, Byungwuek; LeRose, John; Lindgren, Richard; Lott, Gordon; Lu, H.; Marcucci, Laura; Margaziotis, Demetrius; Markowitz, Pete; Marrone, Stefano; Meekins, David; Meziani, Zein-Eddine; Michaels, Robert; Moffit, Bryan; Norum, Blaine; Petratos, Gerassimos; Puckett, Andrew; Qian, Xin; Rondon-Aramayo, Oscar; Saha, Arunava; Sawatzky, Bradley; Segal, John; Hashemi, Mitra; Shahinyan, Albert; Solvignon-Slifer, Patricia; Subedi, Ramesh; Suleiman, Riad; Sulkosky, Vincent; Urciuoli, Guido; Viviani, Michele; Wang, Y.; Wojtsekhowski, Bogdan; Yan, X.; Yao, H.; Zhang, W. -M.; Zheng, X.; Zhu, L.
2014-04-01
The charge form factor of ^{4}He has been extracted in the range 29 fm^{-2} <= Q^{2} <= 77 fm^{-2} from elastic electron scattering, detecting ^{4}He nuclei and electrons in coincidence with the High Resolution Spectrometers of the Hall A Facility of Jefferson Lab. The results are in qualitative agreement with realistic meson-nucleon theoretical calculations. The data have uncovered a second diffraction minimum, which was predicted in the Q^{2} range of this experiment, and rule out conclusively long-standing predictions of dimensional scaling of high-energy amplitudes using quark counting.
Inelastic magnetic electron scattering form factors of the 26Mg nucleus
Indian Academy of Sciences (India)
Khalid S Jassim; Raad A Radhi; Najlla M Hussain
2016-01-01
Magnetic electron scattering (3) form factors with core polarization effects, energy levels and (3) values to 3+ states of the 26Mg nucleus have been studied using shell model calculations. The universal sd of the Wildenthal interaction, universal sd-shell interaction A, universal sd-shell interaction B, are used for the sd-shell orbits. Core polarization effects according to microscopic theory are taken into account by the excitations of nucleons from the (11/2 13/2 11/2) core and also from valence 15/2 21/2 13/2 orbits into higher shells, with $4\\hbar \\omega$ excitation. In form factor calculations, the universal sd-shell interaction B for the sd-shell is used with the Michigan three-range Yakawa effective NN interaction as a residual interaction for the core polarization calculations. The wave functions of the radial single-particle matrix elements have been calculated using harmonic oscillator potentials. The level schemes are compared with the experimental data up to 9.902 MeV. In this study, very good agreements are obtained for all nuclei. Results from 3 form factor calculations with the inclusion of core polarization and new -factors give good agreement with the experimental data.
Nucleon and Delta structure in continuum QCD
Cloet, Ian
2014-03-01
Quantum Chromodynamics (QCD) is the only known example in nature of a fundamental quantum field theory that is innately non-perturbative. Solving QCD will have profound implications for our understanding of the natural world, for example, it will explain how light quarks and massless gluons bind together to form the observed mesons and baryons; hence explaining the origin of more than 98% of the mass in the visible universe. Given the challenges posed by QCD, it is insufficient to study hadron ground-states alone if one seeks a solution; in this regard the delta plays a special role as the lightest baryon resonance. I will discuss recent progress using continuum QCD approaches to the study of nucleon and delta properties, with a focus on insights gained by the calculation (and measurement) of their electromagnetic form factors.
FSI corrections for near threshold meson production in nucleon-nucleon collisions
Moalem, A; Gedalin, E
1995-01-01
A procedure is proposed which accounts for final state interaction corrections for near threshold meson production in nucleon-nucleon scattering. In analogy with the Watson-Migdal approximation, it is shown that in the limit of extremely strong final state effects, the amplitude factorizes into a primary production amplitude and an elastic scattering amplitude describing a 3 \\to 3 transition. This amplitude determines the energy dependence of the reaction cross section near the reaction threshold almost solely. The approximation proposed satisfies the Fermi-Watson theorem and the coherence formalism. Application of this procedure to meson production in nucleon-nucleon scattering shows that, while corrections due to the meson-nucleon interaction are small for s-wave pion production, they are crucial for reproducing the energy dependence of the \\eta production cross section.
Energy Dependence of the πN Amplitude and the Three-Nucleon Interaction
Saito, T.-Y.; Afnan, I. R.
1995-08-01
By calculating the contribution of the ππ three-body force to the three-nucleon binding energy in terms of the πN amplitude using perturbation theory, we are able to determine the importance of the energy dependence and the contribution of the different partial waves of the πN amplitude to the three-nucleon force. A separable representation of the non-pole πN amplitude allows us to write the three-nucleon force in terms of the amplitude for NN → NN*, propagation of the NNN* system, and the amplitude for NN* → NN , with N* being the πN quasi-particle amplitude in a given state. The division of the πN amplitude into a pole and non-pole part gives a procedure for the determination of the πNN form factor within the model. The total contribution of the three-body force to the binding energy of the triton for the separable approximation to the Paris nucleon-nucleon potential (PEST) is found to be very small mainly as a result of the energy dependence of the πN amplitude, the cancellation between the S- and P-wave πN amplitudes, and the soft πNN form factor.
Electromagnetic and Strong Decays in a Collective Model of the Nucleon
Leviatan, A
1997-01-01
We present an analysis of electromagnetic elastic form factors, helicity amplitudes and strong decay widths of non-strange baryon resonances, within a collective model of the nucleon. Flavor-breaking and stretching effects are considered. Deviations from the naive three-constituents description are pointed out.
Effects of an electromagnetic quark form factor on meson properties
Energy Technology Data Exchange (ETDEWEB)
Silvestre-Brac, B. E-mail: silvestre@isn.in2p3.fr
2002-12-30
A form factor is introduced in the quark electromagnetic current. Its effect is analyzed on charge mean square radii and form factors in the mesonic sector. The decay of a vector meson into lepton-antilepton pair is also affected. Two different expressions for the form factors, and two different types of quark potential are tested and some relativistic kinematical corrections are proposed. In any case the introduction of a quark form factor greatly improves the agreement with experimental data.
The pion form factor from analyticity and unitarity
Indian Academy of Sciences (India)
B Ananthanarayan; Irinel Caprini; I Sentitemsu Imsong
2012-11-01
Analyticity and unitarity techniques are employed to estimate Taylor coefficients of the pion electromagnetic form factor at = 0 by exploiting the recently evaluated two-pion contribution to the muon ( − 2) and the phase of the pion electromagnetic form factor in the elastic region, known from scattering by Fermi–Watson theorem and the values of the form factor at several points in the space-like region. Regions in the complex -plane are isolated where the form factor cannot have zeros.
MesonNet Workshop on Meson Transition Form Factors
Eidelman, S; Hanhart, C; Kubis, B; Kupsc, A; Leupold, S; Moskal, P; Schadmand, S
2012-01-01
The mini-proceedings of the Workshop on Meson Transition Form Factors held in Cracow from May 29th to 30th, 2012 introduce the meson transition form factor project with special emphasis on the interrelations between the various form factors (on-shell, single off-shell, double off-shell). Short summaries of the talks presented at the workshop follow.
The SAMPLE Experiment and Weak Nucleon Structure
Beise, E J; Spayde, D T
2004-01-01
One of the key elements to understanding the structure of the nucleon is the role of its quark-antiquark sea in its ground state properties such as charge, mass, magnetism and spin. In the last decade, parity-violating electron scattering has emerged as an important tool in this area, because of its ability to isolate the contribution of strange quark-antiquark pairs to the nucleon's charge and magnetism. The SAMPLE experiment at the MIT-Bates Laboratory, which has been focused on s-sbar contributions to the proton's magnetic moment, was the first of such experiments and its program has recently been completed. In this paper we give an overview of some of the experimental aspects of parity-violating electron scattering, briefly review the theoretical predictions for strange quark form factors, summarize the SAMPLE measurements, and place them in context with the program of experiments being carried out at other electron scattering facilities such as Jefferson Laboratory and the Mainz Microtron.
Chou-Yang model and PHI form factor
Energy Technology Data Exchange (ETDEWEB)
Fazal-e-Aleem; Saleem, M.; Rafique, M.
1988-03-01
By using the deduced differential cross-section data for PHIp elastic scattering at 175 GeV/c in the Chou-Yang model, the PHI form factor has been computed and parametrized. Then in conjunction with the proton form factor this form factor is used in the pristine Chou-Yang model to obtain differential cross-section data at Fermilab energies. The theoretical results agree with the experimental measurements, endorsing the conjecture that the hadronic form factor of neutral particle is proportional to its magnetic form factor.
Feasibility studies for nucleon structure measurements with PANDA
Directory of Open Access Journals (Sweden)
Atomssa Ermias
2014-01-01
Full Text Available The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p̄ p → e+e− and p̄ p → π0 J/ψ → π0e+e− to extract the electromagnetic form factors of protons and π-nucleon Transition Distribution Amplitudes (π-N TDAs. After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of π-N TDAs is discussed. An estimate for the expected signal to background ratio for p̄ p → π0 J/ψ → π0e+e− that takes into account the main background source is given.
Feasibility studies for nucleon structure measurements with PANDA
Atomssa, Ermias; Ma, Binsong
2014-11-01
The study of nucleon structure is one of the main physics goals of PANDA to be built at the FAIR accelerator complex. The excellent particle identification performance of the PANDA detector will enable measurements of exclusive channels p¯ p → e+e- and p¯ p → π0 J/ψ → π0e+e- to extract the electromagnetic form factors of protons and π-nucleon Transition Distribution Amplitudes (π-N TDAs). After a brief description of the PANDA apparatus and a method to handle momentum resolution degradation due to Bremsstrahlung, the physics of π-N TDAs is discussed. An estimate for the expected signal to background ratio for p¯ p → π0 J/ψ → π0e+e- that takes into account the main background source is given.
Lattice Calculation of the Strangeness Magnetic Moment of the Nucleon
Dong, S J; Williams, A G
1998-01-01
We report on a lattice QCD calculation of the strangeness magnetic moment of the nucleon. Our result is $G_M^s(0) = - 0.36 \\pm 0.20 $. The sea contributions from the u and d quarks are about 80% larger. However, they cancel to a large extent due to their electric charges, resulting in a smaller net sea contribution of $ - 0.097 \\pm 0.037 \\mu_N$ to the nucleon magnetic moment. As far as the neutron to proton magnetic moment ratio is concerned, this sea contribution tends to cancel out the cloud-quark effect from the Z-graphs and result in a ratio of $ -0.68 \\pm 0.04$ which is close to the SU(6) relation and the experiment. The strangeness Sachs electric mean-square radius $_E$ is found to be small and negative and the total sea contributes substantially to the neutron electric form factor.
Two-pion exchange nucleon-nucleon potential Model independent features
Robilotta, Manoel R.; da Rocha, Carlos A.
1997-02-01
A chiral pion-nucleon amplitude supplemented by the HJS subthreshold coefficients is used to calculate the the long range part of the two-pion exchange nucleon-nucleon potential. In our expressions the HJS coefficients factor out, allowing a clear identification of the origin of the various contributions. A discussion of the configuration space behaviour of the loop integrals that determine the potential is presented, with emphasis on cancellations associated with chiral symmetry. The profile function for the scalar-isoscalar component of the potential is produced and shown to disagree with those of several semi-phenomenological potentials.
THE FACTORS FORMING QUALITY OF GRANULATED SUGAR
Directory of Open Access Journals (Sweden)
N. G. Kulneva
2015-01-01
Full Text Available Sugar, with good taste and high caloric, is one of the most popular human food. Consumers sugar must be sure that the sugar under normal conditions of use is of high quality and is not harmful to the health of the product. One reason for the decline in the quality of sugar is bacterial contamination. This is because the sugar industry products are good targets for the development of different groups of microorganisms, e.g., Bacillus subtilis, Clostridium perfringes, Leuconostoc dextranicum, Torula alba, Pseudomonas fluorescens, Sarcina lutea and others. These organisms are affected with beets, and then with sugar beet chips and diffusion juice fall into the processing line of sugar production. Their number in the diffusion juice varies and depends on many facto rs such as the quality of raw materials, the quality of cleaning beet root colonization of transporter-washing and the supply of water to the diffusion process, the temperature of the diffusion and others. In the diffusion unit has the most favorable conditions for the development of micro-organisms. Some of them, especially resistant bacteria and thermophilic bacteria or their spores, forming a capsule which protects against external influences occur in the final product sugar. When injected into the fresh crop of product (juice, syrup, they begin to multiply rapidly, causing difficulties in the process. The higher seeding beet microorganisms, the more they decompose and emit sucrose metabolism byproducts. To reduce the negative impact of microbiological and reduce losses from decomposition of sucrose conducted research on the possibility of using chlorine-containing substances in the sugar industry. It was established experimentally that the investigated chlorinated drug has bacteriostatic action and can be recommended for use in sugar beet production.
Park, Kijun; Adhikari, Krishna; Adikaram-Mudiyanselage, Dasuni; Anghinolfi, Marco; Baghdasaryan, Hovhannes; Ball, Jacques; Battaglieri, Marco; Baturin, Vitaly; Bedlinskiy, Ivan; Bennett, Robert; Biselli, Angela; Bookwalter, Craig; Boyarinov, Sergey; Branford, Derek; Briscoe, William; Brooks, William; Burkert, Volker; Carman, Daniel; Celentano, Andrea; Chandavar, Shloka; Charles, Gabriel; Cole, Philip; Contalbrigo, Marco; Crede, Volker; D'Angelo, Annalisa; Daniel, Aji; Dashyan, Natalya; De Vita, Raffaella; De Sanctis, Enzo; Deur, Alexandre; Djalali, Chaden; Doughty, David; Dupre, Raphael; Alaoui, Ahmed El; Elfassi, Lamiaa; Eugenio, Paul; Fedotov, Gleb; Fradi, Ahmed; Gabrielyan, Marianna; Gevorgyan, Nerses; Gilfoyle, Gerard; Giovanetti, Kevin; Girod, Francois-Xavier; Goetz, John; Gohn, Wesley; Golovach, Evgeny; Graham, Lewis; Griffioen, Keith; Guidal, Michel; Guo, Lei; Hafidi, Kawtar; Hakobyan, Hayk; Hanretty, Charles; Heddle, David; Hicks, Kenneth; Holtrop, Maurik; Ilieva, Yordanka; Ireland, David; Ishkhanov, Boris; Isupov, Evgeny; Jenkins, David; Jo, Hyon-Suk; Joo, Kyungseon; Khandaker, Mahbubul; Khetarpal, Puneet; Kim, Andrey; Kim, Wooyoung; Klein, Andreas; Klein, Franz; Kubarovsky, A; Kubarovsky, Valery; Kuhn, Sebastian; Kuleshov, Sergey; Kvaltine, Nicholas; Livingston, Kenneth; Lu, Haiyun; MacGregor, Ian; Markov, Nikolai; Mayer, Michael; McKinnon, Bryan; Mestayer, Mac; Meyer, Curtis; Mineeva, Taisiya; Mirazita, Marco; Mokeev, Viktor; Moutarde, Herve; Espitia, Edwin Munevar; Nadel-Turonski, Pawel; Nasseripour, Rakhsha; Niccolai, Silvia; Niculescu, Gabriel; Niculescu, Maria-Ioana; Osipenko, Mikhail; Ostrovidov, Alexander; Paolone, Michael; Pappalardo, Luciano; Paremuzyan, Rafayel; Park, Seungkyung; Pereira, Sergio; Phelps, Evan; Pisano, Silvia; Pogorelko, Oleg; Pozdnyakov, Sergey; Price, John; Procureur, Sebastien; Prok, Yelena; Ricco, Giovanni; Rimal, Dipak; Ripani, Marco; Ritchie, Barry; Rosner, Guenther; Rossi, Patrizia; Sabatie, Franck; Saini, Mukesh; Salgado, Carlos; Schott, Diane; Schumacher, Reinhard; Seraydaryan, Heghine; Sharabian, Youri; Smith, Elton; Smith, Gregory; Sober, Daniel; Sokhan, Daria; Stepanyan, Samuel; Stepanyan, Stepan; Stoler, Paul; Strakovski, Igor; Strauch, Steffen; Taiuti, Mauro; Tang, Wei; Taylor, Charles; Tian, Ye; Tkachenko, Svyatoslav; Trivedi, Arjun; Ungaro, Maurizio; Vernarsky, Brian; Vlasov, Alexander; Voutier, Eric; Watts, Daniel; Weygand, Dennis; Wood, Michael; Zachariou, Nicholas; Zhao, Bo; Zhao, Zhiwen; Kalantarians, N; Hyde, C E
2012-01-01
We report the first extraction of the pion-nucleon multipoles near the production threshold for the $n\\pi^+$ channel at relatively high momentum transfer ($Q^2$ up to 4.2 $\\rm{GeV^2}$). The dominance of the s-wave transverse multipole ($E_{0+}$), expected in this region, allowed us to access the generalized form factor $G_1$ within the light-cone sum rule (LCSR) framework as well as the axial form factor $G_A$. The data analyzed in this work were collected by the nearly $4\\pi$ CEBAF Large Acceptance Spectrometer (CLAS) using a 5.754 $\\rm{GeV}$ electron beam on a proton target. The differential cross section and the $\\pi-N$-multipole $E_{0+}/G_D$ were measured using two different methods, the LCSR and a direct multipole fit. The results from the two methods are found to be consistent and almost $Q^2$ independent.
The impact of s- anti s asymmetry on the strange electromagnetic form factor
Energy Technology Data Exchange (ETDEWEB)
Ghasempour Nesheli, Ali [Islamic Azad University, Department of Physics, Shiraz Branch, Shiraz (Iran, Islamic Republic of)
2016-09-15
The existence of the strange quark asymmetry in the nucleon sea has been indicated by both the experimental and theoretical analyses. Although it is well known that the s- anti s asymmetry is important for some processes in high-energy hadron collisions, it has also been indicated that it can be related to the strange Dirac form factor F{sub 1}{sup s}. In this work, we have studied the impact of s- anti s asymmetry and its uncertainty from various modern parton distribution functions (PDFs) on F{sub 1} {sup s} and compared the obtained results with the available experimental information. As a result, we found that the uncertainty in F{sub 1}{sup s}(t) due to the s(x) - anti s (x) distribution is rather large so that it dominates the model uncertainty at all values of the squared momentum transfer t. However, taking into account the uncertainties, the theoretical predictions of F{sub 1}{sup s}(t) are fully compatible with the estimate extracted from experiment. We concluded that the future accurate experimental data of the strange Dirac form factor might be used to put direct constraints on the strange content of the proton and reduce its uncertainty that has always been a challenge. (orig.)
Pion-cloud effects on the electromagnetic properties of nucleons in a quark model
Energy Technology Data Exchange (ETDEWEB)
Barik, N. (Utkal Univ., Bhubaneswar (India). Dept. of Physics); Jena, S.N. (Berhampur Univ. (India). Dept. of Physics); Rath, D.P. (Dept. of Physics, Aska Science College, ASKA-761110, Orissa (India))
1992-10-30
This paper reports that incorporating corrections for the center-of-mass motion and pion-cloud effects the nucleon electromagnetic form factors G[sup N][sub E.M] (q[sup 2]) are computed in an independent quark model based on the Dirac equation with a confining potential V[sub q](r) = (1 + [gamma][sup 0]) a 1n (r/b). The static quantities like magnetic moment [mu]n, charge radius (r[sup 2]) [sup 1/2][sub N] and axial vector coupling constant (g[sub A])[sub n [r arrow] pev] of the nucleons computed in this model are in reasonable agreement with the experiment. The pseudoscalar and the pseudovector pion-nucleon coupling constants are obtained as g[sub NN[pi
Analytical evaluation of atomic form factors: application to Rayleigh scattering
Safari, L; Amaro, P; Jänkälä, K; Fratini, F
2014-01-01
Atomic form factors are widely used for the characterization of targets and specimens, from crystallography to biology. By using recent mathematical results, here we derive an analytical expression for the atomic form factor within the independent particle model constructed from nonrelativistic screened hydrogenic wavefunctions. The range of validity of this analytical expression is checked by comparing the analytically obtained form factors with the ones obtained within the Hartee-Fock method. As an example, we apply our analytical expression for the atomic form factor to evaluate the differential cross section for Rayleigh scattering off neutral atoms.
Form factors of charged hadrons and quantum chromodynamics
Energy Technology Data Exchange (ETDEWEB)
Saleem, M.; Fazal-e-Aleem; Rashid, H.; Azhar, I.A.; Rafique, M.
1988-07-01
A new parametrization G/sup New//sub p/ of the proton form factor is proposed. It is shown that this and the conventional parametrization G/sup V//sub ..pi../ = (1-t/m/sup 2//sub p/)/sup -1/ of the pion form factor are consistent with the experimental data wherever available, with lattice-QCD-based computations for small -t, and with perturbative QCD calculations for large -t. The hyperon form factors computed by using lattice QCD are also parametrized. The features of these form factors most relevant to the Chou-Yang Model are also discussed.
The energy dependence of the $\\pi$N amplitude and the three-nucleon interaction
Saitô, T; Saito, T Y
1994-01-01
By calculating the contribution of the \\pi-\\pi three-body force to the three-nucleon binding energy in terms of the \\pi N amplitude using perturbation theory, we are able to determine the importance of the energy dependence and the contribution of the different partial waves of the \\pi N amplitude to the three-nucleon force. A separable representation of the non-pole \\pi N amplitude allows us to write the three-nucleon force in terms of the amplitude for NN\\rightarrow NN^*, propagation of the NNN^* system, and the amplitude for NN^*\\rightarrow NN, with N^* being the \\pi N quasi-particle amplitude in a given state. The division of the \\pi N amplitude into a pole and non-pole gives a procedure for the determination of the \\pi NN form factor within the model. The total contribution of the three-body force to the binding energy of the triton for the separable approximation to the Paris nucleon-nucleon potential (PEST) is found to be very small mainly as a result of the energy dependence of the \\pi N amplitude, th...
Nucleon localization and fragment formation in nuclear fission
Zhang, C. L.; Schuetrumpf, B.; Nazarewicz, W.
2016-12-01
Background: An electron localization measure was originally introduced to characterize chemical bond structures in molecules. Recently, a nucleon localization based on Hartree-Fock densities has been introduced to investigate α -cluster structures in light nuclei. Compared to the local nucleonic densities, the nucleon localization function has been shown to be an excellent indicator of shell effects and cluster correlations. Purpose: Using the spatial nucleon localization measure, we investigate the emergence of fragments in fissioning heavy nuclei. Methods: To illustrate basic concepts of nucleon localization, we employ the self-consistent energy density functional method with a quantified energy density functional optimized for fission studies. Results: We study the particle densities and spatial nucleon localization distributions along the fission pathways of 264Fm, 232Th, and 240Pu. We demonstrate that the fission fragments are formed fairly early in the evolution, well before scission. We illustrate the usefulness of the localization measure by showing how the hyperdeformed state of 232Th can be understood in terms of a quasimolecular state made of 132Sn and 100Zr fragments. Conclusions: Compared to nucleonic distributions, the nucleon localization function more effectively quantifies nucleonic clustering: its characteristic oscillating pattern, traced back to shell effects, is a clear fingerprint of cluster/fragment configurations. This is of particular interest for studies of fragment formation and fragment identification in fissioning nuclei.
Relativistic quark model for the Omega- electromagnetic form factors
Energy Technology Data Exchange (ETDEWEB)
G. Ramalho, K. Tsushima, Franz Gross
2009-08-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
A relativistic quark model for the Omega- electromagnetic form factors
Ramalho, G; Gross, Franz
2009-01-01
We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass.
Molecular form factors in X-ray crystallography
Groenewegen, P.P.M.; Feil, D.
1969-01-01
The calculation of molecular form factors from ab initio molecular electronic wavefunctions is discussed, and a scheme for application to X-ray diffraction structure analysis is given. The method is used to calculate the form factor of the NH+4 molecular ion from three accurate molecular wavefunctio
Octet baryon electromagnetic form factors in nuclear medium
Ramalho, G; Thomas, A W
2012-01-01
We study the octet baryon electromagnetic form factors in nuclear matter using the covariant spectator quark model extended to the nuclear matter regime. The parameters of the model in vacuum are fixed by the study of the octet baryon electromagnetic form factors. In nuclear matter the changes in hadron properties are calculated by including the relevant hadron masses and the modification of the pion-baryon coupling constants calculated in the quark-meson coupling model. In nuclear matter the magnetic form factors of the octet baryons are enhanced in the low $Q^2$ region, while the electric form factors show a more rapid variation with $Q^2$. The results are compared with the modification of the bound proton electromagnetic form factors observed at Jefferson Lab. In addition, the corresponding changes for the bound neutron are predicted.
Nucleon structure using lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Alexandrou, C.; Kallidonis, C. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Constantinou, M.; Hatziyiannakou, K. [Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Drach, V. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Jansen, K. [DESY Zeuthen (Germany). John von Neumann-Institut fuer Computing NIC; Cyprus Univ., Nicosia (Cyprus). Dept. of Physics; Koutsou, G.; Vaquero, A. [The Cyprus Institute, Nicosia (Cyprus). Computational-Based Science and technology Research Center; Leontiou, T. [Frederick Univ, Nicosia (Cyprus). General Dept.
2013-03-15
A review of recent nucleon structure calculations within lattice QCD is presented. The nucleon excited states, the axial charge, the isovector momentum fraction and helicity distribution are discussed, assessing the methods applied for their study, including approaches to evaluate the disconnected contributions. Results on the spin carried by the quarks in the nucleon are also presented.
Axial structure of the nucleon
Energy Technology Data Exchange (ETDEWEB)
Veronique Bernard; Latifa Elouadrhiri; Ulf-G Meissner
2002-01-01
We review the current status of experimental and theoretical understanding of the axial nucleon structure at low and moderate energies. Topics considered include (quasi)elastic (anti)neutrino-nucleon scattering, charged pion electroproduction off nucleons and ordinary as well as radiative muon capture on the proton.
Radiative corrections and parity violating electron-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
S. Barkanova; A. Aleksejevs; P.G. Blunden
2002-11-01
Radiative corrections to the parity-violating asymmetry measured in elastic electron-proton scattering are analyzed in the framework of the Standard Model. We include the complete set of one-loop contributions to one quark current amplitudes. The contribution of soft photon emission to the asymmetry is also calculated, giving final results free of infrared divergences. The one quark radiative corrections, when combines with previous work on many quark effects and recent SAMPLE experimental data, are used to place some new constraints on electroweak form factors of the nucleon.
Radiative corrections and parity-violating electron-nucleon scattering
Barkanova, S; Blunden, P G
2002-01-01
Radiative corrections to the parity-violating asymmetry measured in elastic electron-proton scattering are analyzed in the framework of the Standard Model. We include the complete set of one-loop contributions to one quark current amplitudes. The contribution of soft photon emission to the asymmetry is also calculated, giving final results free of infrared divergences. The one quark radiative corrections, when combined with previous work on many quark effects and recent SAMPLE experimental data, are used to place some new constraints on electroweak form factors of the nucleon.
Nucleon electromagnetic structure studies in the spacelike and timelike regions
Energy Technology Data Exchange (ETDEWEB)
Guttmann, Julia
2013-07-23
The thesis investigates the nucleon structure probed by the electromagnetic interaction. One of the most basic observables, reflecting the electromagnetic structure of the nucleon, are the form factors, which have been studied by means of elastic electron-proton scattering with ever increasing precision for several decades. In the timelike region, corresponding with the proton-antiproton annihilation into a electron-positron pair, the present experimental information is much less accurate. However, in the near future high-precision form factor measurements are planned. About 50 years after the first pioneering measurements of the electromagnetic form factors, polarization experiments stirred up the field since the results were found to be in striking contradiction to the findings of previous form factor investigations from unpolarized measurements. Triggered by the conflicting results, a whole new field studying the influence of two-photon exchange corrections to elastic electron-proton scattering emerged, which appeared as the most likely explanation of the discrepancy. The main part of this thesis deals with theoretical studies of two-photon exchange, which is investigated particularly with regard to form factor measurements in the spacelike as well as in the timelike region. An extraction of the two-photon amplitudes in the spacelike region through a combined analysis using the results of unpolarized cross section measurements and polarization experiments is presented. Furthermore, predictions of the two-photon exchange effects on the e{sup +}p/e{sup -}p cross section ratio are given for several new experiments, which are currently ongoing. The two-photon exchange corrections are also investigated in the timelike region in the process p anti p → e{sup +}e{sup -} by means of two factorization approaches. These corrections are found to be smaller than those obtained for the spacelike scattering process. The influence of the two-photon exchange corrections on
Energy Technology Data Exchange (ETDEWEB)
Kelleher, Aidan [College of William and Mary, Williamsburg, VA (United States)
2010-02-01
Knowledge of the electric and magnetic elastic form factors of the nucleon is essential for an understanding of nucleon structure. Of the form factors, the electric form factor of the neutron has been measured over the smallest range in Q^{2} and with the lowest precision. Jefferson Lab experiment 02-013 used a novel new polarized ^{3} He target to nearly double the range of momentum transfer in which the neutron form factor has been studied and to measure it with much higher precision. Polarized electrons were scattered off this target, and both the scattered electron and neutron were detected. G^{n} _{E} was measured to be 0.0242 ± 0.0020(stat) ± 0.0061(sys) and 0.0247 ± 0.0029(stat) ± 0.0031(sys) at Q^{2} = 1.7 and 2.5 GeV^{2} , respectively.
Probing short-range nucleon-nucleon interactions with an Electron-Ion Collider
Miller, Gerald A; Venugopalan, Raju
2015-01-01
We derive the cross-section for exclusive vector meson production in high energy deeply inelastic scattering off a deuteron target that disintegrates into a proton and a neutron carrying large relative momentum in the final state. This cross-section can be expressed in terms of a novel gluon Transition Generalized Parton Distribution (T-GPD); the hard scale in the final state makes the T-GPD sensitive to the short distance nucleon-nucleon interaction. We perform a toy model computation of this process in a perturbative framework and discuss the time scales that allow the separation of initial and final state dynamics in the T-GPD. We outline the more general computation based on the factorization suggested by the toy computation: in particular, we discuss the relative role of "point-like" and "geometric" Fock configurations that control the parton dynamics of short range nucleon-nucleon scattering. With the aid of exclusive $J/\\Psi$ production data at HERA, as well as elastic nucleon-nucleon cross-sections, w...
A note on connected formula for form factors
He, Song
2016-01-01
In this note we study the connected prescription, originally derived from Witten's twistor string theory, for tree-level form factors in ${\\cal N}=4$ super-Yang-Mills theory. The construction is based on the recently proposed four-dimensional scattering equations with $n$ massless on-shell states and one off-shell state, which we expect to work for form factors of general operators. To illustrate the universality of the prescription, we propose compact formulas for super form factors with chiral stress-tensor multiplet operator, and bosonic ones with scalar operators ${\\rm Tr}(\\phi^m)$ for arbitrary $m$.
A note on connected formula for form factors
He, Song; Liu, Zhengwen
2016-12-01
In this note we study the connected prescription, originally derived from Witten's twistor string theory, for tree-level form factors in N = 4 super-Yang-Mills theory. The construction is based on the recently proposed four-dimensional scattering equations with n massless on-shell states and one off-shell state, which we expect to work for form factors of general operators. To illustrate the universality of the prescription, we propose compact formulas for super form factors with chiral stress-tensor multiplet operator, and bosonic ones with scalar operators Tr( ϕ m ) for arbitrary m.
Roaming form factors for the tricritical to critical Ising flow
Horvath, D X; Takacs, G
2016-01-01
We study the massless flows described by the staircase model introduced by Al.B. Zamolodchikov through the analytic continuation of the sinh-Gordon S-matrix, focusing on the renormalisation group flow from the tricritical to the critical Ising model. We show that the properly defined roaming limits of certain sinh-Gordon form factors are identical to the form factors of the order and disorder operators for the massless flow. As a by-product, we also construct form factors for a semi-local field in the sinh-Gordon model, which can be associated with the twist field in the ultraviolet limiting free massless bosonic theory.
Pion Electromagnetic Form Factor at Lower and Higher Momentum Transfer
de Melo, J P B C; Tsushima, Kazuo
2016-01-01
The pion electromagnetic form factor is calculated at lower and higher momentum transfer in order to explore constituent quark models and the differences among those models. In particular, the light-front constituent quark model is utilized here to calculate the pion electromagnetic form factor at lower and higher energies. The matrix elements of the electromagnetic current, are calculated with both "plus" and "minus" components of the electromagnetic current in the light-front. Further, the electromagnetic form factor is compared with other models in the literature and experimental data.
Normalization Of Thermal-Radiation Form-Factor Matrix
Tsuyuki, Glenn T.
1994-01-01
Report describes algorithm that adjusts form-factor matrix in TRASYS computer program, which calculates intraspacecraft radiative interchange among various surfaces and environmental heat loading from sources such as sun.
nf2 contributions to fermionic four-loop form factors
Lee, Roman N.; Smirnov, Alexander V.; Smirnov, Vladimir A.; Steinhauser, Matthias
2017-07-01
We compute the four-loop contributions to the photon quark and Higgs quark form factors involving two closed fermion loops. We present analytical results for all nonplanar master integrals of the two nonplanar integral families which enter our calculation.
The connected prescription for form factors in twistor space
Brandhuber, Andreas; Panerai, Rodolfo; Spence, Bill; Travaglini, Gabriele
2016-01-01
We propose a connected prescription formula in twistor space for all tree-level form factors of the stress tensor multiplet operator in $\\mathcal{N}=4$ super Yang-Mills, which is a generalisation of the expression of Roiban, Spradlin and Volovich for superamplitudes. By introducing link variables, we show that our formula is identical to the recently proposed four-dimensional scattering equations for form factors. Similarly to the case of amplitudes, the link representation of form factors is shown to be directly related to BCFW recursion relations, and is considerably more tractable than the scattering equations. We also discuss how our results are related to a recent Grassmannian formulation of form factors, and comment on a possible derivation of our formula from ambitwistor strings.
Rare $B$ decays using lattice QCD form factors
Horgan, R R; Meinel, S; Wingate, M
2015-01-01
In this write-up we review and update our recent lattice QCD calculation of $B \\to K^*$, $B_s \\to \\phi$, and $B_s \\to K^*$ form factors [arXiv:1310.3722]. These unquenched calculations, performed in the low-recoil kinematic regime, provide a significant improvement over the use of extrapolated light cone sum rule results. The fits presented here include further kinematic constraints and estimates of additional correlations between the different form factor shape parameters. We use these form factors along with Standard Model determinations of Wilson coefficients to give Standard Model predictions for several observables [arXiv:1310.3887]. The modest improvements to the form factor fits lead to improved determinations of $F_L$, the fraction of longitudinally polarized vector mesons, but have little effect on most other observables.
The connected prescription for form factors in twistor space
Brandhuber, A.; Hughes, E.; Panerai, R.; Spence, B.; Travaglini, G.
2016-11-01
We propose a connected prescription formula in twistor space for all tree-level form factors of the stress tensor multiplet operator in {N} = 4 super Yang-Mills, which is a generalisation of the expression of Roiban, Spradlin and Volovich for superamplitudes. By introducing link variables, we show that our formula is identical to the recently proposed four-dimensional scattering equations for form factors. Similarly to the case of amplitudes, the link representation of form factors is shown to be directly related to BCFW recursion relations, and is considerably more tractable than the scattering equations. We also discuss how our results are related to a recent Grassmannian formulation of form factors, and comment on a possible derivation of our formula from ambitwistor strings.
Elastic and transition form factors of the \\Delta(1232)
Segovia, Jorge; Cloët, Ian C; Roberts, Craig D; Schmidt, Sebastian M; Wan, Shaolong
2013-01-01
Predictions obtained with a confining, symmetry-preserving treatment of a vector-vector contact interaction at leading-order in a widely used truncation of QCD's Dyson-Schwinger equations are presented for \\Delta and \\Omega baryon elastic form factors and the \\gamma N -> \\Delta transition form factors. This simple framework produces results that are practically indistinguishable from the best otherwise available, an outcome which highlights that the key to describing many features of baryons and unifying them with the properties of mesons is a veracious expression of dynamical chiral symmetry breaking in the hadron bound-state problem. The following specific results are of particular interest. The \\Delta elastic form factors are very sensitive to m_\\Delta. Hence, given that the parameters which define extant simulations of lattice-regularised QCD produce \\Delta-resonance masses that are very large, the form factors obtained therewith are a poor guide to properties of the \\Delta(1232). Considering the \\Delta-b...
Roy-Steiner-equation analysis of pion-nucleon scattering
Meißner, U.-G.; Ruiz de Elvira, J.; Hoferichter, M.; Kubis, B.
2017-03-01
Low-energy pion-nucleon scattering is relevant for many areas in nuclear and hadronic physics, ranging from the scalar couplings of the nucleon to the long-range part of two-pion-exchange potentials and three-nucleon forces in Chiral Effective Field Theory. In this talk, we show how the fruitful combination of dispersion-theoretical methods, in particular in the form of Roy-Steiner equations, with modern high-precision data on hadronic atoms allows one to determine the pion-nucleon scattering amplitudes at low energies with unprecedented accuracy. Special attention will be paid to the extraction of the pion-nucleon σ-term, and we discuss in detail the current tension with recent lattice results, as well as the determination of the low-energy constants of chiral perturbation theory.c
Hyperon decay form factors in chiral perturbation theory
Lacour, Andre; Meißner, Ulf-G
2007-01-01
We present a complete calculation of the SU(3)-breaking corrections to the hyperon vector form factors up to O(p^4) in covariant baryon chiral perturbation theory. Partial higher-order contributions are obtained, and we discuss chiral extrapolations of the vector form factor at zero momentum transfer. In addition we derive low-energy theorems for the subleading moments in hyperon decays, the weak Dirac radii and the weak anomalous magnetic moments, up to O(p^4).
Form Factors for Exclusive Semileptonic $B$--Decays
Kim, C S; Kim, Y G; Lee, K Y; Kim, Jae Kwan; Kim, Yeong Gyun; Lee, Kang Young
1996-01-01
We investigate the form factors for exclusive semileptonic decays of $B$-meson to $D,~D^*$, based on the parton picture and helped by the results of the HQET. We obtain the numerical results for the slope of the Isgur-Wise function, which is consistent with the experimental results, and we extracte the dependences of hadronic form factors on $q^2$ by varying input heavy quark fragmentation function without the nearest pole dominance ansätze.
Strange Baryon Electromagnetic Form Factors and SU(3) Flavor Symmetry Breaking
Energy Technology Data Exchange (ETDEWEB)
Lin, Huey-Wen; Orginos, Konstantinos
2009-01-01
We study the nucleon, Sigma and cascade octet baryon electromagnetic form factors and the effects of SU(3) flavor symmetry breaking from 2+1-flavor lattice calculations. We find that electric and magnetic radii are similar; the maximum discrepancy is about 10\\%. In the pion-mass region we explore, both the quark-component and full-baryon moments have small SU(3) symmetry breaking. We extrapolate the charge radii and the magnetic moments using three-flavor heavy-baryon chiral perturbation theory (HBXPT). The systematic errors due to chiral and continuum extrapolations remain significant, giving rise to charge radii for $p$ and $\\Sigma^-$ that are 3--4 standard deviations away from the known experimental ones. Within these systematics the predicted $\\Sigma^+$ and $\\Xi^-$ radii are 0.67(5) and 0.306(15)~fm$^2$ respectively. When the next-to-next-to-leading order of HBXPT is included, the extrapolated magnetic moments are less than 3 standard deviations away from PDG values, and the d
Online Soil Science Lesson 3: Soil Forming Factors
This lesson explores the five major factors of soil formation, namely: 1) climate; 2) organisms; 3) time; 4) topography; and 5) parent material and their influence in forming soil. The distinction between active and passive factors, moisture and temperature regimes, organism and topographic influen...
On a four-loop form factor in N=4
Boels, Rutger H; Yang, Gang
2016-01-01
We report on progress toward computing a four-loop supersymmetric form factor in maximally supersymmetric Yang-Mills theory. A representative example particle content from the involved supermultiplets is a stress-tensor operator with two on-shell gluons. In previous work, the integrand for this form factor was obtained using color-kinematic duality in a particularly simple form. Here the result of applying integration-by-parts identities is discussed and cross-checks of the result is performed. Rational IBP relations and their reduction are introduced as a potentially useful aide.
Wendt, Kyle
2016-03-01
How large is the 48Ca nucleus? While the electric charge distribution of this nucleus was accurately measured decades ago, both experimental and ab initio descriptions of the neutron distribution are deficient. We address this question using ab initio calculations of the electric charge, neutron, and weak distributions of 48Ca based on chiral effective field theory. Historically, chiral effective field theory calculations of systems larger than 4 nucleons have been plagued by strong systematic errors which result in theoretical descriptions that are too dense and over bound. We address these errors using a novel approach that permits us to accurately reproduce binding energy and charge radius of 48Ca, and to constrain electroweak observables such as the neutron radius, electric dipole polarizability, and the weak form factor. For a full list of contributors to this work, please see ``Neutron and weak-charge distributions of the 48Ca nucleus,'' Nature Physics (2015) doi:10.1038/nphys3529.
Ciofi degli Atti, Claudio; Mezzetti, Chiara Benedetta; Morita, Hiko
2017-04-01
Background: Two-nucleon (2 N ) short-range correlations (SRC) in nuclei have been recently thoroughly investigated, both theoretically and experimentally and the study of three-nucleon (3 N ) SRC, which could provide important information on short-range hadronic structure, is underway. Novel theoretical ideas concerning 2 N and 3 N SRC are put forward in the present paper. Purpose: The general features of a microscopic one-nucleon spectral function which includes the effects of both 2 N and 3 N SRC and its comparison with ab initio spectral functions of the three-nucleon systems are illustrated. Methods: A microscopic and parameter-free one-nucleon spectral function expressed in terms of a convolution integral involving ab initio relative and center-of-mass (c.m.) momentum distributions of a 2 N pair and aimed at describing two- and three-nucleon short-range correlations, is obtained by using: (i) the two-nucleon momentum distributions obtained within ab initio approaches based upon nucleon-nucleon interactions of the Argonne family; (ii) the exact relation between one- and two-nucleon momentum distributions; (iii) the fundamental property of factorization of the nuclear wave function at short internucleon ranges. Results: The comparison between the ab initio spectral function of 3He and the one based upon the convolution integral shows that when the latter contains only two-nucleon short-range correlations the removal energy location of the peaks and the region around them exhibited by the ab initio spectral function are correctly predicted, unlike the case of the high and low removal energy tails; the inclusion of the effects of three-nucleon correlations brings the convolution model spectral function in much better agreement with the ab initio one; it is also found that whereas the three-nucleon short-range correlations dominate the high energy removal energy tail of the spectral function, their effects on the one-nucleon momentum distribution are almost one
Tomasi-Gustafsson, E; Bijker, R; Leviatan, A; Iachello, Francesco
1999-01-01
The tensor analyzing power of the process $d + p \\to d + X$, for forward deuteron scattering in the momentum interval 3.7 to 9 GeV/c, is studied in the framework of $\\omega$ exchange in an algebraic collective model for the electroexcitation of nucleon resonances. We point out a special sensitivity of the tensor analyzing power to the isoscalar longitudinal form factor of the Roper resonance excitation. The main argument is that the $S_{11}(1535)$, $D_{13}(1520)$ and $S_{11}(1650)$ resonances have only isovector longitudinal form factors. It is the longitudinal form factor of the Roper excitation, which plays an important role in the $t-$dependence of the tensor analyzing power. We discuss possible evidence of swelling of hadrons with increasing excitation energy.
Energy Technology Data Exchange (ETDEWEB)
Tomasi-Gustafsson, E.; Rekalo, M.P. [DSM-CEA/IN2P3-CNRS, Laboratoire National Saturne, F-91191 Gif-sur-Yvette Cedex (France)]|[DAPNIA/SPhN, C.E.A./Saclay, F-91191 Gif-sur-Yvette Cedex (France); Bijker, R. [Instituto de Ciencias Nucleares, U.N.A.M., A.P. 70-543, 04510 Mexico Distrito Federal (Mexico); Leviatan, A. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Iachello, F. [Center for Theoretical Physics, Sloane Laboratory, Yale University, New Haven, Connecticut 06520-8120 (United States)
1999-03-01
The tensor analyzing power of the process d+p{r_arrow}d+X, for forward deuteron scattering in the momentum interval 3.7 to 9 GeV/c, is studied in the framework of {omega} exchange in an algebraic collective model for the electroexcitation of nucleon resonances. We point out a special sensitivity of the tensor analyzing power to the isoscalar longitudinal form factor of the Roper resonance excitation. The main argument is that the S{sub 11}(1535),thinspD{sub 13}(1520), and S{sub 11}(1650) resonances have only isovector longitudinal form factors. It is the longitudinal form factor of the Roper excitation, which plays an important role in the {ital t} dependence of the tensor analyzing power. We discuss possible evidence of swelling of hadrons with increasing excitation energy. {copyright} {ital 1999} {ital The American Physical Society}
A novel nuclear dependence of nucleon-nucleon short-range correlations
Dai, Hongkai; Huang, Yin; Chen, Xurong
2016-01-01
A linear correlation is found between the magnitude of nucleon-nucleon short-range correlations and the nuclear binding energy per nucleon with pairing energy removed. By using this relation, the strengths of nucleon-nucleon short-range correlations of some unmeasured nuclei are predicted. Discussions on nucleon-nucleon pairing energy and nucleon-nucleon short-range correlations are made. The found nuclear dependence of nucleon-nucleon short-range correlations may shed some lights on the short-range structure of nucleus.
Polarized lepton-nucleon scattering
Energy Technology Data Exchange (ETDEWEB)
Hughes, E.
1994-02-01
Deep inelastic polarized lepton-nucleon scattering is reviewed in three lectures. The first lecture covers the polarized deep inelastic scattering formalism and foundational theoretical work. The second lecture describes the nucleon spin structure function experiments that have been performed up through 1993. The third lecture discusses implication of the results and future experiments aimed at high-precision measurements of the nucleon spin structure functions.
First moments of the nucleon generalized parton distributions from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Sternbeck, A.; Goeckeler, M. [Regensburg Univ. (Germany). Inst. fuer Theoretische Physik; Haegler, P. [Mainz Univ. (DE). Inst. fuer Kernphysik] (and others)
2012-03-15
We report on our lattice calculations of the nucleon's generalized parton distributions (GPDs), concentrating on their first moments for the case of N{sub f}=2. Due to recent progress on the numerical side we are able to present results for the generalized form factors at pion masses as low as 260 MeV. We perform a fit to one-loop covariant baryon chiral perturbation theory with encouraging results.
Energy Technology Data Exchange (ETDEWEB)
Keppel, C. [Virginia Union Univ., Richmond, VA (United States)
1994-04-01
Nucleon resonance electroproduction results from SLAC Experiment E14OX are presented. A CEBAF facility with doubled energy would enable similar high momentum transfer measurements to be made with greater accuracy. Of particular interest are the Delta P{sub 33}(1232) resonance form factor and R = {sigma}{sub L}/{sigma}{sub T}, the ratio of the longitudinal and transverse components of the cross section. A suggestion is made to study these quantities in conjunction with Bloom-Gilman duality.
Parton promenade into the nucleon
Voutier, Eric
2010-01-01
Generalized parton distributions (GPDs) offer a comprehensive picture of the nucleon struture and dynamics and provide a link between microscopic and macroscopic properties of the nucleon. These quantities, which can be interpreted as the transverse distribution of partons carrying a certain longitudinal momentum fraction of the nucleon, can be accessed in deep exclusive processes. This lecture reviews the main features of the nucleon structure as obtained from elastic and inelastic lepton scatterings and unified in the context of the GPDs framework. Particular emphasis is put on the experimental methods to access these distributions and the today experimental status.
Estimates of the Nucleon Tensor Charge
Gamberg, L P; Gamberg, Leonard; Goldstein, Gary R.
2001-01-01
Like the axial vector charges, defined from the forward nucleon matrix element of the axial vector current on the light cone, the nucleon tensor charge, defined from the corresponding matrix element of the tensor current, is essential for characterizing the momentum and spin structure of the nucleon. Because there must be a helicity flip of the struck quark in order to probe the transverse spin polarization of the nucleon, the transversity distribution (and thus the tensor charge) decouples at leading twist in deep inelastic scattering, although no such suppression appears in Drell-Yan processes. This makes the tensor charge difficult to measure and its non-conservation makes its prediction model dependent. We present a different approach. Exploiting an approximate SU(6)xO(3) symmetric mass degeneracy of the light axial vector mesons (a1(1260), b1(1235) and h1(1170)) and using pole dominance, we calculate the tensor charge. The result is simple in form and depends on the decay constants of the axial vector me...
Information content of the weak-charge form factor
Reinhard, P -G; Nazarewicz, W; Agrawal, B K; Paar, N; Rocca-Maza, X
2013-01-01
Parity-violating electron scattering provides a model-independent determination of the nuclear weak-charge form factor that has widespread implications across such diverse areas as fundamental symmetries, nuclear structure, heavy-ion collisions, and neutron-star structure. We assess the impact of precise measurements of the weak-charge form factor of ${}^{48}$Ca and ${}^{208}$Pb on a variety of nuclear observables, such as the neutron skin and the electric-dipole polarizability. We use the nuclear Density Functional Theory with several accurately calibrated non-relativistic and relativistic energy density functionals. To assess the degree of correlation between nuclear observables and to explore systematic and statistical uncertainties on theoretical predictions, we employ the chi-square statistical covariance technique. We find a strong correlation between the weak-charge form factor and the neutron radius, that allows for an accurate determination of the neutron skin of neutron-rich nuclei. We determine the...
Form factor ratio from unpolarized elastic electron-proton scattering
Pacetti, Simone; Tomasi-Gustafsson, Egle
2016-11-01
A reanalysis of unpolarized electron-proton elastic scattering data is done in terms of the electric to magnetic form factor squared ratio. This observable is in principle more robust against experimental correlations and global normalizations. The present analysis shows indeed that it is a useful quantity that contains reliable and coherent information. The comparison with the ratio extracted from the measurement of the longitudinal to transverse polarization of the recoil proton in polarized electron-proton scattering shows that the results are compatible within the experimental errors. Limits are set on the kinematics where the physical information on the form factors can be safely extracted. The results presented in this work bring a decisive piece of information to the controversy on the deviation of the proton form factors from the dipole dependence.
Zero modes method and form factors in quantum integrable models
Directory of Open Access Journals (Sweden)
S. Pakuliak
2015-04-01
Full Text Available We study integrable models solvable by the nested algebraic Bethe ansatz and possessing GL(3-invariant R-matrix. Assuming that the monodromy matrix of the model can be expanded into series with respect to the inverse spectral parameter, we define zero modes of the monodromy matrix entries as the first nontrivial coefficients of this series. Using these zero modes we establish new relations between form factors of the elements of the monodromy matrix. We prove that all of them can be obtained from the form factor of a diagonal matrix element in special limits of Bethe parameters. As a result we obtain determinant representations for form factors of all the entries of the monodromy matrix.
Kaon semileptonic decay form factors with HISQ valence quarks
Gamiz, E; Bazavov, A; Bernard, C; Bouchard, C; DeTar, C; Du, D; El-Khadra, A X; Foley, J; Freeland, E D; Gottlieb, Steven; Heller, U M; Kim, J; Kronfeld, A S; Laiho, J; Levkova, L; Mackenzie, P B; Neil, E T; Oktay, M B; Qiu, Si-Wei; Simone, J N; Sugar, R; Toussaint, D; Van de Water, R S; Zhou, R
2012-01-01
We report on the status of our kaon semileptonic form factor calculations using the highly-improved staggered quark (HISQ) formulation to simulate the valence fermions. We present results for the form factor f_+^{K \\pi}(0) on the asqtad N_f=2+1 MILC configurations, discuss the chiral-continuum extrapolation, and give a preliminary estimate of the total error. We also present a more preliminary set of results for the same form factor but with the sea quarks also simulated with the HISQ action; these results include data at the physical light quark masses. The improvements that we expect to achieve with the use of the HISQ configurations and simulations at the physical quark masses are briefly discussed.
Two-Loop SL(2) Form Factors and Maximal Transcendentality
Loebbert, Florian; Wilhelm, Matthias; Yang, Gang
2016-01-01
Form factors of composite operators in the SL(2) sector of N=4 SYM theory are studied up to two loops via the on-shell unitarity method. The non-compactness of this subsector implies the novel feature and technical challenge of an unlimited number of loop momenta in the integrand's numerator. At one loop, we derive the full minimal form factor to all orders in the dimensional regularisation parameter. At two loops, we construct the complete integrand for composite operators with an arbitrary number of covariant derivatives, and we obtain the remainder functions as well as the dilatation operator for composite operators with up to three covariant derivatives. The remainder functions reveal curious patterns suggesting a hidden maximal uniform transcendentality for the full form factor. Finally, we speculate about an extension of these patterns to QCD.
Form factor and width of a quantum string
Rajantie, Arttu; Weir, David J
2012-01-01
In the Yang-Mills theory, the apparent thickness of the confining string is known to grow logarithmically when its length increases. The same logarithmic broadening also happens to strings in other quantum field theories and domain walls in statistical physics models. Even in quantum field theories, the observables used to measure and characterise this phenomenon are largely borrowed from statistical physics. In this paper, we describe it using the string form factor, which is a meaningful quantum observable, and show how the form factor can be obtained from field correlation functions calculated in lattice Monte Carlo simulations. We apply this method to 2+1-dimensional scalar theory in the strong coupling limit, where it is equivalent to the 3D Ising model, and through duality also to 2+1-dimensional $\\mathbb{Z}_2$ gauge theory. We measure the string form factor by simulating the Ising model, and demonstrate that it displays the same logarithmic broadening as statistical physics observables.
Few-nucleon systems with state-of-the-art chiral nucleon-nucleon forces
Binder, S; Epelbaum, E; Furnstahl, R J; Golak, J; Hebeler, K; Kamada, H; Krebs, H; Langhammer, J; Liebig, S; Maris, P; Meißner, U -G; Minossi, D; Nogga, A; Potter, H; Roth, R; Skibinski, R; Topolnicki, K; Vary, J P; Witala, H
2015-01-01
We apply improved nucleon-nucleon potentials up to fifth order in chiral effective field theory, along with a new analysis of the theoretical truncation errors, to study nucleon-deuteron (Nd) scattering and selected low-energy observables in 3H, 4He, and 6Li. Calculations beyond second order differ from experiment well outside the range of quantified uncertainties, providing truly unambiguous evidence for missing three-nucleon forces within the employed framework. The sizes of the required three-nucleon force contributions agree well with expectations based on Weinberg's power counting. We identify the energy range in elastic Nd scattering best suited to study three-nucleon force effects and estimate the achievable accuracy of theoretical predictions for various observables.
Maekawa, Nobuhiro; Muramatsu, Yu
2017-04-01
Recent discovery of neutrino large mixings implies the large mixings in the diagonalizing matrices of 5 bar fields in SU (5) grand unified theory (GUT), while the diagonalizing matrices of 10 fields of SU (5) are expected to have small mixings like Cabibbo-Kobayashi-Maskawa matrix. We calculate the predictions of flavor changing nucleon decays (FCND) in SU (5), SO (10), and E6 GUT models which have the above features for mixings. We found that FCND can be the main decay mode and play an important role to test GUT models.
Master integrals for the four-loop Sudakov form factor
Directory of Open Access Journals (Sweden)
Rutger H. Boels
2016-01-01
Full Text Available The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally (N=4 supersymmetric Yang–Mills theory (SYM in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. The simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was largely obtained in integrand form in a previous work for N=4 SYM, up to a free parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP identities using a modified version of Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. Moreover, two of the integral topologies vanish after reduction. The appearing master integrals are cross-checked using independent algebraic-geometry techniques explored in the Mint package. The latter results provide the basis of master integrals applicable to generic form factors, including those in Quantum Chromodynamics. Discrepancies between explicitly solving the IBP relations and the MINT approach are highlighted. Remaining bottlenecks to completing the computation of the four-loop non-planar cusp anomalous dimension in N=4 SYM and beyond are identified.
Reanalysis of Rosenbluth measurements of the proton form factors
Gramolin, Alexander; Nikolenko, Dmitry
2017-01-01
We have reanalyzed the elastic electron-proton scattering data from SLAC experiments E140 and NE11. This work was motivated by recent progress in calculating the corresponding radiative corrections and by the apparent discrepancy between the Rosenbluth and polarization transfer measurements of the proton electromagnetic form factors. New, corrected values for the scattering cross sections are presented, as well as a new form factor fit in the Q2 range from 1 to 8 . 83GeV2 . Our reanalysis brings the combined results of the SLAC experiments into better agreement with the polarization transfer data, but a significant discrepancy remains for Q2 > 3GeV2 .
Pion transition form factor through Dyson-Schwinger equations
Raya, Khépani
2016-01-01
In the framework of Dyson-Schwinger equations (DSE), we compute the $\\gamma^*\\gamma\\to\\pi^0$ transition form factor, $G(Q^2)$. For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute $G(Q^2)$ on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well-known asymptotic QCD limit, $2f_\\pi$. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Pion transition form factor through Dyson-Schwinger equations
Raya, Khépani
2016-10-01
In the framework of Dyson-Schwinger equations (DSE), we compute the γ*γ→π0 transition form factor, G(Q2). For the first time, in a continuum approach to quantun chromodynamics (QCD), it was possible to compute G(Q2) on the whole domain of space-like momenta. Our result agrees with CELLO, CLEO and Belle collaborations and, with the well- known asymptotic QCD limit, 2ƒπ. Our analysis unifies this prediction with that of the pion's valence-quark parton distribution amplitude (PDA) and elastic electromagnetic form factor.
Electromagnetic form factors of the Δ with D-waves
Energy Technology Data Exchange (ETDEWEB)
Ramalho, Gilberto T.F. [CFTP, Institute Superior Tecnico, Lisbon (Portugal); Pena, Maria Teresa [CFTP, Institute Superior Tecnico, Lisbon (Portugal); Gross, Franz L. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2010-06-01
The electromagnetic form factors of the Δ baryon are evaluated within the framework of a covariant spectator quark model, where S and D-states are included in the Δ wave function. We predict all the four Δ multipole form factors: the electric charge G_{E0}, the magnetic dipole G_{M1}, the electric quadrupole G_{E2} and the magnetic octupole G_{M3}. We compare our predictions with other theoretical calculations. Our results are compatible with the available experimental data and recent lattice QCD data.
Electromagnetic form factors of the Delta with D-waves
Ramalho, G; Gross, Franz
2010-01-01
The electromagnetic form factors of the Delta baryon are evaluated within the framework of a covariant spectator quark model, where S and D-states are included in the $\\Delta$ wave function. We predict all the four Delta multipole form factors: the electric charge GE0, the magnetic dipole GM1, the electric quadrupole GE2 and the magnetic octupole GM3. We compare our predictions with other theoretical calculations. Our results are compatible with the available experimental data and recent lattice QCD data.
Tensor form factors of the octet hyperons in QCD
kucukarslan, A; Ozpineci, A
2016-01-01
Light-cone QCD sum rules to leading order in QCD are used to investigate the tensor form factors of the $\\Sigma-\\Sigma$, $\\Xi-\\Xi$ and $ \\Sigma-\\Lambda$ transitions in the range $1 GeV^2 \\leq Q^2 \\leq 10 GeV^2$. The DAs of $\\Sigma$, $\\Xi$ and $\\Lambda$ baryon have been calculated without higher order terms. Then, study including higher order corrections have been done for $\\Sigma$ and $\\Lambda$ baryon. The result of form factors are obtained using these two DAs. We make a comparison with the predictions of the chiral quark soliton model.
Deuteron form factor measurements at low momentum transfers
Directory of Open Access Journals (Sweden)
Schlimme B. S.
2016-01-01
Full Text Available A precise measurement of the elastic electron-deuteron scattering cross section at four-momentum transfers of 0.24 fm−1 ≤ Q ≤ 2.7 fm−1 has been performed at the Mainz Microtron. In this paper we describe the utilized experimental setup and the necessary analysis procedure to precisely determine the deuteron charge form factor from these data. Finally, the deuteron charge radius rd can be extracted from an extrapolation of that form factor to Q2 = 0.
The $B\\to K^*$ form factors on the lattice
Agadjanov, Andria; Meißner, Ulf-G; Rusetsky, Akaki
2016-01-01
The extraction of the $B\\to K^*$ transition form factors from lattice data is studied, applying non-relativistic effective field theory in a finite volume. The possible mixing of $\\pi K$ and $\\eta K$ states is taken into account. The two-channel analogue of the Lellouch-L\\"uscher formula is reproduced. Due to the resonance nature of the $K^*$, an equation is derived, which allows to determine the form factors at the pole position in a process-independent manner. The infinitely-narrow width approximation of the results is discussed.
Pion Form Factor in the Light-Front
Pacheco-Bicudo-Cabral de Melo, J
2004-01-01
The pion electromagnetic form factor is calculated with a light-front quark model. The "plus" and "minus" component of the electromagnetic current are used to calculate the electromagnetic form factor in the Breit frame with two models for the q\\bar{q} vertex. The light front constituent quark models describes very well hadronic wave function for pseudo-scalar and vector particles. Symmetry problems arinsing in the light-front approach are solved by the pole dislocation method. The results are compared with new experimental data and with other quark models.
Dimensional versus cut-off renormalization and the nucleon-nucleon interaction
Ghosh, A; Talukdar, B; Ghosh, Angsula; Adhikari, Sadhan K.
1998-01-01
The role of dimensional regularization is discussed and compared with that of cut-off regularization in some quantum mechanical problems with ultraviolet divergence in two and three dimensions with special emphasis on the nucleon-nucleon interaction. Both types of renormalizations are performed for attractive divergent one- and two-term separable potentials, a divergent tensor potential, and the sum of a delta function and its derivatives. We allow energy-dependent couplings, and determine the form that these couplings should take if equivalence between the two regularization schemes is to be enforced. We also perform renormalization of an attractive separable potential superposed on an analytic divergent potential.
Dimensional versus cut-off renormalization and the nucleon-nucleon interaction
Ghosh, Angsula; Adhikari, Sadhan K.; Talukdar, B.
1998-10-01
The role of dimensional regularization is discussed and compared with that of cut-off regularization in some quantum mechanical problems with ultraviolet divergence in two and three dimensions with special emphasis on the nucleon-nucleon interaction. Both types of renormalizations are performed for attractive divergent one- and two-term separable potentials, a divergent tensor potential, and the sum of a delta function and its derivatives. We allow energy-dependent couplings, and determine the form that these couplings should take if equivalence between the two regularization schemes is to be enforced. We also perform renormalization of an attractive separable potential superposed on an analytic divergent potential.
Sudakov effects in B -> pi l nu form factors
Descotes, S
2002-01-01
In order to obtain information about the Standard Model from exclusive hadronic two-body B-decays, we have to quantify non-perturbative QCD effects. Approaches based on the factorization of mass singularities into hadronic distribution amplitudes and form factors provide a rigorous theoretical framework for the evaluation of these effects in the heavy quark limit. But it is not possible to calculate power corrections in a model-independent way, because of non-factorizing long-distance contributions. It has been argued that Sudakov effects suppress these contributions and render the corresponding corrections perturbatively calculable. In this paper we examine this claim for the related example of semileptonic B -> pi decays and conclude that it is not justified. The uncertainties in our knowledge of the mesons' distribution amplitudes imply that the calculations of the form factors are not sufficiently precise to be useful phenomenologically. Moreover, a significant contribution comes from the non-perturbative...
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Energy Technology Data Exchange (ETDEWEB)
Radyushkin, Anatoly V. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Old Dominion Univ., Norfolk, VA (United States)
2016-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion {\\it transverse momentum distribution amplitude} (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asymptotic pQCD predictions and show that in the $Q^2 \\lesssim 10$ GeV$^2$ region there is essentially no sensitivity to the shape of the pion distribution amplitude. Furthermore, the magnitude of the one-gluon exchange contribution in this region is estimated to be an order of magnitude below the Jefferson Lab data, thus leaving the Feynman mechanism as the only one relevant to the pion electromagnetic form factor behavior for accessible $Q^2$.
Pseudo-scalar form factors at three loops in QCD
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Taushif [The Institute of Mathematical Sciences, IV Cross Road,CIT Campus, Chennai 600 113, Tamil Nadu (India); Gehrmann, Thomas [Department of Physics, University of Zürich,Winterthurerstrasse 190, CH-8057 Zürich (Switzerland); Mathews, Prakash [Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar,Kolkata 700 064, West Bengal (India); Rana, Narayan; Ravindran, V. [The Institute of Mathematical Sciences, IV Cross Road,CIT Campus, Chennai 600 113, Tamil Nadu (India)
2015-11-24
The coupling of a pseudo-scalar Higgs boson to gluons is mediated through a heavy quark loop. In the limit of large quark mass, it is described by an effective Lagrangian that only admits light degrees of freedom. In this effective theory, we compute the three-loop massless QCD corrections to the form factor that describes the coupling of a pseudo-scalar Higgs boson to gluons. Due to the axial anomaly, the pseudo-scalar operator for the gluonic field strength mixes with the divergence of the axial vector current. Working in dimensional regularization and using the ’t Hooft-Veltman prescription for the axial vector current, we compute the three-loop pseudo-scalar form factors for massless quarks and gluons. Using the universal infrared factorization properties, we independently derive the three-loop operator mixing and finite operator renormalisation from the renormalisation group equation for the form factors, thereby confirming recent results in the operator product expansion. The finite part of the three-loop form factor is an important ingredient to the precise prediction of the pseudo-scalar Higgs boson production cross section at hadron colliders. We discuss potential applications and derive the hard matching coefficient in soft-collinear effective theory.
Electromagnetic Structure of Two- and Three-Nucleon Systems: An Effective Field Theory Description
Phillips, Daniel R.
2016-10-01
I discuss the use of chiral effective field theory (χEFT) to describe electromagnetic reactions in the two- and three-nucleon systems. I review the results of χEFT power counting for charge and current operators up to [Formula: see text] relative to leading order, before showing that renormalization-group arguments imply that short-distance electromagnetic operators play a larger role than suggested by this standard counting. A detailed examination of χEFT's predictions for the electromagnetic form factors of deuterium and the trinucleons, and for the threshold captures np→dγ and nd→tγ, enables a critical appraisal of the theory's performance in these contexts. Recent χEFT calculations using the [Formula: see text] chiral perturbation theory (χPT) potential yielded both form factors that agree with experimental data for Q2<0.25 GeV2 and an excellent description of the challenging threshold captures. Short-distance M1 operators are essential to this success, and the addition of a short-distance part of the nucleon-nucleon charge operator produces precise predictions of the deuteron charge and quadrupole form factors in this kinematic domain.
Energy Technology Data Exchange (ETDEWEB)
Deur, Alexandre
2009-12-01
We discuss the Jefferson Lab low momentum transfer data on moments of the nucleon spin structure functions $g_1$ and $g_2$ and on single charged pion electroproduction off polarized proton and polarized neutron. A wealth of data is now available, while more is being analyzed or expected to be taken in the upcoming years. Given the low momentum transfer selected by the experiments, these data can be compared to calculations from Chiral Perturbation theory, the effective theory of strong force that should describe it at low momentum transfer. The data on various moments and the respective calculations do not consistently agree. In particular, experimental data for higher moments disagree with the calculations.The absence of contribution from the $\\Delta$ resonance in the various observables was expected to facilitate the calculations and hence make the theory predictions either more robust or valid over a larger $Q^2$ range. Such expectation is verified only for the Bjorken sum, but not for other observables in which the $\\Delta$ is suppressed. Preliminary results on pion electroproduction off polarized nucleons are also presented and compared to phenomenological models for which contributions from different resonances are varied. Chiral Perturbation calculations of these observables, while not yet available, would be valuable and, together with these data, would provide an extensive test of the effective theory.
Burkert, Volker D
2016-01-01
Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and $\\Delta$ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger Equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of $Q^2 > 1.5GeV^2$. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degre...
Burkert, Volker D.
2016-10-01
Recent results of meson photo-production at the existing electron machines with polarized real photon beams and the measurement of polarization observables of the final state baryons have provided high precision data that led to the discovery of new excited nucleon and Δ states using multi-channel partial wave analyses procedures. The internal structure of several prominent excited states has been revealed employing meson electroproduction processes. On the theoretical front, lattice QCD is now predicting the baryon spectrum with very similar characteristics as the constituent quark model, and continuum QCD, such as is represented in the Dyson-Schwinger equations approach and in light front relativistic quark models, describes the non-perturbative behavior of resonance excitations at photon virtuality of Q^2 > 1.5 GeV^2. In this talk I discuss the need to continue a vigorous program of nucleon spectroscopy and the study of the internal structure of excited states as a way to reveal the effective degrees of freedom underlying the excited states and their dependence on the distance scale probed.
Factorization, resummation and sum rules for heavy-to-light form factors
Wang, Yu-Ming
2016-01-01
Precision calculations of heavy-to-light form factors are essential to sharpen our understanding towards the strong interaction dynamics of the heavy-quark system and to shed light on a coherent solution of flavor anomalies. We briefly review factorization properties of heavy-to-light form factors in the framework of QCD factorization in the heavy quark limit and discuss the recent progress on the QCD calculation of $B \\to \\pi$ form factors from the light-cone sum rules with the $B$-meson distribution amplitudes. Demonstration of QCD factorization for the vacuum-to-$B$-meson correlation function used in the sum-rule construction and resummation of large logarithms in the short-distance functions entering the factorization theorem are presented in detail. Phenomenological implications of the newly derived sum rules for $B \\to \\pi$ form factors are further addressed with a particular attention to the extraction of the CKM matrix element $|V_{ub}|$.
Spin-2 Form Factors at Three Loop in QCD
Ahmed, Taushif; Mathews, Prakash; Rana, Narayan; Ravindran, V
2015-01-01
Spin-2 fields are often candidates in physics beyond the Standard Model namely the models with extra-dimensions where spin-2 Kaluza-Klein gravitons couple to the fields of the SM. Also, in the context of Higgs searches, spin-2 fields have been studied as an alternative to the scalar Higgs boson. In this article, we present the complete three loop QCD radiative corrections to the spin-2 quark-antiquark and spin-2 gluon-gluon form factors in SU(N) gauge theory with $n_f$ light flavors. These form factors contribute to both quark-antiquark and gluon-gluon initiated processes involving spin-2 particle in the hadronic reactions at the LHC. We have studied the structure of infrared singularities in these form factors up to three loop level using Sudakov integro-differential equation and found that the anomalous dimensions originating from soft and collinear regions of the loop integrals coincide with those of the electroweak vector boson and Higgs form factors confirming the universality of the infrared singulariti...
Dispersive analysis of the pion transition form factor
Hoferichter, Martin; Leupold, Stefan; Niecknig, Franz; Schneider, Sebastian P
2014-01-01
We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the $e^+e^-\\to 3\\pi$ cross section, generalizing previous studies on $\\omega,\\phi\\to3\\pi$ decays and $\\gamma\\pi\\to\\pi\\pi$ scattering, and verify our result by comparing to $e^+e^-\\to\\pi^0\\gamma$ data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below 1 GeV, and extract the slope of the form factor at vanishing momentum transfer $a_\\pi=(30.7\\pm0.6)\\times 10^{-3}$. We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.
Analytic two-loop form factors in N=4 SYM
Brandhuber, Andreas; Yang, Gang
2012-01-01
We derive a compact expression for the three-point MHV form factors of half-BPS operators in N=4super Yang-Mills at two loops. The main tools of our calculation are generalised unitarity applied at the form factor level, and the compact expressions for supersymmetric tree-level form factors and amplitudes entering the cuts. We confirm that infrared divergences exponentiate as expected, and that collinear factorisation is entirely captured by an ABDK/BDS ansatz. Next, we construct the two-loop remainder function obtained by subtracting this ansatz from the full two-loop form factor and compute it numerically. Using symbology, combined with various physical constraints and symmetries, we find a unique solution for its symbol. With this input we construct a remarkably compact analytic expression for the remainder function, which contains only classical polylogarithms, and compare it to our numerical results. Furthermore, we make the surprising observation that our remainder is equal to the maximally transcendent...
Spin-2 form factors at three loop in QCD
Ahmed, Taushif; Das, Goutam; Mathews, Prakash; Rana, Narayan; Ravindran, V.
2015-12-01
Spin-2 fields are often candidates in physics beyond the Standard Model namely the models with extra-dimensions where spin-2 Kaluza-Klein gravitons couple to the fields of the Standard Model. Also, in the context of Higgs searches, spin-2 fields have been studied as an alternative to the scalar Higgs boson. In this article, we present the complete three loop QCD radiative corrections to the spin-2 quark-antiquark and spin-2 gluon-gluon form factors in SU(N) gauge theory with n f light flavors. These form factors contribute to both quark-antiquark and gluon-gluon initiated processes involving spin-2 particle in the hadronic reactions at the LHC. We have studied the structure of infrared singularities in these form factors up to three loop level using Sudakov integro-differential equation and found that the anomalous dimensions originating from soft and collinear regions of the loop integrals coincide with those of the electroweak vector boson and Higgs form factors confirming the universality of the infrared singularities in QCD amplitudes.
P and T Violating Form Factors of the Deuteron
de Vries, J.; Mereghetti, E.; Timmermans, R. G. E.; van Kolck, U.
2011-01-01
We calculate the electric-dipole and magnetic-quadrupole form factors of the deuteron that arise as a low-energy manifestation of parity and time-reversal violation in quark-gluon interactions. We consider the QCD vacuum angle and the dimension-six operators that originate from physics beyond the st
Measurement of the pion form factor at higher energies
Energy Technology Data Exchange (ETDEWEB)
Mack, D.J. [CEBAF, Newport News, VA (United States)
1994-04-01
One of the strongest arguments for increasing the nominal CEBAF beam energy to equal or exceed 6 GeV is that one would be able to make quality high Q{sup 2} measurements of the charged pion form factor.
On Form Factors and Correlation Functions in Twistor Space
Koster, Laura; Staudacher, Matthias; Wilhelm, Matthias
2016-01-01
In this paper, we continue our study of form factors and correlation functions of gauge-invariant local composite operators in the twistor-space formulation of N=4 super Yang-Mills theory. Using the vertices for these operators obtained in our recent papers arXiv:1603.04471 and arXiv:1604.00012, we show how to calculate the twistor-space diagrams for general N^kMHV form factors via the inverse soft limit, in analogy to the amplitude case. For general operators without $\\dot\\alpha$ indices, we then reexpress the NMHV form factors from the position-twistor calculation in terms of momentum twistors, deriving and expanding on a relation between the two twistor formalisms previously observed in the case of amplitudes. Furthermore, we discuss the calculation of generalized form factors and correlation functions as well as the extension to loop level, in particular providing an argument promised in arXiv:1410.6310.
Ward Identities, B-> \\rho Form Factors and |V_ub|
Gilani, A H S; Riazuddin, M; Gilani, Amjad Hussain Shah
2003-01-01
The exclusive FCNC beauty semileptonic decay B-> \\rho is studied using Ward identities in a general vector meson dominance framework, predicting vector meson couplings involved. The long distance contributions are discussed which results to obtain form factors and |V_ub|. A detailed comparison is given with other approaches.
Spin-2 form factors at three loop in QCD
Energy Technology Data Exchange (ETDEWEB)
Ahmed, Taushif [The Institute of Mathematical Sciences,IV Cross Road, CIT Campus, Chennai 600 113 (India); Das, Goutam; Mathews, Prakash [Saha Institute of Nuclear Physics,1/AF Bidhan Nagar, Kolkata 700 064 (India); Rana, Narayan; Ravindran, V. [The Institute of Mathematical Sciences,IV Cross Road, CIT Campus, Chennai 600 113 (India)
2015-12-15
Spin-2 fields are often candidates in physics beyond the Standard Model namely the models with extra-dimensions where spin-2 Kaluza-Klein gravitons couple to the fields of the Standard Model. Also, in the context of Higgs searches, spin-2 fields have been studied as an alternative to the scalar Higgs boson. In this article, we present the complete three loop QCD radiative corrections to the spin-2 quark-antiquark and spin-2 gluon-gluon form factors in SU(N) gauge theory with n{sub f} light flavors. These form factors contribute to both quark-antiquark and gluon-gluon initiated processes involving spin-2 particle in the hadronic reactions at the LHC. We have studied the structure of infrared singularities in these form factors up to three loop level using Sudakov integro-differential equation and found that the anomalous dimensions originating from soft and collinear regions of the loop integrals coincide with those of the electroweak vector boson and Higgs form factors confirming the universality of the infrared singularities in QCD amplitudes.
Electromagnetic form factors of heavy flavored vector mesons
Priyadarsini, M.; Dash, P. C.; Kar, Susmita; Patra, Sweta P.; Barik, N.
2016-12-01
We study the electromagnetic form factors of heavy flavored vector mesons such as (D*,Ds*,J /Ψ ) , (B*,Bs*,ϒ ) via one photon radiative decays (V →P γ ) in the relativistic independent quark (RIQ) model based on a flavor independent average interaction potential in the scalar vector harmonic form. The momentum dependent spacelike (q2<0 ) form factors calculated in this model are analytically continued to the physical timelike region 0 ≤q2≤(MV-MP)2 . The predicted coupling constant gV P γ=FV P(q2=0 ) for real photon case in the limit q2→0 and decay widths Γ (V →P γ ) are found in reasonable agreement with experimental data and other model predictions.
Gomez-Rocha, Maria
2014-01-01
The point-form version of the Bakamjian-Thomas construction is applied to the description of several semileptonic decays of mesons. Weak form factors are extracted without ambiguity for pseudoscalar-to-pseudoscalar as well as for pseudoscalar-to-vector transitions of mesons from the most general covariant decomposition of the weak current. No manifestation of cluster-separability violation appears in the form of non-physical contributions to the structure of such a current, in contrast to what happens in the electromagnetic case. Moreover, no frame dependence is observed when we extract the form factors from the most general covariant decomposition of the current, which contrasts with analogous front-form calculations that involve vector mesons in the transition. We present our results for heavy-light meson decays, i.e. $B\\to D$, as well as for $B$ and $D$ mesons decaying into $\\pi$, $\\rho$ and $K^{(*)}$ and perform a numerical comparison with the analogous front-form approach. Differences between point and f...
Form factors of the finite quantum XY-chain
Energy Technology Data Exchange (ETDEWEB)
Iorgov, Nikolai, E-mail: iorgov@bitp.kiev.ua [Bogolyubov Institute for Theoretical Physics, Kiev 03680 (Ukraine)
2011-08-19
Explicit factorized formulas for the matrix elements (form factors) of the spin operators {sigma}{sup x} and {sigma}{sup y} between the eigenvectors of the Hamiltonian of the finite quantum periodic XY-chain in a transverse field were derived. The derivation is based on the relations between three models: the model of quantum XY-chain, Ising model on 2D lattice and N = 2 Baxter-Bazhanov-Stroganov {tau}{sup (2)}-model. Due to these relations we transfer the formulas for the form factors of the latter model recently obtained by the use of separation of variables method to the model of quantum XY-chain. Hopefully, the formulas for the form factors will help in analysis of multipoint dynamic correlation functions at a finite temperature. As an example, we re-derive the asymptotics of the two-point correlation function in the disordered phase without the use of the Toeplitz determinants and the Wiener-Hopf factorization method.
Determination of the Charged Pion Form Factor at Q2=1.60 and 2.45 (GeV/c)2
Horn, T; Arrington, J; Barrett, B; Beise, E J; Blok, H P; Boeglin, W; Brash, E J; Breuer, H; Chang, C C; Christy, M E; Ent, R; Gaskell, D; Gibson, E; Holt, R J; Huber, G M; Jin, S; Jones, M K; Keppel, C E; Kim, W; King, P M; Kovaltchouk, V; Liu, J; Lolos, G J; Mack, D J; Margaziotis, D J; Markowitz, P; Matsumura, A; Meekins, D; Miyoshi, T; Mkrtchyan, H; Niculescu, I; Okayasu, Y; Pentchev, L; Perdrisat, C; Potterveld, D; Punjabi, V; Reimer, P; Reinhold, J; Roche, J; Roos, P G; Sarty, A; Smith, G R; Tadevosyan, V; Tang, L G; Tvaskis, V; Vidakovic, S; Volmer, J; Vulcan, W; Warren, G; Wood, S A; Xu, C; Zheng, X
2006-01-01
The H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.22 GeV. The charged pion form factor (F_pi) was extracted from the data by comparing the separated longitudinal pion electroproduction cross section to a Regge model prediction in which F_pi is a free parameter. The results indicate that the pion form factor deviates from the charge-radius constrained monopole form at these values of Q2 by one sigma, but is still far from its perturbative Quantum Chromo-Dynamics prediction.
Roy-Steiner equations for pion-nucleon scattering
Ditsche, C.; Hoferichter, M.; Kubis, B.; Meißner, U.-G.
2012-06-01
Starting from hyperbolic dispersion relations, we derive a closed system of Roy-Steiner equations for pion-nucleon scattering that respects analyticity, unitarity, and crossing symmetry. We work out analytically all kernel functions and unitarity relations required for the lowest partial waves. In order to suppress the dependence on the high energy regime we also consider once- and twice-subtracted versions of the equations, where we identify the subtraction constants with subthreshold parameters. Assuming Mandelstam analyticity we determine the maximal range of validity of these equations. As a first step towards the solution of the full system we cast the equations for the π π to overline N N partial waves into the form of a Muskhelishvili-Omnès problem with finite matching point, which we solve numerically in the single-channel approximation. We investigate in detail the role of individual contributions to our solutions and discuss some consequences for the spectral functions of the nucleon electromagnetic form factors.
Pion-nucleon scattering: from chiral perturbation theory to Roy-Steiner equations
Kubis, Bastian; Hoferichter, Martin; de Elvira, Jacobo Ruiz; Meißner, Ulf-G.
2016-11-01
Ever since Weinberg's seminal predictions of the pion-nucleon scattering amplitudes at threshold, this process has been of central interest for the study of chiral dynamics involving nucleons. The scattering lengths or the pion-nucleon σ-term are fundamental quantities characterizing the explicit breaking of chiral symmetry by means of the light quark masses. On the other hand, pion-nucleon dynamics also strongly affects the long-range part of nucleon-nucleon potentials, and hence has a far-reaching impact on nuclear physics. We discuss the fruitful combination of dispersion-theoretical methods, in the form of Roy-Steiner equations, with chiral dynamics to determine pion-nucleon scattering amplitudes at low energies with high precision.*
Effective nucleon mass and the nuclear caloric curve
Shetty, D V; Galanopoulos, S; Yennello, S J
2009-01-01
Assuming a schematic form of the nucleon effective mass as a function of nuclear excitation energy and mass, we provide a simple explanation for understanding the experimentally observed mass dependence of the nuclear caloric curve. It is observed that the excitation energy at which the caloric curve enters into a plateau region, could be sensitive to the nuclear mass evolution of the effective nucleon mass.
Three pion nucleon coupling constants
Arriola, E Ruiz; Perez, R Navarro
2016-01-01
There exist four pion nucleon coupling constants, $f_{\\pi^0, pp}$, $-f_{\\pi^0, nn}$, $f_{\\pi^+, pn} /\\sqrt{2}$ and $ f_{\\pi^-, np} /\\sqrt{2}$ which coincide when up and down quark masses are identical and the electron charge is zero. While there is no reason why the pion-nucleon-nucleon coupling constants should be identical in the real world, one expects that the small differences might be pinned down from a sufficiently large number of independent and mutually consistent data. Our discussion provides a rationale for our recent determination $$f_p^2 = 0.0759(4) \\, , \\quad f_{0}^2 = 0.079(1) \\,, \\quad f_{c}^2 = 0.0763(6) \\, , $$ based on a partial wave analysis of the $3\\sigma$ self-consistent nucleon-nucleon Granada-2013 database comprising 6713 published data in the period 1950-2013.
Factors Affecting the Form of Substitute Family Care
Directory of Open Access Journals (Sweden)
Monika Chrenková
2015-11-01
Full Text Available Recently, the system of care for endangered children has changed from the institutional as well as legislative point of view. In one of the partial areas of ongoing changes, research activities realised within the Students’ Grant Competition called The Factors Affecting the Form of Substitute Family Care are being focused. We deal with this topic because various forms of substitute family care are distinguished in the Czech Republic, where children are placed for various reasons, but we do not know the correct context of such placements. The main aim of the realised research was to find out the frequency of choosing a given form of placing children in substitute family care according to followed variables. The research sample of the quantitative research was consisted of children placed in one of the forms of substitute family care in the Moravian-Silesian region.
Nucleon Resonance Excitation with Virtual Photons
Tiator, L
2007-01-01
The unitary isobar model MAID is used for a partial wave analysis of pion photoproduction and electroproduction data on the nucleon. In particular we have taken emphasis on the region of the Delta(1232) resonance and have separated the resonance and background amplitudes with the K-matrix approach. This leads to electromagnetic properties of the dressed Delta resonance, where all multipole amplitudes become purely imaginary and all form factors and helicity amplitudes become purely real at the K-matrix pole of W=M_Delta=1232 MeV. The REM=E2/M1 and RSM=C2/M1 ratios of the quadrupole excitation are compared to recent data analysis of different groups. The REM ratio of MAID2005 agrees very well with the data and has a linear behavior over the whole experimentally explored Q^2 region with a small positive slope that predicts a zero crossing around 3.5 GeV^2. The recent RSM data for Q^2 < 0.2 GeV^2 indicate a qualitative change in the shape of the ratio which can be explained by the impact of the Siegert theore...
Master integrals for the four-loop Sudakov form factor
Boels, Rutger; Yang, Gang
2016-01-01
The light-like cusp anomalous dimension is a universal function in the analysis of infrared divergences. In maximally ($\\mathcal{N}=4$) supersymmetric Yang-Mills theory (SYM) in the planar limit, it is known, in principle, to all loop orders. The non-planar corrections are not known in any theory, with the first appearing at the four-loop order. Probably the simplest quantity which contains this correction is the four-loop two-point form factor of the stress tensor multiplet. This form factor was obtained in integrand form in a previous work for $\\mathcal{N}=4$ SYM, up to a single parameter. In this work, a reduction of the appearing integrals obtained by solving integration-by-parts (IBP) identities using (a tweaked version of) Reduze is reported. The form factor is shown to be independent of the remaining parameter at integrand level due to an intricate pattern of cancellations after IBP reduction. The appearing master integrals are cross-checked using algebraic techniques explored in the Mint package. The ...
Pseudo-scalar Form Factors at Three Loops in QCD
Ahmed, Taushif; Mathews, Prakash; Rana, Narayan; Ravindran, V
2015-01-01
The coupling of a pseudo-scalar Higgs boson to gluons is mediated through a heavy quark loop. In the limit of large quark mass, it is described by an effective Lagrangian that only admits light degrees of freedom. In this effective theory, we compute the three-loop massless QCD corrections to the form factor that describes the coupling of a pseudo-scalar Higgs boson to gluons. Due to the axial anomaly, the pseudo-scalar operator for the gluonic field strength mixes with the divergence of the axial vector current. Working in dimensional regularization and using the 't~Hooft-Veltman prescription for the axial vector current, we compute the three-loop pseudo-scalar form factors for massless quarks and gluons. Using the universal infrared factorization properties, we independently derive the three-loop operator mixing and finite operator renormalisation from the renormalisation group equation for the form factors, thereby confirming recent results in the operator product expansion. The finite part of the three-lo...
Pion Electromagnetic Form Factor in Virtuality Distribution Formalism
Radyushkin, A V
2015-01-01
We discuss two applications of the {\\it Virtuality Distribution Amplitudes} (VDA) formalism developed in our recent papers. We start with an overview of the main properties of the pion distribution amplitude emphasizing the quantitative measures of its width, and possibility to access them through the pion transition form factor studies. We formulate the basic concepts of the VDA approach and introduce the pion transverse momentum distribution amplitude (TMDA) which plays, in a covariant Lagrangian formulation, a role similar to that of the pion wave function in the 3-dimensional Hamiltonian light-front approach. We propose simple factorized models for soft TMDAs, and use them to describe existing data on the pion transition form factor, thus fixing the scale determining the size of the transverse-momentum effects. Finally, we apply the VDA approach to the one-gluon exchange contribution for the pion electromagnetic form factor. We observe a very late $Q^2 \\gtrsim 20$ GeV$^2$ onset of transition to the asympt...
Form factors for B --> $\\pi$l$\\overline{\
Burford, D R; Flynn, J M; Gough, B J; Hazel, N M; Nieves, J; Shanahan, H P; Burford, D R; Duong, H D; Flynn, J M; Gough, B J; Hazel, N M; Nieves, J; Shanahan, H P
1995-01-01
We present a unified method for analysing form factors in B -> pi l nu-bar_l and B -> K* gamma decays. The analysis provides consistency checks on the q^2 and 1/M extrapolations necessary to obtain the physical decay rates. For the first time the q^2 dependence of the form factors is obtained at the B scale. In the B -> pi l nu-bar_l case, we show that pole fits to f^+ may not be consistent with the q^2 behaviour of f^0, leading to a possible factor of two uncertainty in the decay rate and hence in the value of |V_{ub}|^2 deduced from it. For B -> K* gamma, from the combined analysis of form factors T_1 and T_2, we find the hadronisation ratio R_{K^*} of the exclusive B -> K* gamma to the inclusive b -> s gamma rates is of order 35% or 15% for constant and pole-type behaviour of T_2 respectively.
A Quark Transport Theory to describe Nucleon--Nucleon Collisions
Kalmbach, U; Biro, T S; Mosel, U
1993-01-01
On the basis of the Friedberg-Lee model we formulate a semiclassical transport theory to describe the phase-space evolution of nucleon-nucleon collisions on the quark level. The time evolution is given by a Vlasov-equation for the quark phase-space distribution and a Klein-Gordon equation for the mean-field describing the nucleon as a soliton bag. The Vlasov equation is solved numerically using an extended testparticle method. We test the confinement mechanism and mean-field effects in 1+1 dimensional simulations.
Probing short-range nucleon-nucleon interactions with an electron-ion collider
Miller, Gerald A.; Sievert, Matthew D.; Venugopalan, Raju
2016-04-01
We derive the cross section for exclusive vector meson production in high-energy deeply inelastic scattering off a deuteron target that disintegrates into a proton and a neutron carrying large relative momentum in the final state. This cross section can be expressed in terms of a novel gluon transition generalized parton distribution (T-GPD); the hard scale in the final state makes the T-GPD sensitive to the short-distance nucleon-nucleon interaction. We perform a toy model computation of this process in a perturbative framework and discuss the time scales that allow the separation of initial- and final-state dynamics in the T-GPD. We outline the more general computation based on the factorization suggested by the toy computation: In particular, we discuss the relative role of "pointlike" and "geometric" Fock configurations that control the parton dynamics of short-range nucleon-nucleon scattering. With the aid of exclusive J /ψ production data at the Hadron-Electron Ring Accelerator at DESY, as well as elastic nucleon-nucleon cross sections, we estimate rates for exclusive deuteron photodisintegration at a future Electron-Ion Collider (EIC). Our results, obtained using conservative estimates of EIC integrated luminosities, suggest that center-of-mass energies sNN˜12 GeV2 of the neutron-proton subsystem can be accessed. We argue that the high energies of the EIC can address outstanding dynamical questions regarding the short-range quark-gluon structure of nuclear forces by providing clean gluon probes of such "knockout" exclusive reactions in light and heavy nuclei.
Generalised form factor dark matter in the Sun
Vincent, Aaron C.; Serenelli, Aldo; Scott, Pat
2015-08-01
We study the effects of energy transport in the Sun by asymmetric dark matter with momentum and velocity-dependent interactions, with an eye to solving the decade-old Solar Abundance Problem. We study effective theories where the dark matter-nucleon scattering cross-section goes as vrel2n and q2n with n = -1, 0, 1 or 2, where vrel is the dark matter-nucleon relative velocity and q is the momentum exchanged in the collision. Such cross-sections can arise generically as leading terms from the most basic nonstandard DM-quark operators. We employ a high-precision solar simulation code to study the impact on solar neutrino rates, the sound speed profile, convective zone depth, surface helium abundance and small frequency separations. We find that the majority of models that improve agreement with the observed sound speed profile and depth of the convection zone also reduce neutrino fluxes beyond the level that can be reasonably accommodated by measurement and theory errors. However, a few specific points in parameter space yield a significant overall improvement. A 3-5 GeV DM particle with σSI propto q2 is particularly appealing, yielding more than a 6σ improvement with respect to standard solar models, while being allowed by direct detection and collider limits. We provide full analytical capture expressions for q- and vrel-dependent scattering, as well as complete likelihood tables for all models.
η' transition form factor from space- and timelike experimental data
Escribano, R.; Gonzàlez-Solís, S.; Masjuan, P.; Sanchez-Puertas, P.
2016-09-01
The η' transition form factor is reanalyzed in view of the recent first observation by BESIII of the Dalitz decay η'→γ e+e- in both space- and timelike regions at low and intermediate energies using the Padé approximants method. The present analysis provides a suitable parametrization for reproducing the measured form factor in the whole energy region and allows one to extract the corresponding low-energy parameters together with a prediction of their values at the origin, related to Γη'→γ γ , and the asymptotic limit. The η - η' mixing is reassessed within a mixing scheme compatible with the large-Nc chiral perturbation theory at next-to-leading order, with particular attention to the Okubo-Zweig-Iizuka-rule-violating parameters. The J /ψ , Z →η(')γ decays are also considered and predictions are reported.
On Form Factors in N=4 SYM Theory and Polytopes
Bork, L V
2014-01-01
In this paper we discuss different recursion relations (BCFW and all-line shift) for the form factors of the operators from the $\\mathcal{N}=4$ SYM stress-tensor current supermultiplet $T^{AB}$ in momentum twistor space. We show that cancelations of spurious poles and equivalence between different types of recursion relations can be naturally understood using geometrical interpretation of the form factors as special limit of the volumes of polytopes in $\\mathbb{C}\\mathbb{P}^4$ in close analogy with the amplitude case. We also show how different relations for the IR pole coefficients can be easily derived using momentum twistor representation. This opens an intriguing question - which of powerful on-shell methods and ideas can survive off-shell ?
Measurement of the gamma gamma* -> pi0 transition form factor
Energy Technology Data Exchange (ETDEWEB)
Aubert, B.
2009-06-02
We study the reaction e{sup +}e{sup -} {yields} e{sup +}e{sup -}{pi}{sup 0} in the single tag mode and measure the differential cross section d{sigma}/dQ{sup 2} and the {gamma}{gamma}* {yields} {pi}{sup 0} transition form factor in the mometum transfer range from 4 to 40 GeV{sup 2}. At Q{sup 2} > 10 GeV{sup 2} the measured form factor exceeds the asymptotic limit predicted by perturbative QCD. The analysis is based on 442 fb{sup -1} of integrated luminosity collected at PEP-II with the BABAR detector at e{sup +}e{sup -} center-of-mass energies near 10.6 GeV.
A reanalysis of Rosenbluth measurements of the proton form factors
Gramolin, A V
2016-01-01
We present a reanalysis of the data from SLAC experiments E140 [R. C. Walker et al., Phys. Rev. D 49, 5671 (1994)] and NE11 [L. Andivahis et al., Phys. Rev. D 50, 5491 (1994)] on elastic electron-proton scattering. This work is motivated by recent progress in calculating the corresponding radiative corrections and by the apparent discrepancy between the Rosenbluth and polarization transfer measurements of the proton electromagnetic form factors. New, corrected values for the scattering cross sections are presented, as well as a new form factor fit in the $Q^2$ range from 1 to 8.83 $\\text{GeV}^2$. We also provide a complete set of revised formulas to account for radiative corrections in single-arm measurements of unpolarized elastic electron-proton scattering.
Reanalysis of Rosenbluth measurements of the proton form factors
Gramolin, A. V.; Nikolenko, D. M.
2016-05-01
We present a reanalysis of the data from Stanford Linear Accelerator Center (SLAC) experiments E140 [R. C. Walker et al., Phys. Rev. D 49, 5671 (1994), 10.1103/PhysRevD.49.5671] and NE11 [L. Andivahis et al., Phys. Rev. D 50, 5491 (1994), 10.1103/PhysRevD.50.5491] on elastic electron-proton scattering. This work is motivated by recent progress in calculating the corresponding radiative corrections and by the apparent discrepancy between the Rosenbluth and polarization transfer measurements of the proton electromagnetic form factors. New, corrected values for the scattering cross sections are presented, as well as a new form factor fit in the Q2 range from 1 to 8.83 GeV2. We also provide a complete set of revised formulas to account for radiative corrections in single-arm measurements of unpolarized elastic electron-proton scattering.
Form factors for semi-leptonic B decays
Zhou, Ran; Bailey, Jon A; Du, Daping; El-Khadra, Aida X; Jain, R D; Kronfeld, Andreas S; Van de Water, Ruth S; Liu, Yuzhi; Meurice, Yannick
2012-01-01
We report on form factors for the B->K l^+ l^- semi-leptonic decay process. We use several lattice spacings from a=0.12 fm down to 0.06 fm and a variety of dynamical quark masses with 2+1 flavors of asqtad quarks provided by the MILC Collaboration. These ensembles allow good control of the chiral and continuum extrapolations. The b-quark is treated as a clover quark with the Fermilab interpretation. We update our results for f_\\parallel and f_\\perp, or, equivalently, f_+ and f_0. In addition, we present new results for the tensor form factor f_T. Model independent results are obtained based upon the z-expansion.
Two-photon transition form factor of c ¯ quarkonia
Chen, Jing; Ding, Minghui; Chang, Lei; Liu, Yu-xin
2017-01-01
The two-photon transition of c ¯c quarkonia are studied within a covariant approach based on the consistent truncation scheme of the quantum chromodynamics Dyson-Schwinger equation for the quark propagator and the Bethe-Salpeter equation for the mesons. We find the decay widths of ηc→γ γ and χc 0 ,2→γ γ in good agreement with experimental data. The obtained transition form factor of ηc→γ γ* for a wide range of spacelike photon-momentum-transfer squared is also in agreement with the experimental findings of the BABAR experiment. As a by-product, the decay widths of ηb,χb 0 ,2→γ γ and the transition form factor of ηb,χc 0 ,b 0→γ γ* are predicted, which await experimental testing.
Massive three-loop form factor in the planar limit
Henn, Johannes; Smirnov, Vladimir A; Steinhauser, Matthias
2016-01-01
We compute the three-loop QCD corrections to the massive quark-anti-quark-photon form factors $F_1$ and $F_2$ in the large-$N_c$ limit. The analytic results are expressed in terms of Goncharov polylogarithms. This allows for a straightforward numerical evaluation. We also derive series expansions, including power suppressed terms, for three kinematic regions corresponding to small and large invariant masses of the photon momentum, and small velocities of the heavy quarks.
FACTORS AFFECTING FORMING PRECISION IN PATTERNLESS CASTING MANUFACTURING
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The patternless casting manufacturing(PCM) technique adopts a new method of double scanning which combines the principle of discreteness and deposition with the resin-bonded sand technique.Two main factors, the liquid penetration regularities in the space between particles and the shape and dimension of the agglomeration unit body, are studied qualitatively and quantitatively.This provides the theoretical basis for selecting the forming technical parameters.The experiments verify the analysis.
Calculation of the π Meson Electromagnetic Form Factor
Institute of Scientific and Technical Information of China (English)
王志刚; 汪克林; 完绍龙
2001-01-01
The modified flat-bottom potential (MFBP) is given by the combination of the flat-bottom potential with considerations for the infrared and ultraviolet asymptotic behaviour of the effective quark-gluon coupling. The πmeson electromagnetic form factor is calculated in the framework of the coupled Schwinger-Dyson equation andthe Bethe-Salpeter equation in the simplified impulse approximation (dressed vertex) with the MFBP. All ournumerical results give a good fit to experimental values.
Low Energy Constants from Kl4 Form-Factors
Amorós, G; Talavera, P
2000-01-01
We have calculated the form-factors F and G in K ---> pi pi e nu decays (Kl4) to two-loop order in Chiral Perturbation Theory (ChPT). Combining this together with earlier two-loop calculations an updated set of values for the L's, the ChPT constants at p^4, is obtained. We discuss the uncertainties in the determination and the changes compared to previous estimates.
Modern Youth Sub-Cultures: Characteristic Features, Forming Factors
Directory of Open Access Journals (Sweden)
D A Koltunov
2011-09-01
Full Text Available The growing complexity of today's world, faster social and technological innovations and the resulting impossibility to explain the universe in terms of the classical, traditional systems lead to the emergence of new social and cultural patterns, behavioral standards and particular thinking which make up new sub-cultural paradigms. In this article the author attempts to identify the basic factors forming youth sub-cultures and define their peculiar features in contemporary Russian society.
Strong CP violation and the neutron electric dipole form factor
Kuckei, J; Faessler, A; Gutsche, T; Kovalenko, S; Lyubovitskij, V E; Pumsa-ard, K; Dib, Claudio; Faessler, Amand; Gutsche, Th.; Kovalenko, Sergey
2005-01-01
We calculate the neutron electric dipole form factor induced by the CP violating theta-term of QCD, within a perturbative chiral quark model which includes pion and kaon clouds. On this basis we derive the neutron electric dipole moment and the electron-neutron Schiff moment. From the existing experimental upper limits on the neutron electric dipole moment we extract constraints on the theta-parameter and compare our results with other approaches.
Pion transverse charge density from timelike form factor data
Energy Technology Data Exchange (ETDEWEB)
Gerald Miller, Mark Strikman, Christian Weiss
2011-01-01
The transverse charge density in the pion can be represented as a dispersion integral of the imaginary part of the pion form factor in the timelike region. This formulation incorporates information from e+e- annihilation experiments and allows one to reconstruct the transverse density much more accurately than from the spacelike pion form factor data alone. We calculate the transverse density using an empirical parametrization of the timelike pion form factor and estimate that it is determined to an accuracy of ~10% at a distance b ~ 0.1 fm, and significantly better at larger distances. The density is found to be close to that obtained from a zero-width rho meson pole over a wide range and shows a pronounced rise at small distances. The resulting two-dimensional image of the fast-moving pion can be interpreted in terms of its partonic structure in QCD. We argue that the singular behavior of the charge density at the center requires a substantial presence of pointlike configurations in the pion's partonic wave function, which can be probed in other high-momentum transfer processes.
Finite volume form factors and correlation functions at finite temperature
Pozsgay, Balázs
2009-01-01
In this thesis we investigate finite size effects in 1+1 dimensional integrable QFT. In particular we consider matrix elements of local operators (finite volume form factors) and vacuum expectation values and correlation functions at finite temperature. In the first part of the thesis we give a complete description of the finite volume form factors in terms of the infinite volume form factors (solutions of the bootstrap program) and the S-matrix of the theory. The calculations are correct to all orders in the inverse of the volume, only exponentially decaying (residual) finite size effects are neglected. We also consider matrix elements with disconnected pieces and determine the general rule for evaluating such contributions in a finite volume. The analytic results are tested against numerical data obtained by the truncated conformal space approach in the Lee-Yang model and the Ising model in a magnetic field. In a separate section we also evaluate the leading exponential correction (the $\\mu$-term) associate...
Convergent and discriminant validity of the Five Factor Form.
Rojas, Stephanie L; Widiger, Thomas A
2014-04-01
The current study tests the convergent and discriminant validity of a modified version of the Five Factor Model Rating Form (FFMRF), a one-page, brief measure of the five-factor model. The Five Factor Form (FFF) explicitly identifies maladaptive variants for both poles of each of the 30 facets of the FFMRF. The purpose of the current study was to test empirically whether this modified version still provides a valid assessment of the FFM, as well as to compare its validity as a measure of the FFM to other brief FFM measures. Two independent samples of 510 and 330 community adults were sampled, one third of whom had a history of some form of mental health treatment. The FFF was compared with three abbreviated and/or brief measures of the FFM (i.e., the FFMRF, the Ten Item Personality Inventory, and the Big Five Inventory), a more extended measure (i.e., International Personality Item Pool-NEO), an alternative measure of general personality (i.e., the HEXACO-Personality Inventory-Revised), and a measure of maladaptive personality functioning (i.e., the Personality Inventory for Diagnostic and Statistical Manual of Mental Disorders, 5th edition). The results of the current study demonstrated convergent and discriminant validity, even at the single-item facet level. © The Author(s) 2013.
Measurement of $K_{e3}^{0}$ form factors
Lai, A; Bevan, A; Dosanjh, R S; Gershon, T J; Hay, B; Kalmus, George Ernest; Lazzeroni, C; Munday, D J; Olaiya, E; Parker, M A; White, T O; Wotton, S A; Barr, G; Bocquet, G; Ceccucci, A; Çuhadar-Dönszelmann, T; Cundy, Donald C; D'Agostini, G; Doble, Niels T; Falaleev, V; Gatignon, L; Gonidec, A; Gorini, B; Govi, G; Grafström, P; Kubischta, Werner; Lacourt, A; Norton, A; Palestini, S; Panzer-Steindel, B; Taureg, H; Velasco, M; Wahl, H; Cheshkov, C; Khristov, P Z; Kekelidze, Vladimir D; Litov, L; Madigozhin, D T; Molokanova, N A; Potrebenikov, Yu K; Stoynev, S; Zinchenko, A I; Knowles, I; Martin, V; Sacco, R; Walker, A; Contalbrigo, M; Dalpiaz, Pietro; Duclos, J; Frabetti, P L; Gianoli, A; Martini, M; Petrucci, F; Savrié, M; Bizzeti, A; Calvetti, M; Collazuol, G; Graziani, G; Iacopini, E; Lenti, M; Martelli, F; Veltri, M; Becker, H G; Eppard, K; Eppard, M; Fox, H; Kalter, A; Kleinknecht, K; Koch, U; Köpke, L; Lopes da Silva, P; Marouelli, P; Pellmann, I A; Peters, A; Renk, B; Schmidt, S A; Schönharting, V; Schué, Yu; Wanke, R; Winhart, A; Wittgen, M; Chollet, J C; Fayard, L; Iconomidou-Fayard, L; Ocariz, J; Unal, G; Wingerter-Seez, I; Anzivino, Giuseppina; Cenci, P; Imbergamo, E; Lubrano, P; Mestvirishvili, A; Nappi, A; Pepé, M; Piccini, M; Bertanza, L; Carosi, R; Casali, R; Cerri, C; Cirilli, M; Costantini, F; Fantechi, R; Giudici, Sergio; Mannelli, I; Pierazzini, G M; Sozzi, M; Chèze, J B; Cogan, J; De Beer, M; Debu, P; Formica, A; Granier de Cassagnac, R; Mazzucato, E; Peyaud, B; Turlay, René; Vallage, B; Holder, M; Maier, A; Ziolkowski, M; Arcidiacono, R; Biino, C; Cartiglia, N; Marchetto, F; Menichetti, E; Pastrone, N; Nassalski, J P; Rondio, Ewa; Szleper, M; Wislicki, W; Wronka, S; Dibon, Heinz; Fischer, G; Jeitler, Manfred; Markytan, Manfred; Mikulec, I; Neuhofer, G; Pernicka, M; Taurok, A; Widhalm, L
2004-01-01
The semileptonic decay of the neutral K meson KL -> pi+-e-+v (Ke3), was used to study the strangeness-changing weak interaction of hadrons. A sample of 5.6 million reconstructed events recorded by the NA48 experiment was used to measure the Dalitz plot density. Admitting all possible Lorentz-covariant couplings, the form factors for vector (f+(q^2)), scalar (fs) and tensor (fT) interactions were measured. The linear slope of the vector form factor lambda+=0.0284+-0.0007+-0.0013 and values for the ratios fs/f+(0)=0.015+0.007-0.010 +-0.012 and fT/f+(0)=0.05+0.03-0.04 +-0.03 were obtained. The values for fS and for fT are consistent with zero. Assuming only Vector-Axial vector couplings, lambda+ = 0.02888 +- 0.0004 +- 0.0011 and a good fit consistent with pure V-A couplings were obtained. Alternatively a fit to a dipole form factor yields a pole mass of M = 859 +- 18 MeV, consistent with the K*(892) mass.
Helicity non-conserving form factor of the proton
Energy Technology Data Exchange (ETDEWEB)
Voutier, E.; Furget, C.; Knox, S. [Universite Joseph Fourier, Grenoble (France)] [and others
1994-04-01
The study of the hadron structure in the high Q{sup 2} range contributes to the understanding of the mechanisms responsible for the confinement of quarks and gluons. Among the numerous experimental candidates sensitive to these mechanisms, the helicity non-conserving form factor of the proton is a privileged observable since it is controlled by non-perturbative effects. The authors investigate here the feasibility of high Q{sup 2} measurements of this form factor by means of the recoil polarization method in the context of the CEBAF 8 GeV facility. For that purpose, they discuss the development of a high energy proton polarimeter, based on the H({rvec p},pp) elastic scattering, to be placed at the focal plane of a new hadron spectrometer. It is shown that this experimental method significantly improves the knowledge of the helicity non-conserving form factor of the proton up to 10 GeV{sup 2}/c{sup 2}.
$\\pi_{e3}$ form factor $f_{-}$ near mass shell
Krivoruchenko, M I
2014-01-01
Generalized Ward-Takahashi identity (gWTI) in the pion sector for broken isotopic symmetry is derived and used for the model-independent calculation of the longitudinal form factor $f_{-}$ of the $\\pi_{e3}$ vector vertex. The on-shell $f_{-}$ is found to be proportional to the mass difference of pions and the difference between vector isospin $ T = 1 $ and scalar isospin $ T = 2 $ pion radii. A numerical estimate of the form factor gives a value two times higher than the earlier estimate in the quark model. Off-shell form factors are known to be ambiguous because of the gauge dependence and the freedom in parameterization of the fields. The near-mass-shell $f_{-}$ appears to be an exception, allowing the experimental verification of the gWTI consequences. We calculate the near-mass-shell $f_{-}$ using the gWTI and dispersion techniques. The results are discussed in the context of the conservation of vector current (CVC) condition.
Meson Transition Form Factors in Light-Front Holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; Cao, Fu-Guang; /Massey U.; de Teramond, Guy F.; /Costa Rica U.
2011-06-22
We study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The Chern-Simons action, which is a natural form in 5-dimensional anti-de Sitter (AdS) space, leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the q{bar q} component of the pion wavefunction, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0} {yields} {gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the q{bar q} component of the pion wavefunction P{sub q{bar q}} = 0.5 is required; thus giving indication that the contributions from higher Fock states in the pion light-front wavefunction need to be included in the analysis. The probability for the Fock state containing four quarks (anti-quarks) which follows from analyzing the hadron matrix elements, P{sub q{bar q}q{bar q}} {approx} 10%, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wavefunction. The results for the TFFs for the {eta} and {eta}{prime} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{prime} TFFs.
Meson Transition Form Factors in Light-Front Holographic QCD
Energy Technology Data Exchange (ETDEWEB)
Brodsky, Stanley J.; /SLAC; Cao, Fu-Guang; /Massey U.; de Teramond, Guy F.; /Costa Rica U.
2011-06-22
We study the photon-to-meson transition form factors (TFFs) F{sub M{gamma}}(Q{sup 2}) for {gamma}{gamma}* {yields} M using light-front holographic methods. The Chern-Simons action, which is a natural form in 5-dimensional anti-de Sitter (AdS) space, leads directly to an expression for the photon-to-pion TFF for a class of confining models. Remarkably, the predicted pion TFF is identical to the leading order QCD result where the distribution amplitude has asymptotic form. The Chern-Simons form is local in AdS space and is thus somewhat limited in its predictability. It only retains the q{bar q} component of the pion wavefunction, and further, it projects out only the asymptotic form of the meson distribution amplitude. It is found that in order to describe simultaneously the decay process {pi}{sup 0} {yields} {gamma}{gamma} and the pion TFF at the asymptotic limit, a probability for the q{bar q} component of the pion wavefunction P{sub q{bar q}} = 0.5 is required; thus giving indication that the contributions from higher Fock states in the pion light-front wavefunction need to be included in the analysis. The probability for the Fock state containing four quarks (anti-quarks) which follows from analyzing the hadron matrix elements, P{sub q{bar q}q{bar q}} {approx} 10%, agrees with the analysis of the pion elastic form factor using light-front holography including higher Fock components in the pion wavefunction. The results for the TFFs for the {eta} and {eta}{prime} mesons are also presented. The rapid growth of the pion TFF exhibited by the BABAR data at high Q{sup 2} is not compatible with the models discussed in this article, whereas the theoretical calculations are in agreement with the experimental data for the {eta} and {eta}{prime} TFFs.
Statistical Error analysis of Nucleon-Nucleon phenomenological potentials
Perez, R Navarro; Arriola, E Ruiz
2014-01-01
Nucleon-Nucleon potentials are commonplace in nuclear physics and are determined from a finite number of experimental data with limited precision sampling the scattering process. We study the statistical assumptions implicit in the standard least squares fitting procedure and apply, along with more conventional tests, a tail sensitive quantile-quantile test as a simple and confident tool to verify the normality of residuals. We show that the fulfilment of normality tests is linked to a judicious and consistent selection of a nucleon-nucleon database. These considerations prove crucial to a proper statistical error analysis and uncertainty propagation. We illustrate these issues by analyzing about 8000 proton-proton and neutron-proton scattering published data. This enables the construction of potentials meeting all statistical requirements necessary for statistical uncertainty estimates in nuclear structure calculations.
Induced Hyperon-Nucleon-Nucleon Interactions and the Hyperon Puzzle
Wirth, Roland
2016-01-01
We present the first ab initio calculations for $p$-shell hypernuclei including hyperon-nucleon-nucleon (YNN) contributions induced by a Similarity Renormalization Group transformation of the initial hyperon-nucleon interaction. The transformation including the YNN terms conserves the spectrum of the Hamiltonian while drastically improving model-space convergence of the Importance-Truncated No-Core Shell Model, allowing a precise extraction of binding and excitation energies. Results using a hyperon-nucleon interaction at leading order in chiral effective field theory for lower- to mid-$p$-shell hypernuclei show a good reproduction of experimental excitation energies while hyperon binding energies are typically overestimated. The induced YNN contributions are strongly repulsive and we show that they are related to a decoupling of the $\\Sigma$ hyperons from the hypernuclear system, i.e., a suppression of the $\\Lambda$-$\\Sigma$ conversion terms in the Hamiltonian. This is linked to the so-called hyperon puzzle ...
Thomas, Anthony William
2001-01-01
As the only stable baryon, the nucleon is of crucial importance in particle physics. Since the nucleon is a building block for all atomic nuclei, there is a need to analyse the its structure in order to fully understand the essential properties of all atomic nuclei. After more than forty years of research on the nucleon, both the experimental and theoretical situations have matured to a point where a synthesis of the results becomes indispensable. Here, A.W. Thomas and W. Weise present a unique report on the extensive empirical studies, theoretical foundations and the different models of t
Nucleon-Nucleon Scattering From Fully-Dynamical Lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Konstantinos Orginos; Martin Savage; Paulo Bedaque; Silas Beane
2006-07-01
We present results of the first fully-dynamical lattice QCD determination of nucleon-nucleon scattering lengths in the 1 S0 channel and 3 S1 - 3 D1 coupled channels. The calculations are performed with domain-wall valence quarks on the MILC staggered configurations with lattice spacing of b = 0.125 fm in the isospin-symmetric limit, and in the absence of electromagnetic interactions
High Precision Measurement of the Proton Elastic Form Factor Ratio at Low Q^{2}
Energy Technology Data Exchange (ETDEWEB)
Zhan, Xiaohui [Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2010-01-01
Experiment E08-007 measured the proton elastic form factor ratio μ_{p}G_{E}/G_{M} in the range of Q^{2} = 0.3-0.7(GeV/c)^{2} by recoil polarimetry. Data were taken in 2008 at the Thomas Jefferson National Accelerator Facility in Virginia, USA. A 1.2 GeV polarized electron beam was scattered off a cryogenic hydrogen target. The recoil proton was detected in the left HRS in coincidence with the elasticly scattered electrons tagged by the BigBite spectrometer. The proton polarization was measured by the focal plane polarimeter (FPP). In this low Q^{2} region, previous measurement from Jefferson Lab Hall A (LEDEX) along with various fits and calculations indicate substantial deviations of the ratio from unity. For this new measurement, the proposed statistical uncertainty (< 1%) was achieved. These new results are a few percent lower than expected from previous world data and fits, which indicate a smaller G_{Ep} at this region. Beyond the intrinsic interest in nucleon structure, the new results also have implications in determining the proton Zemach radius and the strangeness form factors from parity violation experiments.
Electromagnetic rho-meson form factors in point-form relativistic quantum mechanics
Biernat, Elmar P
2014-01-01
The relativistic point-form formalism which we proposed for the study of the electroweak structure of few-body bound states is applied to calculate the elastic form factors of spin-1 mesons, such as the rho, within constituent-quark models. We treat electron-meson scattering as a Poincare-invariant coupled-channel problem for a Bakamjian-Thomas mass operator and extract the meson current from the resulting invariant 1-photon-exchange amplitude. Wrong cluster properties inherent in the Bakamjian-Thomas framework are seen to cause spurious contributions in the current. These contributions, however, can be separated unambiguously from the physical ones and we end up with a meson current with all required properties. Numerical results for the rho-meson form factors are presented assuming a simple harmonic-oscillator bound-state wave function. The comparison with other approaches reveals a remarkable agreement of our results with those obtained within the covariant light-front scheme proposed by Carbonell et al.
Proceedings of RIKEN BNL Research Center Workshop: Brookhaven Summer Program on Nucleon Spin Physics
Energy Technology Data Exchange (ETDEWEB)
Aschenauer, A.; Qiu, Jianwei; Vogelsang, W.; Yuan, F.
2011-08-02
Understanding the structure of the nucleon is of fundamental importance in sub-atomic physics. Already the experimental studies on the electro-magnetic form factors in the 1950s showed that the nucleon has a nontrivial internal structure, and the deep inelastic scattering experiments in the 1970s revealed the partonic substructure of the nucleon. Modern research focuses in particular on the spin and the gluonic structure of the nucleon. Experiments using deep inelastic scattering or polarized p-p collisions are carried out in the US at the CEBAF and RHIC facilities, respectively, and there are other experimental facilities around the world. More than twenty years ago, the European Muon Collaboration published their first experimental results on the proton spin structure as revealed in polarized deep inelastic lepton-nucleon scattering, and concluded that quarks contribute very little to the proton's spin. With additional experimental and theoretical investigations and progress in the following years, it is now established that, contrary to naive quark model expectations, quarks and anti-quarks carry only about 30% of the total spin of the proton. Twenty years later, the discovery from the polarized hadron collider at RHIC was equally surprising. For the phase space probed by existing RHIC experiments, gluons do not seem to contribute any to the proton's spin. To find out what carries the remaining part of proton's spin is a key focus in current hadronic physics and also a major driving force for the new generation of spin experiments at RHIC and Jefferson Lab and at a future Electron Ion Collider. It is therefore very important and timely to organize a series of annual spin physics meetings to summarize the status of proton spin physics, to focus the effort, and to layout the future perspectives. This summer program on 'Nucleon Spin Physics' held at Brookhaven National Laboratory (BNL) on July 14-27, 2010 [http://www.bnl.gov/spnsp/] is the
Lattice QCD Calculation of Nucleon Structure
Energy Technology Data Exchange (ETDEWEB)
Liu, Keh-Fei [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy; Draper, Terrence [University of Kentucky, Lexington, KY (United States). Dept. of Physics and Astronomy
2016-08-30
It is emphasized in the 2015 NSAC Long Range Plan that "understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out first-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large-scale computer simulation. We started out by calculating the nucleon form factors -- electromagnetic, axial-vector, πNN, and scalar form factors, the quark spin contribution to the proton spin, the strangeness magnetic moment, the quark orbital angular momentum, the quark momentum fraction, and the quark and glue decomposition of the proton momentum and angular momentum. The first round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical effects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge configurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at ~ 300 MeV and obtained the strange form factors, charm and strange quark masses, the charmonium spectrum and the D_{s} meson decay constant f_{Ds}, the strangeness and charmness, the meson mass
Lattice QCD Calculation of Nucleon Structure
Energy Technology Data Exchange (ETDEWEB)
Liu, Keh-Fei; Draper, Terrence
2016-08-30
It is emphasized in the 2015 NSAC Long Range Plan [1] that \\understanding the structure of hadrons in terms of QCD's quarks and gluons is one of the central goals of modern nuclear physics." Over the last three decades, lattice QCD has developed into a powerful tool for ab initio calculations of strong-interaction physics. Up until now, it is the only theoretical approach to solving QCD with controlled statistical and systematic errors. Since 1985, we have proposed and carried out rst-principles calculations of nucleon structure and hadron spectroscopy using lattice QCD which entails both algorithmic development and large scale computer simulation. We started out by calculating the nucleon form factors { electromagnetic [2], axial-vector [3], NN [4], and scalar [5] form factors, the quark spin contribution [6] to the proton spin, the strangeness magnetic moment [7], the quark orbital angular momentum [8], the quark momentum fraction [9], and the quark and glue decomposition of the proton momentum and angular momentum [10]. These rst round of calculations were done with Wilson fermions in the `quenched' approximation where the dynamical e ects of the quarks in the sea are not taken into account in the Monte Carlo simulation to generate the background gauge con gurations. Beginning in 2000, we have started implementing the overlap fermion formulation into the spectroscopy and structure calculations [11, 12]. This is mainly because the overlap fermion honors chiral symmetry as in the continuum. It is going to be more and more important to take the symmetry into account as the simulations move closer to the physical point where the u and d quark masses are as light as a few MeV only. We began with lattices which have quark masses in the sea corresponding to a pion mass at 300 MeV and obtained the strange form factors [13], charm and strange quark masses, the charmonium spectrum and the Ds meson decay constant fDs [14], the strangeness and charmness [15], the
Forms and factors of peer violence and victimisation
Directory of Open Access Journals (Sweden)
Dinić Bojana
2014-01-01
Full Text Available The main aim of this study was to explore the latent structure of violence and victimisation based on the factor analysis of the Peer Violence and Victimisation Questionnaire (PVVQ, as well as to examine the correlates of violence and victimisation. The sample included 649 secondary school students (61.8% male from the urban area. Besides the PVVQ, the Aggressiveness questionnaire AVDH was administered. Based on parallel analysis, three factors were extracted in the violence domain, as well as in the victimisation domain of the PVVQ. The factors were interpreted as a physical, verbal and relational form of violence and victimisation, which is in line with common classifications. The correlations of those forms with the aggressiveness dimensions were positive. The relationships with gender, school grade and school achievement referred to the importance of interaction effects between the mentioned characteristics of students and the tendency towards violence or being exposed to it. The main result is that boys from lower school grades and students with lower school achievement in general, are more prone to manifesting physical violence and more often are the target of physical violence. These groups of students are the target groups for preventive programs. The resulting effects indicated the complexity of the violence phenomenon and pointed to the need to consider the wider context of student’s characteristics in the determination of violence. [Projekat Ministarstva nauke Republike Srbije, br. 179037 i br. 179053
Clostridial pore-forming toxins: powerful virulence factors.
Popoff, Michel R
2014-12-01
Pore formation is a common mechanism of action for many bacterial toxins. More than one third of clostridial toxins are pore-forming toxins (PFTs) belonging to the β-PFT class. They are secreted as soluble monomers rich in β-strands, which recognize a specific receptor on target cells and assemble in oligomers. Then, they undergo a conformational change leading to the formation of a β-barrel, which inserts into the lipid bilayer forming functional pore. According to their structure, clostridial β-PFTs are divided into several families. Clostridial cholesterol-dependent cytolysins form large pores, which disrupt the plasma membrane integrity. They are potent virulence factors mainly involved in myonecrosis. Clostridial heptameric β-PFTs (aerolysin family and staphylococcal α-hemolysin family) induce small pores which trigger signaling cascades leading to different cell responses according to the cell types and toxins. They are mainly responsible for intestinal diseases, like necrotic enteritis, or systemic diseases/toxic shock from intestinal origin. Clostridial intracellularly active toxins exploit pore formation through the endosomal membrane to translocate the enzymatic component or domain into the cytosol. Single chain protein toxins, like botulinum and tetanus neurotoxins, use hydrophobic α-helices to form pores, whereas clostridial binary toxins encompass binding components, which are structurally and functionally related to β-PFTs, but which have acquired the specific activity to internalize their corresponding enzymatic components. Structural analysis suggests that β-PFTs and binding components share a common evolutionary origin.
Electric and magnetic form factors of the proton
Bernauer, J C; Friedrich, J.; Walcher, Th.; Achenbach, P.; Gayoso, C. Ayerbe; Böhm, R.; Bosnar, D.; Debenjak, L.; Doria, L.; Esser, A.; Fonvieille, H.; Gomez Rodriguez de la Paz, M.; Friedrich, J.M.; Makek, M.; Merkel, H.; Middleton, D.G.; Müller, U.; Nungesser, L.; Pochodzalla, J.; Potokar, M.; Sanchez Majos, S.; Schlimme, B.S.; Sirca, S.; Weinriefer, M.
2014-01-01
The paper describes a precise measurement of electron scattering off the proton at momentum transfers of $0.003 \\lesssim Q^2 \\lesssim 1$\\ GeV$^2$. The average point-to-point error of the cross sections in this experiment is $\\sim$ 0.37%. These data are used for a coherent new analysis together with all world data of unpolarized and polarized electron scattering from the very smallest to the highest momentum transfers so far measured. The extracted electric and magnetic form factors provide new insight into their exact shape, deviating from the classical dipole form, and of structure on top of this gross shape. The data reaching very low $Q^2$ values are used for a new determination of the electric and magnetic radii. An empirical determination of the Two-Photon-Exchange (TPE) correction is presented. The implications of this correction on the radii and the question of a directly visible signal of the pion cloud are addressed.
Scattering form factors for self-assembled network junctions
Foster, T.; Safran, S. A.; Sottmann, T.; Strey, R.
2007-11-01
The equilibrium microstructures in microemulsions and other self-assembled systems show complex, connected shapes such as symmetric bicontinuous spongelike structures and asymmetric bicontinuous networks formed by cylinders interconnected at junctions. In microemulsions, these cylinder network microstructures may mediate the structural transition from a spherical or globular phase to the bicontinuous microstructure. To understand the structural and statistical properties of such cylinder network microstructures as measured by scattering experiments, models are needed to extract the real-space structure from the scattering data. In this paper, we calculate the scattering functions appropriate for cylinder network microstructures. We focus on such networks that contain a high density of network junctions that connect the cylindrical elements. In this limit, the network microstructure can be regarded as an assembly of randomly oriented, closed packed network junctions (i.e., the cylinder scattering contributions are neglected). Accordingly, the scattering spectrum of the network microstructure can be calculated as the product of the junction number density, the junction form factor, which describes the scattering from the surface of a single junction, and a structure factor, which describes the local correlations of different junctions due to junction interactions (including their excluded volume). This approach is applied to analyze the scattering data from a bicontinuous microemulsion with equal volumes of water and oil. In a second approach, we included the cylinder scattering contribution in the junction form factor by calculating the scattering intensity of Y junctions to which three rods with spherical cross section are attached. The respective theoretical predictions are compared with results of neutron scattering measurements on a water-in-oil microemulsion with a connected microstructure.
Measurement of the π0 electromagnetic transition form factor slope
Directory of Open Access Journals (Sweden)
C. Lazzeroni
2017-05-01
Full Text Available The NA62 experiment collected a large sample of charged kaon decays in 2007 with a highly efficient trigger for decays into electrons. A measurement of the π0 electromagnetic transition form factor slope parameter from 1.11×106 fully reconstructed K±→π±πD0, πD0→e+e−γ events is reported. The measured value a=(3.68±0.57×10−2 is in good agreement with theoretical expectations and previous measurements, and represents the most precise experimental determination of the slope in the time-like momentum transfer region.
Baryon octet electromagnetic form factors in a confining NJL model
Directory of Open Access Journals (Sweden)
Manuel E. Carrillo-Serrano
2016-08-01
Full Text Available Electromagnetic form factors of the baryon octet are studied using a Nambu–Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result that rEp
Kaon Eletromagnetic Form Factor in the Light-Front Formalism
Pereira, F P; Frederico, T; Tomio, L; Pereira, Fabiano P.; Tomio, Lauro
2005-01-01
Numerical calculations are performed and compared to the experimental data for the electromagnetic form factor of the kaon, which is extracted from both components of the electromagnetic current, $J^{+}$ and $J^{-}$, with a pseudo-scalar coupling of the quarks to the kaon. In the case of $J^{+}$ there is no pair term contribution in the Drell-Yan frame ($q^{+}=0$). However, for $J^{-}$, the pair term contribution is different from zero and necessary in order to preserve the rotational symmetry of the current. The free parameters are the quark masses and the regulator mass.
The JLab polarization transfer measurements of proton elastic form factor
Indian Academy of Sciences (India)
C F Perdrisat; V Punjabi
2003-11-01
The ratio of the electric and magnetic proton form factors, /, has been obtained in two Hall A experiments, from measurements of the longitudinal and transverse polarizations of the recoil proton, ℓ and , in the elastic scattering of polarized electrons, $\\overrightarrow{e}p→ e\\overrightarrow{p}$. Together these experiments cover the 2 range of 0.5 to 5.6 GeV2. A new experiment is currently being prepared, to extend the 2 range to 9 GeV2 in Hall C.
CEBAF at higher energies and the kaon electromagnetic form factor
Energy Technology Data Exchange (ETDEWEB)
Baker, O.K.
1994-04-01
The electromagnetic production of strangeness, the physics of exciting systems having strangeness degrees of freedom (production of hadrons with one or more strange constituent quarks) using electromagnetic probes (real or virtual photons), is one of the frontier areas of research which will be investigated at the Continuous Electron Beam Accelerator Facility (CEBAF) when it becomes operational. CEBAF is expected to have an important impact upon this field of research using its specialized set of detection instruments and high quality electron beam. This paper focusses upon one aspect of the associated production of strangeness - the determination of the kaon electromagnetic form factor at high squared momentum transfers.
Minimal form factor digital-image sensor for endoscopic applications
Wäny, Martin; Voltz, Stephan; Gaspar, Fabio; Chen, Lei
2009-02-01
This paper presents a digital image sensor SOC featuring a total chip area (including dicing tolerances) of 0.34mm2 for endoscopic applications. Due to this extremely small form factor the sensor enables integration in endoscopes, guide wires and locater devices of less than 1mm outer diameter. The sensor embeds a pixel matrix of 10'000 pixels with a pitch of 3um x 3um covered with RGB filters in Bayer pattern. The sensor operates fully autonomous, controlled by an on chip ring oscillator and readout state machine, which controls integration AD conversion and data transmission, thus the sensor only requires 4 pin's for power supply and data communication. The sensor provides a frame rate of 40Frames per second over a LVDS serial data link. The endoscopic application requires that the sensor must work without any local power decoupling capacitances at the end of up to 2m cabling and be able to sustain data communication over the same wire length without deteriorating image quality. This has been achieved by implementation of a current mode successive approximation ADC and current steering LVDS data transmission. An band gap circuit with -40dB PSRR at the data frequency was implemented as on chip reference to improve robustness against power supply ringing due to the high series inductance of the long cables. The B&W versions of the sensor provides a conversion gain of 30DN/nJ/cm2 at 550nm with a read noise in dark of 1.2DN when operated at 2m cable. Using the photon transfer method according to EMVA1288 standard the full well capacity was determined to be 18ke-. According to our knowledge the presented work is the currently world smallest fully digital image sensor. The chip was designed along with a aspheric single surface lens to assemble on the chip without increasing the form factor. The extremely small form factor of the resulting camera permit's to provide visualization with much higher than state of the art spatial resolution in sub 1mm endoscopic
Tests of Higgs boson compositeness through the HHH form factor
Gounaris, G J
2015-01-01
We show how the $q^2$-dependence of the triple Higgs boson HHH form factor can reveal the presence of various types of new physics contributions, like new particles coupled to the Higgs boson or Higgs boson constituents, without directly observing them. We compare the effect of such new contributions to the one of higher order SM corrections to the point-like HHH coupling, due to triangle, 4-leg and s.e. diagrams. We establish simple analytic expressions describing accurately at high energy these SM corrections, as well as the examples of new physics contributions.
Neutral pion form factor measurement at NA62
Goudzovski, Evgueni
2016-01-01
The NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger for decays into electrons in 2007. The kaon beam represents a source of tagged neutral pion decays in vacuum. A measurement of the electromagnetic transition form factor slope of the neutral pion in the time-like region from $1.05\\times10^6$ fully reconstructed $\\pi^0$ Dalitz decay is presented. The limits on dark photon production in $\\pi^0$ decays from the earlier kaon experiment at CERN, NA48/2, are also reported.
Introducing soil forming factors with mini campus field trips
Quinton, John; Haygarth, Phil
2013-04-01
Students like field work, yet the proportion of time spent in the field during many soil science courses is small. Here we describe an introductory lecture on the soil forming factors based around a mini field trip in which we spend 45 minutes exploring these factors on the Lancaster University campus. In the 'trip' we visit some woodland to consider the effects of organic matter , vegetation and time on soil development and then take in a football pitch to examine the effects of landscape position, parent material and climate. Student responses are overwhelmingly positive and we suggest that more use can be made of our often mundane surroundings to explore soil formation. Soil functions and soil processes.
Energy Technology Data Exchange (ETDEWEB)
Araujo, Vanilse da Silva
1997-12-31
In this work we study the effects of chiral symmetry in the pion-nucleon coupling constant in the context of the linear {sigma}- model. First, we introduce the linear {sigma}-model and we discuss the phenomenological hypothesis of CVC and PCAC. Next, we calculate the coupling constant g+{pi}{sub NN}(q{sup 2}) and the nucleon pionic mean square radius considering the contribution of all the diagrams up to one-loop in the framework of the linear {sigma}-model for different values of the mass of the sigma meson and we compare them with the phenomenological form factors. Finally we make an extension of the linear {sigma}-model that consists of taking into account the mass differences of ions and nucleons into the Lagrangian of the model, to study the change dependence of g{sub {pi}nn} (q{sup 2}) and of the mean square radius. (author) 21 refs., 17 figs., 4 tabs.
Khoa, D T
2004-01-01
Fully quantal calculations of the total reaction cross sections \\sigR and interaction cross sections \\sigI, induced by stable and unstable He, Li, C and O isotopes on $^{12}$C target at $E_{\\rm lab}\\approx 0.8$ and 1 GeV/nucleon have been performed, for the first time, in the distorted wave impulse approximation (DWIA) using the microscopic \\emph{complex} optical potential and inelastic form factors given by the folding model. Realistic nuclear densities for the projectiles and $^{12}$C target as well as the complex $t$-matrix parameterization of free nucleon-nucleon interaction by Franey and Love were used as inputs of the folding calculation. Our \\emph{parameter-free} folding + DWIA approach has been shown to give a very good account (within 1--2%) of the experimental \\sigI measured at these energies for the stable, strongly bound isotopes. With the antisymmetrization of the dinuclear system properly taken into account, this microscopic approach is shown to be more accurate than the simple optical limit of ...
Measurement of the Neutral Weak Form Factors of the Proton
Energy Technology Data Exchange (ETDEWEB)
Deur, Alexandre; Fleck, Andre; Saha, Arunava; Gasparian, Ashot; Frois, Bernard; Wojtsekhowski, Bogdan; Vlahovic, Branislav; Perdrisat, Charles; Cavata, Christian; Jutier, Christophe; De Jager, Cornelis; Neyret, Damien; Dale, Daniel; Armstrong, David; Lhuillier, David; Prout, David; Margaziotis, Demetrius; Kim, Donghee; Burtin, Etienne; Chudakov, Eugene; Hersman, F.; Garibaldi, Franco; Marie, Frederic; Miller, Greg; Rutledge, Gary; Gerstner, George; Petratos, Gerassimos; Quemener, Gilles; Cates, Gordon; Thompson, J.; Martino, Jacques; Gomez, Javier; Jorda, Jean-Paul; Hansen, Jens-Ole; Chen, Jian-Ping; Jardillier, Johann; Calarco, John; LeRose, John; Price, John; Gao, Juncai; McIntyre, Justin; McCormick, Kathy; Fissum, Kevin; Kramer, Kevin; Aniol, Konrad; Kumar, Krishna; Wijesooriya, Krishni; Ewell, Lars; Todor, Luminita; Spradlin, Marcus; Jones, Mark; Leuschner, Mark; Epstein, Martin; Baylac, Maud; Holtrop, Maurik; Finn, Michael; Kuss, Michael; Kim, Min; Falletto, Nicolas; Liyanage, Nilanga; Glamazdin, Oleksandr; Rutt, Paul; Souder, Paul; Ulmer, Paul; Mastromarino, Peter; Djawotho, Pibero; Wilson, Richard; Suleiman, Riad; Holmes, Richard; Madey, Richard; Lourie, Robert; Michaels, Robert; Pomatsalyuk, Roman; Gilman, Ronald; Incerti, Sebastien; Escoffier, Stephanie; Pussieux, Thierry; Humensky, Thomas; Gorbenko, Viktor; Punjabi, Vina; Kahl, William; Meziani, Zein-Eddine
1999-02-01
We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from the proton. The kinematic point [(Theta_{lab}) = 12.3r and (Q^{2}) = 0.48 (GeV/c)^{2}] is chosen to provide sensitivity, at a level that is of theoretical interest, to the strange electric form factor G^{s}_{E}. The result, A = - 14.5 + or - 2.2 ppm, is consistent with the electroweak standard model and no additional contributions from strange quarks. In particular, the measurement implies G^{s}_{E} + 0.39G^{s}_{M} = 0.023 + or - 0.034(stat) + or - 0.022(syst) + or - 0.026(delta-G^{n}_{E}), where the last uncertainty arises from the estimated uncertainty in the neutron electric form factor.
Vector meson dominance and the pi^0 transition form factor
Lichard, Peter
2010-01-01
It is shown that the pi^0 transition form factor F(Q_1^2,Q_2^2) differs substantially from its one-real-photon limit F(Q_1^2,0) even for rather small values of Q_2^2 (approx 0.1 GeV^2), which cannot be excluded in experiments with one "untagged" electron. It indicates that the comparison of data with theoretical calculations, which usually assume Q_2^2=0, may be untrustworthy. Our phenomenological model of the pi^0 transition form factor is based on the vector-meson-dominance (VMD) hypothesis and all its parameters are fixed by using the experimental data on the decays of vector mesons. The model soundness is checked in the two-real-photon limit, where it provides a good parameter-free description of the pi^0 -> 2 gamma decay rate, and in the pi^0 Dalitz decay. The dependence of F(Q_1^2,Q_2^2) on Q_1^2 at several fixed values of Q_2^2 is presented and the comparison with existing data performed.
Measurement of the $\\Lambda_{b}^{0}$ Decay Form Factor
Abdallah, J; Adam, W; Adzic, P; Albrecht, T; Alderweireld, T; Alemany-Fernandez, R; Allmendinger, T; Allport, P P; Amaldi, Ugo; Amapane, N; Amato, S; Anashkin, E; Andreazza, A; Andringa, S; Anjos, N; Antilogus, P; Apel, W D; Arnoud, Y; Ask, S; Åsman, B; Augustin, J E; Augustinus, A; Baillon, Paul; Ballestrero, A; Bambade, P; Barbier, R; Bardin, Dimitri Yuri; Barker, G; Baroncelli, A; Battaglia, Marco; Baubillier, M; Becks, K H; Begalli, M; Behrmann, A; Ben-Haim, E; Benekos, N C; Benvenuti, Alberto C; Bérat, C; Berggren, M; Berntzon, L; Bertrand, D; Besançon, M; Besson, N; Bloch, D; Blom, M; Bluj, M; Bonesini, M; Boonekamp, M; Booth, P S L; Borisov, G; Botner, O; Bouquet, B; Bowcock, T J V; Boyko, I; Bracko, M; Brenner, R; Brodet, E; Brückman, P; Brunet, J M; Bugge, L; Buschmann, P; Calvi, M; Camporesi, T; Canale, V; Carena, F; Castro, N; Cavallo, F R; Chapkin, M M; Charpentier, P; Checchia, P; Chierici, R; Shlyapnikov, P; Chudoba, J; Chung, S U; Cieslik, K; Collins, P; Contri, R; Cosme, G; Cossutti, F; Costa, M J; Crawley, B; Crennell, D J; Cuevas-Maestro, J; D'Hondt, J; Dalmau, J; Da Silva, T; Da Silva, W; Della Ricca, G; De Angelis, A; de Boer, Wim; De Clercq, C; De Lotto, B; De Maria, N; De Min, A; De Paula, L S; Di Ciaccio, Lucia; Di Simone, A; Doroba, K; Drees, J; Dris, M; Eigen, G; Ekelöf, T J C; Ellert, M; Elsing, M; Espirito-Santo, M C; Fanourakis, G K; Fassouliotis, D; Feindt, M; Fernández, J; Ferrer, A; Ferro, F; Flagmeyer, U; Föth, H; Fokitis, E; Fulda-Quenzer, F; Fuster, J A; Gandelman, M; García, C; Gavillet, P; Gazis, E N; Gokieli, R; Golob, B; Gómez-Ceballos, G; Gonçalves, P; Graziani, E; Grosdidier, G; Grzelak, K; Guy, J; Haag, C; Hallgren, A; Hamacher, K; Hamilton, K; Haug, S; Hauler, F; Hedberg, V; Hennecke, M; Herr, H; Hoffman, J; Holmgren, S O; Holt, P J; Houlden, M A; Hultqvist, K; Jackson, J N; Jarlskog, G; Jarry, P; Jeans, D; Johansson, E K; Johansson, P D; Jonsson, P; Joram, C; Jungermann, L; Kapusta, F; Katsanevas, S; Katsoufis, E C; Kernel, G; Kersevan, Borut P; Kerzel, U; Kiiskinen, A P; King, B T; Kjaer, N J; Kluit, P; Kokkinias, P; Kourkoumelis, C; Kuznetsov, O; Krumshtein, Z; Kucharczyk, M; Lamsa, J; Leder, G; Ledroit, F; Leinonen, L; Leitner, R; Lemonne, J; Lepeltier, V; Lesiak, T; Liebig, W; Liko, D; Lipniacka, A; Lopes, J H; López, J M; Loukas, D; Lutz, P; Lyons, L; MacNaughton, J; Malek, A; Maltezos, S; Mandl, F; Marco, J; Marco, R; Maréchal, B; Margoni, M; Marin, J C; Mariotti, C; Markou, A; Martínez-Rivero, C; Masik, J; Mastroyiannopoulos, N; Matorras, F; Matteuzzi, C; Mazzucato, F; Mazzucato, M; McNulty, R; Meroni, C; Meyer, W T; Myagkov, A; Migliore, E; Mitaroff, W A; Mjörnmark, U; Moa, T; Moch, M; Mönig, K; Monge, R; Montenegro, J; Moraes, D; Moreno, S; Morettini, P; Müller, U; Münich, K; Mulders, M; Mundim, L M; Murray, W; Muryn, B; Myatt, Gerald; Myklebust, T; Nassiakou, M; Navarria, Francesco Luigi; Nawrocki, K; Nicolaidou, R; Nikolenko, M; Oblakowska-Mucha, A; Obraztsov, V F; Olshevskii, A G; Onofre, A; Orava, Risto; Österberg, K; Ouraou, A; Oyanguren, A; Paganoni, M; Paiano, S; Palacios, J P; Palka, H; Papadopoulou, T D; Pape, L; Parkes, C; Parodi, F; Parzefall, U; Passeri, A; Passon, O; Peralta, L; Perepelitsa, V F; Perrotta, A; Petrolini, A; Piedra, J; Pieri, L; Pierre, F; Pimenta, M; Piotto, E; Podobnik, T; Poireau, V; Pol, M E; Polok, G; Poropat, P; Pozdnyakov, V; Pukhaeva, N; Pullia, Antonio; Rames, J; Ramler, L; Read, A; Rebecchi, P; Rehn, J; Reid, D; Reinhardt, R; Renton, P B; Richard, F; Rídky, J; Rivero, M; Rodríguez, D; Romero, A; Ronchese, P; Rosenberg, E I; Roudeau, Patrick; Rovelli, T; Ruhlmann-Kleider, V; Ryabtchikov, D; Sadovskii, A; Salmi, L; Salt, J; Savoy-Navarro, A; Schwickerath, U; Segar, A; Sekulin, R L; Siebel, M; Sissakian, A N; Smadja, G; Smirnova, O G; Sokolov, A; Sopczak, A; Sosnowski, R; Spassoff, Tz; Stanitzki, M; Stocchi, A; Strauss, J; Stugu, B; Szczekowski, M; Szeptycka, M; Szumlak, T; Tabarelli de Fatis, T; Taffard, A C; Tegenfeldt, F; Timmermans, J; Tkatchev, L G; Tobin, M; Todorovova, S; Tomé, B; Tonazzo, A; Tortosa, P; Travnicek, P; Treille, D; Tristram, G; Trochimczuk, M; Troncon, C; Turluer, M L; Tyapkin, I A; Tyapkin, P; Tzamarias, S; Uvarov, V; Valenti, G; van Dam, P; Van Eldik, J; Van Lysebetten, A; Van Remortel, N; Van Vulpen, I B; Vegni, G; Veloso, F; Venus, W A; Verdier, P; Verzi, V; Vilanova, D; Vitale, L; Vrba, V; Wahlen, H; Washbrook, A J; Weiser, C; Wicke, D; Wickens, J H; Wilkinson, G; Winter, M; Witek, M; Yushchenko, O P; Zalewska-Bak, A; Zalewski, Piotr; Zavrtanik, D; Zhuravlov, V; Zimin, N I; Zinchenko, A I; Zupan, M
2004-01-01
The form factor of Lambda_b^0 baryons is estimated using 3.46 10^6 hadronic Z decays collected by the DELPHI experiment between 1992 and 1995. Charmed Lambda_c^+ baryons fully reconstructed in the pK-pi+, pK0_S, and Lambda pi+pi+pi- modes, are associated to a lepton with opposite charge in order to select Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l decays. From a combined likelihood and event rate fit to the distribution of the Isgur-Wise variable w, and using the Heavy Quark Effective Theory (HQET), the slope of the b-baryon form factor is measured to be: rho-hat^2 = 2.03 +/- 0.46 (stat) ^{+0.72}_{-1.00} (syst). The exclusive semileptonic branching fraction Br(Lambda_b^0 -> Lambda_c^+ l^- anti-nu_l) can be derived from rho-hat^2 and is found to be (5.0^{+1.1}_{-0.8} (stat) ^{+1.6}_{-1.2} (syst))%. Limits on other branching fractions are also obtained.
Electromagnetic Meson Production in the Nucleon Resonance Region
Energy Technology Data Exchange (ETDEWEB)
Volker Burkert; T.-S. H. Lee
2004-10-01
Recent experimental and theoretical advances in investigating electromagnetic meson production reactions in the nucleon resonance region are reviewed. The article gives a description of current experimental facilities with electron and photon beams and presents a unified derivation of most of the phenomenological approaches being used to extract the resonance parameters from the data. The analyses of {pi} and {eta} production data and the resulting transition form factors for the {Delta}(1232)P{sub 33}, N(1535)S{sub 11}, N(1440)P{sub 11}, and N(1520)D{sub 13} resonances are discussed in detail. The status of our understanding of the reactions with production of two pions, kaons, and vector mesons is also reviewed.
The Anapole Moment of the Deuteron with the Argonne v18 Nucleon-Nucleon Interaction Model
Hyun, C H; Hyun, Chang Ho; Desplanques, Bertrand
2003-01-01
We calculate the deuteron anapole moment with the wave functions obtained from the Argonne $v18$ nucleon-nucleon interaction model. The anapole moment operators are considered at the leading order. To minimize the uncertainty due to a lack of current conservation, we calculate the matrix element of the anapole moment from the original definition. In virtue of accurate wave functions, we can obtain a more precise value of the deuteron anapole moment which contains less uncertainty than the former works. We obtain a result reduced by more than 25% in the magnitude of the deuteron anapole moment. The reduction of individual nuclear contributions is much more important however, varying from a factor 2 for the spin part to a factor 4 for the convection and associated two-body currents.
Pion Form Factor in QCD at Intermediate Momentum Transfers
Braun, V M; Maul, M
1999-01-01
We present a quantitative analysis of the electromagnetic pion form factor in the light-cone sum rule approach, including radiative corrections and higher-twist effects. The comparison to the existing data favors the asymptotic profile of the pion distribution amplitude and allows to estimate the deviation: $(\\int du/u \\phi_\\pi(u))/ (\\int du/u \\phi^{\\rm as}_\\pi(u))=$ 1.1$\\pm$ 0.1 at the scale 1 GeV. Special attention is payed to the precise definition and interplay of soft and hard contributions at intermediate momentum transfer, and to matching of the sum rule to the perturbative QCD prediction. We observe a strong numerical cancellation between the soft (end point) contribution and power suppressed hard contributions of higher twist, so that the total nonperturbative correction to the usual pQCD result turns out to be of order 30% for $Q^2\\sim 1$ GeV$^2$.
Study of the phi-pi0 transition form factor
Pacetti, Simone
2009-01-01
Recently the BaBar Collaboration published new data on the cross section for the annihilation e+e- -> phi pi0, obtained using the initial state radiation technique at a center of mass energy of 10.6 GeV. Such a process represents an interesting test bed for the quark model. Indeed, since the phi-pi0 production via e+e- annihilation proceeds through a mechanism which violates the Okubo-Zweig-Iizuka rule, the corresponding cross section could be characterized by contributions from non-qqbar bound states, like hybrids or tetraquarks. The phi-pi0 cross section is analyzed in connection with other data coming from different processes, that involve the same mesons, using a method which implements the analyticity in the phi-pi0 transition form factor by means of a dispersion relation procedure.
Geometrical form factor calculation using Monte Carlo integration for lidar
Mao, Feiyue; Gong, Wei; Li, Jun
2012-06-01
We proposed a geometrical form factor (GFF) calculation using Monte Carlo integration (GFF-MC) for lidar that is practical and can be applied to any laser intensity distribution. Theoretical results have been calculated with our method based on the functions of measured, uniform and Gaussian laser intensity distribution. Two experimental GFF traces on clear days are obtained to verify the validity of the theoretical results. The results indicated that the measured distribution function outperformed the Gaussian and uniform functions. That means that the deviation of the measured laser intensity distribution from an ideal one can be too large to neglect. In addition, the theoretical GFF of the uniform distribution had a larger error than that of the Gaussian distribution. Furthermore, the effects of the inclination angle of the laser beam and the central obstruction of the support structure of the second mirror of the telescope are discussed in this study.
Thin and small form factor cells : simulated behavior.
Energy Technology Data Exchange (ETDEWEB)
Clews, Peggy Jane; Pluym, Tammy; Grubbs, Robert K.; Cruz-Campa, Jose Luis; Zubia, David (University of Texas at El Paso, El Paso, TX); Young, Ralph Watson; Okandan, Murat; Gupta, Vipin P.; Nielson, Gregory N.; Resnick, Paul James
2010-07-01
Thin and small form factor cells have been researched lately by several research groups around the world due to possible lower assembly costs and reduced material consumption with higher efficiencies. Given the popularity of these devices, it is important to have detailed information about the behavior of these devices. Simulation of fabrication processes and device performance reveals some of the advantages and behavior of solar cells that are thin and small. Three main effects were studied: the effect of surface recombination on the optimum thickness, efficiency, and current density, the effect of contact distance on the efficiency for thin cells, and lastly the effect of surface recombination on the grams per Watt-peak. Results show that high efficiency can be obtained in thin devices if they are well-passivated and the distance between contacts is short. Furthermore, the ratio of grams per Watt-peak is greatly reduced as the device is thinned.
Meson Form Factors and Deep Exclusive Meson Production Experiments
Energy Technology Data Exchange (ETDEWEB)
Horn, Tanja [The Catholic Univ. of America, Washington, DC (United States); Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
2017-05-01
Pion and kaon electroproduction data play a unique role in Nature and our understanding of them is essential for explaining hadron structure. Precision longitudinaltransverse separated pion and kaon cross sections are of particular interest. They allow for the extraction of meson form factors and validation of understanding of hard exclusive and semi-inclusive reactions (π+, K+, π0, γ) towards 3D hadron imaging and potential future flavor decomposition. We review recent data and present prospects for deep exclusive pion and kaon electroproduction at the 12 GeV Jefferson Lab including the prospects to use projected charged- and neutral pion data to further determine the spin, charge-parity and flavor of GPDs, including the helicity-flip GPDs.
The neutral pion form factor at NA62
Cenci, Patrizia
2016-11-01
In 2007 the NA62 experiment at CERN collected a large sample of charged kaon decays with a highly efficient trigger selecting events with electrons in the final state. The kaon beam represents a rich source of tagged neutral pion decays in vacuum. The electromagnetic transition form factor slope of the π0 in the time-like region has been measured from about 106 fully reconstructed π0 Dalitz decays collected in 2007. The preliminary result a = (3.68 ± 0.51stat ± 0.25syst) × 10-2 is the most precise to date. This value is compatible with theoretical expectations and consistent with the previous measurements.
K -> pi l nu form factors with staggered quarks
Gamiz, E; El-Khadra, A X; Kronfeld, A S; Mackenzie, P B; Simone, J
2011-01-01
We report on the status of the Fermilab-MILC calculation of the form factor f_+^{K pi}(0), needed to extract the CKM matrix element |V_{us}| from experimental data on K semileptonic decays. The HISQ formulation is used in the simulations for the valence quarks, while the sea quarks are simulated with the asqtad action (MILC N_f=2+1 configurations). We discuss the general methodology of the calculation, including the use of twisted boundary conditions to get values of the momentum transfer close to zero and the different techniques applied for the correlators fits. We present initial results for lattice spacings a=0.12fm and a=0.09fm, and several choices of the light quark masses.
Form factors and related quantities in clothed-particle representation
Directory of Open Access Journals (Sweden)
Shebeko Alexander
2017-01-01
Full Text Available We show new applications of the notion of clothed particles in quantum field theory. Its realization by means of the clothing procedure put forward by Greenberg and Schweber allows one to express the total Hamiltonian H and other generators of the Poincaré group for a given system of interacting fields through the creation (annihilation operators for the so-called clothed particles with physical (observed properties. Here such a clothed particle representation is used to calculate the matrix elements (shortly, form factors of the corresponding Nöther current operators sandwiched between the H eigenstates. Our calculations are performed with help of an iterative technique suggested by us earlier when constructing the NN → πNN transition operators. As an illustration, we outline some application of our approach in the spinor quantum electrodynamics.
Current correlators and form factors in the resonance region
Energy Technology Data Exchange (ETDEWEB)
Rosell, I. [Departamento de Ciencias Fisicas, Matematicas y de la Computacion, Universidad CEU Cardenal Herrera, c/Sant Bartomeu 55, E-46115 Alfara del Patriarca, Valencia (Spain); IFIC, Universitat de Valencia - CSIC, Apt. Correus 22085, E-46071 Valencia (Spain)
2009-01-15
Within Resonance Chiral Theory and in the context of QCD current correlators at next-to-leading order in 1/N{sub C}, we have analyzed the two-body form factors which include resonances as a final state. The short-distance constraints have been studied. One of the main motivations is the estimation of the chiral low-energy constants at subleading order, that is, keeping full control of the renormalization scale dependence. As an application we show the resonance estimation of some coupling, L{sub 10}{sup r}({mu}{sub 0})=(-4.4{+-}0.9).10{sup -3} and C{sub 87}{sup r}({mu}{sub 0})=(3.1{+-}1.1).10{sup -5}.
Exposing strangeness: Projections for kaon electromagnetic form factors
Gao, Fei; Chang, Lei; Liu, Yu-Xin; Roberts, Craig D.; Tandy, Peter C.
2017-08-01
A continuum approach to the kaon and pion bound-state problems is used to reveal their electromagnetic structure. For both systems, when used with parton distribution amplitudes appropriate to the scale of the experiment, Standard Model hard-scattering formulas are accurate to within 25% at momentum transfers Q2≈8 GeV2. There are measurable differences between the distribution of strange and normal matter within the kaons, e.g. the ratio of their separate contributions reaches a peak value of 1.5 at Q2≈6 GeV2. Its subsequent Q2 evolution is accurately described by the hard scattering formulas. Projections for the ratio of kaon and pion form factors at timelike momenta beyond the resonance region are also presented. These results and projections should prove useful in planning next-generation experiments.
Form factors and related quantities in clothed-particle representation
Shebeko, Alexander; Arslanaliev, Adam
2017-03-01
We show new applications of the notion of clothed particles in quantum field theory. Its realization by means of the clothing procedure put forward by Greenberg and Schweber allows one to express the total Hamiltonian H and other generators of the Poincaré group for a given system of interacting fields through the creation (annihilation) operators for the so-called clothed particles with physical (observed) properties. Here such a clothed particle representation is used to calculate the matrix elements (shortly, form factors) of the corresponding Nöther current operators sandwiched between the H eigenstates. Our calculations are performed with help of an iterative technique suggested by us earlier when constructing the NN → πNN transition operators. As an illustration, we outline some application of our approach in the spinor quantum electrodynamics.
Measurement of Baryon Electromagnetic Form Factors at BESIII
Morales, Cristina Morales
2016-01-01
The Beijing $e^+e^-$-collider (BEPCII) is a double-ring symmetric collider running at center-of-mass energies between 2.0 and 4.6 GeV. This energy range allows the BESIII-experiment to measure baryon electromagnetic form factors in direct $e^+e^-$-annihilation and in initial state radiation processes. In this paper, results on $e^+e^-\\rightarrow p\\bar{p}$ and $e^+e^-\\rightarrow \\Lambda \\bar{\\Lambda}$ based on data collected by BESIII in 2011 and 2012 are presented. Expectations from the BESIII high luminosity energy scan from 2015 and from radiative return at different center-of-mass energies are also reported.
Conformal anomaly of generalized form factors and finite loop integrals
Chicherin, Dmitry
2017-01-01
We reveal a new mechanism of conformal symmetry breaking at Born level. It occurs in generalized form factors with several local operators and an on-shell state of massless particles. The effect is due to hidden singularities on collinear configurations of the momenta. This conformal anomaly is different from the holomorphic anomaly of amplitudes. We present a number of examples in four and six dimensions. We find an application of the new conformal anomaly to finite loop momentum integrals with one or more massless legs. The collinear region around a massless leg creates a contact anomaly, made visible by the loop integration. The anomalous conformal Ward identity for an $\\ell-$loop integral is a 2nd-order differential equation whose right-hand side is an $(\\ell-1)-$loop integral. We show several examples, in particular the four-dimensional scalar double box.
Form Factor $g$ In Longitudinal Space Charge Impedance
Baartman, R
2015-01-01
In carrying out calculations of the effect of longitudinal space charge on longitudinal motion, the transverse beam size appears in a form factor which is usually written as $g=1+2\\ln (b/a)$. In fact, this expression applies to particles with vanishing betatron amplitude in a beam with uniform transverse distribution. It is argued that an average over the transverse distribution should be used instead of the value on axis. It is shown that for the realistic `binomial' family of distributions the 1 in the above expression for $g$ should be replaced by a value near 0.5 if $a$ is interpreted as twice the rms width of the beam.
Algebraic approach to form factors in the complex sinh-Gordon theory
Lashkevich, Michael
2016-01-01
We study form factors of the quantum complex sinh-Gordon theory in the algebraic approach. In the case of exponential fields the form factors can be obtained from the known form factors of the $Z_N$-symmetric Ising model. The algebraic construction also provides an Ansatz for form factors of descendant operators. We obtain generating functions of such form factors and establish their main properties: the cluster factorization and reflection equations.
Algebraic approach to form factors in the complex sinh-Gordon theory
Lashkevich, Michael; Pugai, Yaroslav
2017-01-01
We study form factors of the quantum complex sinh-Gordon theory in the algebraic approach. In the case of exponential fields the form factors can be obtained from the known form factors of the ZN-symmetric Ising model. The algebraic construction also provides an Ansatz for form factors of descendant operators. We obtain generating functions of such form factors and establish their main properties: the cluster factorization and reflection equations.
Nucleon-nucleon scattering from effective field theory
Kaplan, D B; Wise, M B; Kaplan, David B; Savage, Martin J; Wise, Mark B
1996-01-01
We perform a nonperturbative calculation of the 1S0 nucleon-nucleon scattering amplitude, using an effective field theory (EFT) expansion. We use dimensional regularization throughout, and the MS-bar renormalization scheme; our final result depends only on physical observables. We show that the EFT expansion of the real part of the inverse of the Feynman amplitude converges at momenta much greater than the scale that characterizes the derivative expansion of the EFT Lagrangian. Our conclusions are optimistic about the applicability of an EFT approach to the quantitative study of nuclear matter.
Rybczyński, Maciej
2011-01-01
We investigate the influence of the nucleon-nucleon collision profile (probability of interaction as a function of the nucleon-nucleon impact parameter) in the wounded nucleon model and its extensions on several observables measured in relativistic heavy-ion collisions. We find that the participant eccentricity coefficient, $\\epsilon^\\ast$, as well as the higher harmonic coefficients, $\\epsilon_n^\\ast$, are reduced by 10-20% for mid-peripheral collisions when the realistic (Gaussian) profile is used, as compared to the case with the commonly-used hard-sphere profile. Similarly, the multiplicity fluctuations, treated as the function of the number of wounded nucleons in one of the colliding nuclei, are reduced by 10-20%. This demonstrates that the Glauber Monte Carlo codes should necessarily use the realistic nucleon-nucleon collision profile in precision studies of these observables. The Gaussian collision profile is built-in in {\\tt GLISSANDO}.
Fundamental nucleon-nucleon interaction: probing exotic nuclear structure using GEANIE at LANCE/WNR
Energy Technology Data Exchange (ETDEWEB)
Bernstein, L
2000-02-25
The initial goal of this project was to study the in-medium nucleon-nucleon interaction by testing the fundamental theory of nuclear structure, the shell model, for nuclei between {sup 8}Zr and {sup 100}Sn. The shell model predicts that nuclei with ''magic'' (2,8,20,28,40,50, and 82) numbers of protons or neutrons form closed shells in the same fashion as noble gas atoms [may49]. A ''doubly magic'' nucleus with a closed shell of both protons and neutrons has an extremely simple structure and is therefore ideal for studying the nucleon-nucleon interaction. The shell model predicts that doubly magic nuclei will be spherical and that they will have large first-excited-state energies ({approx} 1 to 3 MeV). Although the first four doubly-magic nuclei exhibit this behavior, the N = Z = 40 nucleus, {sup 80}Zr, has a very low first-excited-state energy (290 keV) and appears to be highly deformed. This breakdown is attributed to the small size of the shell gap at N = Z = 40. If this description is accurate, then the N = Z = 50 doubly magic nucleus, {sup 100}Sn, will exhibit ''normal'' closed-shell behavior. The unique insight provided by doubly-magic nuclei from {sup 80}Zr to {sup 100}Sn has made them the focus of tremendous interest in the nuclear structure community. However, doubly-magic nuclei heavier than {sup 56}Ni become increasingly difficult to form due to the coulomb repulsion between the protons which favors the formation of neutron-rich nuclei. The coulomb repulsion creates a ''proton drip-line'' beyond which the addition of any additional bound protons is energetically impossible. The drip line renders the traditional experimental technique used in their formation, the heavy-ion reaction, less than ideal as a method of forming doubly-magic nuclei beyond {sup 80}Zr. The result has been a lack of an new spectroscopic information on doubly magic nuclei in more than a decade [lis87
Stopped nucleons in configuration space
Bialas, Andrzej; Koch, Volker
2016-01-01
In this note, using the colour string model, we study the configuration space distribution of stopped nucleons in heavy-ion collisions. We find that the stopped nucleons from the target and the projectile end up separated from each other by the distance increasing with the collision energy. In consequence, for the center of mass energies larger than 6 or 10 GeV (depending on the details of the model) it appears that the system created is not in thermal and chemical equilibrium, and the net baryon density reached is likely not much higher than that already present in the colliding nuclei.
Hammer events, neutrino energies, and nucleon-nucleon correlations
Weinstein, L B; Piasetzky, E
2016-01-01
Neutrino oscillation measurements depend on a difference between the rate of neutrino-nucleus interactions at different neutrino energies or different distances from the source. Knowledge of the neutrino energy spectrum and neutrino-detector interactions are crucial for these experiments. Short range nucleon-nucleon correlations in nuclei (SRC) affect properties of nuclei. The ArgoNeut liquid Argon Time Projection Chamber (lArTPC) observed neutrino-argon scattering events with two protons back-to-back in the final state ("hammer" events) which they associated with SRC pairs. The MicroBoone lArTPC will measure far more of these events. We simulate hammer events using two simple models. We use the well-known electron-nucleon cross section to calculate e-argon interactions where the e- scatters from a proton, ejecting a pi+, and the pi+ is then absorbed on a moving deuteron-like $np$ pair. We also use a model where the electron excites a nucleon to a Delta, which then deexcites by interacting with a second nucle...
Studies of the dilepton emission from nucleon-nucleon interactions
Bacelar, JCS; Fujiwara, M; Shima, T
2002-01-01
real- and virtual-photon emission during interactions between few-nucleon systems have been investigated at KVI with a 190 MeV proton beam. Here I will concentrate the discussion on the results of the virtual-photon emission for the proton-proton system and proton-deuteron capture. Predictions of a
Nuclear effects on neutrino emissivities from nucleon-nucleon bremsstrahlung
Stoica, S.; Paun, V. P.; Negoita, A. G.
2004-06-01
The rates of neutrino pair emission by nucleon-nucleon (NN) bremsstrahlung are calculated with the inclusion of the full contribution from a nuclear one pion exchange potential (OPEP). We compute the contributions from the neutron-neutron (nn), proton-proton (pp), and neutron-proton (np) processes for physical conditions encountered in supernovae and neutron stars, both in the degenerate (D) and nondegenerate (ND) limits. We find a significant reduction of these rates, especially for the nn and pp processes, in comparison with the case when the whole nuclear contribution was replaced by constants, representing the high-momentum limits of the expressions of the nuclear potential. Furthermore, we also perform the calculations by including contributions due to the ρ meson exchange between nucleons, in the OPEP. This may be relevant for processes produced in the inner core of neutron stars, where the density may exceed several times the standard nuclear density, and the short-range part of the NN interaction should be taken into account. These corrections lead to an additional suppression of the neutrino emission rates between (8 and 36)%, depending on the process [nn (pp) or np] and physical conditions (temperature and degeneracy of the nucleons).
Studies of the dilepton emission from nucleon-nucleon interactions
Bacelar, JCS; Fujiwara, M; Shima, T
2002-01-01
real- and virtual-photon emission during interactions between few-nucleon systems have been investigated at KVI with a 190 MeV proton beam. Here I will concentrate the discussion on the results of the virtual-photon emission for the proton-proton system and proton-deuteron capture. Predictions of a
Impact of Nucleon-Nucleon Bremsstrahlung Rates Beyond One-Pion Exchange
Bartl, Alexander; Janka, Hans-Thomas; Schwenk, Achim
2016-01-01
Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on a modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2-5 in the neutrinospheric region, models with the improved treatment exhibit only $\\lesssim$5% changes of the neutrino luminosities and an increase of $\\lesssim$0.7 MeV of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by $\\lesssim$0.5-1 s.
Impact of nucleon-nucleon bremsstrahlung rates beyond one-pion exchange
Bartl, A.; Bollig, R.; Janka, H.-T.; Schwenk, A.
2016-10-01
Neutrino-pair production and annihilation through nucleon-nucleon bremsstrahlung is included in current supernova simulations by rates that are based on the one-pion-exchange approximation. Here we explore the consequences of bremsstrahlung rates based on modern nuclear interactions for proto-neutron star cooling and the corresponding neutrino emission. We find that despite a reduction of the bremsstrahlung emission by a factor of 2-5 in the neutrinospheric region, models with the improved treatment exhibit only ≲5 % changes of the neutrino luminosities and an increase of ≲0.7 MeV of the average energies of the radiated neutrino spectra, with the largest effects for the antineutrinos of all flavors and at late times. Overall, the proto-neutron star cooling evolution is slowed down modestly by ≲0.5 - 1 s .
Precision nucleon-nucleon potential at fifth order in the chiral expansion
Epelbaum, E; Meißner, U -G
2014-01-01
We present a nucleon-nucleon potential at fifth order in chiral effective field theory. We find a substantial improvement in the description of nucleon-nucleon phase shifts as compared to the fourth-order results of Ref. [E. Epelbaum, H. Krebs, U.-G. Mei{\\ss}ner, arXiv:1412.0142 [nucl-th
Leading chiral logarithms for the nucleon mass
Energy Technology Data Exchange (ETDEWEB)
Vladimirov, Alexey A.; Bijnens, Johan [Department of Astronomy and Theoretical Physics, Lund University, Sölvegatan 14A, SE 223 62 Lund (Sweden)
2016-01-22
We give a short introduction to the calculation of the leading chiral logarithms, and present the results of the recent evaluation of the LLog series for the nucleon mass within the heavy baryon theory. The presented results are the first example of LLog calculation in the nucleon ChPT. We also discuss some regularities observed in the leading logarithmical series for nucleon mass.
Polarized strangeness in the nucleon
Sapozhnikov, M G
2001-01-01
A large violation of the Okubo-Zweig-Iizuka rule was discovered in the annihilation of stopped antiprotons. The explanation of these experimental data is discussed in the framework of the model assumed that the nucleon strange sea quarks are polarized.
Nucleon structure from lattice QCD
Energy Technology Data Exchange (ETDEWEB)
Dinter, Simon
2012-11-13
In this thesis we compute within lattice QCD observables related to the structure of the nucleon. One part of this thesis is concerned with moments of parton distribution functions (PDFs). Those moments are essential elements for the understanding of nucleon structure and can be extracted from a global analysis of deep inelastic scattering experiments. On the theoretical side they can be computed non-perturbatively by means of lattice QCD. However, since the time lattice calculations of moments of PDFs are available, there is a tension between these lattice calculations and the results from a global analysis of experimental data. We examine whether systematic effects are responsible for this tension, and study particularly intensively the effects of excited states by a dedicated high precision computation. Moreover, we carry out a first computation with four dynamical flavors. Another aspect of this thesis is a feasibility study of a lattice QCD computation of the scalar quark content of the nucleon, which is an important element in the cross-section of a heavy particle with the nucleon mediated by a scalar particle (e.g. Higgs particle) and can therefore have an impact on Dark Matter searches. Existing lattice QCD calculations of this quantity usually have a large error and thus a low significance for phenomenological applications. We use a variance-reduction technique for quark-disconnected diagrams to obtain a precise result. Furthermore, we introduce a new stochastic method for the calculation of connected 3-point correlation functions, which are needed to compute nucleon structure observables, as an alternative to the usual sequential propagator method. In an explorative study we check whether this new method is competitive to the standard one. We use Wilson twisted mass fermions at maximal twist in all our calculations, such that all observables considered here have only O(a{sup 2}) discretization effects.
DVCS on the nucleon to the twist-3 accuracy
Kivel, N A
2001-01-01
The amplitude of the deeply virtual Compton scattering off nucleon is computed to the twist-3 accuracy in the Wandzura-Wilczek (WW) approximation. The result is presented in the form which can be easily used for analysis of DVCS observables.
Quark Contributions to Nucleon Momentum and Spin from Domain Wall fermion calculations
Energy Technology Data Exchange (ETDEWEB)
Syritsyn, Sergey N.; Green, Jeremy R. [MIT; Negele, John W. [MIT; Pochinsky, Andrew [MIT; Hagler, Philipp G. [Tech. U. Munich; Musch, Bernhard U. [Tech. U. Munich; Schroers, Wolfram
2011-12-01
We report contributions to the nucleon spin and momentum from light quarks calculated using dynamical domain wall fermions with pion masses down to 300 MeV and fine lattice spacing a=0.084 fm. Albeit without disconnected diagrams, we observe that spin and orbital angular momenta of both u and d quarks are opposite, almost canceling in the case of the d quark, which agrees with previous calculations using a mixed quark action. We also present the full momentum dependence of n=2 generalized form factors showing little variation with the pion mass.
Status of nucleon structure calculations with 2+1 flavors of domain wall fermions
Lin, Meifeng
2013-01-01
We report the status of our nucleon structure calculations with 2+1 flavors of domain wall fermions on the RBC-UKQCD $32^3\\times64$ gauge ensembles with the Iwasaki+DSDR action. These ensembles have a fixed lattice scale of 1/a = 1.37 GeV, and two pion masses of about 170 and 250 MeV. Preliminary results for the isovector electromagnectic form factors and their corresponding root-mean-squared (r.m.s.) radii will be presented.
Chiral Symmetry and the Nucleon-Nucleon Interaction
Directory of Open Access Journals (Sweden)
Ruprecht Machleidt
2016-04-01
Full Text Available We review how nuclear forces emerge from low-energy quantum chromodynamics (QCD via chiral effective field theory (EFT. During the past two decades, this approach has evolved into a powerful tool to derive nuclear two- and many-body forces in a systematic and model-independent way. We then focus on the nucleon-nucleon (N N interaction and show in detail how, governed by chiral symmetry, the long- and intermediate-range of the N N potential builds up order by order. We proceed up to sixth order in small momenta, where convergence is achieved. The final result allows for a full assessment of the validity of the chiral EFT approach to the N N interaction.
Open and Hidden Strangeness Production in Nucleon-Nucleon Collisions
Shyam, Radhey
2008-01-01
We present an overview of the description of K and eta meson productions in nucleon-nucleon collisions within an effective Lagrangian model where meson production proceeds via excitation, propagation and subsequent decay of intermediate baryonic resonant states. The $K$ meson contains a strange quark ($s$) or antiquark ($\\bar s$) while the $\\eta$ meson has hidden strangeness as it contains some component of the $s{\\bar s}$ pair. Strange meson production is expected to provide information on the manifestation of quantum chromodynamics in the non-perturbative regime of energies larger than that of the low energy pion physics. We discuss specific examples where proper understanding of the experimental data for these reactions is still lacking.
Can the 4He experiments serve as a database for determining the three-nucleon force?
Hofmann, H M; Hale, Gerald M.; Hofmann, Hartmut M.
2005-01-01
We report on microscopic calculations for the 4He compound system in the framework of the resonating group model employing realistic nucleon-nucleon and three nucleon forces. The resulting scattering phase shifts are compared to those of a comprehensive R-matrix analysis of all data in this system, which are available in numerical form. The agreement between calculation and analysis is in most cases very good. Adding three-nucleon forces yields in many cases large effects. For a few cases the new agreement is striking. We relate some differencies between calculation and analysis to specific data and discuss neccessary experiments to clarify the situation. From the results we conclude that the data of the 4He system might be well suited to determine the structure of the three-nucleon force.
Cottingham formula and nucleon polarisabilities
Energy Technology Data Exchange (ETDEWEB)
Gasser, J.; Leutwyler, H. [Universitaet Bern, Albert Einstein Center for Fundamental Physics, Institut fuer theoretische Physik, Bern (Switzerland); Hoferichter, M. [Universitaet Bern, Albert Einstein Center for Fundamental Physics, Institut fuer theoretische Physik, Bern (Switzerland); Technische Universitaet Darmstadt, Institut fuer Kernphysik, Darmstadt (Germany); GSI Helmholtzzentrum fuer Schwerionenforschung GmbH, ExtreMe Matter Institute EMMI, Darmstadt (Germany); University of Washington, Institute for Nuclear Theory, Seattle, WA (United States); Rusetsky, A. [Universitaet Bonn, Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Bonn (Germany)
2015-08-15
The difference between the electromagnetic self-energies of proton and neutron can be calculated with the Cottingham formula, which expresses the self-energies as an integral over the electroproduction cross sections - provided the nucleon matrix elements of the current commutator do not contain a fixed pole. We show that, under the same proviso, the subtraction function occurring in the dispersive representation of the virtual Compton forward scattering amplitude is determined by the cross sections. The representation in particular leads to a parameter-free sum rule for the nucleon polarisabilities. We evaluate the sum rule for the difference between the electric polarisabilities of proton and neutron by means of the available parameterisations of the data and compare the result with experiment. (orig.)
Nucleon Polarizibilities for Virtual Photons
Edelmann, J; Piller, G; Weise, W
1998-01-01
We generalize the sum rules for the nucleon electric plus magnetic polarizability $\\Sigma=\\alpha+\\beta$ and for the nucleon spin-polarizability sections are represented in our calculation by one-pion-loop graphs of relativistic baryon chiral perturbation theory and the $\\Delta(1232)$-resonance excitation. For the proton we find good agreement of the calculated electroproduction data for $Q^2<0.4 GeV^2$. The proton spin-polarizability "partonic" curve, extracted from polarized deep-inelastic scattering, around $Q^2=0.7 GeV^2$. For the neutron our predictions of $\\Sigma_n(Q^2)$ and Upcoming (polarized) electroproduction experiments will be able to test the generalized polarizability sum rules investigated here.
Local Quark-Hadron Duality and Magnetic Form Factors of Bound Proton
Institute of Scientific and Technical Information of China (English)
WANG Hong-Min; ZHANG Ben-Ai
2005-01-01
We discuss the consequence of local duality for elastic scattering, and derive a model-independent equation between structure functions at x ～ 1 and elastic electromagnetic form factors. Then the electromagnetic form factors of proton are discussed using the quark-hadron duality theory. We also debate the form factor of proton in a bound state.It may be an effective approach to study the form factor of proton in media.
Fission: statistical nucleon pair breaking
Energy Technology Data Exchange (ETDEWEB)
Montoya, M. (Instituto Peruano de Energia Nuclear, Lima (Peru))
1984-06-01
In order to explain the odd-even effect observed in low energy fission fragment distributions it has been recently required a double mechanism of nucleon pair breaking: before scission (early pair breaking) and at scission (late pair breaking), respectively. In the present work we show that, using the same formulae but considering only the early pair breaking mechanism, one can reproduce fairly well all the available experimental data on the odd-even effects.
Energy Technology Data Exchange (ETDEWEB)
Ghosh, Sabyasachi, E-mail: sabyaphy@gmail.com [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), Sao Paulo, SP (Brazil). Instituto de Fisica Teorica
2015-12-15
Owing to the Kubo relation, the shear viscosities of pionic and nucleonic components have been evaluated from their corresponding retarded correlators of viscous stress tensor in the static limit, which become non-divergent only for the non-zero thermal widths of the constituent particles. In the real-time thermal field theory, the pion and nucleon thermal widths have respectively been obtained from the pion self-energy for different meson, baryon loops, and the nucleon self-energy for different pion-baryon loops. We have found non-monotonic momentum distributions of pion and nucleon thermal widths, which have been integrated out by their respective Bose-enhanced and Pauli-blocked phase space factors during evaluation of their shear viscosities. The viscosity to entropy density ratio for this mixed gas of pion-nucleon system decreases and approaches its lower bound as the temperature and baryon chemical potential increase within the relevant domain of hadronic matter. (author)
Bs → f0(980) Transition Form Factors Within the kT Factorization Approach
Institute of Scientific and Technical Information of China (English)
ZENG Dai-Min; FANG Zhen-Yun
2013-01-01
In the paper,we apply the kT factorization approach to deal with the Bs → f0(980) transition form factors in the large recoil regions,i.e.the small q2 regions.For the purpose,we adopt the B-meson wave-functions ΨB,ψ B and δ that include the three-Fock states contributions to do our discussion.Although the scalar meson f0(980) is widely perceived as the 4-quark bound state (scenario 2),but the distribution amplitudes of 4-quark states are still unknown to us,so we adopt 2-quark model (scenario 1) for scalar meson f0(980) in our discussion.By varying the B-meson wave-function parameters within their reasonable regions,we obtain F0(0) =F+(0) =0.20 ± 0.02,FT(0) =0.24 ± 0.02.Our present results for these form factors are consistent with the light-cone sum rule results obtained in the literature.
Chemical Forms of Mercury in Soils and Their Influencing Factors
Institute of Scientific and Technical Information of China (English)
QINGCHANGLE; MOUSHUSEN; 等
1998-01-01
Experiments were carried out study the transformation of mercury in soils,Results showed that Hg2+ was immediatel converted into other forms once it entered into soils,Bentonite,humus or CaCO3 accelerated the transformaiton of Hg2+ by various mechanisms.Bentonite could convert Hg2+ into residual form eventually,and application of CaCO3 enhanced the formation of inorganic Hg,Humus competed strongly with clay minerals for binding Hg2+,thus increase of soil hums content led to increased formation of organically bound Hg.
Fujiwara, Y; Kohno, M; Suzuki, Y
2004-01-01
Quark-model nucleon-nucleon and hyperon-nucleon interactions by the Kyoto- Niigata group are applied to the hypertriton calculation in a new three-cluster Faddeev formalism using the two-cluster resonating-group method kernels. The most recent model, fss2, gives a reasonable result similar to the Nijmegen soft-core model NSC89, except for an appreciable contributions of higher partial waves.
Investigation on influence factors of dual laterologs curve form
Institute of Scientific and Technical Information of China (English)
Xiaomin FAN; Lei LU
2008-01-01
In order to investigate the influences of caliper, formation thickness and invaded zone on the form of dual laterologs, forward modeling technique were applied to calculate the dual laterologs for different cases. The result shows that the resistivity logs become smoother and lower as the borehole diameter increases, the increase of the contrast between mud resistivity and formation resistivity induce the logs to be more pointed. When the formation thickness is less than 1m, the two-peak on the logs for resistive invasion vanished, and for thickness between 1 m and 4 m, the form of logs does not vary significantly. If the formation thickness is greater than 4 m, a platform appears on the logs at the middle of the formation. The thinner the invaded zone is, the more obvious the invasion feature on the laterologs is. For thick invaded zone the form of logs tend to be that of an uninvaded resistive formation. The form and amplitude of logs depend on the resistivity contrast between invaded zone, uninvaded formation and adjacentlayers.
FACTORS FORMING RELATIONSHIPS AND EVERYDAY RUSSIAN AND BELARUSIANS
Directory of Open Access Journals (Sweden)
Emir Nodarievich Tuzhba
2016-11-01
Full Text Available Purpose. It consists in the analysis of the factors influencing the process of interaction, the nature of relationships and everyday life of the Russian and Belarusian communities. Methodology. Use the ideas of the system, interactionist, phenomenological and socio-psychological approaches. The empirical base totaled questionnaire data of the Russian population of the Krasnodar Territory; secondary analysis of sociological data of Russian and Belarusian research teams on studies. Results. Identified and analyzed factors of relationships and the culture of everyday life, especially their impact on the processes of interaction between Russian and Belarusian ethnic communities. Practical implications. Knowledge of the factors and content of the mutual influence of ethnic and cultural practices of the ethnic communities of Belarus and Russia will help to predict the interaction processes contribute to their consolidation and integration.
A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model
Fujiwara, Y; Kohno, M; Nakamoto, C; Suzuki, Y
2001-01-01
We upgrade a SU_6 quark-model description for the nucleon-nucleon and hyperon-nucleon interactions by improving the effective meson-exchange potentials acting between quarks. For the scalar- and vector-meson exchanges, the momentum-dependent higher-order term is incorporated to reduce the attractive effect of the central interaction at higher energies. The single-particle potentials of the nucleon and Lambda, predicted by the G-matrix calculation, now have proper repulsive behavior in the momentum region q_1=5 - 20 fm^-1. A moderate contribution of the spin-orbit interaction from the scalar-meson exchange is also included. As to the vector mesons, a dominant contribution is the quadratic spin-orbit force generated from the rho-meson exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up to T_lab=350 MeV are greatly improved especially for the 3E states. The low-energy observables of the nucleon-nucleon and the hyperon-nucleon interactions are also reexamined. The isospin symmetry break...
The Scattering of Fast Nucleons from Nuclei
Kerman, A. K.; McManus, H.; Thaler, R. M.
2000-04-01
The formal theory of the scattering of high-energy nucleons by nuclei is developed in terms of the nucleon-nucleon scattering amplitude. The most important approximations necessary to make numerical calculation feasible are then examined. The optical model potential is derived on this basis and compared with the optical model parameters found from experiment. The elastic scattering and polarization of nucleons from light nuclei is predicted and compared with experiment. The effect of nuclear correlations is discussed. The polarization of inelastically scattered nucleons is discussed and predictions compared with experiments. To within the validity of the approximations the experimental data on the scattering of nucleons from nuclei at energies above ˜100 Mev appears to be consistent with the theory.
The scattering of fast nucleons from nuclei
Energy Technology Data Exchange (ETDEWEB)
Kerman, A. K. [Massachusetts Institute of Technology, Cambridge, Massachusetts (United States); McManus, H. [Chalk River Laboratory, Chalk River, Ontario, (Canada); Thaler, R. M. [Los Alamos Scientific Laboratory, Los Alamos, New Mexico (United States)
2000-04-10
The formal theory of the scattering of high-energy nucleons by nuclei is developed in terms of the nucleon nucleon scattering amplitude. The most important approximations necessary to make numerical calculation feasible are then examined. The optical model potential is derived on this basis and compared with the optical model parameters found from experiment. The elastic scattering and polarization of nucleons from light nuclei is predicted and compared with experiment. The effect of nuclear correlations is discussed. The polarization of inelastically scattered nucleons is discussed and predictions compared with experiments. To within the validity of the approximations the experimental data on the scattering of nucleons from nuclei at energies above {approx}100 Mev appears to be consistent with the theory. (c) 2000 Academic Press, Inc.
Nucleon localization in light and heavy nuclei
Zhang, C L; Nazarewicz, W
2016-01-01
An electron localization measure was originally introduced to characterize chemical bond structures in molecules. Recently, a nucleon localization based on Hartree-Fock densities has been introduced to investigate $\\alpha$-cluster structures in light nuclei. Compared to the local nucleonic densities, the nucleon localization function has been shown to be an excellent indicator of shell effects and cluster correlations. Using the spatial nucleon localization measure, we investigate the cluster structures in deformed light nuclei and study the emergence of fragments in fissioning heavy nuclei. To illustrate basic concepts of nucleon localization, we employ the deformed harmonic oscillator model. Realistic calculations are carried out using self-consistent nuclear density functional theory with quantified energy density functionals optimized for fission studies. We study particle densities and spatial nucleon localization distributions for deformed cluster configurations of $^{8}$Be and $^{20}$Ne, and also along...
Chiral nucleon-nucleon forces in nuclear structure calculations
Directory of Open Access Journals (Sweden)
Coraggio L.
2016-01-01
Full Text Available Realistic nuclear potentials, derived within chiral perturbation theory, are a major breakthrough in modern nuclear structure theory, since they provide a direct link between nuclear physics and its underlying theory, namely the QCD. As a matter of fact, chiral potentials are tailored on the low-energy regime of nuclear structure physics, and chiral perturbation theory provides on the same footing two-nucleon forces as well as many-body ones. This feature fits well with modern advances in ab-initio methods and realistic shell-model. Here, we will review recent nuclear structure calculations, based on realistic chiral potentials, for both finite nuclei and infinite nuclear matter.