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The proton's elastic electromagnetic form factors are calculated using an Ansatz for the nucleon's Poincare' covariant Faddeev amplitude that only retains scalar diquark correlations. A spectator approximation is employed for the current.…

Nuclear Theory · Physics 2009-01-14 J. C. R. Bloch , A. Krassnigg , C. D. Roberts

A Poincare' covariant Faddeev equation, which describes baryons as composites of confined-quarks and -nonpointlike-diquarks, is solved to obtain masses and Faddeev amplitudes for the nucleon and Delta. The amplitudes are a component of a…

Nuclear Theory · Physics 2010-03-04 R. Alkofer , A. Hoell , M. Kloker , A. Krassnigg , C. D. Roberts

In treating the relativistic three-quark problem, a dressed-quark propagator parameterization is used which is compatible with recent lattice data and pion observables. Furthermore two-quark correlations are modeled as a series of quark…

High Energy Physics - Phenomenology · Physics 2008-11-26 M. Oettel , R. Alkofer

Working with a Poincar\'e-covariant quark + diquark, $q(qq)$, Faddeev equation approach to nucleon structure, a refined symmetry preserving current for electron + nucleon elastic scattering is developed. The parameters in the interaction…

High Energy Physics - Phenomenology · Physics 2025-07-21 Peng Cheng , Zhao Qian Yao , Daniele Binosi , Ya Lu , Craig D. Roberts

We compute the electromagnetic form factors of the nucleon in the Poincare-covariant Faddeev framework based on the Dyson-Schwinger equations of QCD. The general expression for a baryon's electromagnetic current in terms of three…

High Energy Physics - Phenomenology · Physics 2011-08-08 Gernot Eichmann

We compute nucleon and Roper e.m. elastic and transition form factors using a symmetry-preserving treatment of a contact-interaction. Obtained thereby, the e.m. interactions of baryons are typically described by hard form factors. In…

Nuclear Theory · Physics 2015-06-03 D. J. Wilson , I. C. Cloet , L. Chang , C. D. Roberts

A dressed-quark core contribution to nucleon electromagnetic form factors is calculated. It is defined by the solution of a Poincare' covariant Faddeev equation in which dressed-quarks provide the elementary degree of freedom and…

Nuclear Theory · Physics 2010-03-04 I. C. Cloet , G. Eichmann , B. El-Bennich , T. Klahn , C. D. Roberts

A Poincare' covariant Faddeev equation is presented, which enables the simultaneous prediction of meson and baryon observables using the leading-order in a truncation of the Dyson-Schwinger equations that can systematically be improved. The…

Nuclear Theory · Physics 2010-04-15 G. Eichmann , I. C. Cloet , R. Alkofer , A. Krassnigg , C. D. Roberts

Nucleon form factors are calculated on q^2 in [0,3] GeV^2 using an Ansatz for the nucleon's Fadde'ev amplitude motivated by quark-diquark solutions of the relativistic Fadde'ev equation. Only the scalar diquark is retained, and it and the…

Nuclear Theory · Physics 2009-01-14 J. C. R. Bloch , C. D. Roberts , S. M. Schmidt , A. Bender , M. R. Frank

Electromagnetic form factors of the nucleon in the space-like region are investigated within the framework of a covariant and confining Nambu-Jona-Lasinio model. The bound state amplitude of the nucleon is obtained as the solution of a…

Nuclear Theory · Physics 2014-10-15 Ian C. Cloët , Wolfgang Bentz , Anthony W. Thomas

A symmetry-preserving Poincar\'e-covariant quark+diquark Faddeev equation treatment of the nucleon is used to deliver parameter-free predictions for the nucleon's axial and induced pseudoscalar form factors, $G_A$ and $G_P$, respectively.…

High Energy Physics - Phenomenology · Physics 2021-03-17 Chen Chen , Christian S. Fischer , Craig D. Roberts , Jorge Segovia

Electron scattering at large Q^2 probes a nucleon's quark core. This core's contribution to electromagnetic form factors may be calculated using Poincare' covariant Faddeev amplitudes combined with a nucleon-photon vertex that automatically…

Nuclear Theory · Physics 2008-11-26 A Hoell , R. Alkofer , M. Kloker , A. Krassnigg , C. D. Roberts , S. V. Wright

Nucleon elastic electromagnetic form factors obtained using both the three-body and quark + fully-interacting-diquark pictures of nucleon structure are employed to calculate an array of light-front transverse densities for the proton and…

High Energy Physics - Phenomenology · Physics 2026-02-23 Z. -N. Xu , Z. -Q. Yao , P. Cheng , C. D. Roberts , J. Rodriguez-Quintero , J. Segovia

We present a unified description of elastic and transition form factors involving the nucleon and its resonances; in particular, the $N(1440)$, $\Delta(1232)$ and $\Delta(1600)$. We compare predictions made using a framework built upon a…

Nuclear Theory · Physics 2020-08-26 J. Segovia , C. Chen , Z. -F. Cui , Y. Lu , C. D. Roberts

We present a simple covariant constituent diquark-quark model for the nucleon. The nucleon is assumed to be composed of a scalar diquark and a quark which interact via a quark exchange. Starting from the Bethe-Salpeter equation, the…

High Energy Physics - Phenomenology · Physics 2011-07-19 V. Keiner

We report the first study of the nucleon where the full Poincare-covariant structure of the three-quark amplitude is implemented in the Faddeev equation. We employ an interaction kernel which is consistent with contemporary studies of meson…

High Energy Physics - Phenomenology · Physics 2014-07-24 G. Eichmann , R. Alkofer , A. Krassnigg , D. Nicmorus

A covariant, composite scalar diquark, Fadde'ev amplitude model for the nucleon is used to calculate pseudoscalar, isoscalar- and isovector-vector, axial-vector and scalar nucleon form factors. The last yields the nucleon sigma-term and…

Nuclear Theory · Physics 2009-01-14 J. C. R. Bloch , C. D. Roberts , S. M. Schmidt

Using a Poincar\'e-covariant quark+diquark Faddeev equation and related symmetry-preserving weak interaction current, we deliver parameter-free predictions for the nucleon axialvector form factor, $G_A(Q^2)$, on the domain $0\leq…

High Energy Physics - Phenomenology · Physics 2022-11-23 Chen Chen , Craig D. Roberts

Proton and neutron electric and magnetic form factors are the primary characteristics of their spatial structure and have been studied extensively over the past half-century. At large values of the momentum transfer $Q^2$ they should reveal…

High Energy Physics - Lattice · Physics 2025-02-25 S. Syritsyn , M. Engelhardt , S. Krieg , J. Negele , A. Pochinsky

Deuteron elastic and deep inelastic electromagnetic properties have been studied within the front-form Hamiltonian dynamics, using a Poincar\'e-covariant current operator. The deuteron elastic form factors are strongly sensitive to…

Nuclear Theory · Physics 2016-11-23 E. Pace , G. Salme`
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