Dependence of electromagnetic form factors of hadrons on light-cone frames

Weber, H. J.; Xu, Xiaoming

doi:10.1016/0375-9474(95)00503-x

Cited by 3 publications

(2 citation statements)

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“…In the usual formulation of LFD on the plane t + z = 0, the form factors of spin 1/2 systems are found from the plus-component of the current (see, e.g., [89,90,91,92]), i.e., with our notation, from the contraction of Jρ in eq. (6.25), with ω ρ .…”

Section: Comparison With Other Approachesmentioning

confidence: 99%

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Explicitly covariant light-front dynamics and relativistic few-body systems

Carbonell¹,

Desplanques²,

et al. 1998

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The wave function of a composite system is defined in relativity on a space-time surface. In the explicitly covariant light-front dynamics, reviewed in the present article, the wave functions are defined on the plane ω·x = 0, where ω is an arbitrary four-vector with ω 2 = 0. The standard non-covariant approach is recovered as a particular case for ω = (1, 0, 0, −1). Using the light-front plane is of crucial importance, while the explicit covariance gives strong advantages emphasized through all the review.The properties of the relativistic few-body wave functions are discussed in detail and are illustrated by examples in a solvable model. The three-dimensional graph technique for the calculation of amplitudes in the covariant light-front perturbation theory is presented.The structure of the electromagnetic amplitudes is studied. We investigate the ambiguities which arise in any approximate light-front calculations, and which lead to a non-physical dependence of the electromagnetic amplitude on the orientation of the lightfront plane. The elastic and transition form factors free from these ambiguities are found for spin 0, 1/2 and 1 systems.The formalism is applied to the calculation of the relativistic wave functions of twonucleon systems (deuteron, scattering state), with particular attention to the role of their new components in the deuteron elastic and electrodisintegration form factors and to their connection with meson exchange currents. Straigthforward applications to the pion and nucleon form factors and the ρ − π transition are also made. ,0 = − 2η(F 1 − ηF 2 + G 1 /2) + η/2B 6 ,(6.63)The matrix elementsJ 11 ,J 1−1 have the same form as J 11 , J 1−1 , whereasJ 10 ,J 00 differ from J 10 , J 00 by the items containing the nonphysical form factors B 5 , B 6 , B 7 . Other nonphysical form factors B 1−4 and B 8 do not contribute to these matrix elements.The matrix elementsJ λ ′ λ do not satisfy the condition (6.61). SubstitutingJ λ ′ λ in eq.(6.61) instead of J λ ′ λ , we get: ∆ ≡ (1 + 2η)J 11 +J 1−1 − 2 2ηJ 10 −J 00 = −(B 5 + B 7 ) .(6.64)

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Section: Comparison With Other Approachesmentioning

confidence: 99%

“…A similar expression for Γρ was given in[85]. In this reference however, as well as in[89], the structure ωP ρ /ω•p was used instead of the structure proportioanl to B 1 in(6.25). In this case, the form factor G E (0) does not coincide with the normalization integral.…”

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confidence: 99%

Explicitly covariant light-front dynamics and relativistic few-body systems

Carbonell¹,

Desplanques²,

et al. 1998

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The nucleon wave function in light-front dynamics

Karmanov¹

1998

Nuclear Physics A

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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.Comment: 35 pages, Latex, Submitted to Nucl. Phys.

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Violations of Lorentz Covariance in Light Front Quark Models

et al. 2000

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Electromagnetic form factors of the nucleon from relativistic quark models are analyzed: results from null-plane projection of the Feynman triangle diagram are compared with a Bakamjian-Thomas model. The magnetic form factors of the models differ by about 15% at spacelike momentum transfer 0.5 GeV 2 , while the charge form factors are much closer. Spurious contributions to electromagnetic form factors due to violations of rotational symmetry are eliminated for both models. One method changes magnetic form factors by about 10%, whereas the charge form factors stay nearly the same. Another one changes the charge form factor of the Bakamjian-Thomas model by more than 50%.

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Dependence of electromagnetic form factors of hadrons on light-cone frames

Cited by 3 publications

References 44 publications

Explicitly covariant light-front dynamics and relativistic few-body systems

Explicitly covariant light-front dynamics and relativistic few-body systems

The nucleon wave function in light-front dynamics

Violations of Lorentz Covariance in Light Front Quark Models

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