Constituent-Quark Model with Pionic Contributions: Electromagnetic 
                
                  
                
                $${\varvec{N\rightarrow \varDelta }}$$
                
                  
                    
                      N
                      →
                      Δ
                    
                  
                
               Transition

Jung, Ju-Hyun; Schweiger, Wolfgang; Biernat, Elmar P.

doi:10.1007/s00601-018-1479-3

Cited by 4 publications

(2 citation statements)

References 22 publications

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“…As in the spin-0 pion case we also find for the spin-1 ρ-meson remarkable similarities with the covariant light-front approach of Carbonell et al [9]. Current and future applications of our quite general formalism include deuteron form factors [10], electroweak form factors of heavy-light mesons [11,12,13], nucleon form factors and pion-cloud effects [14], baryon transition form factors such as N-∆ transition form factors [15], and mesonbaryon vertices [16].…”

Section: Discussionsupporting

confidence: 69%

$\rho $-Meson Form Factors in the Point Form

Biernat¹,

Schweiger²

2017

Acta Phys. Pol. B Proc. Suppl.

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We present a calculation of the electromagnetic form factors of the ρ + meson. Our formalism is based on the point-form of relativistic quantum mechanics. Electron-ρ-meson scattering is formulated as a coupled-channel problem for a Bakamjian-Thomas mass operator, such that the dynamics of the exchanged photon is taken explicitly into account. The ρ-meson current is extracted from on-shell matrix elements of the optical potential of the scattering process. As a consequence of the violation of cluster separability in the Bakamjian-Thomas framework, our current includes additional, unphysical contributions, which can be separated from the physical ones uniquely. Our results for the form factors are in good agreement with other approaches.

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Section: Discussionsupporting

confidence: 69%

$\rho $-Meson Form Factors in the Point Form

Biernat¹,

Schweiger²

2017

Acta Phys. Pol. B Proc. Suppl.

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“…the valence contribution) and a non-valence D 0 B * c state. This way of including non-valence contributions has already been pursued for the (non-perturbative) calculation of hadron decay widths [33,34] and pion-cloud effects in electromagnetic baryon form factors [35,36]. The new piece in our case would be a vertex that provides the transition from the bū channel to the cūbc channel or, rephrased in terms of hadronic degrees of freedom, the B * c B − D 0 vertex which has to be expressed in terms of quark degrees-of-freedom.…”

Section: Discussionmentioning

confidence: 99%

Weak transition form factors of heavy-light pseudoscalar mesons for space- and timelike momentum transfers

Heger,

Gómez-Rocha,

Schweiger

2021

Preprint

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This paper deals with the description of weak B − → D 0 , π 0 and D − → K 0 , π 0 transition form factors in both, the space-and time-like momentum transfer regions, within a constituent-quark model. To this aim neutrino-meson scattering and semileptonic weak decays are formulated within the framework of point-form relativistic quantum mechanics to end up with relativistic invariant process amplitudes from which meson transition currents and form factors are extracted in an unambiguous way. For space-like momentum transfers, these form factors depend on the frame in which the W M M vertex is considered. On physical grounds such a frame dependence is expected from a pure valence-quark picture, since a complete, frame independent description of form factors is supposed to require valence as well as non-valence contributions. Non-valence contributions, the most important being the Z-graphs, are, however, suppressed in the infinite-momentum frame (q 2 < 0). On the other hand, they can play a significant role in the Breit frame (q 2 < 0) and in the direct decay calculation (q 2 > 0), as a comparison with the infinite-momentum-frame form factors (analytically continued to q 2 > 0) reveals. Numerical results for the analytically continued infinite-momentum-frame form factors are found to agree very well with lattice data in the time-like momentum transfer region and also the experimental value for the slope of the F + B→D transition form factor at zero recoil is reproduced satisfactorily. Furthermore, these predictions satisfy heavyquark-symmetry constraints and their q 2 dependence is well approximated by a pole fit, reminiscent of a vector-meson-dominance-like decay mechanism. We discuss how such a decay mechanism can be accommodated within an extension of our constituent-quark model, by allowing for a non-valence component in the meson wave functions, and we also address the question of wrong cluster properties inherent in the formulation of relativistic quantum mechanics employed in this article.

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Pion-Cloud Contribution to the $$N\rightarrow \varDelta $$ Transition Form Factors

Jung

Schweiger

2020

Recent Progress in Few-Body Physics

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We examine the contribution of the pion cloud to the electromagnetic N → ∆ transition form factors within a relativistic hybrid constituent-quark model. In this model baryons consist not only of the 3q valence component, but contain, in addition, a 3qπ non-valence component. We start with constituent quarks which are subject to a scalar, isoscalar confining force. This leads to an SU (6) spin-flavor symmetric spectrum with degenerate nucleon and Delta masses. Mass splitting is caused by pions which are assumed to couple directly to the quarks. The point-form of relativistic quantum mechanics is employed to achieve a relativistically invariant description of this system. The N → ∆ transition current is then determined from the one-photon exchange contribution to the ∆ electroproduction amplitude. We will give predictions for the ratios REM and RSM of electric to magnetic and Coulomb to magnetic form factors, which are supposed to be most sensitive to pion-cloud effects.

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Constituent-Quark Model with Pionic Contributions: Electromagnetic $${\varvec{N\rightarrow \varDelta }}$$ N → Δ Transition

Cited by 4 publications

References 22 publications

$\rho $-Meson Form Factors in the Point Form

$\rho $-Meson Form Factors in the Point Form

Weak transition form factors of heavy-light pseudoscalar mesons for space- and timelike momentum transfers

Pion-Cloud Contribution to the $$N\rightarrow \varDelta $$ Transition Form Factors

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