Electromagnetic form factors of the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Δ</mml:mi></mml:math>with D-waves

Ramalho, G.; Peña, M. T.; Gross, Franz

doi:10.1103/physrevd.81.113011

Cited by 62 publications

(89 citation statements)

References 149 publications

(619 reference statements)

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“…In the covariant spectator quark model of Refs. [545,605] the magnetic octupole form factor is strongly dependent on the d-wave content of the wave function; two different parametrizations for the ∆ wave function lead to different signs although in both cases the result is negative at zero photon momentum. We note again that in the Dyson-Schwinger calculations the partial-wave content of the nucleon and ∆ amplitudes in terms of s, p, d and f waves is not restricted in any way but determined dynamically when solving the bound-state equations.…”

Section: Delta Electromagnetic Form Factorsmentioning

confidence: 99%

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Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

436

530

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We review the spectrum and electromagnetic properties of baryons described as relativistic three-quark bound states within QCD. The composite nature of baryons results in a rich excitation spectrum, whilst leading to highly non-trivial structural properties explored by the coupling to external (electromagnetic and other) currents. Both present many unsolved problems despite decades of experimental and theoretical research. We discuss the progress in these fields from a theoretical perspective, focusing on nonperturbative QCD as encoded in the functional approach via Dyson-Schwinger and Bethe-Salpeter equations. We give a systematic overview as to how results are obtained in this framework and explain technical connections to lattice QCD. We also discuss the mutual relations to the quark model, which still serves as a reference to distinguish 'expected' from 'unexpected' physics. We confront recent results on the spectrum of non-strange and strange baryons, their form factors and the issues of two-photon processes and Compton scattering determined in the DysonSchwinger framework with those of lattice QCD and the available experimental data. The general aim is to identify the underlying physical mechanisms behind the plethora of observable phenomena in terms of the underlying quark and gluon degrees of freedom.

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Section: Delta Electromagnetic Form Factorsmentioning

confidence: 99%

“…Another covariant approach is the covariant spectator model of Ref. [541], which has been actively explored for a range of observables including various elastic and transition form factors of octet and decuplet baryons [542][543][544][545][546][547]; a recent overview can be found in Ref. [548].…”

Section: B Kinematics Andmentioning

confidence: 99%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

436

530

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“…The wave functions of the nucleon, N (1520) and N (1535) are discussed in Refs. [8,9,22].The covariant spectator quark model was already applied to the nucleon [22,23,[36][37][38], several nucleon resonances [8-10, 25, 27], ∆ resonances [10,34,35,[39][40][41][42], and other transitions between baryon states [24,30,[43][44][45].When the baryon wave functions are represented in terms of the single quark and quark-pair states, one can write the transition current in a relativistic impulse approximation as [22][23][24] where j µ q is the quark current operator and Γ labels the scalar diquark and vectorial diquark (projections Λ = 0, ±) polarizations. The factor 3 takes account of the contributions of all the quark-pairs by symmetry.…”

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confidence: 99%

Semirelativistic approximation to the γN→N(1520) and γN
Ramalho
¹

2017
Phys. Rev. D
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The representation of the wave functions of the nucleon resonances within a relativistic framework is a complex task. In a nonrelativistic framework the orthogonality between states can be imposed naturally. In a relativistic generalization, however, the derivation of the orthogonality condition between states can be problematic, particularly when the states have different masses. In this work we study the N (1520) and N (1535) states using a relativistic framework. We considered wave functions derived in previous works, but impose the orthogonality between the nucleon and resonance states using the properties of the nucleon, ignoring the difference of masses between the states (semirelativistic approximation). The N (1520) and N (1535) wave functions are then defined without any adjustable parameters and are used to make predictions for the valence quark contributions to the transition form factors. The predictions compare well with the data particularly for high momentum transfer, where the dominance of the quark degrees of freedom is expected. I. INTRODUCTIONIn the last century we learned that the hadrons, including the nucleon (N ) and the nucleon excitations (N * ) are not pointlike particles and have their own internal structure. The structure of those states is the result of the internal constituents, quarks and gluons, and the interactions ruled by Quantum Chromodynamics (QCD). In the last decades experimental facilities such as Jefferson Lab (JLab), MAMI (Mainz) and MIT-Bates have accumulated information (data) about the electromagnetic structure of the nucleon resonances, parametrized in terms of structure form factors for masses up to 3 GeV [1,2].Several theoretical models have been proposed to interpret the nucleon resonance spectrum and the information associated with its internal structure [1][2][3]. Different models provide different parametrizations of the internal structure in terms of the effective degrees of freedom. Some of the more successful models are the constituent quark models (CQM) based on nonrelativistic kinematics like the Karl-Isgur model [3,4] and the Light Front quark models (LFQM) defined in the infinite momentum frame [5][6][7]. In those extreme cases, nonrelativistic models or LFQM, the kinematics is simplified. In general, however, the transition between the nonrelativistic and relativistic regimes is not a trivial task.In this work we discuss the γ * N → N * transition form factors for resonances N * with negative parity. The definition of the wave functions of the nucleon (mass M N ) and a nucleon excitation (mass M R ), in terms of the internal quark degrees of freedom, can be done first in the rest frame of the particle, and extended later for a moving frame using a Lorentz transformation. In a nonrelativistic framework the mass and energy of the state are not relevant for the definition of the states. Moreover, the orthogonality between the nucleon and the resonance N * is ensured, since the wave functions are independent of their masses. To understand the complexity of ...

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“…For this purpose, we rely on the covariant spectator quark model [32][33][34][35][36][37][38], since it was successful in the studies of the electromagnetic structure of nucleon [39][40][41], octet and decuplet baryons [34][35][36][37][42][43][44][45], transition form factors of the reactions Ã N ! Áð1232Þ, Ã N !…”

Section: Introductionmentioning

confidence: 99%

Octet to decuplet electromagnetic transition in a relativistic quark model

Ramalho

Tsushima

2013

Phys. Rev. D

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We study the octet to decuplet baryon electromagnetic transitions using the covariant spectator quark model and predict the transition magnetic dipole form factors for those involving the strange baryons. Utilizing SU (3) symmetry, the valence quark contributions are supplemented by the pion cloud dressing based on the one estimated in the γ * N → ∆ reaction. Although the valence quark contributions are dominant in general, the pion cloud effects turn out to be very important to describe the experimental data. We also show that other mesons besides the pion in particular the kaon, may be relevant for some reactions such as γ * Σ + → Σ * + , based on our analysis for the radiative decay widths of the strange decuplet baryons.

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Electromagnetic form factors of theΔwith D-waves

Cited by 62 publications

References 149 publications

Baryons as relativistic three-quark bound states

Baryons as relativistic three-quark bound states

Semirelativistic approximation to the γN→N(1520) and γN
Ramalho
¹

2017
Phys. Rev. D
Self Cite
19
2
12
0
View full text Add to dashboard Cite

Octet to decuplet electromagnetic transition in a relativistic quark model

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Electromagnetic form factors of theΔwith D-waves

Cited by 62 publications

References 149 publications

Baryons as relativistic three-quark bound states

Baryons as relativistic three-quark bound states

Semirelativistic approximation to the γ*N→N(1520) and γ*NRamalho1 2017Phys. Rev. DSelf Cite192120View full textAdd to dashboardCite

Octet to decuplet electromagnetic transition in a relativistic quark model

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Semirelativistic approximation to the γN→N(1520) and γN
Ramalho
¹

2017
Phys. Rev. D
Self Cite
19
2
12
0
View full text Add to dashboard Cite