Flavor Decomposition of the Elastic Nucleon Electromagnetic Form Factors

Cates, G. D.; Jager, C. W. de; Riordan, S.; Wojtsekhowski, B.

doi:10.1103/physrevlett.106.252003

Cited by 151 publications

(243 citation statements)

References 44 publications

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“…This suppression was explicitly confirmed in Ref. [582] for both F 1 and F 2 using the latest data for the electric neutron form factor. The faster falloff of the d-quark form factors implies that the u quarks have a significantly tighter distribution than the d quarks in impact-parameter space [566].…”

Section: Dyson-schwinger Calculationsmentioning

confidence: 66%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

421

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: Dyson-schwinger Calculationsmentioning

confidence: 66%

Baryons as relativistic three-quark bound states

Eichmann

Sanchis-Alepuz

Williams

et al. 2016

Progress in Particle and Nuclear Physics

421

530

View full text Add to dashboard Cite

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“…[10] and references therein as an indication of the possibility of sizable nonzero strange matrix elements at large Q 2 or the importance of diquark degrees of freedom. While existing measurements of parityviolating elastic scattering yield very small contributions from the strange quarks up to Q 2 ≈ 1 (GeV/c) 2 [88][89][90][91], they still leave open the possibility for significant contributions from G s E and G s M which cancel in the parityviolating observables [91,92], although there are also results from lattice QCD that the strange-quark contribution is small for the charge and magnetic form factors [93,94].…”

Section: Flavor-dependent Contributions To σRmentioning

confidence: 99%

“…For Q 2 < ∼ 1 (GeV/c) 2 , we [33,34,37,[43][44][45][46][47][48] (open dark-green squares). Also shown the CJRW extractions [10] (solid black triangles), the AMT-Hadronic [63] (short-dashed black line) and VAMZ [65] (solid black line) fits, and the values from the GPD [85] (dotted magenta line), DSE [81] (long-dashed black line), PC-RCQM [82] (dasheddotted black line), and GBE-RCQM [83,84] (large-dotted red line) models. Note that for the proton, the up-and downquark contributions have weighting factors of 2/3 and -1/3 (Eq.…”

Section: Flavor Separation Of the Nucleon Form Factorsmentioning

confidence: 99%

“…In the diquark model, the singly occurring down-quark in the proton is more likely to be associated with an axial-vector diquark than a scalar diquark, and the contribution of the axial-vector diquark yields a more rapid falloff of the form factors. The up quarks are generally associated with the more tightly bound scalar diquarks, yielding a harder form factors [10,81,82,85,[95][96][97][98][99][100][101][102]. Recent calculations [99] suggest that pion loop corrections play a crucial rule for Q 2 < ∼ 1.0 (GeV/c) 2 .…”

Section: Flavor-dependent Contributions To σRmentioning

confidence: 99%

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Flavor decomposition of the nucleon electromagnetic form factors at lowQ2

2015

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Background The spatial distribution of charge and magnetization within the proton is encoded in the elastic form factors.These have been precisely measured in elastic electron scattering, and the combination of proton and neutron form factors allows for the separation of the up-and down-quark contributions.Purpose In this work, we extract the proton and neutron form factors from world's data with an emphasis on precise new data covering the low-momentum region, which is sensitive to the large-scale structure of the nucleon. From these, we separate the up-and down-quark contributions to the proton form factors.Method We combine cross section and polarization measurements of elastic electron-proton scattering to separate the proton form factors and two-photon exchange (TPE) contributions. We combine the proton form factors with parameterization of the neutron form factor data and uncertainties to separate the up-and down-quark contributions to the proton's charge and magnetic form factors.Results The extracted TPE corrections are compared to previous phenomenological extractions, TPE calculations, and direct measurements from the comparison of electron and positron scattering. The flavor-separated form factors are extracted and compared to models of the nucleon structure.Conclusions With the inclusion of the precise new data, the extracted TPE contributions show a clear change of sign at low Q 2 , necessary to explain the high-Q 2 form factor discrepancy while being consistent with the known Q 2 → 0 limit. We find that the new Mainz data yield a significantly different result for the proton magnetic form factor and its flavorseparated contributions. We also observe that the RMS radius of both the up-and down-quark distributions are smaller than the RMS charge radius of the proton.

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“…Many properties of baryons are successfully described via a Poincaré covariant Faddeev equation that expresses the presence of nonpointlike diquark correlations [21], evidence for the existence of which is accumulating [19,[22][23][24]. There is a fundamental mathematical similarity between diquark correlations and uniquely identified meson analogues [25].…”

mentioning

confidence: 99%

Features and flaws of a contact interaction treatment of the kaon

et al. 2013

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Elastic and semileptonic transition form factors for the kaon and pion are calculated using the leading-order in a global-symmetry-preserving truncation of the Dyson-Schwinger equations and a momentum-independent form for the associated kernels in the gap and Bethe-Salpeter equations. The computed form factors are compared both with those obtained using the same truncation but an interaction that preserves the one-loop renormalisation-group behaviour of QCD and with data. The comparisons show that: in connection with observables revealed by probes with |Q 2 | M 2 , where M ≈ 0.4 GeV is an infrared value of the dressed-quark mass, results obtained using a symmetry-preserving regularisation of the contact-interaction are not realistically distinguishable from those produced by more sophisticated kernels; and available data on kaon form factors do not extend into the domain whereupon one could distinguish between the interactions. The situation is different if one includes the domain Q 2 > M 2 . Thereupon, a fully consistent treatment of the contact interaction produces form factors that are typically harder than those obtained with QCD renormalisation-group-improved kernels. Amongst other things also described are a Ward identity for the inhomogeneous scalar vertex, similarity between the charge distribution of a dressed-u-quark in the K + and that of the dressed-u-quark in the π + , and reflections upon the point whereat one might begin to see perturbative behaviour in the pion form factor. Interpolations of the form factors are provided, which should assist in working to chart the interaction between light-quarks by explicating the impact on hadron properties of differing assumptions about the behaviour of the Bethe-Salpeter kernel.

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Flavor Decomposition of the Elastic Nucleon Electromagnetic Form Factors

Cited by 151 publications

References 44 publications

Baryons as relativistic three-quark bound states

Baryons as relativistic three-quark bound states

Flavor decomposition of the nucleon electromagnetic form factors at lowQ2

Features and flaws of a contact interaction treatment of the kaon

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