A Coherent Interpretation of the Form Factors of the Nucleon in Terms of a Pion Cloud and Constituent Quarks

Abstract

The recent unbiased measurements of the electric form factor of the neutron suggest that its shape may be interpreted as a smooth broad distribution with a bump at Q^2 \approx 0.3(GeV/c)^2 superimposed. As a consequence the corresponding charge distribution in the Breit frame shows a negative charge extending as far out as 2fm. It is natural to identify this charge with the pion cloud. This realisation is then used to reanalyse all old and new data of the electric and magnetic from factors of the proton and the neutron by a phenomenological fit and by a fit based on the constituent quark model. It is shown that it is possible to fit all form factors coherently with both ansaetzen and that they all show the signal of the pion cloud.

arXiv comment17 pages, 17 figures

References in corpus (17)

• The ratio of proton's electric to magnetic form factors measured by polarization transfer
• Measurement of GEp/GMp in ep -> ep to Q2 = 5.6 GeV2
• Dispersion-Theoretical Analysis of the Nucleon Electromagnetic Formfactors
• Precise Neutron Magnetic Form Factors
• The Charge Form Factor of the Neutron from the Reaction \pol{2H}(\pol{e},e'n)p
• A Measurement of the Electric Form Factor of the Neutron through $\vec{d}(\vec{e},e^{\prime }n)p$ at $Q^2=0.5$ (GeV/c)${}^2$
• The Transverse Asymmetry ${\mathbf{A}}_{{\mathbf{T}}^{\prime }}$ from Quasi-elastic ${}^3\overrightarrow{\mathrm{He}}(\vec{e},e^{\prime })$ Process and the Neutron Magnetic Form Factor
• Nucleon Charge and Magnetization Densities from Sachs Form Factors
• Extraction of electromagnetic neutron form factors through inclusive and exclusive polarized electron scattering on polarized 3He target
• Polarization transfer in the ${}^4$He$(\vec{e},e^{\prime }{\vec{p}}^3$H reaction
• New empirical fits to the proton electromagnetic form factors
• Electromagnetic Form Factors of the Nucleon in an Improved Quark Model
• PWIA Extraction of the Neutron Magnetic Form Factor from Quasi-Elastic 3He(e,e') at Q^2 = 0.3 to 0.6 (GeV/c)^2
• A Comparison of Polarization Observables in Electron Scattering from the Proton and Deuteron
• Incorporating Chiral Symmetry and Heavy Quark Theory in Extrapolations of Octet Baryon Charge Radii
• Interpreting the Neutron's Electric Form Factor: Rest Frame Charge Distribution or Foldy Term?
• Electromagnetic Gauge Invariance of the Cloudy Bag Model

Cited by in corpus (110)

• High-precision determination of the electric and magnetic form factors of the proton
• Nucleon Electromagnetic Form Factors
• Proton elastic form factor ratios to $Q^2$ = 3.5 GeV${}^2$ by polarization transfer
• The electric and magnetic form factors of the proton
• Strange Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment
• Nucleon structure from mixed action calculations using 2+1 flavors of asqtad sea and domain wall valence fermions
• Dispersion analysis of the nucleon form factors including meson continua
• Measurement of Strange Quark Contributions to the Nucleon's Form Factors at Q^2=0.230 (GeV/c)^2
• High Precision Measurement of the Proton Elastic Form Factor Ratio ${\mu }_p{G}_E/G_M$ at low $Q^2$
• Precision Measurements of the Nucleon Strange Form Factors at Q^2 ~0.1 GeV^2
• Parity-violating electroweak asymmetry in $\vec{e}p$ scattering
• Evidence for Strange Quark Contributions to the Nucleon's Form Factors at $Q^2$ = 0.108 (GeV/c)${}^2$
• Electromagnetic Form Factors of the Nucleon and Compton Scattering
• Aspects of Hadron Physics
• Parity-Violating Electron Scattering from 4He and the Strange Electric Form Factor of the Nucleon
• Nucleon form factors, generalized parton distributions and quark angular momentum
• Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
• Constraints on the Nucleon Strange Form Factors at Q^2 ~ 0.1 GeV^2
• Nucleon electromagnetic form factors from the covariant Faddeev equation
• Measurement of the proton electric to magnetic form factor ratio from \vec ^1H(\vec e, e'p)
• Charge and matter distributions and form factors of light, medium and heavy neutron-rich nuclei
• Density dependence of the symmetry energy from neutron skin thickness in finite nuclei
• Low Q^2 measurements of the proton form factor ratio $m{u}_p{G}_E/G_M$
• Nucleon electromagnetic form factors from lattice QCD using a nearly physical pion mass
• Axial, induced pseudoscalar, and pion-nucleon form factors in manifestly Lorentz-invariant chiral perturbation theory
• Origin of the neutron skin thickness of 208Pb in nuclear mean-field models
• Measurements of the neutron electric to magnetic form factor ratio GEn/GMn via the ^2H(\vec{e},e'\vec{n})^1H reaction to Q^2 = 1.45 (GeV/c)^2
• Nucleon Electromagnetic Form Factors from Lattice QCD using 2+1 Flavor Domain Wall Fermions on Fine Lattices and Chiral Perturbation Theory
• A pure S-wave covariant model for the nucleon
• Updated dispersion-theoretical analysis of the nucleon electromagnetic form factors
• The Charge Form Factor of the Neutron at Low Momentum Transfer from the ${}^2\vec{\mathrm{H}}(\vec{\mathrm{e}},{\mathrm{e}}^{\prime }\mathrm{n})\mathrm{p}$ Reaction
• Flavor decomposition of the nucleon electromagnetic form factors
• Electromagnetic form factors of the nucleon in chiral perturbation theory including vector mesons
• Electromagnetic form factors of the nucleon in relativistic baryon chiral perturbation theory
• Precise determination of low-Q nucleon electromagnetic form factors and their impact on parity-violating e-p elastic scattering
• Proton structure corrections to electronic and muonic hydrogen hyperfine splitting
• The nuclear symmetry energy and the breaking of the isospin symmetry: how do they reconcile with each other?
• Electroweak structure of the nucleon, meson cloud and light-cone wavefunctions
• A covariant view on the nucleons' quark core
• The Proton Elastic Form Factor Ratio at Low Momentum Transfer
• Chiral Perturbation Theory: Introduction and Recent Results in the One-Nucleon Sector
• Octet baryon electromagnetic form factors in a relativistic quark model
• Hadron structure at low Q^2
• On the pion cloud of the nucleon
• Nucleon Form Factors - A Jefferson Lab Perspective
• Measurements of the gamma*p->Delta Reaction At Low Q^2: Probing the Mesonic Contribution
• Measurements of the Generalized Electric and Magnetic Polarizabilities of the Proton at Low Q2 Using the VCS Reaction
• Nucleon Form Factors of the Isovector Axial-Vector Current: Situation of Experiments and Theory
• Novel evaluation of the two-pion contribution to the nucleon isovector form factors
• Large-$N_c$ relations for the electromagnetic N to Delta(1232) transition
• Electromagnetic Transition Form Factors of Baryon Resonances
• Measurement of the neutron electric to magnetic form factor ratio at Q2 = 1.58 GeV2 using the reaction 3He(e,e'n)pp
• Testing axial and electromagnetic nucleon form factors in time-like regions in the processes $\bar{p}+n\to {\pi }^{-}+{\ell }^{-}+{\ell }^{+}$ and $\bar{p}+p\to {\pi }^0+{\ell }^{-}+{\ell }^{+}$, $\ell =e$, $\mu$
• The Role of Mesons in the Electromagnetic Form Factors of the Nucleon
• Quantifying the nucleon's pion cloud with transverse charge densities
• A new measurement of the structure functions $P_{LL}-P_{TT}/epsilon$ and $P_{LT}$ in virtual Compton scattering at $Q^2=$ 0.33 (GeV/c)${}^2$
• Light-front interpretation of Proton Generalized Polarizabilities
• Nucleon resonances in Compton scattering
• Proton Electromagnetic Form Factor Ratios at Low Q^2
• Nonidentical protons
• Quadrupole moments of low lying baryons with spin 1/2^+, spin 3/2^+, and spin 3/2^+ \to 1/2^+ transitions
• Dressing the electromagnetic nucleon current
• Improved empirical parametrizations of the ${\gamma }^{\ast }N\to \Delta (1232)$ and ${\gamma }^{\ast }N\to N(1520)$ helicity amplitudes and the Siegert's theorem
• Light Cone QCD Sum Rules Analysis of the Axial N -> Delta Transition Form Factors
• Comparison of Nucleon Form Factors from Lattice QCD Against the Light Front Cloudy Bag Model and Extrapolation to the Physical Mass Regime
• Second and fourth moments of the charge density and neutron-skin thickness of atomic nuclei
• Realizing vector meson dominance with transverse charge densities
• Real and Virtual Compton Scattering: the nucleon polarisabilities
• New low-$Q^2$ measurements of the ${\gamma }^{\ast }N\to \Delta (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem
• Effects of Coulomb and isospin symmetry breaking interactions on neutron-skin thickness
• How much two-photon exchange is needed to resolve the proton form factor discrepancy?
• The Role of 5-quark Components on the Nucleon Form Factors
• New Insight in the $Q^2$-Dependence of Proton Generalized Polarizabilities
• Nucleon Form Factors in Dispersion Theory
• Effects of finite nucleon size, vacuum polarization, and electromagnetic spin-orbit interaction on nuclear binding energies and radii in spherical nuclei
• Determining the size of the proton
• Chiral perturbation theory - Success and challenge
• Measurement of the Beam-Recoil Polarization in Low-Energy Virtual Compton Scattering from the Proton
• The electric form factor of the neutron and its chiral content
• Pauli radius of the proton
• Non-spherical proton shape and hydrogen hyperfine splitting
• Electromagnetic multipole moments of baryons
• Overview and Perspectives in Nuclear Physics
• Measurement of the Generalized Polarizabilities of the Proton at Intermediate $Q^2$
• Combined parametrization of the neutron electric form factor and the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors
• Nucleon Polarizabilities: Theory
• Magnetization screening from gluonic currents and scaling law violation in the ratio of magnetic form factors for neutron and proton
• Precision calculation of processes used for luminosity measurement at the ZEUS experiment
• Direct calculation of the K-matrix for pion electro-production in the Delta channel
• Baryon chiral perturbation theory
• Breit type equation for mesonic atoms
• Neutron structure effects in the deuteron and one neutron halos
• Phenomenological insight into JLab proton polarization data puzzle by deuteron impulse approximation
• Note on the electromagnetic radius of proton
• Hadron structure at small momentum transfer
• Chiral effective field theories of the strong interactions
• Experiments with polarized 3He at MAMI
• The Higgs oscillator on the hyperbolic plane and Light-Front Holography
• Overview of nucleon structure studies
• Short Range Interactions in the Hydrogen Atom
• Logarithmic corrections and soft photon phenomenology in the multipole model of the nucleon form factors
• Recent developments in effective field theory
• On Geometric Structure of Point Particles
• Meson loop effects on the pion electromagnetic form factor
• Unpolarized nucleon structure studies utilizing polarized electromagnetic probes
• Comparisons of electric charge and axial charge meson cloud distributions in the PCQM
• Comprehensive table of calculated Huff factors
• Nucleon electroweak form factors in a meson-cloud model
• Nucleon electromagnetic form factors with 2+1 flavors of domain wall fermions
• On the physics behind the form factor ratio ${\mu }_p{G}_E^p(Q^2)/G_M^p(Q^2)$