The Role of 5-quark Components on the Nucleon Form Factors

Abstract

The covariant quark model is shown to allow a phenomenological description of the neutron electric form factor, G_E^n(Q^2), in the impulse approximation, provided that the wave function contains minor (~ 3 %) admixtures of the lowest sea-quark configurations. While that form factor is not very sensitive to whether the \bar q in the qqqq\bar q component is in the P-state or in the S-state, the calculated nucleon magnetic form factors are much closer to the empirical values in the case of the former configuration. In the case of the electric form factor of the proton, G_E^p(Q^2), a zero appears in the impulse approximation close to 9 GeV^2, when the \bar q is in the P-state. That configuration, which may be interpreted as a pion loop ("cloud") fluctuation, also leads to a clearly better description of the nucleon magnetic moments. When the amplitude of the sea-quark admixtures are set so as to describe the electric form factor of the neutron, the qqqq\bar q admixtures have the phenomenologically desirable feature, that the electric form factor of the proton falls at a more rapid rate with momentum transfer than the magnetic form factor.

arXiv commentTo appear in Nuclear Physics A

References in corpus (20)

• 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
• Improved Measurement of the $\bar{d}/\bar{u}$ Asymmetry in the Nucleon Sea
• Dispersion-Theoretical Analysis of the Nucleon Electromagnetic Formfactors
• Two-photon exchange in elastic electron-nucleon scattering
• A Coherent Interpretation of the Form Factors of the Nucleon in Terms of a Pion Cloud and Constituent Quarks
• Dynamical Study of the Delta Excitation in N(e,e' pi) Reactions
• The Flavor Asymmetry of the Light Quark Sea from Semi-inclusive Deep-inelastic Scattering
• The two-photon exchange contribution to elastic electron-nucleon scattering at large momentum transfer
• Measurements of GEn/GMn from the ^2H(vec{e},e'vec{n})^1H Reaction to Q^2=1.45 (GeV/c)^2
• Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
• Dynamical Model of Weak Pion Production Reactions
• Neutron charge form factor at large $q^2$
• Low lying $qqqq\bar{q}$ states in the baryon spectrum
• 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
• The $s\bar{s}$ component of the proton and the strangeness magnetic moment
• Baryon Form Factors of Relativistic Constituent-Quark Models
• The $qqqq\bar{q}$ components and hidden flavor contributions to the baryon magnetic moments
• Precise Determination of the Neutron Magnetic Form Factor to Higher $Q^2$
• Scaling of Hadronic Form Factors in Point Form Kinematics

Cited by in corpus (9)

• Unquenched quark model for baryons: magnetic moments, spins and orbital angular momenta
• Electroweak structure of the nucleon, meson cloud and light-cone wavefunctions
• Electromagnetic nucleon form factors in instant and point form
• Electromagnetic Transition Form Factors of Baryon Resonances
• Strong decay of low-lying $S_{11}$ and $D_{13}$ nucleon resonances to pseudoscalar mesons and octet baryons
• The small axial charge of the N(1535) resonance
• The contributions of $qqqq\bar{q}$ components to the axial charges of proton and its resonances
• Sea-quark effects in the pion charge form factor
• Flavor asymmetry of the nucleon sea in an unquenched quark model