The role of the pion cloud in electroproduction of the $\Delta$(1232)

Abstract

We calculate the ratios $E2/M1$ and $C2/M1$ of the multipole amplitudes for electroproduction of the $\Delta$(1232) in the range of photon virtuality $0<-K^2<1$~GeV${}^2$ in a chiral chromodielectric model and a linear $\sigma$-model. We find that relatively large experimental values can be explained in terms of the pion contribution alone; the contribution arising from d-state quark admixture remains below 10\%. We describe the pion cloud as a coherent state and use spin and isospin projection to obtain the physical nucleon and the $\Delta$. The $A_{1/2}$ and $A_{3/2}$ amplitudes are reasonably well reproduced in the $\sigma$-model; in the chromodielectric model, however, they are a factor of two too small.

arXiv comment10 pages LaTeX2e, 3 LaTeX figures within the text; Requires elsart.cls (included in the self-unpacking uuencoded gzipped file). (Accepted for publication in Phys. Lett. B)

References in corpus (3)

• Baryon Current Matrix Elements in a Light-Front Framework
• Quark Matter in the Chiral Color Dielectric Model
• $E2/M1$ Ratio for the $\gamma N\to \Delta$ Transition in the Chiral Quark Soliton Model

Cited by in corpus (30)

• Electromagnetic excitation of the Delta(1232)-resonance
• Electroexcitation of nucleon resonances
• A chiral bag model approach to delta electroproduction
• Recoil Polarization for Delta Excitation in Pion Electroproduction
• Measurement of the Transverse-Longitudinal Cross Sections in the p (e,e'p)pi0 Reaction in the Delta Region
• Measurements of the gamma*p->Delta Reaction At Low Q^2: Probing the Mesonic Contribution
• Helicity amplitudes and electromagnetic decays of hyperon resonances
• Recoil Polarization Measurements for Neutral Pion Electroproduction at Q^2=1 (GeV/c)^2 Near the Delta Resonance
• Electromagnetic Transition Form Factors of Baryon Resonances
• Moments of the neutron charge form factor and the N->Delta quadrupole transition
• Pion electro-production in the Roper region in chiral quark models
• The electroproduction of the $\Delta$(1232) in the chiral quark-soliton model
• A chiral quark model for meson electro-production in the region of D-wave resonances
• Electroexcitation of the ${\Delta }^{+}(1232)$ at low momentum transfer
• Parametrizations of the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors and Siegert's theorem
• Measurements of the γ* p --> Δ(1232) reaction at low Q2
• Baryon transition form factors at the pole
• New low-$Q^2$ measurements of the ${\gamma }^{\ast }N\to \Delta (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem
• N^* electroproduction amplitudes in a model with dynamical confinement
• Virtual Compton Scattering measurements in the nucleon resonance region
• Axial amplitudes for Delta excitation in chiral quark models
• $\Delta$(1232) electroproduction amplitudes in chiral soliton models of the nucleon
• Electromagnetic transition form factors, $E2/M1$ and $C2/M1$ ratios of the baryon decuplet
• Q^2-evolution of nucleon-to-resonance transition form factors in a QCD-inspired vector-meson-dominance model
• Nucleon to $\Delta$ transition form factors and empirical transverse charge densities
• Eta and kaon production in a chiral quark model
• Combined parametrization of the neutron electric form factor and the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors
• Direct calculation of the K-matrix for pion electro-production in the Delta channel
• Dynamical generation of resonances in the P33 partial wave
• Pion electroproduction measurements in the nucleon resonance region