Measurements of the γ* p --> Δ(1232) reaction at low Q2

Abstract

We report new p$(\vec{e},e^{\prime }p){\pi }^{\circ }$ measurements in the ${\Delta }^{+}(1232)$ resonance at the low momentum transfer region utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The mesonic cloud dynamics are predicted to be dominant and appreciably changing in this region while the momentum transfer is sufficiently low to be able to test chiral effective calculations. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations with pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements suggest that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements.

References in corpus (8)

• Chiral Effective-Field Theory in the Delta(1232) Region: Pion Electroproduction on the Nucleon
• The nucleon to Delta electromagnetic transition form factors in lattice QCD
• Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
• Nucleon to Delta transition form factors with $N_F=2+1$ domain wall fermions
• Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2
• Measurements of the gamma*p->Delta Reaction At Low Q^2: Probing the Mesonic Contribution
• Neutral Pion Electroproduction in the Resonance Region at High $Q^2$
• Electromagnetic form factors in the Hypercentral Constituent Quark Model

Cited by in corpus (12)

• Measurement of the neutron charge radius and the role of its constituents
• Electromagnetic Transition Form Factors of Baryon Resonances
• Nucleon resonances in Compton scattering
• Electromagnetic form factors of the baryon decuplet with flavor SU(3) symmetry breaking
• Electroexcitation of the ${\Delta }^{+}(1232)$ at low momentum transfer
• New low-$Q^2$ measurements of the ${\gamma }^{\ast }N\to \Delta (1232)$ Coulomb quadrupole form factor, pion cloud parametrizations and Siegert's theorem
• Impact of JLab data on the determination of GPDs at zero skewness and new insights from transition form factors $N\to \Delta$
• Virtual Compton Scattering measurements in the nucleon resonance region
• Low-$Q^2$ empirical parametrizations of the $N^{\ast }$ helicity amplitudes
• Two-Photon-Exchange Effects and $\Delta (1232)$ Deformation
• Combined parametrization of the neutron electric form factor and the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors
• Pion electroproduction measurements in the nucleon resonance region