Electroexcitation of the ${\Delta }^{+}(1232)$ at low momentum transfer

Abstract

We report on new p$(e,e^{\prime }p){\pi }^{\circ }$ measurements at the ${\Delta }^{+}(1232)$ resonance at the low momentum transfer region. The mesonic cloud dynamics is predicted to be dominant and rapidly changing in this kinematic region offering a test bed for chiral effective field theory calculations. The new data explore the low $Q^2$ dependence of the resonant quadrupole amplitudes while extending the measurements of the Coulomb quadrupole amplitude to the lowest momentum transfer ever reached. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations that include 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.

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Cited by in corpus (17)

• Measurement of the neutron charge radius and the role of its constituents
• Electromagnetic Transition Form Factors of Baryon Resonances
• Nucleon resonances in Compton scattering
• $N^{\ast }$ Form Factors based on a Covariant Quark Model
• 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
• Nucleon-to-Delta transition form factors in chiral effective field theory using the complex-mass scheme
• Virtual Compton Scattering and Nucleon Generalized Polarizabilities
• Low-$Q^2$ empirical parametrizations of the $N^{\ast }$ helicity amplitudes
• Electromagnetic transition form factors, $E2/M1$ and $C2/M1$ ratios of the baryon decuplet
• Electromagnetic multipole moments of baryons
• Combined parametrization of the neutron electric form factor and the ${\gamma }^{\ast }N\to \Delta (1232)$ quadrupole form factors
• Constituent-quark model with pionic contributions: electromagnetic $N\to \Delta$ transition
• Quark model calculations of transition form factors at high photon virtualities
• Pion electroproduction measurements in the nucleon resonance region
• Axial-vector nucleon-to-delta transition form factors using the complex-mass renormalization scheme