Determination of quadrupole strengths in the gamma*p-->Delta(1232) transition at Q2= 0.20 (GeV/c)2

Abstract

We report new precise p$(\vec{e},e^{\prime }p){\pi }^0$ measurements at the peak of the ${\Delta }^{+}(1232)$ resonance at $Q^2=\unit[0.20](GeV/c)^2$ performed at the Mainz Microtron (MAMI). The new data are sensitive to both the electric quadrupole ($E2$) and the coulomb quadrupole ($C2$) amplitudes of the ${\gamma }^{\ast }N\to \Delta$ transition. They yield precise quadrupole to dipole amplitude ratios CMR $=(-5.09\pm 0.28_{stat+sys}\pm 0.30_{model})$ and EMR $=(-1.96\pm 0.68_{stat+sys}\pm 0.41_{model})$ for $M_{1+}^{3/2}=(39.57\pm 0.75_{stat+sys}\pm 0.40_{model})(10^{-3}/m_{{\pi }^{+}})$. The new results are in disagreement with Constituent Quark Model predictions and in qualitative agreement with models that account for mesonic contributions, including recent Lattice calculations. They thus give further credence to the conjecture of deformation in hadronic systems favoring the attribution of the origin of deformation to the dominance of mesonic effects.

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References in corpus (3)

• Chiral Effective-Field Theory in the Delta(1232) Region: Pion Electroproduction on the Nucleon
• Lowest Q^2 Measurement of the gamma*p -> Delta Reaction: Probing the Pionic Contribution
• Electromagnetic form factors in the Hypercentral Constituent Quark Model

Cited by in corpus (20)

• The nucleon to Delta electromagnetic transition form factors in lattice QCD
• D-state effects in the electromagnetic N-Delta transition
• Nucleon to Delta transition form factors with $N_F=2+1$ domain wall fermions
• Measurements of $ep\to e^{\prime }{\pi }^{+}n$ at W = 1.6 - 2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS
• Extraction of Electromagnetic Transition Form Factors for Nucleon Resonances within a Dynamical Coupled-Channels Model
• Hadron structure at low Q^2
• Measurement of the neutron charge radius and the role of its constituents
• Measurements of the gamma*p->Delta Reaction At Low Q^2: Probing the Mesonic Contribution
• Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles
• Large-$N_c$ relations for the electromagnetic N to Delta(1232) transition
• Electromagnetic Transition Form Factors of Baryon Resonances
• Neutral Pion Electroproduction in the Resonance Region at High $Q^2$
• Electromagnetic Nucleon-to-Delta Transition in Holographic QCD
• Coupled-channel analysis of pion- and eta-electroproduction with the Jülich-Bonn-Washington model
• Virtual Compton Scattering measurements in the ${\gamma }^{\ast }N\to \Delta$ transition
• Impact of JLab data on the determination of GPDs at zero skewness and new insights from transition form factors $N\to \Delta$
• Light-cone sum rules for the $N\gamma \Delta$ transitions for real photons
• N to $\Delta$ transition amplitudes from QCD sum rules
• Electromagnetic transition form factors, $E2/M1$ and $C2/M1$ ratios of the baryon decuplet
• Pion electroproduction measurements in the nucleon resonance region