Abstract. To determine nonspherical angular-momentum amplitudes in hadrons at long ranges (low Q 2 ), data were taken for the p( e, e p)π 0 reaction in the ∆ region at Q 2 = 0.060 (GeV/c) 2 utilizing the magnetic spectrometers of the A1 Collaboration at MAMI. The results for the dominant transition magnetic dipole amplitude and the quadrupole to dipole ratios at W = 1232 MeV are M Experimental confirmation of the presence of nonspherical hadron amplitudes (i.e. d states in quark models or p-wave π-N states) is fundamental and has been the subject of intense experimental and theoretical interest (for reviews see [1][2][3]). This effort has focused on the measurement of the electric and Coulomb quadrupole amplitudes (E2, C2) in the predominantly M 1 (maga Current address:
We report new p(e, e ′ p)π • measurements in the ∆ + (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.PACS. 13.60.Le Meson production -13.40.Gp Electromagnetic form factors
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