Unitary ambiguity in the extraction of the E2/M1 ratio for the $\gamma N\leftrightarrow \Delta$ transition

Abstract

The resonant electric quadrupole amplitude in the transition $\gamma N\leftrightarrow \Delta (1232)$ is of great interest for the understanding of baryon structure. Various dynamical models have been developed to extract it from the corresponding photoproduction multipole of pions on nucleons. It is shown that once such a model is specified, a whole class of unitarily equivalent models can be constructed, all of them providing exactly the same fit to the experimental data. However, they may predict quite different resonant amplitudes. Therefore, the extraction of the E2/M1($\gamma N\leftrightarrow \Delta$) ratio (bare or dressed) which is based on a dynamical model using a largely phenomenological $\pi N$ interaction is not unique.

10 pages revtex including 4 postscript figures

Cited by in corpus (12)

• Multipole analysis of pion photoproduction based on fixed t dispersion relations and unitarity
• Determination of the E2/M1 Ratio in the γN \to Δ(1232) Transition from a Simultaneous Measurement of p(\vecγ,p)π^0 and p(\vecγ,π^+)n
• Electromagnetic Properties of the Delta(1232)
• Precise Measurement of Sigma Beam Asymmetry for Positive Pion Photoproduction on the Proton from 800 to 1500 Mev
• Two-phonon 1- state in 112Sn observed in resonant photon scattering
• Hints on the quadrupole deformation of the $\Delta$(1232)
• On the extraction of electromagnetic properties of the Delta(1232) excitation from pion photoproduction
• The P_33(1232) resonance contribution into the amplitudes M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2} from an analysis of the p(e,e'p)π^0 data at Q^2 = 2.8, 3.2, and 4 (GeV/c)^2 within dispersion relation approach
• Two-body effects in coherent eta-meson photoproduction on the deuteron in the region of the S_11(1535) resonance
• Electromagnetic N-$\Delta$ transition form factors in a covariant quark-diquark model
• Stability of the E2/M1 ratio at the T-matrix pole
• The pion photoproduction in the Δ(1232) region