N→ΔTransition from Simultaneous Measurements ofp(γ→

Quadrupole moments of baryons

“…In order to determine the two constants B and C we need two experimental inputs. From recent measurements of the ratio of electric quadrupole over magnetic dipole amplitudes in electromagnetic pionproduction (E2/M 1 and C2/M 1 ratios) [8,9], one can extract the N → ∆ transition quadrupole moment Q p→∆ + . For a first determination of Q ∆ + from photo-pionproduction data in the ∆ resonance region see Ref.…”

“…For a first determination of Q ∆ + from photo-pionproduction data in the ∆ resonance region see Ref. [8]. Because the decuplet quadrupole moments or other octet-decuplet transition quadrupole moments are not yet very well known, we cannot fix the smaller constant C with sufficient accuracy at this stage.…”

Low-energy Compton scattering of polarized photons on polarized nucleons

“…Compton scattering on the proton at low and intermediate energies has thus far been studied mainly with unpolarized photons. Many recent data are available on the unpolarized differential cross section both in the region below pion threshold [1][2][3] and in the Delta region [4][5][6][7][8]. They have led to a determination of the dipole electric and magnetic polarizabilities of the proton, have given useful constraints on pion photoproduction amplitudes near the Delta peak, and have provided sensitive tests for different models of Compton scattering, such as those based on resonance saturation [9][10][11][12], chiral perturbation theory [13,14], and dispersion relations [15][16][17][18][19].…”

Electromagnetic excitation of nucleon resonances

“…Already in the mid-nineties, the resonant multipoles (FFs at Q 2 = 0) and in particular the E/M ratio were investigated in experimental programs at MAMI in Mainz [20] and LEGS in Brookhaven [21]. In [20,24] and Hanstein et al [22,23], respectively.…”