ar X iv : n uc l - th / 0 11 10 62 v 1 2 2 N ov 2 00 1 Recent progress in pion photo - and electroproduction analysis
نویسندگان
چکیده
Pion photo-and electroproduction has been studied at threshold and in the resonance region below W < 2 GeV. At threshold π 0 production can be very well explained within a dynamical model derived from an effective chiral Lagrangian. The final state interaction is nearly saturated by single charge exchange rescattering. In the resonance region new electroproduction data at Q 2 = 1 GeV 2 has been analyzed with M AID and longitudinal and transverse photon helicity amplitudes have been determined for different resonances. A detailed study of the E/M and S/M ratios of the N → ∆ transition shows a zero crossing of R EM near Q 2 = 4 GeV 2 , whereas the R SM becomes increasingly negative at large Q 2 .
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