Dynamical study of ${\gamma }^{\ast }N\leftrightarrow \Delta$ transition with $N(e,e^{\prime }p)\pi$

Abstract

The Dubna-Mainz-Taipei (DMT) dynamical model for pion electromagnetic production, which describe well the existing data from threshold up to 1 GeV photon lab energy is presented and used to analyze recent data in the $\Delta$ region . We find that within DMT model, the bare $\Delta$ is almost spherical while the physical $\Delta$ is oblate. The deformation is almost saturated by the pion cloud effects.

Comments: 4 pages, 2 postscript figures, contr. to Int. Conf. on QCD and Hadronic Physics, Beijing from Jun 16-20, 2005