Soft Contribution to Form Factors of ${\gamma }^{\ast }p\to {\Delta }^{+}$ Transition

Abstract

The purely nonperturbative soft contribution to the ${\gamma }^{\ast }p\to {\Delta }^{+}$ transition form factors is estimated using the local quark-hadron duality approach. Our results show that the soft contribution is dominated by the magnetic transition: the ratio $G_E^{\ast }(Q^2)/G_M^{\ast }(Q^2)$ is small for all accessible $Q^2$, in contrast to pQCD expectations that $G_E^{\ast }(Q^2)\to -G_M^{\ast }(Q^2)$. We also found that the soft contribution to the magnetic form factor is large enough to explain the magnitude of existing experimental data.

Comments: 29 pages, REVTeX, 5 eps-figures in uuencoded gz-compressed .tar file