Chiral symmetry and the Delta-Nucleon transition form factors

Abstract

The three complex form factors entering the $\Delta \to N{\gamma }^{\ast }$ vertex are calculated to $\mathcal{O}({ϵ}^3)$ in the framework of a chiral effective theory with explicit \Delta(1232) degrees of freedom included. It is shown that the low q^2 behavior of the form factors is governed by $\pi N$, $\pi \Delta$ loop effects. Predictions are given for the q^2-dependence of the three transition-multipoles $M1(q^2),E2(q^2),C2(q^2)$. Furthermore, the role of presently unknown low energy constants that affect the values of the multipole ratios EMR(q^2) and CMR(q^2) is elucidated.

Comments: 37 pages, 12 figures