Chiral symmetry and the Delta-Nucleon transition form factors

Abstract

The three complex form factors entering the $Δ\to Nγ^\ast$ vertex are calculated to ${\cal O}(ε^3)$ in the framework of a chiral effective theory with explicit Δ(1232) degrees of freedom included. It is shown that the low q^2 behavior of the form factors is governed by $πN$, $πΔ$ 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.