this work, the Coulomb quadrupole is known to vanish. Thus precision measurements are only available for the ratio $E2/M1$ [@Blanpied:2001ae; @Beck:1999ge; @Sandorfi:1998xr; @Beck:1997ew].

On the theoretical side various approaches have been suggested. In quark models with unbroken $SU(6)$-spin-flavour symmetry $E2/M1$ is predicted to be exactly zero, whereas a broken $SU(6)$ symmetry yields values ranging from $0$ to $-2\%$ [@Isgur:1981yz; @Gershtein:1981zf; @Gogilidze:1986tu]. Other models, among them Skyrme models and the large $N_c$ limit of QCD, also find the ratio to be small and negative [@Wirzba:1986sc; @Jenkins:2002rj]. Given that the $\Delta$ decays almost entirely into a nucleon and a pion, it is not surprising, that chiral bag models tend to agree well with experimental data [@Bermuth:1988ms]. In recent years studies using chiral effective field theory have been quite popular and yield rather precise results [@Gail:2005gz; @Pascalutsa:2005vq], in addition to that lattice calculations also predict $E2/M1$ to be around $-3\%$ [@Alexandrou:2004xn]. Only recently a detailed review summarising various theoretical approaches to the nucleon-$\Delta$-transition has been published [@Pascalutsa:2006up].

On the other hand, the attempts to understand the nucleon-$\Delta$-transition at the microscopic level i.e. in terms of the underlying quark-gluon structure have been less successful. In particular, the calculation of Ioffe and Smilga [@Ioffe:1983ju] in 