$N^{\ast }(1520)$ transition form factors from dispersion theory

The electromagnetic transition form factors (TFFs) of the nucleon provide important information on the internal structure of hadrons. A model-independent dispersive calculation of the electromagnetic TFFs $N^{\ast }(1520)\to N$ at low energies is presented. Taking pion rescattering into consideration, we derived dispersive relations for the $N^{\ast }(1520)\to N$ TFFs that relate space-like and time-like regions from the first principles. Based on the space-like data from JLab and hadronic data measured by HADES, we make predictions for TFFs in the time-like region. Our predictions can be tested in future experiments (e.g. HADES).