Status of Nucleon Resonances with Masses M < MN + Mπ

We discuss different interpretations of the peaks observed a few years ago by Tatischeff et al. ¹ in the missing mass spectra of the reaction pp → π⁺pX, which were declared as new exited nucleon states with small masses. A study of the possible production of such states in the process γp → π⁺N* → π⁺ + γγn by analyzing the invariant mass spectrum of γγn is proposed. It is shown that the experimental data obtained at MAMI-B allows one to analyze this process and to get information about the existence of excited nucleon states with small masses.