Status of Nucleon Resonances with Masses $M<M_N+M_π$

R. Beck, S. N. Cherepnya, L. V. Fil'kov, V. L. Kashevarov, M. Rost, Th. Walcher

Published 2001-04-24Version 1

We discuss different interpretations of peaks observed a few years ago by Tatischeff et al. in missing mass spectra of the reaction $pp->pi^+pX$, which were declared as new exited nucleon states with small masses. A study of the possible production of such states in the process $\gamma p->pi^+N^*->pi^+ +\gamma\gamma n$ by analyzing the invariant mass spectrum of $\gamma\gamma n$ is proposed. It is shown that the data, obtained recently at MAMI-B, can allow to analyze this process and to get information about an existence of exited nucleon states with small masses.