Sixty years ago, the first excited state of a proton/neutron was ``born.'' During this time, we learned a lot about it, specifically - how unique this case is: a single resonance with two pole positions on different Riemann sheets. Let me present a brief history to remind readers how development progressed. Sure, history is sometimes something that never happened, described by those who were never there...
Categories: hep-ph hep-ex nucl-ex nucl-th