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 provide a brief history to remind the readers how development progressed. Sure, history is sometimes what never happened, described by those who were never there … Abstract Published by the Jagiellonian University 2026 authors
Igor Strakovsky (Tue,) studied this question.