60\textsuperscript {th} Anniversary of the “Roper Resonance” Discovery

The Roper resonance was discovered in L. David Roper’s Ph.D. thesis research at MIT with Prof. Bernard T. Feld as advisor, with the extensive computing done at Livermore Radiation Laboratory with Dr. Michael J. Moravcsik and programmer Robert M. Wright. The basic coding was taken from the nucleon–nucleon coding of Dr. Richard A. Arndt. Despite the fact of a negative scattering length, which had led to thinking that there would be no \(P_{11}\) resonance, the computer code and large amount of data at that time insisted that the resonance existed. This article discusses some features, including the serendipity, of the discovery and of the unusual Roper resonance. Abstract Published by the Jagiellonian University 2026 authors