A consistent explanation of the Roper phenomenology
We study the electromagnetic transitions of the Roper N(1440) resonance. Our results, when combined with the previously obtained for the mass and the pionic strong decay widths of the Roper, show that within a non-relativistic constituent quark model scheme, a comprehensible understanding of the Roper phenomenology can be achieved. They also seem to support the view of the Roper as a radial excitation of the nucleon, though more experimental data are needed to reach a definitive conclusion.
Cano Vargas, Florencio González Marhuenda, Pedro 1998 A consistent explanation of the Roper phenomenology Physics Letters B 431 270 276