New results on the Roper resonance and the P_{11} partial wave

Understand

Properties of the Roper resonance, the first scalar excitation of the nucleon, are determined.

• Pole positions and residues of the $P_{11}$ partial wave are studied in a combined analysis of pion- and photo-induced reactions.
• We find the Roper pole at $\{(1371\pm7)-i(92\pm10)\}$ MeV and an elasticity of $0.61\pm 0.03$.
• The largest decay coupling is found for the $N\sigma$ ($\sigma=(\pi\pi)$-$S$-wave).