In this talk I will present results from our recent lattice QCD study of $N\pi$ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance $N^*(1440)$ resides in experiment. Using a variety of hadron operators, that include $qqq$-like, $N\pi$ in $p$-wave and $N\sigma$ in $s$-wave, we systematically extract the excited lattice spectrum in the nucleon channel up to 1.65 GeV. Our lattice results indicate that N$\pi$ scattering in the elastic approximation alone does not describe a low-lying Roper. Coupled channel effects between $N\pi$ and $N\pi\pi$ seem to be crucial, reinforcing the notion that this state could be a dynamically generated resonance. After giving a brief motivation for studying the Roper channel and the relevant technical details to this study, I will discuss the results and the conclusions based on our lattice investigation and in comparison with other lattice calculations.

Hadron Spectroscopy and Interactions