Search for low-lying lattice QCD eigenstates in the Roper regime

Understand

The positive-parity nucleon spectrum is explored in $2 + 1$-flavour lattice QCD in a search for new low-lying energy eigenstates near the energy regime of the Roper resonance.

• In addition to conventional three-quark operators, we consider novel, local five-quark meson-baryon type interpolating fields that hold the promise to reveal new eigenstates that may have been missed in previous analyses.
• Drawing on phenomenological insight, five-quark operators based on $\sigma{N}$, $\pi{N}$ and $a_0{N}$ channels are constructed.
• Spectra are produced in a high-statistics analysis on the PACS-CS dynamical gauge-field configurations with $m_{\pi} = 411\textrm{ MeV}$ via variational analyses of several operator combinations.