Excited state nucleon spectrum with two flavors of dynamical fermions

Abstract

Highly excited states for isospin $\frac{1}{2}$ baryons are calculated for the first time using lattice QCD with two flavors of dynamical quarks. Anisotropic lattices are used with two pion masses, ${m}_{\ensuremath{\pi}}=416(36)\text{ }\text{ }\mathrm{MeV}$ and 578(29) MeV. The lowest four energies are reported in each of the six irreducible representations of the octahedral group at each pion mass. The lattices used have dimensions ${24}^{3}\ifmmode\times\else\texttimes\fi{}64$, spatial lattice spacing ${a}_{s}\ensuremath{\approx}0.11\text{ }\text{ }\mathrm{fm}$, and temporal lattice spacing ${a}_{t}=\frac{1}{3}{a}_{s}$. Clear evidence is found for a $\frac{{5}^{\ensuremath{-}}}{2}$ state in the pattern of negative-parity excited states. This agrees with the pattern of physical states and spin $\frac{5}{2}$ has been realized for the first time on the lattice.