Excited state nucleon spectrum with two flavors of dynamical fermions

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, $m_{\pi }=416(36)\mathrm{MeV}$ 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 ${24}^3\times 64$, spatial lattice spacing $a_s\approx 0.11\mathrm{fm}$, and temporal lattice spacing $a_t=\frac{1}{3}{a}_s$. Clear evidence is found for a $\frac{5^{-}}{2}$ 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.