QCD with two light dynamical chirally improved quarks: Baryons

Abstract

We present a study of baryon ground states and low lying excitations of nonstrange and strange baryons. The results are based on seven gauge field ensembles with two dynamical light chirally improved quarks corresponding to pion masses between 255 and 596 MeV and a strange valence quark with mass fixed by the $\ensuremath{\Omega}$ baryon. The lattice spacing varies between 0.1324 and 0.1398 fm. Given in lattice units, the bulk of our results are for size ${16}^{3}\ifmmode\times\else\texttimes\fi{}32$; for two ensembles with light pion masses (255 and 330 MeV) we also use ${24}^{3}\ifmmode\times\else\texttimes\fi{}48$ lattices and perform an infinite volume extrapolation. We derive energy levels for the spin $1/2$ and $3/2$ channels for both parities. In general, our results in the infinite volume limit compare well with experiment. We analyze the flavor symmetry content by identifying the singlet/octet/decuplet contributions of the resulting eigenstates. The ground states' compositions agree with quark model expectations. In some cases the excited states, however, disagree and we discuss possible reasons.