Toward the excited isoscalar meson spectrum from lattice QCD

We report on the extraction of an excited spectrum of isoscalar mesons using lattice QCD. Calculations on several lattice volumes are performed with a range of light quark masses corresponding to pion masses down to ∼400MeV. The distillation method enables us to evaluate the required disconnected contributions with high statistical precision for a large number of meson interpolating fields. We find relatively little mixing between (1)/(2)(uu¯+dd¯) and ss¯ in most J^PC channels; one notable exception is the pseudoscalar sector where the approximate SU(3)_F octet, singlet structure of the η, η^' is reproduced. We extract exotic J^PC states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet qq¯ pair, along with nonexotic hybrid mesons embedded in a qq¯-like spectrum.