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 $\sim 400\mathrm{MeV}$. 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 $\frac{1}{\sqrt{2}}(u\overline{u}+d\overline{d})$ and $s\overline{s}$ in most $J^{PC}$ channels; one notable exception is the pseudoscalar sector where the approximate $SU(3{)}_F$ octet, singlet structure of the $\eta$, ${\eta }^{\prime }$ is reproduced. We extract exotic $J^{PC}$ states, identified as hybrid mesons in which an excited gluonic field is coupled to a color-octet $q\overline{q}$ pair, along with nonexotic hybrid mesons embedded in a $q\overline{q}$-like spectrum.

• Received 13 September 2013

DOI:https://doi.org/10.1103/PhysRevD.88.094505