Lattice calculation of $1^{-+}$ hybrid mesons with improved Kogut-Susskind fermions

TL;DR

This paper presents a lattice QCD calculation of the mass of the exotic $1^{-+}$ hybrid meson using improved Kogut-Susskind fermions, comparing quenched and dynamical quark results and discussing effects of sea quarks.

Contribution

It provides the first lattice determination of the $1^{-+}$ hybrid meson mass with improved fermion actions, including effects of sea quarks and comparison with experimental candidates.

Findings

Lattice results suggest the hybrid meson mass is somewhat heavier than experimental values.

Sea quarks influence hybrid propagators, likely due to coupling with two-meson states.

Extrapolated quenched results are consistent with the $ ext{pi}_1(1600)$}.

Abstract

We report on a lattice determination of the mass of the exotic $1^{-+}$ hybrid meson using an improved Kogut-Susskind action. Results from both quenched and dynamical quark simulations are presented. We also compare with earlier results using Wilson quarks at heavier quark masses. The results on lattices with three flavors of dynamical quarks show effects of sea quarks on the hybrid propagators which probably result from coupling to two meson states. We extrapolate the quenched results to the physical light quark mass to allow comparison with experimental candidates for the $1^{-+}$ hybrid meson. The lattice result remains somewhat heavier than the experimental result, although it may be consistent with the $\pi_1(1600)$.