Glueball relevant study on isoscalars from $N_f=2$ lattice QCD

TL;DR

This study uses lattice QCD to identify a likely glueball state in the scalar channel and explores the spectrum of isoscalars, including potential glueball states, in dynamical quark simulations.

Contribution

It provides evidence that the scalar ground state is a glueball and investigates the spectrum of isoscalars, including a possible 2.6 GeV glueball-like state.

Findings

Scalar ground state is a single-particle glueball candidate

Weak coupling of $qar{q}$ operator to the scalar state

Existence of a 2.6 GeV glueball-like state in pseudoscalar spectrum

Abstract

We perform a glueball-relevant study on isoscalars based on anisotropic $N_f=2$ lattice QCD gauge configurations. In the scalar channel, we identify the ground state obtained through gluonic operators to be a single-particle state through its dispersion relation. When $q\bar{q}$ operator is included, we find the mass of this state does not change, and the $q\bar{q}$ operator couples very weakly to this state. So this state is most likely a glueball state. For pseudoscalars, along with the exiting lattice results, our study implies that both the conventional $q\bar{q}$ state $\eta_2$ (or $\eta'$ in flavor $SU(3)$) and a heavier glueball-like state with a mass of roughly 2.6 GeV exist in the spectrum of lattice QCD with dynamical quarks.