Glueballs and topology with O(a)-improved lattice QCD

TL;DR

This paper investigates unquenching effects in lattice QCD with two flavors, revealing evidence of string breaking, a reduction in scalar glueball mass, and consistent topological susceptibility measurements, highlighting discretisation effects and topological properties.

Contribution

It provides new evidence of unquenching effects, including string breaking signals and a reduction in scalar glueball mass, with consistent topological charge measurements in lattice QCD.

Findings

Evidence of string breaking from torelon VEVs

15-20% reduction in scalar glueball mass compared to quenched

Chiral suppression of topological susceptibility

Abstract

We present evidence for unquenching effects in N_f=2, 16^3 32 ensembles by comparing with `equivalent' quenched data at r_0~5.0. A (small) VEV for torelons signals (weak) string breaking. A 15-20 % reduction in the scalar glueball mass relative to quenched is argued to be (in part at least) a discretisation effect. We find a chiral suppression of the topological susceptibility consistent with expectations, and agreement between fermionic and gluonic methods for measuring the topological charge.