Aspects of model dependence of eta'-eta complex treated by going beyond the isospin limit

TL;DR

This paper investigates how breaking isospin symmetry affects the model dependence of the eta'-eta complex in QCD, showing that realistic quark mass ratios improve the consistency of the results at finite temperature.

Contribution

It demonstrates that allowing isospin symmetry breaking with realistic quark mass ratios reduces model dependence issues in the eta'-eta complex analysis.

Findings

Breaking isospin symmetry improves model agreement at T > 0

Realistic quark mass ratios mitigate unwanted effects in the topological susceptibility

Model dependence is significantly reduced when isospin symmetry is broken

Abstract

Exploring the extent of model dependence, we study effects of certain Ansaetze for the T-dependence of the correction term in the QCD topological susceptibility. The one producing unwanted effects on results at T > 0 in the eta'-eta complex in the usual limit of isospin symmetry, is largely cured from its peculiar behavior and brought into agreement with the other, when breaking of isospin symmetry is allowed and the realistic quark mass ratio m_u/m_d = 0.50 is adopted.