Eur. Phys. J. A (2020) 56: 257
https://doi.org/10.1140/epja/s10050-020-00254-1

Regular Article - Theoretical Physics

Aspects of model dependence of $$\eta '$$–$$\eta $$ complex treated by going beyond the isospin limit

¹ Physics Department, Faculty of Science-PMF, University of Zagreb, Bijenička cesta 32, 10000, Zagreb, Croatia
² Rugjer Bošković Institute, Bijenička cesta 54, 10000, Zagreb, Croatia

^* e-mail: klabucar@phy.hr

Received: 10 July 2020
Accepted: 13 September 2020
Published online: 8 October 2020

Abstract

Exploring the extent of model dependence, we study effects of certain Ansätze 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.