A partially quenched analysis of the eta-eta' system in N_f=2 QCD

TL;DR

This study uses a partially quenched approach to analyze the eta-eta' system in two-flavor QCD, providing insights into the mass matrix and chiral Lagrangian parameters with clear spectral signals.

Contribution

It presents the first comprehensive partially quenched analysis of the eta-eta' system in N_f=2 QCD, including determination of the eta-eta' mass matrix and the alpha parameter.

Findings

Clear plateau formation in effective masses

Determined eta-eta' mass matrix

Measured alpha parameter as 0.028 ± 0.013

Abstract

We report on a first, comprehensive partially quenched study of the eta-eta' problem, based on SESAM configurations on a 16^3x32 lattice at beta=5.6 QCD with two (mass degenerate) active sea quark flavours. By means of the spectral approximation of the two-loop (hairpin) diagrams, we find clear plateau formation in the effective masses which enables us both to determine the eta-eta' mass matrix and the alpha-parameter in the effective chiral Lagrangian for the flavour singlet sector, alpha=0.028 +- 0.013.