$\eta'$-$\eta_c$-mixing with improved stochastic estimators

TL;DR

This paper investigates the mixing between $ ext{eta'}$ and $ ext{eta}_c$ mesons using advanced stochastic estimators to accurately compute disconnected quark diagrams affecting their masses.

Contribution

It introduces improved stochastic all-to-all propagator techniques, including new methods, to study flavor singlet meson mixing effects in lattice QCD.

Findings

First study to include both direct and mixing effects on $ ext{eta'}$ and $ ext{eta}_c$

Employs improved stochastic estimators for disconnected diagrams

Initial results on $N_f=2$ lattice configurations

Abstract

Charmonia are flavour singlet mesons and thus in principle contributions from disconnected quark line diagrams might affect their masses, either directly or via mixing with other flavour singlet channels. We present a first study that takes both effects into account. We employ improved stochastic all-to-all propagator techniques (including new methods) to calculate the diagrams that appear within the mixing matrix between the $\eta'$ and the $\eta_c$. The runs are initially performed on $N_f=2$ $16^3\times 32$ configurations with the non-perturbatively improved Sheikholeslami-Wilson action, both for valence and sea quarks.