{\eta} and {\eta}' mesons from Nf=2+1+1 twisted mass lattice QCD

TL;DR

This study uses Nf=2+1+1 twisted mass lattice QCD to accurately determine the masses and mixing angles of eta and eta' mesons, providing insights into their flavor structure and lattice formulation effects.

Contribution

It presents a novel lattice QCD calculation of eta and eta' meson properties with multiple lattice spacings and quark masses, including treatment of flavor singlet states.

Findings

Eta mass: 557(15)(45) MeV

Mixing angle: 44(5) degrees

Results consistent across lattice spacings

Abstract

We determine mass and mixing angles of eta and eta' states using Nf=2+1+1 Wilson twisted mass lattice QCD. We describe how those flavour singlet states need to be treated in this lattice formulation. Results are presented for three values of the lattice spacing, a=0.061 fm, a=0.078 fm and a=0.086 fm, with light quark masses corresponding to values of the charged pion mass in a range of 230 to 500 MeV and fixed bare strange and charm quark mass values. We obtain 557(15)(45) MeV for the eta mass (first error statistical, second systematic) and 44(5) degrees for the mixing angle in the quark flavour basis, corresponding to -10(5) degrees in the octet-singlet basis.