Extracting the η ' meson mass from gluonic correlators in lattice QCD

Calculation of the η ′ meson mass is a notoriously difficult problem, as it requires evaluation of the disconnected diagram which is costly and noisy. In this work, we use a gluonic operator to extract the eta-prime state after smearing the link variables throu gh the Wilson flow. With this choice, one can avoid a large cancellation of pion contribution between the connected and disconnected diagrams. We obtain the η ′ meson mass on lattices with three different lattice spacing s and two