2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/202417We study the flavour singlet pseudoscalar mesons from first principles using lattice QCD. We explore the quark content of the $η$ and $η'$ mesons and we discuss their decay constants.Figure 1 correctedHigh Energy Physics - LatticeHigh Energy Physics - Phenomenologytext