Impact of Dynamical Charm Quark and Mixed Action Effect on Light Hadron Masses and Decay Constants

We investigate the impact of including a dynamical charm quark on the properties of light hadrons. Our study uses gauge ensembles generated with the tadpole-improved Symanzik gauge action, comparing 2+1+1 flavor (HISQ fermion) ensembles at four lattice spacings to 2+1 flavor (clover fermion) ensembles at six lattice spacings. For the light and strange flavor observables, we employ the same tadpole-improved clover fermion action. From numerical results for light and strange quark masses, pion and kaon decay constants, and $\mathrm{\Omega }$ baryon masses, we find that the values obtained after continuum, chiral, and infinite-volume extrapolations are consistent within uncertainties. Even though the mixed action setup can introduce additional discretization effects, our calculation shows evidences that those effects can cancel with the discretization error in the unitary setup, resulting in better convergence in the continuum extrapolation.