We propose a Lattice QCD mixed-action approach in which sea quarks are
regularized using Nf = 2 + 1 non-perturbatively O(a)-improved Wilson fermions
with open boundary conditions in the time direction, while a Wilson twisted mass
action at maximal twist is used for valence quarks. In this setup, fermionic observables
are free from O(a) lattice artifacts proportional to the valence quark
masses.
Two alternative procedures for the matching of sea and valence quark masses
are discussed. We perform a universality check by comparing continuum limit
extrapolations of quark masses and of pseudoscalar meson decay constants obtained
with two setups: the mixed action and the standard approach where Wilson
fermions are used in sea and valence sectors.
We use the gradient flow scale t0 and physical input from the pion and kaon
decay constants to carry out a scale setting procedure. This is applied to the
determination of the light and strange quark masses. A particular attention is
given to the statistical analysis of the lattice data and to the assessment of the
systematic uncertainties.
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