Isospin-breaking corrections pose a significant challenge to lattice simulations, both because of the splitting between the up and down quark masses and, in particular, the need to include QED effects. The RC* collaboration has developed the openQxD code, based on openQCD, which enables fully dynamical QCD+QED simulations through the implementation of C-periodic boundary conditions.
We use this code to measure baryon masses, with a special focus on the $\Omega^-$ baryon mass, whose precise determination is especially important since it has been used to set the scale of lattice simulations.
Due to the use of C-periodic boundary conditions, the two-point function of the $\Omega^-$ baryon gets additional partially connected contributions, which vanish in the infinite-volume limit and which we are computing for the first time.
We will present preliminary results for baryon masses obtained on QCD ensembles with C-periodic boundary conditions, at an unphysical pion mass of approximately 400 MeV.