Speaker
Description
Due to the long-range nature of QED, finite-volume corrections to observables appear as inverse powers of lattice extent, which may be much larger than the exponentially suppressed corrections. For precision computations, it is crucial to determine these effects, which depend on the QED formulation. As a first step, we investigate the power-law finite-volume effects in the QCD+QED setup with C* boundary conditions on pseudoscalar meson masses. We measure the spectrum on four ensembles generated by the RC$*$ collaboration with $L= 1.7-3.5 \,\mathrm{fm}$ and $N_f=1+2+1$ $\mathcal{O}(a)$-improved Wilson fermions. The isospin-breaking effects are added perturbatively to $\mathcal{O}(e^2)$ via the RM123 method. We compare the observations to the expected electromagnetic finite-volume effects in the continuum, which can be expressed in terms of known hadronic amplitudes and form factors.