Speaker
Description
Staggered fermions comprise an important theoretical framework in modern lattice QCD calculations due to their low computational cost. However, the theory manifests highly non-trivial lattice artifacts that complicate the extraction of scattering amplitudes from finite-volume energies using the Lüscher formalism. At non-zero lattice spacing, the meson sector of the theory contains multiple non-mass-degenerate pions as a result of taste splitting, thus requiring the fourth rooting procedure to recover the correct number of pions in the continuum limit. This procedure, however, is known to break unitarity of the quantum theory. Although these artifacts vanish in the continuum limit, it remains a challenge to extract scattering amplitudes from staggered lattice data at non-zero lattice spacing. In this talk, we focus on pion-pion scattering amplitudes and present recent developments towards a generalized formalism that accounts for $\mathcal{O}(a^2)$ staggered lattice artifacts in the scattering amplitude. Our central observation is that the multiple pion tastes naturally enter the formalism via coupled-channel scattering that reduces to a single channel in the continuum limit.