1pm - 2pm: Toward pion-pion scattering from lattice QCD with staggered quarks

Scattering processes featuring the strong interactions can be studied using lattice QCD by means of the Lüscher formalism. This approach relies on analyticity and unitarity of the S-matrix to relate finite-volume energy levels to infinite-volume scattering amplitudes. One of the most common fermion actions in lattice QCD studies is based on staggered fermions, due to their high computational efficiency. However, simulations employing staggered fermions manifest unitarity-violating effects. Moreover, the meson sector of this theory contains multiple pions as a result of the so-called taste-splitting effects. Both of these discretization artifacts scale with the square power of the lattice spacing and thus disappear in the continuum. Nevertheless, at non-zero lattice spacing, unitarity violation and taste splitting hinder the applicability of the Lüscher formalism to observables computed using staggered fermions. In this talk, we will discuss two approaches to deal with the challenges of extracting scattering amplitudes from staggered lattice QCD: (1) extrapolating the energy levels, at a fixed volume, to the continuum, where the standard version of the Lüscher formalism works, and (2) generalizing the formalism to incorporate staggered lattice artifacts. In both cases, we use the effective theory describing low-energy QCD with staggered fermions, i.e., Rooted Staggered Chiral Perturbation Theory. Specifically, we focus on the simpler case of pion-pion scattering in the isospin-2 channel, and discuss prospects for other isospin channels.