Extracting scattering amplitudes — and consequently cross-sections — from non-perturbative lattice techniques has seen significant advances in recent years. People have so far relied on Luescher’s method, which relates Euclidean finite-volume effects of lattice correlators to infinite-volume Minkowskian Scattering Amplitudes. While this method has achieved enormous success, its limitations are somewhat discouraging: the invalidity beyond the inelastic threshold limits predictions to lower-point exclusive particle-scattering processes. New lattice methods by Hansen/Bulava and Tantalo/Patella have addressed this by rethinking the computation of scattering amplitudes on the lattice in terms of spectral densities, which we can extract from large lattices with increasing precision. These methods allow the examination of exclusive processes even above the inelastic threshold and are consequently an invaluable tool for comparing and complementing perturbative computations with lattice results.I will present preliminary results for the Hansen/Bulava method in a particularly tractable theory that models a gauge-invariant implementation of the electroweak sector.
https://indico.ijs.si/event/3407/