Scattering Ampltidues for Multi-hadrons Processes in Lattice-QCD

forthcoming

The goal of SAMPL-QCD (Scattering Amplitudes for Multi-hadrons Processes in Lattice-QCD) is to compute, with a novel method, exclusive scattering amplitudes involving multiple hadrons in the final state, such as J to ππ or J to πππ, with J=B,D,e+e-,...from Euclidean correlation functions computed in lattice QCD. The motivation is to provide new theoretical predictions to compare with experimental data that already exists, and that will keep being produced, with the ultimate goal of finding evidence for physics beyond the Standard Model. The state-of-the-art for theory predictions of multi-hadron processes is the K→ ππ study from the RBC/UKQCD collaboration. The methodology employed there is based on the Lellouch Lüscher formalism, which appears hard to generalise to processes where many inelastic thresholds can open simultaneously. A different strategy that does not suffer the same complications is now possible, because of two factors: on one side, a mathematically-robust relation between Euclidean correlators (available from lattice QCD) and scattering amplitudes was given by A. Patella & N. Tantalo in terms of an inverse problem. On the technical side, progress made by my collaborators and I in the last few years in solving the inverse problem with reliable estimates of its systematics, paves the way for first QCD calculations of this kind, potentially opening the way to a new generation of lattice calculations. In this project, we intend to explore the level of precision that can be reached, within this formalism, for scattering amplitudes, given the current state-of-the-art lattice simulations.