Speaker
Description
In this work we present the first determination of the time-like isovector two-pion form factor from Lattice QCD from an infinite-volume approach based on inverse-problem techniques. Starting from a three-point correlation function involving the vector current and two temporally displaced pion interpolating operators, we reconstruct the spectral density related to the $\gamma\to\pi\pi$ scattering amplitude. We extract the $I=1$ phase shift together with the real and imaginary parts of the form factor from two (Domain-Wall) ensembles at the physical pion mass but with different spatial volumes. By confronting our results with phenomenological estimates and, in the elastic regime, with the traditional finite-volume approach, we validate this methodology which can be extended to the inelastic region.