Speaker: John Bulava (CP3-Origins, Odense)
Title: Pion-pion scattering amplitudes and the timelike pion form factor from $N_{\mathrm{f}}=2+1$ lattice QCD
Abstract: Lattice QCD calculations of scattering amplitudes have improved markedly thanks to advances in the algorithms which treat quark propagation. I will present a recent benchmark $N_{\mathrm{f}}=2+1$ calculation of the total isospin $I=1$ and $I=2$ elastic pion-pion scattering amplitudes on a large-volume anisotropic lattice. I will then show preliminary results for the $I=1$ amplitude and the isovector timelike pion form factor on two ensembles from the Coordinated Lattice Simulations (CLS) consortium. This form factor is a prototypical resonance photo-production amplitude and is related to the low-energy hadronic vacuum polarization, making it relevant for phenomenology both in and beyond the Standard Model.