Scattering amplitude from Bethe-Salpeter wave function inside the interaction range

摘要

We propose a method to calculate scattering amplitudes using theBethe-Salpeter wave function inside the interaction range on the lattice. As anexploratory study of this method, we evaluate a scattering length of $I=2$S-wave two pions by use of the on-shell scattering amplitude. Our result isconfirmed to be consistent with the value obtained from the conventional finitevolume method. The half off-shell scattering amplitude is also evaluated.