Speaker
Description
We present a calculation of $NN$ scattering amplitudes in both isospin states, $I = 0$ (deuteron) and $I = 1$ (dineutron), on CLS ensembles with pion masses ranging from 700 MeV down to 200 MeV. A particular focus of our analysis is on the left-hand cut arising from one-pion exchange, which induces effects not accounted for in the usual two-particle finite-volume formalism. We explore two alternatives which are valid in the presence of the left-hand cut: the plane-wave quantization condition and the relativistic left-hand-cut formalism. While the effects of the left-hand cut are suppressed at large pion masses, we find them to be significant at the lower pion masses. We find that the deuteron is a virtual state even at the lowest pion mass considered (200 MeV); however, there is a clear trend of decreasing inverse scattering length with lower quark mass.