Speaker
Description
We determine, from Lattice QCD, the elastic $\pi \pi$ scattering amplitude in the isoscalar $I=0$ channel, and the $\sigma$ resonance. We extract its lineshape for two different quark masses corresponding with $m_\pi \sim 283$ and $330$ MeV; where it is predicted that this state transitions from bound to virtual bound. In order to provide an accurate picture we use a high statistics volume for the heavier pion mass, and two for the lighter. The comparison between the two masses showcases very different lineshapes for the phase shifts. This is related to the different behavior of the $\sigma$ resonance for these values of its quark mass dependence.