Pi-Pi Scattering with Nf=2+1+1 Twisted Mass Fermions
  Pi-Pi scattering is investigated for the first time for Nf=2+1+1 dynamical quark flavours using Wilson twisted mass fermions. L\"uscher's finite size method is used to relate energy shifts in finite volume to scattering quantities like the scattering length in the I=2 channel. The computation is performed at several pion masses and lattice spacings utilising the stochastic LapH method. 
Christopher Helmes, Christian Jost, Bastian Knippschild, Liuming Liu,   Carsten Urbach, Markus Werner
hep-lat