  Pion-pion elastic scattering in the isospin I=2 channel is investigated in
two-flavor dynamical lattice QCD. Six ensembles are used with lattices
elongated in one of the spatial dimensions at two quark masses corresponding to
a pion mass of 315 MeV and 226 MeV. The energy of the low-lying states below
the inelastic threshold are extracted in each case using the standard
variational method.The extracted finite-volume spectrum is fitted by the
inverse amplitude method simultaneously for both quark masses and extrapolated
thereafter to the physical point. The resulting phase-shifts and scattering
length are compared with those from experiment, leading-order chiral
perturbation theory and other lattice studies. Our calculations match the
experimental results.
