  The two pion channel in Lattice QCD has long been a primary testing ground
for studying multiparticle scattering in finite volume QCD. With the
development of sophisticated techniques such as distillation, it is possible to
carefully study two-pion scattering in order to constrain associated low-energy
constants. In this work, correlation functions with multiparticle interpolating
operators are constructed to compute pion scattering phase shifts and
scattering lengths in the isospin 0 and 2 channels with both sea and valence
quarks at physical mass. Contamination from vacuum and thermal contributions
are explicitly quantified with dedicated calculations and the results obtained
after subtracting these nuisance terms are compared with the traditional
correlator time series subtraction method. Two physical point ensembles with
different lattice actions are used, and our finest ensemble gives results for
scattering lengths and phase shifts consistent with phenomenology to within the
reported statistical uncertainty.
