Improved sensitivities of ESS$ν$SB from a two-detector fit

We discuss the improvement of the sensitivity of ESS$ν$SB to the discovery of CP violation and to new neutrino physics which can be obtained with a two-detector fit of the data of the near and far detectors. In particular, we consider neutrino non-standard interactions generated by very heavy vector mediators, nonunitary neutrino mixing, and neutrino oscillations due to the mixing of the ordinary active neutrinos with a light sterile neutrino.