The ESS$\nu$SB project proposes to use the very intense proton beam of the European Spallation Source (ESS) to produce a relatively low energy neutrino super beam. This will allow to reach the second maximum in the neutrino oscillation probability few hundreds of kilometers away from the target station, improving the sensitivity for the discovery of CP violation in the leptonic sector in the channel $\nu_{\mu}\rightarrow\nu_{e}$ compared with the first maximum. We present here a parametric study on the magnetic horn and the decay tunnel in order to improve the discovery potential of the project and its precision on the measurement of the value of $\delta_{CP}$.