Physics Potential of ESS$ν$SB in the presence of a Light Sterile Neutrino

Abstract: ESS$\nu$SB is a proposed neutrino super-beam project at the ESS facility. We study the performance of this setup in the presence of a light eV-scale sterile neutrino, considering 540 km baseline with 2 years (8 years) of $\nu$ ($\bar\nu$) run-plan. This baseline offers the possibility to work around the second oscillation maximum, providing high sensitivity towards CP-violation (CPV). We explore in detail its capability in resolving CPV generated by the standard CP phase $\delta_{13}$, the new CP phase $\delta_{14}$, and the octant of $\theta_{23}$. We find that the sensitivity to CPV induced by $\delta_{13}$ deteriorates noticeably when going from $3\nu$ to 4$\nu$ case. The two phases $\delta_{13}$ and $\delta_{14}$ can be reconstructed with a 1$\sigma$ uncertainty of $\sim15^0$ and $ \sim35^0$ respectively. Concerning the octant of $\theta_{23}$, we find poor sensitivity in both $3\nu$ and $4\nu$ schemes. Our results show that a setup like ESS$\nu$SB working around the second oscillation maximum with a baseline of 540 km, performs quite well to explore CPV in 3$\nu$ scheme, but it is not optimal for studying CP properties in 3+1 scheme.