Enhancing the hierarchy and octant sensitivity of ESS?SB in conjunction with T2K, NO?A and ICAL@INO

Abstract

The main aim of the ESSνSB proposal is the discovery of the leptonic CP phase δCP with a high significance (5σ for 50% values of δCP) by utilizing the physics at the second oscillation maxima of the Pμe channel. It can achieve 3σ sensitivity to hierarchy for all values of δCP. In this work, we concentrate on the hierarchy and octant sensitivity of the ESSνSB experiment. We show that combining the ESSνSB experiment with the atmospheric neutrino data from the proposed India-based Neutrino Observatory(INO) experiment can result in an increased sensitivity to mass hierarchy. In addition, we also combine the results from the ongoing experiments T2K and NOνA assuming their full runtime and present the combined sensitivity of ESSνSB + ICAL@INO + T2K + NOνA. We show that while by itself ESSνSB can have up to 3σ hierarchy sensitivity, the combination of all the experiments can give up to 5σ sensitivity depending on the true hierarchy-octant combination. The octant sensitivity of ESSνSB is low by itself. However the combined sensitivity of all the above experiments can give up to 3σ sensitivity depending on the choice of true hierarchy and octant. We discuss the various degeneracies and the synergies that lead to the enhanced sensitivity when combining different experimental data.