Can the Hint of $$\delta _{\textit{CP}}$$ δ CP from T2K Also Indicate the Hierarchy and Octant?

Abstract

The T2K neutrino data has already given a hint for the best-fit value of the leptonic CP phase \(\delta _{\textit{CP}}\) as \(-90^\circ \). In this paper we ask the question that if this hint is confirmed by the subsequent neutrino and anti-neutrino runs of T2K, then can it also give any information about the other two remaining unknown oscillation parameters—the neutrino mass hierarchy and octant of \(\theta _{23}\). We find that if T2K runs in only neutrino mode with its full targeted exposure, then \(\delta _{\textit{CP}} = -90^\circ \) would indicate the true hierarchy as normal and the true octant as higher. On the other hand if T2K runs in equal neutrino and anti-neutrino mode then the true hierarchy can be confirmed as normal but the octant will remain undetermined. We have also studied the effect of anti-neutrino runs on CP sensitivity of T2K.