A hybrid setup for fundamental unknowns in neutrino oscillations using T2HK ( ν) and μ-DAR $$ \left(\overline{\nu}\right) $$

Neutrino mass hierarchy, CP-violation, and octant of $theta_{23}$ are the fundamental unknowns in neutrino oscillations. In order to address all these three unknowns, we study the physics reach of a setup, where we replace the antineutrino run of T2HK with antineutrinos from muon decay at rest ($mu$-DAR). This approach has the advantages of having higher statistics in both neutrino and antineutrino modes, and background-free environment for antineutrino beam with reduced systematics. We find that a hybrid setup consisting of T2HK ($nu$) and $mu$-DAR ($barnu$) in conjunction with full exposure from T2K and NO$nu$A can resolve the issue of mass hierarchy at greater than 3$sigma$ C.L. irrespective of the choices of hierarchy, $delta_{mathrm{CP}}$, and $theta_{23}$. This hybrid setup can also establish the CP-violation at 5$sigma$ C.L. for $sim$ 55% choices of $delta_{mathrm{CP}}$, whereas the same for conventional T2HK ($nu + barnu$) setup along with T2K and NO$nu$A is around 30%. As far as the octant of $theta_{23}$ is concerned, this hybrid setup can exclude the wrong octant at 5$sigma$ C.L. if $theta_{23}$ is at least $3^{circ}$ away from maximal mixing for any $delta_{mathrm{CP}}$.