Physics Reach of DUNE with a Light Sterile Neutrino

We investigate the implications of one light eV scale sterile neutrino on the physics potential of the proposed long-baseline experiment DUNE. If the future short-baseline experiments confirm the existence of sterile neutrinos, then it can affect the mass hierarchy (MH) and CP-violation (CPV) searches at DUNE. The MH sensitivity still remains above 5$sigma$ if the three new mixing angles ($theta_{14}, theta_{24}, theta_{34}$) are all close to $theta_{13}$. In contrast, it can decrease to 4$sigma$ if the least constrained mixing angle $theta_{34}$ is close to its upper limit $sim 30^0$. We also assess the sensitivity to the CPV induced both by the standard CP-phase $delta_{13} equiv delta$, and the new CP-phases $delta_{14}$ and $delta_{34}$. In the 3+1 scheme, the discovery potential of CPV induced by $delta_{13}$ gets deteriorated compared to the 3$ u$ case. In particular, the maximal sensitivity (reached around $delta_{13}$ $sim$ $pm$ $90^0$) decreases from $5sigma$ to $4sigma$ if all the three new mixing angles are close to $theta_{13}$. It can further diminish to almost $3sigma$ if $theta_{34}$ is large ($sim 30^0$). The sensitivity to the CPV due to $delta_{14}$ can reach 3$sigma$ for an appreciable fraction of its true values. Interestingly, $theta_{34}$ and its associated phase $delta_{34}$ can influence both the $ u_e$ appearance and $ u_mu$ disappearance channels via matter effects, which in DUNE are pronounced. Hence, DUNE can also probe CPV induced by $delta_{34}$ provided $theta_{34}$ is large. We also reconstruct the two phases $delta_{13}$ and $delta_{14}$. The typical 1$sigma$ uncertainty on $delta_{13}$ ($delta_{14}$) is $sim20^0$ ($30^0$) if $theta_{34} =0$. The reconstruction of $delta_{14}$ (but not that of $delta_{13}$) degrades if $theta_{34}$ is large.