  We investigate the detection prospects of a non-standard dark sector in the
context of boosted dark matter. We consider a scenario where two stable
particles have a large mass difference and the heavier particle accounts for
most of dark matter in our current universe. The heavier candidate is assumed
to have no interaction with the standard model particles at tree-level, hence
evading existing constraints. Although subdominant, the lighter dark matter
particles are efficiently produced via pair-annihilation of the heavier ones in
the center of the Galaxy or the Sun. The large Lorentz boost enables detection
of the non-minimal dark sector in large volume terrestrial experiments via
exchange of a light dark photon with electrons or nuclei. Various experiments
designed for neutrino physics and proton decay are examined in detail,
including Super-K and Hyper-K. In this study, we focus on the sensitivity of
the far detector at the Deep Underground Neutrino Experiment for boosted dark
matter produced in the center of the Sun, and compare our findings with recent
results for boosted dark matter produced in the galactic center.
