  "Portal" models that connect the Standard Model to a Dark Sector allow for a
wide variety of scenarios beyond the simplest WIMP models. Kinetic mixing of
gauge fields in particular has allowed a broad range of new ideas. However, the
models that evade CMB constraints are often non-generic, with new mass scales
and operators to split states and suppress indirect detection signals. Models
with a "portalino", a neutral fermion that marries a linear combination of a
standard model neutrino and dark sector fermion and carries a conserved quantum
number, can be simpler. This is especially interesting for interacting dark
sectors; then the unmarried linear combination which we identify as the
standard model neutrino inherits these interactions too, and provides a new,
effective interaction between the dark sector and the standard model. These
interactions can be simple $Z'$ type interactions or lepton-flavor changing.
Dark matter freezes out into neutrinos, thereby evading CMB constraints, and
conventional direct detection signals are largely absent. The model offers
different signals, however. The "portalino" mechanism itself predicts small
corrections to the standard model neutrino couplings as well as the possibility
of discovering the portalino particle in collider experiments. Possible
cosmological and astroparticle signatures include monochromatic neutrino
signals from annihilation, spectral features in high energy CR neutrinos as
well as conventional signals of additional light species and dark matter
interactions.
