Chiral Dark Sector
  We present a simple and natural dark sector model in which dark matter
particles arise as composite states of hidden strong dynamics and their
stability is ensured by accidental symmetries. The model has only a few free
parameters. In particular, the gauge symmetry of the model forbids the masses
of dark quarks, and the confinement scale of the dynamics provides the unique
mass scale of the model. The gauge group contains an Abelian symmetry $U(1)_D$,
which couples the dark and standard model sectors through kinetic mixing. This
model, despite its simple structure, has rich and distinctive phenomenology. In
the case where the dark pion becomes massive due to $U(1)_D$ quantum
corrections, direct and indirect detection experiments can probe thermal relic
dark matter which is generically a mixture of the dark pion and the dark
baryon, and the Large Hadron Collider can discover the $U(1)_D$ gauge boson.
Alternatively, if the dark pion stays light due to a specific $U(1)_D$ charge
assignment of the dark quarks, then the dark pion constitutes dark radiation.
The signal of this radiation is highly correlated with that of dark baryons in
dark matter direct detection.
