Probing below the neutrino floor with the first generation of stars
  We show that the mere observation of the first stars (Pop III stars) in the
universe can be used to place tight constraints on the strength of the
interaction between dark matter and regular, baryonic matter. We apply this
technique to a candidate Pop III stellar complex discovered with the Hubble
Space Telescope at $z \sim 7$ and find bounds that are competitive with, or
even stronger than, current direct detection experiments, such as XENON1T, for
dark matter particles with mass ($m_X$) larger than about $100$ GeV. We also
show that the discovery of sufficiently massive Pop III stars could be used to
bypass the main limitations of direct detection experiments: the neutrino
background to which they will be soon sensitive.
