Freezing In with Lepton Flavored Fermions
  Dark, chiral fermions carrying lepton flavor quantum numbers are natural
candidates for freeze-in. Small couplings with the Standard Model fermions of
the order of lepton Yukawas are `automatic' in the limit of Minimal Flavor
Violation. In the absence of total lepton number violating interactions,
particles with certain representations under the flavor group remain absolutely
stable. For masses in the GeV-TeV range, the simplest model with three flavors,
leads to signals at future direct detection experiments like DARWIN.
Interestingly, freeze-in with a smaller flavor group such as $SU(2)$ is already
being probed by XENON1T.
