WIMPless Dark Matter in Anomaly-Mediated Supersymmetry Breaking with
  Hidden QED
  In anomaly-mediated supersymmetry breaking, superpartners in a hidden sector
have masses that are proportional to couplings squared, and so naturally freeze
out with the desired dark matter relic density for a large range of masses. We
present an extremely simple realization of this possibility, with WIMPless dark
matter arising from a hidden sector that is supersymmetric QED with N_F
flavors. Dark matter is multi-component, composed of hidden leptons and
sleptons with masses anywhere from 10 GeV to 10 TeV, and hidden photons provide
the thermal bath. The dark matter self-interacts through hidden sector Coulomb
scatterings that are potentially observable. In addition, the hidden photon
contribution to the number of relativistic degrees of freedom is in the range
\Delta N_eff ~ 0 - 2, and, if the hidden and visible sectors were initially in
thermal contact, the model predicts \Delta N_eff ~ 0.2 - 0.4. Data already
taken by Planck may provide evidence of such deviations.
