Mirror dark matter cosmology – predictions for N eff [ CMB ] and N eff [ BBN ]

摘要

Mirror dark matter interacting with ordinary matter via photon-mirror photon kinetic mixing can explain the DAMA, CoGeNT and CRESST-II direct detection experiments. This explanation requires kinetic mixing of strength ? ～ 10 ? 9 . Such kinetic mixing will have important implications for early Universe cosmology. We calculate the additional relativistic energy density at recombination, δ N eff [ CMB ] . We also calculate the effects for big bang nucleosynthesis, δ N eff [ BBN ] . Current hints that both δ N eff [ CMB ] and δ N eff [ BBN ] are non-zero and positive can be accommodated within this framework if ? ≈ few × 10 ? 9 . In the near future, measurements from the Planck mission will either confirm these hints or constrain ? ? 10 ? 9 .