Current Dark Matter Annihilation Constraints from CMB and Low-Redshift
  Data
  Updated constraints on dark matter cross section and mass are presented
combining CMB power spectrum measurements from Planck, WMAP9, ACT, and SPT as
well as several low-redshift datasets (BAO, HST, supernovae). For the CMB
datasets, we combine WMAP9 temperature and polarization data for l <= 431 with
Planck temperature data for 432 < l < 2500, ACT and SPT data for l > 2500, and
Planck CMB four-point lensing measurements. We allow for redshift-dependent
energy deposition from dark matter annihilation by using a `universal' energy
absorption curve. We also include an updated treatment of the excitation,
heating, and ionization energy fractions, and provide updated deposition
efficiency factors (f_eff) for 41 different dark matter models. Assuming
perfect energy deposition (f_eff = 1) and a thermal cross section, dark matter
masses below 26 GeV are excluded at the 2-sigma level. Assuming a more generic
efficiency of f_eff = 0.2, thermal dark matter masses below 5 GeV are
disfavored at the 2-sigma level. These limits are a factor of ~2 improvement
over those from WMAP9 data alone. These current constraints probe, but do not
exclude, dark matter as an explanation for reported anomalous indirect
detection observations from AMS-02/PAMELA and the Fermi Gamma-ray Inner Galaxy
data. They also probe relevant models that would explain anomalous direct
detection events from CDMS, CRESST, CoGeNT, and DAMA, as originating from a
generic thermal WIMP. Projected constraints from the full Planck release should
improve the current limits by another factor of ~2, but will not definitely
probe these signals. The proposed CMB Stage IV experiment will more decisively
explore the relevant regions and improve upon the Planck constraints by another
factor of ~2.
