The CoGeNT collaboration has recently presented the results of their first 15 months of data, including the measurement of the spectrum of nuclear recoil candidate events, and the time variation of those events. These results appear consistent with the signal anticipated from a relatively light dark matter particle scattering elastically with nuclei. In this paper, we independently analyze the data set collected by CoGeNT and explore the implications of these results for dark matter. We find that the observed spectrum and rate is consistent with originating from dark matter particles with a mass in the range of 4.5-12 GeV and an elastic scattering cross section with nucleons of approximately ∼10 −40 cm 2 . We confirm the conclusion of the CoGeNT collaboration that the data also includes a somewhat statistically significant (2.7σ) indication of annual modulation, with a phase, period, and amplitude consistent with that predicted for dark matter. CoGeNT's phase is also consistent with the annual modulation reported by the DAMA/LIBRA collaboration. We also discuss the null results reported by CDMS and XENON100, and comment on the prospects for other experiments to detect a dark matter particle with the properties implied by CoGeNT.PACS numbers: 95.36.+x; FERMILAB-PUB-11-248-A

For any realistic halo profile, the Galactic Center is predicted to be the brightest source of gammarays from dark matter annihilations. Due in large part to uncertainties associated with the dark matter distribution and astrophysical backgrounds, however, the most commonly applied constraints on the dark matter annihilation cross section have been derived from other regions, such as dwarf spheroidal galaxies. In this article, we study Fermi Gamma-Ray Space Telescope data from the direction of the inner Galaxy and derive stringent upper limits on the dark matter's annihilation cross section. Even for the very conservative case of a dark matter distribution with a significant (∼kpc) constant-density core, normalized to the minimum density needed to accommodate rotation curve and microlensing measurements, we find that the Galactic Center constraint is approximately as stringent as those derived from dwarf galaxies (which were derived under the assumption of an NFW distribution). For NFW or Einasto profiles (again, normalized to the minimum allowed density), the Galactic Center constraints are typically stronger than those from dwarfs.

Three dark matter direct detection experiments (DAMA/LIBRA, CoGeNT, and CRESST-II) have each reported signals which are not consistent with known backgrounds, but resemble that predicted for a dark matter particle with a mass of roughly ∼10 GeV and an elastic scattering cross section with nucleons of ∼10 −41 -10 −40 cm 2 . In this article, we compare the signals of these experiments and discuss whether they can be explained by a single species of dark matter particle, without conflicting with the constraints of other experiments. We find that the spectrum of events reported by CoGeNT and CRESST-II are consistent with each other and with the constraints from CDMS-II, although some tension with xenon-based experiments remains. Similarly, the modulation signals reported by DAMA/LIBRA and CoGeNT appear to be compatible, although the corresponding amplitude of the observed modulations are a factor of at least a few higher than would be naively expected, based on the event spectra reported by CoGeNT and CRESST-II. This apparent discrepancy could potentially be resolved if tidal streams or other non-Maxwellian structures are present in the local distribution of dark matter.