Search for An Annual Modulation in Three Years of CoGeNT Dark Matter
  Detector Data
  Weakly Interacting Massive Particles (WIMPs) are well-established dark matter
candidates. WIMP interactions with sensitive detectors are expected to display
a characteristic annual modulation in rate. We release a dataset spanning 3.4
years of operation from a low-background germanium detector, designed to search
for this signature. A previously reported modulation persists, concentrated in
a region of the energy spectrum populated by an exponential excess of unknown
origin. Its phase and period agree with phenomenological expectations, but its
amplitude is a factor $\sim$4-7 larger than predicted for a standard WIMP
galactic halo. We consider the possibility of a non-Maxwellian local halo
velocity distribution as a plausible explanation, able to help reconcile
recently reported WIMP search anomalies.
