New Dark Matter Limits from a P-type Point Contact Germanium Detector

Nicole Fields, University of Chicago

We present a low energy spectrum from a 56-day run at the Soudan Underground Laboratory in Minnesota. We have reduced the backgrounds by an order of magnitude from previous runs. This has been accomplished by improving the radio purity of material in the detector and by implementing new rise time cuts. The rise time cuts are able to remove surface events with partial energy deposition from the spectrum. This spectrum shows several low energy cosmogenic peaks, many of which are being seen for the first time. There is also an unexplained exponential rise at low energies. From this spectrum we derive new dark matter limits on light mass WIMPs. We also derive a favored region in mass and cross section if the exponential excess is to be explained by a model which includes a WIMP signature.

Abstract Author(s): N. E. Fields for the CoGeNT Collaboration