Results from a search for light-mass dark matter with a p-type point contact germanium detector

Phys Rev Lett. 2011 Apr 1;106(13):131301. doi: 10.1103/PhysRevLett.106.131301. Epub 2011 Mar 29.

Abstract

We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, a number of cosmogenic peaks can be observed for the first time. We discuss an irreducible excess of bulklike events below 3 keV in ionization energy. These could be caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible to determine their origin. Improved constraints are placed on a cosmological origin for the DAMA/LIBRA effect.