About a week ago, the Majorana collaboration released a new MALBEK conference proceeding presenting a preliminary WIMP dark matter limit curve. MALBEK uses p-type point contact germanium detectors to search for new physics. In particular, the MALBEK detectoris basically identical to the germanium detectors used by the CoGeNT collaboration. A few years ago, CoGeNT famously released a result that appeared to display hints of the annually modulating event rate expected from a galactic WIMP dark matter halo. With the same type of detector in a different location, MALBEK could potentially hope to confirm or reject the existence of the proposed CoGeNT signal.
There’s nothing groundbreaking here, but MALBEK has obtained results that reject the CoGeNT result with certain analysis choices but not with others. They use a wavelet-based pulse shape discrimination variable to remove surface events but don’t have a very good way yet to quantify the efficiency for bulk nuclear recoils or the contamination from background.
Juan Collar (from CoGeNT) has already responded. He criticizes the rather opaque nature of the MALBEK pulse shape analysis. MALBEK resorted to these methods because it was found that a simple variable such as the pulse rise time does not separate surface and bulk events at energies below 2 keV. CoGeNT is able to separate these events due to a much lower amount of electronics noise.
At any rate, the best results in the low mass region from CDMS and LUX already seem to rule out the CoGeNT dark matter hypothesis by a fairly wide margin. CDMS even uses germanium so one can’t argue that maybe the Ge cross section is enhanced compared to the standard assumptions for the Xe cross section.