Physics Opportunities from Irreducible Backgrounds in Dark Matter Direct Detection
- Josef Pradler, Johns Hopkins University
Wednesday, February 19, 4:10 PM - Nuclear Science Seminar
NSCL Lecture Hall
Dark Matter (DM) direct detection experiments are currently limited in sensitivity by the presence of in-situ radioactive backgrounds and their future discovery potential will ultimately be constrained by the flux of solar neutrinos. In a first part of the talk, we will scrutinize the most prominent of tentative signals (anomalies) that have been observed in direct detection: the DAMA collaboration claims a firm detection of DM from a 2% modulating signal rate. We show that the presence of 40K decays via electron capture to the ground state of 40Ar, as well as other backgrounds, poses a challenge to this interpretation in terms of a DM model with a modulation fraction as small as 2%. We point out that the respective 40K decay mode has not yet been verified experimentally, and a dedicated measurement is called for. In a second part, we will take on the discussion of other direct detection anomalies and show that the elastic nuclear recoil signal may not only be interpreted as coming from the interaction of nuclei with light DM but also from the scattering of new species of MeV-energy neutrinos. The most promising model for the latter case is a neutrino that interacts with baryon number, and with a flux sourced by the oscillations of regular solar neutrinos. In contrast to the light-DM interpretation of various anomalies that is now seriously challenged by the negative results of the LUX experiment, the neutrino interpretation remains a viable explanation to most of the anomalies.