Speaker
Description
Although the nature and properties of dark matter (DM) are not well known, it is expected to have some large scale gravitational effects. The DAMA collaboration claims to have made a direct detection of DM through the observation of an annual modulated signal in the 2-6 keV region, which is an expected feature of the currently accepted model for DM. However, the NaI crystals used for this experiment are inherently contaminated by a radioactive isotope: 40K, due to its chemical affinities with Na. 40K decays to the ground state of 40Ar through electron capture (EC) releasing 3.2 keV X-rays and Augers that may appear in the signal observed by DAMA. It also decays to an excited state of 40Ar (EC) releasing an additional 1460 keV gamma-ray that DAMA tags to exclude the contribution of the EC decay. To this day, the contribution of the 40K EC decay to the background in the DAMA experiment remains poorly known, notably because of the uncertainty on the branching ratios of 40K. This issue is addressed by the KDK experiment that will be conducted at Oak Ridge National Laboratories, in Tennessee, USA. This experiment uses two detectors, one for the low-energy Augers and X-rays and the MTAS detector for the higher-energy gamma-rays emitted through the EC* decay. To achieve the needed precision, MTAS will be calibrated using two radioactive isotopes with similar, but well-known decay schemes: 54Mn and 65Zn. This poster will describe the KDK experiment and its motivations, explain the calibration of MTAS and present systematic effects including those introduced by uncertainties on the branching ratios in the decays of 54Mn and 65Zn.
