First Results from the DRIFT-IIa Dark Matter Detector

Understand

Data from the DRIFT-IIa directional dark matter experiment are presented, collected during a near continuous 6 month running period.

• A detailed calibration analysis comparing data from gamma-ray, x-ray and neutron sources to a GEANT4 Monte Carlo simulations reveals an efficiency for detection of neutron induced recoils of 94+/-2(stat.)+/-5(sys.)%.
• Software-based cuts, designed to remove non-nuclear recoil events, are shown to reject 60Co gamma-rays with a rejection factor of better than 8x10-6 for all energies above threshold.
• An unexpected event population has been discovered and is shown here to be due to the alpha-decay of 222Rn daughter nuclei that have attached to the central cathode.