Measurements of low energy nuclear recoil tracks and their implications for directional dark matter detectors

Directional dark matter detection is needed to unambiguously detect a dark matter particle interaction in a detector. This is due to the fact that only a dark matter signature will have its incoming direction vary throughout the day due to the rotation of the earth. This directional signature could only be measured in a gaseous detector as used by the DRIFT detector, currently taking data with one module at the Boulby mine in the UK. Gas has to be used as the detection media to allow for longer tracks that can be resolved in three dimensions and a vector direction, resulting in the possibility of measuring the incoming direction of the WIMP that created the recoil. The prototype detector presented in this Dissertation is used to fundamentally investigate the properties of the low energy nuclear recoils induced by WIMP interactions in a real directional dark matter detector. Measurements are presented that have been performed using neutrons to create nuclear recoils in the detector that are in the range of recoil energies expected from WIMP interactions. It has been measured how well the track can be reconstructed in three dimensions using the detector described. Furthermore, it is expected that the nuclear recoils at these low energies have an asymmetry of charge along the track. This asymmetry, if it is distinctly different at the beginning of the track than the end, can be used to assign a vector direction to the nuclear recoil. If this is possible for WIMP interactions expected, the amount of events needed to positively detect a dark matter signal can be significantly decreased. A fundamental study of this so called Head-tail asymmetry in the charge distribution has been performed with the prototype detector and is presented