Discrimination of single-site and multi-site events in CZT-CPG detectors for the COBRA experiment

The aim of the COBRA experiment is to search for the existence of neutrinoless double beta-decay (0nββ-decay) with CZT semiconductor detectors. One key instrument to reach the required half-life sensitivity of several 10
²⁶
years is to differentiate between signal and background events. The 0nββ-signal is expected to be almost always a single-site event (SSE) within only one detector. Hence, all multi-site events (MSEs) can be vetoed as background. Recently, an identification routine has been developed to distinguish between signal-like SSEs and background-like MSEs based on pulse-shape analysis. For the verification of this method a laboratory experiment was performed which makes use of coincident Compton scattering to build up a library of definite SSEs. The results of this investigation, the analysis behind it as well as the application and prospects of the MSE identification algorithm will be presented.