A genetic algorithm for the decomposition of multiple hit events in the γγ-ray tracking detector MARS

A crucial step in the process of γγ-ray tracking is the determination of the interaction points of the γγ-rays within the detectors. This can be achieved by pulse shape analysis of the signals from highly segmented HPGe detectors. We present an approach for this task based on a genetic algorithm. Our algorithm makes no a priori assumption on the distribution of interaction points and hit segments in the detector but addresses the decomposition problem in full generality. In the analysis of simulated signals the number of interactions can be determined at a success rate of up to 83% and the interaction points can be localised within an average positional error in the order of 2.5–5.4 mm. Similar positional errors have been obtained also in the analysis of measured signals, demonstrating the capability of our approach to decompose measured multiple hit events using a base system of calculated signals.