Surface Alpha Background Rejection through Pulse Shape Discrimination in the MAJORANA DEMONSTRATOR

The MAJORANA DEMONSTRATOR is an experiment searching for neutrinoless double-beta decay in ⁷⁶Ge. The experiment consists of two modular arrays with about 45 kg of high purity Germanium detectors, 30 kg of which is enriched to 88% in ⁷⁶Ge, operating at the 4850' level of the Sanford Underground Research Facility in Lead, SD. P-type point contact detector technology allows for the rejection of specific background event populations through pulse-shape analysis. For the MAJORANA analysis of the total exposure collected with enriched detectors, the main parameter used to reduce the observed alpha background is called DCR (delayed charge recovery). This parameter estimates the slope of an event's waveform after the rising edge to identify alpha-like events that originate from the passivated surface of the detector; such events have a characteristic delayed charge collection component. We present the performance of, and improvements to, surface alpha background rejection using DCR, and show its influence on the sensitivity of the experiment.