Multi-site event discrimination for the MAJORANA DEMONSTRATOR

The Majorana Demonstrator is searching for neutrinoless double-beta decay (0⁢𝜈⁢𝛽⁢𝛽) in ⁷⁶Ge using arrays of point-contact germanium detectors operating at the Sanford Underground Research Facility. Background results in the 0⁢𝜈⁢𝛽⁢𝛽 region of interest from data taken during construction, commissioning, and the start of full operations have been recently published. A pulse shape analysis cut applied to achieve this result, named 𝐴⁢𝑣⁢𝑠⁢𝐸, is described in this paper. This cut is developed to remove events whose waveforms are typical of multisite energy deposits while retaining (90±3.5)% of single-site events. This pulse shape discrimination is based on the relationship between the maximum current and energy, and tuned using ²²⁸Th calibration source data. The efficiency uncertainty accounts for variation across detectors, energy, and time, as well as for the position distribution difference between calibration and 0⁢𝜈⁢𝛽⁢𝛽 events, established using simulations.