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Exploring hit positions of recorded events can help to understand andsuppress backgrounds in rare event searching experiments. In this study, wevirtually segment a small contact P-type high purity germanium detector (HPGe)into two layers. Single-site events (SSEs) in each layer are selected by analgorithm based on two pulse shape parameters: the charge pulse drift time($T_{Q}$) and current pulse rise time ($T_{I}$). To determine the shapes andvolumes of the two layers, a Th-228 source is placed at top and side positionsto irradiate the detector. The double escape peak events from 2614.5 keV$\gamma$-ray are selected as typical SSEs, their numbers in the two layers areused to calculate the volumes and shapes of those layers. Considering thestatistical and systematic uncertainties, the inner layer volume is evaluatedto be 47.2\%$\pm$0.26(stat.)\%$\pm$0.22(sys.)\% of the total sensitive volume.We extend our analysis for SSEs in 1400-2100 keV, the spectra of inner layerevents acquired from experimental data using the selection algorithm are ingood agreement with those from the simulation. For sources outside the HPGedetector, the outer layer can act as a shielding for the inner layer. Selectingthe inner layer as the analysis volume can reduce the externalbackground in thesignal region of Ge-76 neutrinoless double beta (0$\nu\beta\beta$) decay. Weuse the Th-228 source to evaluate the background suppression power of thevirtual segmentation. After performing the single and multi-site eventdiscrimination, the event rate in the 0$\nu\beta\beta$ signal region can befurther suppressed by 12\% by selecting the inner layer as the analysis volume.The virtual segmentation could be used to efficiently suppress surfacebackground like electrons from Ar-42/K-42 decay in 0$\nu\beta\beta$ experimentsusing germanium detector immersed in liquid argon.

Virtual segmentation of a small contact HPGe detector: inference of hit positions of single-site events via pulse shape analysis