{"paper":{"title":"Pulse shape discrimination for $\\alpha$ event rejection in BEGe-type high-purity germanium detectors","license":"http://creativecommons.org/licenses/by/4.0/","headline":"Classifiers trained only on gamma-ray pulse shapes can reject alpha events in germanium detectors with over 27,000-to-1 efficiency while preserving more than 80% of signal-like events.","cross_cats":["hep-ex"],"primary_cat":"physics.ins-det","authors_text":"Alex Biondi, Grzegorz Zuzel, Krzysztof Szczepaniec, Marcin Misiaszek, Tomasz Mr\\'oz","submitted_at":"2026-05-13T13:20:52Z","abstract_excerpt":"High-purity germanium detectors are widely used in rare-event searches due to their excellent energy resolution and extremely high intrinsic (radio)purity. In experiments searching for neutrinoless double beta decay in $^{76}$Ge such as LEGEND, pulse shape discrimination is required to suppress multi-site $\\gamma$ events. In this work, we investigate whether pulse shape discrimination classifiers trained exclusively on $\\gamma$ ray data can be used to identify and reject $\\alpha$ events, without the need for dedicated $\\alpha$ training. In detectors such as LEGEND, the total number of register"},"claims":{"count":4,"items":[{"kind":"strongest_claim","text":"The multilayer perceptron provides the best overall performance, with a signal-like event survival greater than 80%, a background-like event survival below 20%, and an α-rejection factor exceeding 2.71×10^4.","source":"verdict.strongest_claim","status":"machine_extracted","claim_id":"C1","attestation":"unclaimed"},{"kind":"weakest_assumption","text":"That the pulse shapes produced by 209Po and 210Po alphas deposited on a thin gold foil on the p+ surface are representative of the alpha events that will occur in the actual LEGEND-style detector during long-term underground operation.","source":"verdict.weakest_assumption","status":"machine_extracted","claim_id":"C2","attestation":"unclaimed"},{"kind":"one_line_summary","text":"Gamma-only trained multilayer perceptron and likelihood classifiers achieve >2.71e4 alpha rejection in BEGe detectors with >80% signal survival and <20% background survival.","source":"verdict.one_line_summary","status":"machine_extracted","claim_id":"C3","attestation":"unclaimed"},{"kind":"headline","text":"Classifiers trained only on gamma-ray pulse shapes can reject alpha events in germanium detectors with over 27,000-to-1 efficiency while preserving more than 80% of signal-like events.","source":"verdict.pith_extraction.headline","status":"machine_extracted","claim_id":"C4","attestation":"unclaimed"}],"snapshot_sha256":"b04c6af0c12e64bf27100dffbfecbb83cacb4445c9413fd8e4ba1adaaf8fe9ae"},"source":{"id":"2605.13498","kind":"arxiv","version":1},"verdict":{"id":"c0028134-c309-4dae-a10a-40f6fde4c0c2","model_set":{"reader":"grok-4.3"},"created_at":"2026-05-14T18:08:57.341696Z","strongest_claim":"The multilayer perceptron provides the best overall performance, with a signal-like event survival greater than 80%, a background-like event survival below 20%, and an α-rejection factor exceeding 2.71×10^4.","one_line_summary":"Gamma-only trained multilayer perceptron and likelihood classifiers achieve >2.71e4 alpha rejection in BEGe detectors with >80% signal survival and <20% background survival.","pipeline_version":"pith-pipeline@v0.9.0","weakest_assumption":"That the pulse shapes produced by 209Po and 210Po alphas deposited on a thin gold foil on the p+ surface are representative of the alpha events that will occur in the actual LEGEND-style detector during long-term underground operation.","pith_extraction_headline":"Classifiers trained only on gamma-ray pulse shapes can reject alpha events in germanium detectors with over 27,000-to-1 efficiency while preserving more than 80% of signal-like events."},"references":{"count":25,"sample":[{"doi":"10.1103/physrevlett.129.111801","year":2022,"title":"CUPID Collaboration, Phys. Rev. Lett.129, 111801 (2022). DOI 10.1103/PhysRevLett.129.111801","work_id":"b32a1645-515d-4826-bd55-3d626c8b402b","ref_index":1,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1103/physrevd.92.072011","year":2015,"title":"NEMO Collaboration, Phys. Rev. D92, 072011 (2015). DOI 10.1103/PhysRevD.92.072011","work_id":"9160c85e-121a-4617-9c4a-a3e8e51f90e9","ref_index":2,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1103/physrevlett.134.082501","year":2025,"title":"AMoRE Collaboration, Phys. Rev. Lett.134, 082501 (2025). DOI 10.1103/PhysRevLett.134.082501","work_id":"d5d003a8-5409-4b10-b137-02c26d996165","ref_index":3,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1140/epjc/","year":2022,"title":"DOI 10.1140/epjc/ s10052-022-10942-5","work_id":"bf7f3f64-80c5-4847-8cb1-3a6dbe2cdf14","ref_index":4,"cited_arxiv_id":"","is_internal_anchor":false},{"doi":"10.1126/science.adp6474","year":2025,"title":"doi:10.1126/science.adp6474","work_id":"efefd07c-50b6-458e-9411-90e370dbec0e","ref_index":5,"cited_arxiv_id":"","is_internal_anchor":false}],"resolved_work":25,"snapshot_sha256":"b7be6bcb2592e4d887f3f7aef3f3fe08bdd192a14749972ba07a97631c21ee1c","internal_anchors":0},"formal_canon":{"evidence_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"author_claims":{"count":0,"strong_count":0,"snapshot_sha256":"258153158e38e3291e3d48162225fcdb2d5a3ed65a07baac614ab91432fd4f57"},"builder_version":"pith-number-builder-2026-05-17-v1"}