{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"c7b23959e63dd64bcbb29e6a153985e8e0ffb030d72b1e8764bf990682ff5f30","created":"2026-10-03T07:18:05Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"5809c8877a9ea0c6c5663613dbcdfeb70e9df737cd2b64e48b412f10460972ca","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"identification","assisted_by":[],"external_id":"hep.low-energy-excess.damic-bulk-excess","kind":"phenomenon","literature_status":"open","n":"1","parents":[],"plain":"Silicon camera chips used to search for dark matter deep underground see extra small charge signals from inside the silicon, beyond all known radioactivity. The cause is unknown.","posed_since":"2020","precise":"DAMIC at SNOLAB reported an excess of bulk ionization events above the radiogenic background model, with characteristic rate about 7 events/(kg day) at electron-equivalent energies about 80 eV, later confirmed with skipper CCDs. An answer identifies the source (unmodeled background such as low-energy Compton or surface events, a detector effect, or new physics) and predicts the rate and spectrum in other silicon detectors.","problem_ref":null,"references":"","settled_by":"Comparison of the bulk excess across silicon CCDs with different fabrication, depth, shielding and cosmogenic exposure (DAMIC-M, SENSEI, Oscura prototypes) and with calibrated low-energy Compton spectra.","status_note":"Confirmed with skipper CCDs at SNOLAB (Phys. Rev. D 109, 062007, 2024, arXiv 2306.01717); origin unknown.","title":"What causes the bulk ionization excess in DAMIC CCDs at 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