{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"bb20d67d3b15fbdde9a85d95d91ed3e1abe5d9b51a22d6ed278ada3c7516b778","created":"2026-10-03T07:18:05Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"162de44f9ef4cc6a8339d7342ec5184aa47039ade8ae9556e88a026ee500e51d","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"value","assisted_by":[],"external_id":"hep.low-energy-excess.ccd-single-electron","kind":"well-posed","literature_status":"open","n":"1","parents":[],"plain":"Skipper CCDs can count single electrons, but they register stray single electrons at a low steady rate that mimics the faintest dark matter signals. The question is where these stray electrons come from and how low the rate can go.","posed_since":"","precise":"Skipper CCDs (SENSEI, DAMIC-M, Oscura) measure a rate of 1-electron events per pixel per day that limits searches for dark matter-electron scattering in the 1-2 electron bins. Candidate sources are thermal dark current, spurious charge from readout clocking, Cherenkov and recombination photons from high-energy tracks, and charge release from defects. An answer is a quantitative decomposition of the measured rate into sources and the irreducible floor for silicon at the operating temperature.","problem_ref":null,"references":"","settled_by":"Rate measurements versus temperature, clocking scheme, readout timing, shielding and track density in otherwise identical CCDs, compared with a calibrated source model.","status_note":"The 2025 DAMIC-M prototype search (Phys. Rev. Lett. 135, 071002) ran with a 50-fold lower single-electron rate than its previous search, showing much of the earlier rate was instrumental; the floor is not known.","title":"What sets the residual single-electron event rate in skipper 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