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Title: What sets the residual single-electron event rate in skipper CCDs?
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.
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.
Settled by: Rate measurements versus temperature, clocking scheme, readout timing, shielding and track density in otherwise identical CCDs, compared with a calibrated source model.
Kind: well-posed
Answer type: value
References: (empty)
Literature status: open
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.
Posed since: (empty)