{"schema":"pubphys.bundle/1","record":{"author":{"account_ref":null,"orcid":null},"builds_on":[],"content_schema":"pubphys.content.revision/1","content_sha256":"3b1bd2935357ce3fada74d16dbde3691c50538b92870f5449a36a36d582f697b","created":"2026-10-03T07:18:05Z","files":[],"origin":{"assisted_by":[],"kind":"seed"},"parents":["5475cf5dc5b1a72283d26dc95dc6e00d7ea4e00096a7c6492e409a1816eeb011"],"salt":"e95494ccf9e419c3a7b1a7ac42d58043a807e3774efdb092264f1bef0a2748ef","schema":"pubphys.record/2","site":"pubphys.com","target":null,"type":"revision"},"content":{"answer_type":"mechanism","assisted_by":[],"external_id":"hep.low-energy-excess.calorimeter-mechanism","kind":"phenomenon","literature_status":"contested","n":"1","parents":[],"plain":"Crystals cooled near absolute zero record many more small heat pulses below a few hundred electron volts than expected, and the rate fades over weeks after cooling. The question is what inside the detector releases this energy.","posed_since":"","precise":"Cryogenic calorimeters (CRESST CaWO4, Al2O3, Si; SuperCDMS-type Si and Ge; NUCLEUS; EDELWEISS) observe a rate $\\mathrm{d}R/\\mathrm{d}E$ rising steeply below about 200 eV, uncorrelated with particle backgrounds and decaying after cooldown. Candidate sources include stress relaxation at holders, glue and sensor films; dislocation motion from differential thermal contraction; and annealing of radiation-induced lattice defects. An answer is a mechanism that reproduces the energy spectrum, the time dependence, the material dependence and the sensor-geometry dependence, confirmed by a controlled test that turns the excess on or off.","problem_ref":null,"references":"","settled_by":"A detector in which removing or adding the hypothesized source (e.g., stress in the holder or film, or a defect population) changes the excess rate by a predicted factor.","status_note":"In 2026 NUCLEUS (Eur. Phys. J. C 86, 831) found slower cooldown lowers the initial rate and the rate decays as a power law independent of particle background; stress-relaxation (Nature Commun. 2024), thermal-contraction (2026 preprint) and defect-annealing (Phys. Rev. Mater. 2025) explanations all remain under discussion.","title":"What microscopic process produces the excess in cryogenic 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