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Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection


Norcini, D; et al; Gadola, N; Kilminster, Ben; Lee, Steven; Robmann, Peter (2022). Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection. Physical review D, 106(9):092001.

Abstract

Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of O(10  eV). In this regime, ionization signals from small-angle Compton scatters of environmental γ rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23 eV. A skipper charge-coupled device with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241Am γ-ray source over several months. Features associated with the silicon K-, L1-, and L2,3-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100 eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5 keV. The data are in better agreement with ab initio calculations originally developed for x-ray absorption spectroscopy.

Abstract

Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of O(10  eV). In this regime, ionization signals from small-angle Compton scatters of environmental γ rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23 eV. A skipper charge-coupled device with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241Am γ-ray source over several months. Features associated with the silicon K-, L1-, and L2,3-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100 eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5 keV. The data are in better agreement with ab initio calculations originally developed for x-ray absorption spectroscopy.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Scopus Subject Areas:Physical Sciences > Nuclear and High Energy Physics
Language:English
Date:3 November 2022
Deposited On:03 Jan 2023 17:02
Last Modified:28 Jun 2024 01:37
Publisher:American Physical Society
ISSN:2470-0010
OA Status:Green
Publisher DOI:https://doi.org/10.1103/physrevd.106.092001
Project Information:
  • : FunderH2020
  • : Grant ID788137
  • : Project TitleDAMIC-M - Unveiling the Hidden: A Search for Light Dark Matter with CCDs
  • : FunderUniversity of Chicago
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  • : FunderKavli Foundation
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  • : FunderBlond McIndoe Research Foundation
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  • : FunderSchweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
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  • : Project Title
  • : FunderOffice of Science
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  • Content: Published Version