Abstract

We present results from a 3.25 kg-day target exposure of two silicon charge-coupled devices (CCDs), each with 24 megapixels and skipper readout, deployed in the DAMIC setup at SNOLAB. With a reduction in pixel readout noise of a factor of 10 relative to the previous detector, we investigate the excess population of low-energy events in the CCD bulk previously observed above expected backgrounds. We address the dominant systematic uncertainty of the previous analysis through a depth fiducialization designed to reject surface backgrounds on the CCDs. The measured bulk ionization spectrum confirms the presence of an excess population of low-energy events in the CCD target with characteristic rate of ∼7 events per kg-day and electron-equivalent energies of ∼80 eV, whose origin remains unknown.

Original languageEnglish
Article number062007
JournalPhysical Review D
Volume109
Issue number6
DOIs
StatePublished - 15 Mar 2024

Funding

FundersFunder number
Kavli Institute for Cosmological Physics, University of Chicago
Ministry of Training, Colleges and Universities
Ministerio de Ciencia e Innovación
University of Chicago
Major Science Initiatives Fund
Swiss Canton of Zurich
Canada Foundation for Innovation
Kavli Foundation
Agencia Estatal de Investigación
Office of Science
University of Washington
European Research Council
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung200021_153654
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
U.S. Department of EnergyDE-AC02-05CH11231
U.S. Department of Energy
Agence Nationale de la RechercheANR-11-IDEX-0004-02
Agence Nationale de la Recherche
FermilabDE-AC02-07CH11359
Fermilab
Horizon 2020 Framework Programme788137
Horizon 2020 Framework Programme
Heising-Simons FoundationPHY-2110585, 79921
Heising-Simons Foundation
National Science FoundationPHY-1812654
National Science Foundation
Consejo Nacional de Ciencia y TecnologíaCF-2023-I-1169
Consejo Nacional de Ciencia y Tecnología
Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de MéxicoIN106322
Dirección General de Asuntos del Personal Académico, Universidad Nacional Autónoma de México
Institut Lagrange de Paris Laboratoire d’ExcellenceANR-10-LABX-63
Instituto de Física de CantabriaPID2019–109829 GB-I00
Instituto de Física de Cantabria

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