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arXiv · 2110.13133

Characterization of the background spectrum in DAMIC at SNOLAB

A. Aguilar-Arevalo·D. Amidei·I. Arnquist·D. Baxter·G. Cancelo·B. A. Cervantes Vergara·A. E. Chavarria·N. Corso·E. Darragh-Ford·M. L. Di Vacri·J. C. D'Olivo·J. Estrada·F. Favela-Perez·R. Gaïor·Y. Guardincerri·T. W. Hossbach·B. Kilminster·I. Lawson·S. J. Lee·A. Letessier-Selvon·A. Matalon·P. Mitra·A. Piers·P. Privitera·K. Ramanathan·J. Da Rocha·M. Settimo·R. Smida·R. Thomas·J. Tiffenberg·D. Torres Machado·M. Traina·R. Vilar·A. L. Virto
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Abstract

We construct the first comprehensive radioactive background model for a dark matter search with charge-coupled devices (CCDs). We leverage the well-characterized depth and energy resolution of the DAMIC at SNOLAB detector and a detailed GEANT4-based particle-transport simulation to model both bulk and surface backgrounds from natural radioactivity down to 50 eV$_{\text{ee}}$. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk $^{3}$H from silicon cosmogenic activation and surface $^{210}$Pb from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as $3.1 \pm 0.6$ counts kg$^{-1}$ day$^{-1}$ keV$_{\text{ee}}^{-1}$, making it the most sensitive silicon dark matter detector. Finally, we discuss the properties of a statistically significant excess of events over the background model with energies below 200 eV$_{\text{ee}}$.

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A. Aguilar-Arevalo, D. Amidei, I. Arnquist, D. Baxter, G. Cancelo, B. A. Cervantes Vergara, A. E. Chavarria, N. Corso, E. Darragh-Ford, M. L. Di Vacri, J. C. D'Olivo, J. Estrada, F. Favela-Perez, R. Gaïor, Y. Guardincerri, T. W. Hossbach, B. Kilminster, I. Lawson, S. J. Lee, A. Letessier-Selvon, A. Matalon, P. Mitra, A. Piers, P. Privitera, K. Ramanathan, J. Da Rocha, M. Settimo, R. Smida, R. Thomas, J. Tiffenberg, D. Torres Machado, M. Traina, R. Vilar, A. L. Virto. 2021-10-25. Characterization of the background spectrum in DAMIC at SNOLAB. https://doi.org/10.1103/physrevd.105.062003

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