Characterization of the background spectrum in DAMIC at SNOLAB

Le résumé fourni par la source

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 $50\text{ }\text{ }{\mathrm{eV}}_{\mathrm{ee}}$. We fit to the energy and depth distributions of the observed ionization events to differentiate and constrain possible background sources, for example, bulk $^{3}\mathrm{H}$ from silicon cosmogenic activation and surface $^{210}\mathrm{Pb}$ from radon plate-out. We observe the bulk background rate of the DAMIC at SNOLAB CCDs to be as low as $3.1\ifmmode\pm\else\textpm\fi{}0.6\text{ }\text{ }\mathrm{counts}\text{ }{\mathrm{kg}}^{\ensuremath{-}1}\text{ }{\mathrm{day}}^{\ensuremath{-}1}\text{ }{\mathrm{keV}}_{\mathrm{ee}}^{\ensuremath{-}1}$, 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 $200\text{ }\text{ }{\mathrm{eV}}_{\mathrm{ee}}$.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.