SENSEI at SNOLAB: Single-Electron Event Rate and Implications for Dark Matter
Itay M. Bloch, Ana Martina Botti, Mariano Cababié, Gustavo Cancelo, Brenda A. Cervantes-Vergara, M. Daal, Ansh Desai, A. Drlica-Wagner, Rouven Essig, J. Estrada, E. Etzion, Guillermo Fernández Moroni, S. Holland, Jonathan Kehat, Ian Lawson, Steffon Luoma, Aviv Orly, Santiago Pérez, Darío Rodrigues, Nate Saffold, S. Scorza, Miguel Sofo-Haro, Kelly Stifter, Javier Tiffenberg, Sho Uemura, Edgar Marrufo Villalpando, Tomer Volansky, Federico Winkel, Yikai Wu, T. Yu
Abstract
We present results from data acquired by the SENSEI experiment at SNOLAB after a major upgrade in May 2023, which includes deploying 16 new sensors and replacing the copper trays that house the CCDs with a new light-tight design. We observe a single-electron event rate of $(1.39\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{e}}^{\ensuremath{-}}/\mathrm{pix}/\mathrm{day}$, corresponding to $(39.8\ifmmode\pm\else\textpm\fi{}3.1)\text{ }\text{ }{\mathrm{e}}^{\ensuremath{-}}/\mathrm{gram}/\mathrm{day}$. This is an order-of-magnitude improvement compared to the previous lowest single-electron rate in a silicon detector and the lowest for any photon detector in the wavelength range between near-infrared and ultraviolet. We use these data to obtain a 90% confidence level upper bound of $1.53\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}\text{ }\text{ }{\mathrm{e}}^{\ensuremath{-}}/\mathrm{pix}/\mathrm{day}$ and to set constraints on sub-GeV dark matter candidates that produce single-electron events. We hypothesize that the data taken at SNOLAB in the previous run, with an older tray design for the sensors, contained a larger rate of single-electron events due to light leaks. We test this hypothesis using data from the SENSEI detector located in the MINOS cavern at Fermilab.