SENSEI at SNOLAB: Single-Electron Event Rate and Implications for Dark Matter

Le résumé fourni par la source

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.

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