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

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 $(1.39\pm 0.11)\times 10^{-5}$ e${}^{-}$/pix/day, corresponding to $(39.8\pm 3.1)$ e${}^{-}$/gram/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 near-infrared-ultraviolet range. We use these data to obtain a 90% confidence level upper bound of $1.53\times 10^{-5}$ e${}^{-}$/pix/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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• Dark Matter Internal Pair Production -- A Novel Direct Detection Mechanism
• Dark Matter Haloscope with a Disordered Dielectric Absorber
• Earth-Scattering Induced Modulation in Low-Threshold Dark Matter Experiments
• SENSEI: A Search for Diurnal Modulation in sub-GeV Dark Matter Scattering
• Light-tight skipper-CCDs for X-ray detection in space
• Monophotons from Scalar Portal Dark Matter at Neutrino Experiments