SENSEI: Direct-Detection Constraints on Sub-GeV Dark Matter from a Shallow Underground Run Using a Prototype Skipper...

Area of Science:

• Particle Physics
• Astrophysics
• Cosmology

Background:

• The nature of dark matter remains one of the most significant unsolved problems in physics.
• Direct-detection experiments aim to observe dark matter particles interacting with ordinary matter.
• Previous experiments have faced challenges in detecting low-mass dark matter candidates, particularly those interacting with electrons.

Purpose of the Study:

• To present new direct-detection constraints on dark matter interacting with electrons.
• To explore dark matter candidates in the eV-to-GeV mass range.
• To utilize a prototype Sub-Electron-Noise Skipper-CCD Experimental Instrument for enhanced sensitivity.

Main Methods:

• Data acquisition using a prototype Sub-Electron-Noise Skipper-CCD at Fermilab's MINOS cavern.
• Employing two distinct readout strategies: continuous readout and a novel method with amplifiers switched off during exposure.
• Analyzing event rates for one, two, and three or more electron signals to establish background and signal characteristics.

Main Results:

• The continuous readout strategy revealed high background rates attributed to amplifier-induced spurious events.
• The novel readout strategy significantly reduced the one-electron event rate by nearly two orders of magnitude.
• No events with three or more electrons were observed in either strategy, setting upper limits.

Conclusions:

• The improved readout strategy yields world-leading constraints on dark matter-electron scattering for masses between 500 keV and 5 MeV.
• New constraints are also established for dark-photon dark matter absorption by electrons for masses below 12.4 eV.
• The Sub-Electron-Noise Skipper-CCD technology demonstrates significant potential for future dark matter searches.