Confirmation of the spectral excess in DAMIC at SNOLAB with skipper CCDs

We present results from a 3.25 kg -day target exposure of two silicon charge -coupled devices (CCDs), each with 24 megapixels and skipper readout, deployed in the DAMIC setup at SNOLAB. With a reduction in pixel readout noise of a factor of 10 relative to the previous detector, we investigate the excess population of low -energy events in the CCD bulk previously observed above expected backgrounds. We address the dominant systematic uncertainty of the previous analysis through a depth fiducialization designed to reject surface backgrounds on the CCDs. The measured bulk ionization spectrum confirms the presence of an excess population of low -energy events in the CCD target with characteristic rate of -7 events per kg -day and electron -equivalent energies of -80 eV, whose origin remains unknown.