We present the first direct-detection search for sub-GeV dark matter using a new ∼2-gram high-resistivity Skipper CCD from a dedicated fabrication batch that was optimized for dark matter searches. Using 24 days of data acquired in the MINOS cavern at the Fermi National Accelerator Laboratory, we measure the lowest rates in silicon detectors of events containing one, two, three, or four electrons, and achieve world-leading sensitivity for a large range of sub-GeV dark matter masses. Data taken with different thicknesses of the detector shield suggest a correlation between the rate of high-energy tracks and the rate of single-electron events previously classified as "dark current." We detail key characteristics of the new Skipper CCDs, which augur well for the planned construction of the ∼100-gram SENSEI experiment at SNOLAB.

We report direct-detection constraints on light dark matter particles interacting with electrons. The results are based on a method that exploits the extremely low levels of leakage current of the DAMIC detector at SNOLAB of 2-6×10 −22 A cm −2 . We evaluate the charge distribution of pixels that collect < 10 e − for contributions beyond the leakage current that may be attributed to dark matter interactions. Constraints are placed on so-far unexplored parameter space for dark matter masses between 0.6 and 100 MeV c −2 . We also present new constraints on hidden-photon dark matter with masses in the range 1.2-30 eV c −2 .There is overwhelming astrophysical and cosmological evidence for Dark Matter (DM) as a major constituent of the universe. Still, its nature remains elusive. The compelling Weakly Interacting Massive Particle (WIMP) dark matter paradigm [1] -implying DM is made of hitherto unknown particles with mass in the GeV-TeV scale -has been intensely scrutinized during the last two decades by detectors up to the tonne-scale looking for nuclear recoils induced by coherent scattering of WIMPs. Despite the impressive improvements in sensitivity, notably by noble liquid experiments [2], WIMPs have so far escaped detection. Other viable candidates include DM particles from a hidden-sector [3], which couple weakly with ordinary matter through, for example, mixing of a hidden-photon with an ordinary photon [4]. A phenomenological consequence is that hiddensector DM particles also interact with electrons, with sufficiently large energy transfers to be detectable down to DM masses of ≈ MeV [5]. Also, eV-mass hidden-photon DM particles can be probed through absorption by electrons in detection targets [The DAMIC (Dark Matter in CCDs) experiment [7] is well-suited for a sensitive search of this class of DM candidates. DAMIC detects ionization events induced in the bulk silicon of thick, fully depleted Charge Coupled Devices (CCDs). By exploiting the charge resolution of the CCDs (≈ 2 e − ) and their extremely low leakage current (≈ 4 e − mm −2 d −1 ), DAMIC has already placed constraints on hidden-photon DM with masses in the range 1.2-30 eV c −2 [8] with data collected during the experiment's commissioning phase. In this Letter we apply a similar approach to explore DM-e − interactions with high-quality data from the DAMIC science run at the SNOLAB underground laboratory. We also present improved limits on hidden-photon DM particles.To model DM-e − interactions we follow Ref.[9] where the bound nature of the electrons and crystalline band structure of the target are properly taken into account. The differential event rate in the detector for a DM mass m χ , with transferred energy E e , and momentum q is parametrized as dR dE e ∝σ e dq q 2 η(m χ , q, E e )|F DM (q)| 2 |f c (q, E e )| 2 , (1) whereσ e is a reference cross section for free electron arXiv:1907.12628v1 [astro-ph.CO]

International audienceWe present results of a dark matter search performed with a 0.6 kg d exposure of the DAMIC experiment at the SNOLAB underground laboratory. We measure the energy spectrum of ionization events in the bulk silicon of charge-coupled devices down to a signal of 60 eV electron equivalent. The data are consistent with radiogenic backgrounds, and constraints on the spin-independent WIMP-nucleon elastic-scattering cross section are accordingly placed. A region of parameter space relevant to the potential signal from the CDMS-II Si experiment is excluded using the same target for the first time. This result obtained with a limited exposure demonstrates the potential to explore the low-mass WIMP region (<10  GeV c-2) with the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB

The Coherent Neutrino-Nucleus Interaction Experiment (CONNIE) uses low-noise fully depleted charge-coupled devices (CCDs) with the goal of measuring low-energy recoils from coherent elastic scattering (CEνNS) of reactor antineutrinos with silicon nuclei. This standard model process has not yet been observed at recoil energies below 20 keV. We report here the first results of the detector array deployed in 2016, with an active mass of 73.2 g (12 CCDs), which is operating at a distance of 30 m from the core of the Angra 2 nuclear reactor, with a thermal power of 3.8 GW. A search for neutrino events is performed by comparing data collected with reactor on (2.1 kg-day) and reactor off (1.6 kg-day). The results show no excess in the reactor-on data, reaching the world record sensitivity down to recoil energies of about 1 keV (0.1 keV electron-equivalent). A 95% confidence level limit for new physics is established at an event rate of 40 times the one expected from the standard model at this energy scale. The results presented here provide a new window to the low-energy neutrino physics, which allows one to explore for the first time the lowest energies accessible through the CEνNS with antineutrinos from nuclear reactors.

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