Constraints on the electron-hole pair creation energy and Fano factor below 150 eV from Compton scattering in a Skipper-CCD

Fully-depleted thick silicon Skipper-charge-coupled devices (Skipper-CCDs) are an important technology to probe neutrino and light-dark-matter interactions due to their sub-electron read-out noise. However, the successful search for rare neutrino or dark-matter events requires the signal and all backgrounds to be fully characterized. In particular, a measurement of the electron-hole pair creation energy below 150 eV and the Fano factor are necessary for characterizing the dark matter and neutrino signals. Moreover, photons from background radiation may Compton scatter in the silicon bulk, producing events that can mimic a dark matter or neutrino signal. We present a measurement of the Compton spectrum using a Skipper-CCD and a $^{241}$Am source. With these data, we estimate the electron-hole pair-creation energy to be $\left(3.71 \pm 0.08\right)$ eV at 130 K in the energy range between 99.3 eV and 150 eV. By measuring the widths of the steps at 99.3 eV and 150 eV in the Compton spectrum, we introduce a novel technique to measure the Fano factor, setting an upper limit of 0.31 at 90% C.L. These results prove the potential of Skipper-CCDs to characterize the Compton spectrum and to measure precisely the Fano factor and electron-hole pair creation energy below 150 eV

First results from a multiplexed and massive instrument with sub-electron noise Skipper-CCDs

We present a new instrument composed of a large number of sub-electron noise Skipper-CCDs operated with a two stage analog multiplexed readout scheme suitable for scaling to thousands of channels. New, thick, $1.35$ Mpix sensors, from a new foundry, are glued into a Multi-Chip Module (MCM) printed circuit board on a ceramic substrate which has 16 sensors each. The instrument, that can hold up-to 16 MCMs, a total of 256 Skipper-CCD sensors (called a Super-Module with $\approx 130$ grams of active mass and $346$ Mpix), is part of the R$\&$D effort of the OSCURA experiment which will have $\approx 94$ super-modules. Experimental results with $10$ MCMs and $160$ Skipper-CCDs sensors are presented in this paper. This is already the largest ever build instrument with single electron sensitivity CCDs using nondestructive readout, both, in terms of active mass and number of channels.Comment: Corrected minor typo

Results of the engineering run of the coherent neutrino nucleus interaction experiment (CONNIE)

The CONNIE detector prototype is operating at a distance of 30 m from the core of a 3.8 GWth nuclear reactor with the goal of establishing Charge-Coupled Devices (CCD) as a new technology for the detection of coherent elastic neutrino-nucleus scattering. We report on the results of the engineering run with an active mass of 4 g of silicon. The CCD array is described, and the performance observed during the first year is discussed. A compact passive shield was deployed around the detector, producing an order of magnitude reduction in the background rate. The remaining background observed during the run was stable, and dominated by internal contamination in the detector packaging materials. The in-situ calibration of the detector using X-ray lines from fluorescence demonstrates good stability of the readout system. The event rates with the reactor ON and OFF are compared, and no excess is observed coming from nuclear fission at the power plant. The upper limit for the neutrino event rate is set two orders of magnitude above the expectations for the standard model. The results demonstrate the cryogenic CCD-based detector can be remotely operated at the reactor site with stable noise below2 e RMS and stable background rates. The success of the engineering test provides a clear path for the upgraded 100 g detector to be deployed during 2016.Fil: Aguilar Arevalo, A.. Universidad Nacional Autónoma de México; MéxicoFil: Bertou, Xavier Pierre Louis. Comisión Nacional de Energía Atómica; Argentina. Comisión Nacional de Energía Atómica. Fundación José A. Balseiro; ArgentinaFil: Bonifazi, C.. Universidade Federal do Rio de Janeiro; BrasilFil: Butner, M.. Fermi National Accelerator Laboratory; Estados UnidosFil: Cancelo, G.. Fermi National Accelerator Laboratory; Estados UnidosFil: Castañeda Vazquez, A.. Universidad Nacional Autónoma de México; MéxicoFil: Cervantes Vergara, B.. Universidad Nacional Autónoma de México; MéxicoFil: Chavez, C. R.. Universidad Nacional de Asunción; ParaguayFil: Da Motta, H.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: D'Olivo, J. C.. Universidad Nacional Autónoma de México; MéxicoFil: Dos Anjos, J.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Estrada, J.. Fermi National Accelerator Laboratory; Estados UnidosFil: Fernández Moroni, Guillermo. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ford, R.. Fermi National Accelerator Laboratory; Estados UnidosFil: Foguel, A.. Centro Brasileiro de Pesquisas Físicas; Brasil. Universidade Federal do Rio de Janeiro; BrasilFil: Hernandez Torres, K. P.. Universidad Nacional Autónoma de México; MéxicoFil: Izraelevitch, F.. Fermi National Accelerator Laboratory; Estados UnidosFil: Kavner, A.. University of Michigan; Estados UnidosFil: Kilminster, B.. Universitat Zurich; SuizaFil: Kuk, K.. Fermi National Accelerator Laboratory; Estados UnidosFil: Lima Jr, H. P.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Makler, M.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Molina, J.. Universidad Nacional de Asunción; ParaguayFil: Moreno Granados, G.. Universidad Nacional Autónoma de México; MéxicoFil: Moro, Juan Manuel. Universidad Nacional del Sur. Departamento de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Paolini, Eduardo Emilio. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto ; ArgentinaFil: Sofo Haro, Miguel Francisco. Comision Nacional de Energia Atomica. Gerencia D/area de Energia Nuclear; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tiffenberg, Javier Sebastian. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trillaud, F.. Universidad Nacional Autónoma de México; MéxicoFil: Wagner, S.. Centro Brasileiro de Pesquisas Físicas; Brasil. Pontificia Universidade Católica do Rio Grande do Sul; Brasi

Search for low-mass WIMPs in a 0.6 kg day exposure of the DAMIC experiment at SNOLAB

We present results of a dark matter search performed with a 0.6 kg day 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/$c^{2}$) of the upcoming DAMIC100, a 100 g detector currently being installed in SNOLAB.Comment: 11 pages, 11 figure

SENSEI: Characterization of Single-Electron Events Using a Skipper-CCD

We use a science-grade Skipper Charge Coupled Device (Skipper-CCD) operating in a low-radiation background environment to develop a semi-empirical model that characterizes the origin of single-electron events in CCDs. We identify, separate, and quantify three independent contributions to the single-electron events, which were previously bundled together and classified as ``dark counts'': dark current, amplifier light, and spurious charge. We measure a dark current, which depends on exposure, of (5.89+-0.77)x10^-4 e-/pix/day, and an unprecedentedly low spurious charge contribution of (1.52+-0.07)x10^-4 e-/pix, which is exposure-independent. In addition, we provide a technique to study events produced by light emitted from the amplifier, which allows the detector's operation to be optimized to minimize this effect to a level below the dark-current contribution. Our accurate characterization of the single-electron events allows one to greatly extend the sensitivity of experiments searching for dark matter or coherent neutrino scattering. Moreover, an accurate understanding of the origin of single-electron events is critical to further progress in ongoing R&D efforts of Skipper and conventional CCDs.Comment: 9 pages, 6 figures, 4 table

Exploring low-energy neutrino physics with the Coherent Neutrino Nucleus Interaction Experiment

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 ( CE ν NS ) of reactor antineutrinos with silicon nuclei and testing nonstandard neutrino interactions (NSI). We report here the first results of the detector array deployed in 2016, considering an active mass 47.6 g (eight 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 the 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 low-energy neutrino physics, allowing one to explore for the first time the energies accessible through the low threshold of CCDs. They will lead to new constraints on NSI from the CEνNS of antineutrinos from nuclear reactors.Fil: Aguilar Arevalo, Alexis. Universidad Nacional Autónoma de México; MéxicoFil: Bertou, Xavier Pierre Louis. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Universidad Nacional de Cuyo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Bonifazi, Carla Brenda. Universidade Federal do Rio de Janeiro; Brasil. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Cancelo, Gustavo Indalecio. Fermi National Accelerator Laboratory; Estados UnidosFil: Castañeda, Alejandro. Universidad Nacional Autónoma de México; MéxicoFil: Cervantes Vergara, Brenda. Universidad Nacional Autónoma de México; MéxicoFil: Chavez, Claudio. Universidad Nacional de Asunción; ParaguayFil: D’Olivo, Juan C.. Universidad Nacional Autónoma de México; MéxicoFil: Dos Anjos, João C.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Estrada, Juan. Fermi National Accelerator Laboratory; Estados UnidosFil: Fernandes Neto, Aldo R.. Centro Federal de Educacão Tecnológica Celso Suckow Da Fonseca; BrasilFil: Fernández Moroni, Guillermo. Fermi National Accelerator Laboratory; Estados Unidos. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Foguel, Ana. Universidade Federal do Rio de Janeiro; BrasilFil: Ford, Richard. Fermi National Accelerator Laboratory; Estados UnidosFil: Gonzalez Cuevas, Juan. Universidad Nacional de Asunción; ParaguayFil: Hernández, Pamela. Universidad Nacional Autónoma de México; MéxicoFil: Hernandez, Susana. Fermi National Accelerator Laboratory; Estados UnidosFil: Izraelevitch, Federico Hernán. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de San Martín; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kavner, Alexander R.. University of Michigan; Estados UnidosFil: Kilminster, Ben. Universitat Zurich; SuizaFil: Kuk, Kevin. Fermi National Accelerator Laboratory; Estados UnidosFil: Lima, H.P.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Makler, Martín. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Molina, Jorge. Universidad Nacional de Asunción; ParaguayFil: Mota, Philipe. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Nasteva, Irina. Universidade Federal do Rio de Janeiro; BrasilFil: Paolini, Eduardo Emilio. Universidad Nacional del Sur; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca; ArgentinaFil: Romero, Carlos. Universidad Nacional de Asunción; ParaguayFil: Sarkis, Y.. Universidad Nacional Autónoma de México; MéxicoFil: Sofo Haro, Miguel Francisco. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional de Cuyo; Argentina. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnol.conicet - Patagonia Norte. Unidad de Adm.territorial; ArgentinaFil: Souza, Iruatã M. S.. Centro Brasileiro de Pesquisas Físicas; BrasilFil: Tiffenberg, Javier Sebastian. Fermi National Accelerator Laboratory; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Wagner, Stefan. Centro Brasileiro de Pesquisas Físicas; Brasil. Pontifícia Universidade Católica do Rio de Janeiro; Brasi