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Evidence of Coherent Elastic Neutrino-Nucleus Scattering with COHERENT's Germanium Array

S. Adamski, M. Ahn, P. S. Barbeau, V. Belov, I. Bernardi, C. Bock, A. Bolozdynya, R. Bouabid, J. Browning, B. Cabrera-Palmer, N. Cedarblade-Jones, A. I. Colón Rivera, E. Conley, V. da Silva, J. Daughhetee, J. Detwiler, K. Ding, M. R. Durand, Y. Efremenko, S. R. Elliott, A. Erlandson, L. Fabris, A. Galindo-Uribarri, M. P. Green, J. Hakenmüller, M. R. Heath, S. Hedges, H. Jeong, B. A. Johnson, T. Johnson, H. Jones, A. Khromov, D. Kim, A. Konovalov, E. Kozlova, A. Kumpan, O. Kyzylova, Y. Lee, G. Li, L. Li, J. M. Link, J. Liu, M. Luxnat, A. Major, K. Mann, D. M. Markoff, J. Mattingly, J. Moye, P. E. Mueller, J. Newby, N. Ogoi, J. O'Reilly, D. S. Parno, D. Pérez-Loureiro, D. Pershey, C. G. Prior, J. Queen, R. Rapp, H. Ray, O. Razuvaeva, D. Reyna, G. C. Rich, D. Rudik, J. Runge, D. J. Salvat, J. Sander, K. Scholberg, A. Shakirov, G. Simakov, W. M. Snow, V. Sosnovtsev, M. Stringer, T. Subedi, B. Suh, B. Sur, R. Tayloe, K. Tellez-Giron-Flores, Y. -T. Tsai, E. E. van Nieuwenhuizen, C. J. Virtue, G. Visser, K. Walkup, E. M. Ward, T. Wongjirad, Y. Yang, J. Yoo, C. -H. Yu, A. Zaalishvili

Abstract

We report the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) on natural germanium, measured at the Spallation Neutron Source at Oak Ridge National Laboratory. The Ge-Mini detector of the COHERENT collaboration employs large-mass, low-noise, high-purity germanium spectrometers, enabling excellent energy resolution, and an analysis threshold of 1.5 keV electron-equivalent ionization energy. We observe a on-beam excess of 20.6 +7.1 -6.3 counts with a total exposure of 10.22 GWhkg and we reject the no-CEvNS hypothesis with 3.9 sigma significance. The result agrees with the predicted standard model of particle physics signal rate within 2 sigma.

Evidence of Coherent Elastic Neutrino-Nucleus Scattering with COHERENT's Germanium Array

Abstract

We report the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) on natural germanium, measured at the Spallation Neutron Source at Oak Ridge National Laboratory. The Ge-Mini detector of the COHERENT collaboration employs large-mass, low-noise, high-purity germanium spectrometers, enabling excellent energy resolution, and an analysis threshold of 1.5 keV electron-equivalent ionization energy. We observe a on-beam excess of 20.6 +7.1 -6.3 counts with a total exposure of 10.22 GWhkg and we reject the no-CEvNS hypothesis with 3.9 sigma significance. The result agrees with the predicted standard model of particle physics signal rate within 2 sigma.
Paper Structure (8 sections, 6 figures, 1 table)

This paper contains 8 sections, 6 figures, 1 table.

Table of Contents

  1. Coherent elastic neutrino-nucleus scattering on germanium.-
  2. Experiment.-
  3. Data taking.-
  4. Data analysis.-
  5. Signal expectation.-
  6. Results.-
  7. Summary and outlook.-
  8. Acknowledgements.-

Figures (6)

  • Figure 1: Schematic view of the Ge-Mini detector system: the detectors are enclosed by a radiation shield surrounded on five sides by plastic scintillator panels read out with PMTs used as a muon veto. The inset shows the ICPC design of the Ge crystals. Ge-Mini has a total capacity for 12 ICPC detectors.
  • Figure 2: Example pulse at the analysis threshold of 1.5 keV$_{\textrm{ee}}$ (black) compared to the pulse after applying the symmetric trapezoidal filter (red) to derive the energy value (red horizontal line) and to the pulse after applying the asymmetric trapezoidal filter (green) to extract t$_{50}$, the time of the arrival of the charges at the readout (orange vertical line).
  • Figure 3: The steady-state background spectral shape (40 $\mu$s window) agrees for externally-triggered and rescaled internally-triggered background (used in likelihood fit) within statistics. The red curves indicate the reconstruction efficiencies of energy and timing. The blue histogram illustrates the expected CEvNS signal count rate.
  • Figure 4: Top: on-beam data including the CEvNS related excess; bottom: off-beam data flat within statistical fluctuations.
  • Figure 5: Background-subtracted spectra in time and energy for on-beam and off-beam data. The signal extracted by the likelihood fit is depicted in green; the red and blue lines represent the different neutrino flavors.
  • ...and 1 more figures