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Search for neutrinoless double- β decay in Ge 76 with 26 kg yr of exposure from the M ajorana D emonstrator SEARCH for NEUTRINOLESS DOUBLE- β DECAY ... S. I. ALVIS et al.

  • Author(s): Cuesta, C
  • Alvis, SI
  • Arnquist, IJ
  • Avignone, FT
  • Barabash, AS
  • Barton, CJ
  • Basu, V
  • Bertrand, FE
  • Bos, B
  • Busch, M
  • Buuck, M
  • Caldwell, TS
  • Chan, YD
  • Christofferson, CD
  • Chu, PH
  • Clark, M
  • Cuesta, C
  • Detwiler, JA
  • Efremenko, Y
  • Ejiri, H
  • Elliott, SR
  • Gilliss, T
  • Giovanetti, GK
  • Green, MP
  • Gruszko, J
  • Guinn, IS
  • Guiseppe, VE
  • Haufe, CR
  • Hegedus, RJ
  • Hehn, L
  • Henning, R
  • Hervas Aguilar, D
  • Hoppe, EW
  • Howe, MA
  • Kidd, MF
  • Konovalov, SI
  • Kouzes, RT
  • Lopez, AM
  • Martin, RD
  • Massarczyk, R
  • Meijer, SJ
  • Mertens, S
  • Myslik, J
  • Othman, G
  • Pettus, W
  • Piliounis, A
  • Poon, AWP
  • Radford, DC
  • Rager, J
  • Reine, AL
  • Rielage, K
  • Ruof, NW
  • Shanks, B
  • Shirchenko, M
  • Tedeschi, D
  • Varner, RL
  • Vasilyev, S
  • White, BR
  • Wilkerson, JF
  • Wiseman, C
  • Xu, W
  • Yakushev, E
  • Yu, CH
  • Yumatov, V
  • Zhitnikov, I
  • Zhu, BX
  • et al.

© 2019 American Physical Society. The Majorana Collaboration is operating an array of high-purity Ge detectors to search for the neutrinoless double-β decay of Ge76. The Majorana Demonstrator consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in Ge76) split between two modules constructed from ultraclean materials. Both modules are contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota. We present updated results on the search for neutrinoless double-β decay in Ge76 with 26.0±0.5 kg yr of enriched exposure. With the Demonstrator's energy resolution of 2.53 keV FWHM at Qββ, which is the best among all neutrinoless double-β decay experiments, we observe one event in the region of interest with 0.65 events expected from the estimated background, resulting in a lower limit on the Ge76 neutrinoless double-β decay half-life of 2.7×1025 yr [90% confidence level (CL)] with a median sensitivity of 4.8×1025 yr (90% CL). Depending on the matrix elements used, a 90% CL upper limit on the effective Majorana neutrino mass in the range of 200-433 meV is obtained. The measured background in the configurations with full shielding and optimized grounding is 11.9±2.0 counts/(FWHM t yr).

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