Search for neutrinoless double- β decay in Ge76 with 26 kg yr of exposure from the Majorana Demonstrator

• DOI: 10.1103/physrevc.100.025501
• Publication Date: 2019-08-26T08:27:01Z
• Authors: S. I. Alvis; I. J. Arnquist; F. T. Avignone; A. S. Barabash; C. J. Barton; V. Basu; F. E. Bertrand; B. Bos; M. Busch; M. Buuck; T. S. Caldwell; Y-D. Chan; C. D. Christofferson; P.-H. Chu; M. Clark; C. Cuesta; J. A. Detwiler; Yu. Efremenko; H. Ejiri; S. R. Elliott; T. Gilliss; G. K. Giovanetti; M. P. Green; J. Gruszko; I. S. Guinn; V. E. Guiseppe; C. R. Haufe; R. J. Hegedus; L. Hehn; R. Henning; D. Hervas Aguilar; E. W. Hoppe; M. A. Howe; M. F. Kidd; S. I. Konovalov; R. T. Kouzes; A. M. Lopez; R. D. Martin; R. Massarczyk; S. J. Meijer; S. Mertens; J. Myslik; G. Othman; W. Pettus; A. Piliounis; A. W. P. Poon; D. C. Radford; J. Rager; A. L. Reine; K. Rielage; N. W. Ruof; B. Shanks; M. Shirchenko; D. Tedeschi; R. L. Varner; S. Vasilyev; B. R. White; J. F. Wilkerson; C. Wiseman; W. Xu; E. Yakushev; C.-H. Yu; V. Yumatov; I. Zhitnikov; B. X. Zhu
• Keywords: hep-ex; FOS: Physical sciences; Particle and High Energy Physics; Nuclear and Plasma Physics; nucl-ex; 7. Clean energy; 01 natural sciences; Nuclear and plasma physics; High Energy Physics - Experiment; High Energy Physics - Experiment (hep-ex); Physical Sciences; 0103 physical sciences; Nuclear Experiment (nucl-ex); Nuclear Experiment

The Majorana Collaboration is operating an array of high-purity Ge detectors to search for the neutrinoless double-$\ensuremath{\beta}$ decay $^{76}\mathrm{Ge}$. Demonstrator consists 44.1 kg (29.7 enriched 88% in $^{76}\mathrm{Ge}$) split between two modules constructed from ultraclean materials. Both are contained a low-background shield at Sanford Underground Research Facility Lead, South Dakota. We present updated results on $^{76}\mathrm{Ge}$ with $26.0\ifmmode\pm\else\textpm\fi{}0.5$ yr exposure. With Demonstrator's energy resolution 2.53 keV FWHM ${Q}_{\ensuremath{\beta}\ensuremath{\beta}}$, which best among all experiments, we observe one event region interest 0.65 events expected estimated background, resulting lower limit half-life $2.7\ifmmode\times\else\texttimes\fi{}{10}^{25}$ [90% confidence level (CL)] median sensitivity $4.8\ifmmode\times\else\texttimes\fi{}{10}^{25}$ (90% CL). Depending matrix elements used, 90% CL upper effective neutrino mass range 200--433 meV obtained. measured background configurations full shielding and optimized grounding $11.9\ifmmode\pm\else\textpm\fi{}2.0$ counts/(FWHM t yr).