Abstract
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).
| Original language | English |
|---|---|
| Article number | 025501 |
| Journal | Physical Review C |
| Volume | 100 |
| Issue number | 2 |
| DOIs | |
| State | Published - Aug 23 2019 |
Funding
The authors appreciate the technical assistance of J. F. Amsbaugh, J. Bell, B. A. Bos, T. H. Burritt, G. Capps, K. Carney, R. Daniels, L. DeBraeckeleer, C. Dunagan, G. C. Harper, C. Havener, G. Holman, R. Hughes, K. Jeskie, K. Lagergren, D. Lee, M. Middlebook, A. Montoya, A. W. Myers, D. Peterson, D. Reid, L. Rodriguez, H. Salazar, A. R. Smith, G. Swift, M. Turqueti, J. Thompson, P. Thompson, C. Tysor, T. D. Van Wechel, R. Witharm, and H. Yaver. This material is based upon work supported by the US Department of Energy, Office of Science, Office of Nuclear Physics under Awards No. DE-AC02-05CH11231, No. DE-AC05-00OR22725, No. DE-AC05-76RL0130, No. DE-AC52-06NA25396, No. DE-FG02-97ER41020, No. DE-FG02-97ER41033, No. DE-FG02-97ER41041, No. DE-SC0010254, No. DE-SC0012612, No. DE-SC0014445, and No. DE-SC0018060. We acknowledge support from the Particle Astrophysics Program and Nuclear Physics Program of the National Science Foundation through Grants No. MRI-0923142, No. PHY-1003399, No. PHY-1102292, No. PHY-1206314, No. PHY-1614611, No. PHY-1812409, and No. PHY-1812356. We gratefully acknowledge the support of the U.S. Department of Energy through the LANL/LDRD Program and through the PNNL/LDRD Program for this work. We acknowledge support from the Russian Foundation for Basic Research, Grant No. 15-02-02919. We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, Funding Reference No. SAPIN-2017-00023, and from the Canada Foundation for Innovation John R. Evans Leaders Fund. This research used resources provided by the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory and by the National Energy Research Scientific Computing Center, a US Department of Energy Office of Science User Facility. We thank our hosts and colleagues at the Sanford Underground Research Facility for their support.
| Funders | Funder number |
|---|---|
| Canada Foundation for Innovation John R. Evans Leaders Fund | |
| LANL/LDRD | |
| National Energy Research Scientific Computing Center | |
| Office of Nuclear Physics | DE-SC0014445 |
| PNNL/LDRD | |
| US Department of Energy | |
| US Department of Energy Office of Science | |
| National Science Foundation | PHY-1812409, 0923142, 1102292, 1812356, 1003399, 1206314, 1812409 |
| U.S. Department of Energy | |
| Office of Science | |
| Oak Ridge National Laboratory | |
| Natural Sciences and Engineering Research Council of Canada | SAPIN-2017-00023 |
| Russian Foundation for Basic Research | 15-02-02919 |