The Majorana Demonstrator's Search for Double-Beta Decay of $^{76}$Ge to Excited States of $^{76}$Se
I. J. Arnquist, F. T. Avignone, A. S. Barabash, C. J. Barton, F. E. Bertrand, E. Blalock, B. Bos, M. Busch, M. Buuck, T. S. Caldwell, Y-D. Chan, C. D. Christoff… 展开作者
I. J. Arnquist, F. T. Avignone, A. S. Barabash, C. J. Barton, F. E. Bertrand, E. Blalock, B. Bos, M. Busch, M. Buuck, T. S. Caldwell, Y-D. Chan, C. D. Christofferson, P. -H. Chu, M. L. Clark, C. Cuesta, J. A. Detwiler, A. Drobizhev, T. R. Edwards, D. W. Edwins, 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. Henning, D. Hervas Aguilar, E. W. Hoppe, A. Hostiuc, M. F. Kidd, I. Kim, R. T. Kouzes, A. M. Lopez, J. M. López-Castaño, E. L. Martin, R. D. Martin, R. Massarczyk, S. J. Meijer, S. Mertens, J. Myslik, T. K. Oli, G. Othman, L. S. Paudel, W. Pettus, A. W. P. Poon, D. C. Radford, A. L. Reine, K. Rielage, N. W. Ruof, B. Saykı, M. J. Stortini, D. Tedeschi, R. L. Varner, S. Vasilyev, J. F. Wilkerson, C. Wiseman, W. Xu, C. -H. Yu, B. X. Zhu
The Majorana Demonstrator is a neutrinoless double-beta decay search consisting of a low-background modular array of high-purity germanium detectors, $\sim2/3$ of which are enriched to 88\% in $^{76}$Ge. The experiment is also searching for double-beta decay of $^{76}$Ge to excited states (e.s.) in $^{76}$Se. $^{76}$Ge can decay into three daughter states of $^{76}$Se, with clear event signatures consisting of a $ββ$-decay followed by the prompt emission of one or two $γ$-rays. This results with high probability in multi-detector coincidences. The granularity of the Demonstrator detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9~kg-y of isotopic exposure, the Demonstrator has set world leading limits for each e.s.\ decay of $^{76}$Ge, with 90\% CL lower half-life limits in the range of $(0.75-4.0)\times10^{24}$~y. In particular, for the $2ν$ transition to the first $0^+$ e.s.\ of $^{76}$Se, a lower half-life limit of $7.5\times10^{23}$~y at 90\% CL was achieved.
The MAJORANA collaboration is pursuing the development of the so-called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne-scale germanium-based experiment to search for the neutrinoless double-beta decay of Ge-76. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1-10 GeV/c^2 mass range. It will consist of approximately 60-kg of germanium detectors in an ultra-low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform bac…
The MAJORANA collaboration is actively pursuing research and development aimed at a tonne-scale 76Ge neutrinoless double-beta decay) experiment. The current, primary focus is the construction of the MAJORANA DEMONSTRATOR experiment, an R&D effort that will field approximately 40kg of germanium detectors with mixed enrichment levels. This article provides a status update on the construction of the DEMONSTRATOR.
The Majorana Demonstrator is currently searching for neutrinoless double-beta decay in $^{76}$Ge and will demonstrate the feasibility to deploy a tonne-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and $^{76}$Ge-enriched germanium detectors totaling 44.1 kg, of which 29.7 kg is enriched, located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. The low-backgrounds and low trigger thresholds ($<$1 keV) achieved by the Demonstrator allow for additional rare-event searches at low-energies, e.g. searches for…
The MAJORANA DEMONSTRATOR is searching for double-beta decay of $^{76}$Ge to excited states (E.S.) in $^{76}$Se using a modular array of high purity Germanium detectors. $^{76}$Ge can decay into three E.S.s of $^{76}$Se. The E.S. decays have a clear event signature consisting of a $ββ$-decay with the prompt emission of one or two $γ$-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leadin…
The observation of neutrinoless double-beta decay would determine whether the neutrino is a Majorana particle and provide information on the absolute scale of neutrino mass. The MAJORANA Collaboration is constructing the DEMONSTRATOR, an array of germanium detectors, to search for neutrinoless double-beta decay of 76-Ge. The DEMONSTRATOR will contain 40 kg of germanium; up to 30 kg will be enriched to 86% in 76-Ge. The DEMONSTRATOR will be deployed deep underground in an ultra-low-background shielded environment. Operation of the DEMONSTRATOR aims to determine whether a future tonne-scale germ…
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44.8-kg (29.7 kg enriched >88% in Ge-76) to search for neutrinoless double beta decay in Ge-76. The next generation of tonnescale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONS…
The MAJORANA Collaboration is constructing the MAJORANA DEMONSTRATOR, an ultra-low background, modular, HPGe detector array with a mass of 44-kg (29 kg 76Ge and 15 kg natGe) to search for neutrinoless double beta decay in Ge-76. The next generation of tonne-scale Ge-based neutrinoless double beta decay searches will probe the neutrino mass scale in the inverted-hierarchy region. The MAJORANA DEMONSTRATOR is envisioned to demonstrate a path forward to achieve a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value of 2039 keV. The MAJORANA DEMONSTRATO…
A brief review of the history and neutrino physics of double beta decay is given. A description of the MAJORANA DEMONSTRATOR research and development program including background reduction techniques is presented in some detail. The application of point contact (PC) detectors to the experiment is discussed, including the effectiveness of pulse shape analysis. The predicted sensitivity of a PC detector array enriched to 86% in 76Ge is given.
The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay in $^{76}$Ge with two modular arrays of natural and $^{76}$Ge-enriched germanium detectors. It is located at the 4850 level of Sanford Underground Research Facility in Lead, South Dakota, USA, and its total mass of germanium detectors is 44.1 kg, of which 29.7 kg is enriched. The analysis of the first 26 kg-yr of data provides an unprecedented energy resolution of 0.13% in the region of interest at 2039 keV and a background level of 15.4 $\pm$ 2.0 counts/(FWHM t yr). It establishes the lower limit of the half-life of neu…
The MAJORANA Collaboration is constructing the MAJORANA Demonstrator, an ultra-low background, 40-kg modular high purity Ge detector array to search for neutrinoless double-beta decay in Ge. In view of the next generation of tonne-scale Ge-based neutrinoless double-beta decay searches that will probe the neutrino mass scale in the inverted-hierarchy region, a major goal of the Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 count/tonne/year in the 4 keV region of interest around the Q-value at 2039 keV. The current status of the Demonstrator is discus…
The Majorana Collaboration is using an array of high-purity Ge detectors to search for neutrinoless double-beta decay in 76Ge. Searches for neutrinoless double-beta decay are understood to be the only viable experimental method for testing the Majorana nature of the neutrino. Observation of this decay would imply violation of lepton number, that neutrinos are Majorana in nature, and provide information on the neutrino mass. The Majorana Demonstrator comprises 44.1 kg of p-type point-contact Ge detectors (29.7 kg enriched in 76Ge) surrounded by a low-background shield system. The experiment ach…
The MAJORANA Collaboration is constructing the MAJORANA Demonstrator, an ultra-low background, 44-kg modular high-purity Ge (HPGe) detector array to search for neutrinoless double-beta decay in Ge-76. The phenomenon of surface micro-discharge induced by high-voltage has been studied in the context of the MAJORANA Demonstrator. This effect can damage the front-end electronics or mimic detector signals. To ensure the correct performance, every high-voltage cable and feedthrough must be capable of supplying HPGe detector operating voltages as high as 5 kV without exhibiting discharge. R&D measure…
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The MAJORANA Collaboration assembled an array of high purity Ge detectors to search for neutrinoless double-beta decay in Ge-76. The MAJORANA DEMONSTRATOR is comprised of 44.1 kg (29.7 kg enriched in Ge-76) of Ge detectors divided between two modules contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota, USA. The initial goals of the DEMONSTRATOR are to establish…
The MAJORANA DEMONSTRATOR will search for the neutrinoless double-beta decay of the 76Ge isotope with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own anti-particle, demonstrate that lepton number is not conserved, and provide information on the absolute mass-scale of the neutrino. The DEMONSTRATOR is being assembled at the 4850 foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be contained in a low-background environment and surrounded by passive and active shielding…
The MAJORANA DEMONSTRATOR is a neutrinoless double-beta decay ($0νββ$) experiment containing $\sim$30 kg of p-type point contact germanium detectors enriched to 88% in 76Ge and $\sim$14 kg of natural germanium detectors. The detectors are housed in two electroformed copper cryostats and surrounded by a graded passive shield with active muon veto. An extensive radioassay campaign was performed prior to installation to insure the use of ultra-clean materials. The DEMONSTRATOR achieved one of the lowest background rates in the region of the $0νββ$ Q-value, 15.7 $\pm$ 1.4 cts/(FWHM t y) from the l…
The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decay in $^{76}$Ge and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modules of natural and $^{76}$Ge-enriched germanium detectors totalling 44.1 kg, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Commissioning of the experiment began in June 2015, followed by data production with the full detector array in August 2016. The ultra-low background and record energy resolution ach…
The MAJORANA Collaboration has assembled an array of high purity Ge detectors to search for neutrinoless double-beta decay in $^{76}$Ge with the goal of establishing the required background and scalability of a Ge-based next-generation ton-scale experiment. The MAJORANA DEMONSTRATOR consists of 44 kg of high-purity Ge (HPGe) detectors (30 kg enriched in $^{76}$Ge) with a low-noise p-type point contact (PPC) geometry. The detectors are split between two modules which are contained in a single lead and high-purity copper shield at the Sanford Underground Research Facility in Lead, South Dakota. …
The MAJORANA DEMONSTRATOR is a planned 40 kg array of Germanium detectors intended to demonstrate the feasibility of constructing a tonne-scale experiment that will seek neutrinoless double beta decay ($0νββ$) in $^{76}\mathrm{Ge}$. Such an experiment would require backgrounds of less than 1 count/tonne-year in the 4 keV region of interest around the 2039 keV Q-value of the $ββ$ decay. Designing low-noise electronics, which must be placed in close proximity to the detectors, presents a challenge to reaching this background target. This paper will discuss the MAJORANA collaboration's solutions …
The MAJORANA Collaboration will seek neutrinoless double beta decay (0nbb) in 76Ge using isotopically enriched p-type point contact (PPC) high purity Germanium (HPGe) detectors. A tonne-scale array of HPGe detectors would require background levels below 1 count/ROI-tonne-year in the 4 keV region of interest (ROI) around the 2039 keV Q-value of the decay. In order to demonstrate the feasibility of such an experiment, the MAJORANA DEMONSTRATOR, a 40 kg HPGe detector array, is being constructed with a background goal of <3 counts/ROI-tonne-year, which is expected to scale down to <1 count/ROI-ton…
Neutrinoless double-beta decay is a hypothesized process where in some even-even nuclei it might be possible for two neutrons to simultaneously decay into two protons and two electrons without emitting neutrinos. This is possible only if neutrinos are Majorana particles, i.e. fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and might play a role in the matter-antimatter asymmetry in the universe. The observation of neutrinoless double-beta decay would also provide complementary information related to neutrino mas…
Neutrinoless double-beta decay searches seek to determine the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The {\sc Majorana} Collaboration is assembling an array of high purity Ge detectors to search for neutrinoless double-beta decay in $^{76}$Ge. The {\sc Majorana Demonstrator} is composed of 44.8~kg (29.7 kg enriched in $^{76}$Ge) of Ge detectors in total, split between two modules contained in a low background shield at the Sanford Underground Research Facility in Lead, South Dakota. The initial goals of the {\sc Demonstrator}…
The MAJORANA DEMONSTRATOR is sensitive to rare events near its energy threshold, including bosonic dark matter, solar axions, and lightly ionizing particles. In this analysis, a novel training set of low energy small-angle Compton scatter events is used to determine the efficiency of pulse shape analysis cuts, and we present updated bosonic dark matter and solar axion results from an 11.17 kg-y dataset using a 5 keV analysis threshold.
The MAJORANA DEMONSTRATOR neutrinoless double beta-decay experiment is currently under construction at the Sanford Underground Research Facility in South Dakota, USA. An overview and status of the experiment are given.
The MAJORANA Collaboration is constructing a system containing 44 kg of high-purity Ge (HPGe) detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale to ~15 meV. To realize this, a major goal of the MAJORANA DEMONSTRATOR is to demonstrate a path forward to achieving a background rate at or below 1 count/(ROI-t-y) in the 4 keV region of interest (ROI) around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials and analytical m…
The {\sc Majorana Demonstrator will search for the neutrinoless double-beta decay of the isotope Ge-76 with a mixed array of enriched and natural germanium detectors. The observation of this rare decay would indicate the neutrino is its own antiparticle, demonstrate that lepton number is not conserved, and provide information on the absolute mass scale of the neutrino. The {\sc Demonstrator} is being assembled at the 4850-foot level of the Sanford Underground Research Facility in Lead, South Dakota. The array will be situated in a low-background environment and surrounded by passive and active…
Neutrinoless double beta decay searches play a major role in determining neutrino properties, in particular the Majorana or Dirac nature of the neutrino and the absolute scale of the neutrino mass. The consequences of these searches go beyond neutrino physics, with implications for Grand Unification and leptogenesis. The \textsc{Majorana} Collaboration is assembling a low-background array of high purity Germanium (HPGe) detectors to search for neutrinoless double-beta decay in $^{76}$Ge. The \textsc{Majorana Demonstrator}, which is currently being constructed and commissioned at the Sanford Un…
The MAJORANA Collaboration is operating an array of high purity Ge detectors to search for the neutrinoless double-beta decay of $^{76}$Ge. The MAJORANA DEMONSTRATOR consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in $^{76}$Ge) split between two modules constructed from ultra-clean 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-beta decay in $^{76}$Ge with $26.0\pm0.5$ kg-yr of enriched exposure. With the DEMONSTRATOR's unprecedente…
The MAJORANA DEMONSTRATOR comprises two arrays of high-purity germanium detectors constructed to search for neutrinoless double-beta decay in 76-Ge and other physics beyond the Standard Model. Its readout electronics were designed to have low electronic noise, and radioactive backgrounds were minimized by using low-mass components and low-radioactivity materials near the detectors. This paper provides a description of all components of the MAJORANA DEMONSTRATOR readout electronics, spanning the front-end electronics and internal cabling, back-end electronics, digitizer, and power supplies, alo…
Axions were originally proposed to explain the strong-CP problem in QCD. Through the axion-photon coupling, the Sun could be a major source of axions, which could be measured in solid state detection experiments with enhancements due to coherent Primakoff-Bragg scattering. The Majorana Demonstrator experiment has searched for solar axions with a set of $^{76}$Ge-enriched high purity germanium detectors using a 33 kg-yr exposure collected between Jan. 2017 and Nov. 2019. A temporal-energy analysis gives a new limit on the axion-photon coupling as $g_{aγ}<1.45\times 10^{-9}$ GeV$^{-1}$ (95% C.I.…
An assay-based background projection for the MAJORANA DEMONSTRATOR using Monte Carlo Uncertainty Propagation
Pacific Northwest National Laboratory（太平洋西北国家实验室）；University of South Carolina（南卡罗来纳大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；National Research Center “Kurchatov Institute”（库尔恰托夫研究所国家研究中心）；University of South Dakota（南达科他大学）；University of North Carolina（北卡罗来纳大学）；Triangle Universities Nuclear Laboratory（三角大学核实验室）；North Carolina State University（北卡罗来纳州立大学）；Duke University（杜克大学）；Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）
Neutrinoless double-beta decay searches play a major role in determining the nature of neutrinos, the existence of a lepton violating process, and the effective Majorana neutrino mass. The Majorana Collaboration proposes to assemble an array of HPGe detectors to search for neutrinoless double-beta decay in Ge-76. Our proposed method uses the well-established technique of searching for neutrinoless double-beta decay in high purity Ge-diode radiation detectors that play both roles of source and detector. The technique is augmented with recent improvements in signal processing and detector design…
We report the first measurement of the total MUON flux underground at the Davis Campus of the Sanford Underground Research Facility at the 4850 ft level. Measurements were done with the Majorana Demonstrator veto system arranged in two different configurations. The measured total flux is (5.31+/-0.17) x 10^-9 muons/s/cm^2.
The MAJORANA DEMONSTRATOR is a neutrinoless double beta decay experiment utilizing enriched Ge-76 detectors in 2 separate modules inside of a common solid shield at the Sanford Underground Research Facility. The DEMONSTRATOR has utilized world leading assay sensitivities to develop clean materials and processes for producing ultra-pure copper and plastic components. This experiment is now operating, and initial data provide new insights into the success of cleaning and processing. Post production copper assays after the completion of Module 1 showed an increase in U and Th contamination in fin…
Imperfections in analog-to-digital conversion (ADC) cannot be ignored when signal digitization requirements demand both wide dynamic range and high resolution, as is the case for the Majorana Demonstrator 76Ge neutrinoless double beta decay search. Enabling the experiment's high-resolution spectral analysis and efficient pulse shape discrimination required careful measurement and correction of ADC nonlinearites. A simple measurement protocol was developed that did not require sophisticated equipment or lengthy data taking campaigns. A slope-dependent hysteresis was observed and characterized. …
The MAJORANA DEMONSTRATOR searched for neutrinoless double-$β$ decay ($0νββ$) of $^{76}$Ge using modular arrays of high-purity Ge detectors operated in vacuum cryostats in a low-background shield. The arrays operated with up to 40.4 kg of detectors (27.2 kg enriched to $\sim$88\% in $^{76}$Ge). From these measurements, the DEMONSTRATOR has accumulated 64.5 kg yr of enriched active exposure. With a world-leading energy resolution of 2.52 keV FWHM at the 2039 keV $Q_{ββ}$ (0.12\%), we set a half-life limit of $0νββ$ in $^{76}$Ge at $T_{1/2}>8.3\times10^{25}$ yr (90\% C.L.). This provides a range…
The MAJORANA Collaboration is searching for the neutrinoless double-beta decay of the nucleus $^{76}$Ge. The MAJORANA DEMONSTRATOR is an array of germanium detectors deployed with the aim of implementing background reduction techniques suitable for a 1-tonne $^{76}$Ge-based search. The ultra low-background conditions require regular calibrations to verify proper function of the detectors. Radioactive line sources can be deployed around the cryostats containing the detectors for regular energy calibrations. When measuring in low-background mode, these line sources have to be stored outside the …
Experiments searching for very rare processes such as neutrinoless double-beta decay require a detailed understanding of all sources of background. Signals from radioactive impurities present in construction and detector materials can be suppressed using a number of well-understood techniques. Background from in-situ cosmogenic interactions can be reduced by siting an experiment deep underground. However, the next generation of such experiments have unprecedented sensitivity goals of 10$^{28}$ years half-life with background rates of 10$^{-5}$cts/(keV kg yr) in the region of interest. To achie…
Neutrinoless double-$β$ decay ($0νββ$ decay) is a hypothetical process that can occur if the neutrino is its own antiparticle. The COBRA collaboration operates a demonstrator to search for these decays at the Laboratori Nazionali del Gran Sasso in Italy using CdZnTe semiconductor detectors. The exposure of $234.7\,$kg\,d considered in this analysis was collected between September 2011 and February 2015. The analysis focuses on the decay of the nuclides $^{114}$Cd, $^{128}$Te, $^{70}$Zn, $^{130}$Te and $^{116}$Cd. A Bayesian analysis is performed to estimate the signal strength of $0νββ$ decay.…
The objective of the Majorana Experiment is to study neutrinoless double beta decay (0nbb) with an effective Majorana-neutrino mass sensitivity below 50 meV in order to characterize the Majorana nature of the neutrino, the Majorana mass spectrum, and the absolute mass scale. An experimental study of the neutrino mass scale implied by neutrino oscillation results is now technically within our grasp. This exciting physics goal is best pursued using the well-established technique of searching for 0nbb of 76Ge, augmented with recent advances in signal processing and detector design. The Majorana E…
Neutron captures and delayed decays of reaction products are common sources of backgrounds in ultra-rare event searches. In this work, we studied $^{13}$C($α,n)^{16}$O reactions induced by $α$-particles emitted within the calibration sources of the \textsc{Majorana Demonstrator}. These sources are thorium-based calibration standards enclosed in carbon-rich materials. The reaction rate was estimated by using the 6129-keV $γ$-rays emitted from the excited $^{16}$O states that are populated when the incoming $α$-particles exceed the reaction Q-value. Thanks to the excellent energy performance of …
The {\sc Majorana} collaboration is searching for neutrinoless double beta decay using $^{76}$Ge, which has been shown to have a number of advantages in terms of sensitivities and backgrounds. The observation of neutrinoless double-beta decay would show that lepton number is violated and that neutrinos are Majorana particles and would simultaneously provide information on neutrino mass. Attaining sensitivities for neutrino masses in the inverted hierarchy region, $15 - 50$ meV, will require large, tonne-scale detectors with extremely low backgrounds, at the level of $\sim$1 count/t-y or lower …
We present new limits on exotic keV-scale physics based on 478 kg d of MAJORANA DEMONSTRATOR commissioning data. Constraints at the 90% confidence level are derived on bosonic dark matter (DM) and solar axion couplings, Pauli exclusion principle violating (PEPV) decay, and electron decay using monoenergetic peak signal-limits above our background. Our most stringent DM constraints are set for 11.8 keV mass particles, limiting $g_{Ae} <4.5\times 10^{-13}$ for pseudoscalars and $\frac{α'}α < 9.7\times 10^{-28}$ for vectors. We also report a 14.4 keV solar axion coupling limit of $g_{AN}^{\mathrm…
At present, MAJORANA is a research and development (R&D) project to investigate the feasibility and cost of constructing and operating a one ton decay experiment with ~1000 kg of Ge detectors fabricated from germanium enriched to 86% in . The study will include three separate cryostats with various types of detectors: un-segmented, un-segmented point-contact, minimally segmented, and highly segmented. One cryostat will contain at least 30 kg of enriched (preferably point-contact) detectors. The performance of the cryostats and detectors as well as background levels will be investigated. The go…
The Majorana Collaboration is constructing a system containing 40 kg of HPGe detectors to demonstrate the feasibility and potential of a future tonne-scale experiment capable of probing the neutrino mass scale in the inverted-hierarchy region. To realize this, a major goal of the Majorana Demonstrator is to demonstrate a path forward to achieving a background rate at or below 1 cnt/(ROI-t-y) in the 4 keV region of interest around the Q-value at 2039 keV. This goal is pursued through a combination of a significant reduction of radioactive impurities in construction materials with analytical met…
The Majorana Demonstrator is an ultra low-background experiment searching for neutrinoless double-beta decay in $^{76}$Ge. The heavily shielded array of germanium detectors, placed nearly a mile underground at the Sanford Underground Research Facility in Lead, South Dakota, also allows searches for new exotic physics. We present the first limits for tri-nucleon decay-specific modes and invisible decay modes for Ge isotopes. We find a half-life limit of $4.9 \times 10^{25}$ yr for the decay $^{76}{\rm Ge(ppn)} \to {}^{73}{\rm Zn}\ e^+π^+$ and $4.7\times10^{25}$ yr for the decay $^{76}{\rm Ge(pp…
The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay in 76Ge using arrays of point-contact germanium detectors operating at the Sanford Underground Research Facility. Background results in the neutrinoless double-beta decay region of interest from data taken during construction, commissioning, and the start of full operations have been recently published. A pulse shape analysis cut applied to achieve this result, named AvsE, is described in this paper. This cut is developed to remove events whose waveforms are typical of multi-site energy deposits while retaining (90 +/- 3…
The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decays in germanium-76 and to demonstrate the feasibility to deploy a ton-scale experiment in a phased and modular fashion. It consists of two modular arrays of natural and $^{76}\textrm{Ge}$-enriched germanium detectors totaling 44.1 kg (29.7 kg enriched detectors), located at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Data taken with this setup since summer 2015 at different construction stages of the experiment show a clear reduction of the observed bac…
High purity germanium (HPGe) crystals will be used for the MAJORANA DEMONSTRATOR, where they serve as both the source and the detector for neutrinoless double beta decay. It is crucial for the experiment to understand the performance of the HPGe crystals. A variety of crystal properties are being investigated, including basic properties such as energy resolution, efficiency, uniformity, capacitance, leakage current and crystal axis orientation, as well as more sophisticated properties, e.g. pulse shapes and dead layer and transition layer distributions. In this paper, we will present our measu…
Interpretable Boosted Decision Tree Analysis for the Majorana Demonstrator
Pacific Northwest National Laboratory（太平洋西北国家实验室）；University of South Carolina（南卡罗来纳大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；National Research Center “Kurchatov Institute”（库尔恰托夫研究所）；Institute for Theoretical and Experimental Physics（理论与实验物理研究所）；University of South Dakota（南达科他大学）；University of North Carolina（北卡罗来纳大学）；Triangle Universities Nuclear Laboratory（三角大学核实验室）；North Carolina State University（北卡罗来纳州立大学）；Duke University（杜克大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；University of Washington（华盛顿大学）
Neutrinoless double-beta decay($0νββ$) decay is a hypothetical process that violates lepton number, and whose observation would unambiguously indicate that neutrinos are Majorana fermions. In the standard inverted-ordering neutrino mass scenario, the minimum possible value of m$_{ββ}$ corresponds to a half-life around 10$^{28}$ yr for $0νββ$ decay in $^{76}$Ge, which is the target of the next generation of experiments. The current limits of GERDA and \textsc{Majorana Demonstrator} indicate a half-life higher than 10$^{26}$ yr. These experiments use high-purity germanium (HPGe) detectors that a…
The MAJORANA collaboration is constructing the MAJORANA DEMONSTATOR at the Sanford Underground Research Facility at the Homestake gold mine, in Lead, SD. The apparatus will use Ge detectors, enriched in isotope \nuc{76}{Ge}, to demonstrate the feasibility of a large-scale Ge detector experiment to search for neutrinoless double beta decay. The long half-life of this postulated process requires that the apparatus be extremely low in radioactive isotopes whose decays may produce backgrounds to the search. The radioassay program conducted by the collaboration to ensure that the materials comprisi…
Building a \BBz experiment with the ability to probe neutrino mass in the inverted hierarchy region requires the combination of a large detector mass sensitive to \BBz, on the order of 1-tonne, and unprecedented background levels, on the order of or less than 1 count per year in the \BBz signal region. The MAJORANA Collaboration proposes a design based on using high-purity enriched Ge-76 crystals deployed in ultra-low background electroformed Cu cryostats and using modern analysis techniques that should be capable of reaching the required sensitivity while also being scalable to a 1-tonne size…
Majorana Demonstrator Data Release for AI/ML Applications
Pacific Northwest National Laboratory（太平洋西北国家实验室）；University of South Carolina（南卡罗来纳大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；National Research Center “Kurchatov Institute”（国家研究中心“库尔恰托夫研究所”）；University of South Dakota（南达科他大学）；University of North Carolina（北卡罗来纳大学）；Triangle Universities Nuclear Laboratory（三角大学核实验室）；North Carolina State University（北卡罗来纳州立大学）；Duke University（杜克大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；University of Washington（华盛顿大学）
