The MAJORANA DEMONSTRATOR is an ultra-low-background experiment searching for neutrinoless double-beta decay in Ge76. 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 trinucleon decay-specific modes and invisible decay modes for Ge isotopes. We find a half-life limit of 4.9×1025 yr for the decay Ge76(ppn)→Zn73 e+π+ and 4.7×1025 yr for the decay Ge76(ppp)→Cu73 e+π+π+. The half-life limit for the invisible triproton decay mode of Ge76 was found to be 7.5×1024 yr.
The MAJORANA DEMONSTRATOR is searching for neutrinoless double-beta decay($0\nu\beta\beta$) in 76Ge using arrays of point-contact germanium detectors operating at the Sanford Underground Research ...Facility. Background results in the $0\nu\beta\beta$ 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 ± 3.5)% of single-site events. This pulse shape discrimination is based on the relationship between the maximum current and energy, and tuned using 228Th calibration source data. In conclusion, the efficiency uncertainty accounts for variation across detectors, energy, and time, as well as for the position distribution difference between calibration and $0\nu\beta\beta$ events, established using simulations.
Abstract
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, along with the grounding scheme. The
spectroscopic performance achieved with these readout electronics is
also demonstrated.
P-type point contact (PPC) high-purity germanium detectors are an important technology in astroparticle and nuclear physics due to their superb energy resolution, low noise, and pulse shape ...discrimination capabilities. Analysis of data from the Majorana Demonstrator, a neutrinoless double-β decay experiment deploying PPC detectors enriched in 76Ge, has led to several novel improvements in the analysis of PPC signals. In this work we discuss charge trapping in PPC detectors and its effect on energy resolution. Small dislocations or impurities in the crystal lattice result in trapping of charge carriers from an ionization event of interest, attenuating the signal, and degrading the measured energy. We present a modified digital pole-zero correction to the signal energy estimation that counters the effects of charge trapping and improves the energy resolution of the Majorana Demonstrator by approximately 30 % to around 2.4 keV full width at half-maximum at 2039 keV, the 76Ge Q value. An alternative approach achieving similar resolution enhancement is also presented.
$^{180m}$$\mathrm{Ta}$ is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known $β$ and electron capture decays due to ...the large K-spin differences and small energy differences between the isomeric and lower-energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter, and K-spin violation. For this study, we repurposed the Majorana Demonstrator, an experimental search for the neutrinoless double-beta decay of $^{76}$$\mathrm{Ge}$ using an array of high-purity germanium detectors, to search for the decay of $^{180m}$$\mathrm{Ta}$. Here, more than 17 kg, the largest amount of tantalum metal ever used for such a search, was installed within the ultralow-background detector array. In this Letter, we present results from the first year of Ta data taking and provide an updated limit for the $^{180m}$$\mathrm{Ta}$ half-life on the different decay channels. In conclusion, with new limits up to $\mathrm{1.5 × 10^{19} yr}$, we improved existing limits by 1–2 orders of magnitude which are the most sensitive searches for a single $β$ and electron capture decay ever achieved. Over all channels, the decay can be excluded for $T_\frac{1}{2} < 0.29 × 10^{18}$$\mathrm{yr}$.
Constraints on the Decay of Ta 180 m Arnquist, I. J.; Avignone, F. T.; Barabash, A. S. ...
Physical review letters,
10/2023, Letnik:
131, Številka:
15
Journal Article
PDF
