We search for tri-nucleon decays of
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Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to
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Cu,
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Zn, and
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Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of
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Ga to
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Ge (stable). We search for the
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Ga decay exploiting the fact that it dominantly populates the 66.7 keV
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m
Ga state with half-life of 0.5 s. The nnn-decays of
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Ge that proceed via
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m
Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2
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×
10
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yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
Abstract Neutrinoless double- $$\beta $$ β decay of $$^{76}$$ 76 Ge is searched for with germanium detectors where source and detector of the decay are identical. For the success of future ...experiments it is important to increase the mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in $$^{76}$$ 76 Ge. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the Gerda setup. The measured resolutions at the Q-value for double- $$\beta $$ β decay of $$^{76}$$ 76 Ge ( $$Q_{\beta \beta }$$ Q β β = 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array (Gerda) experiment and an accumulated exposure of 8.5 kg $$\cdot $$ · year, the background index after analysis cuts is measured to be $$4.9^{+7.3}_{-3.4}\times 10^{-4} \ \text {counts}/(\text {keV} \cdot \text {kg} \cdot \text {year})$$ 4 . 9 - 3.4 + 7.3 × 10 - 4 counts / ( keV · kg · year ) around $$Q_{\beta \beta }$$ Q β β . This work confirms the feasibility of IC detectors for the next-generation experiment Legend.
We present the first search for bosonic superweakly interacting massive particles (super-WIMPs) as keV-scale dark matter candidates performed with the GERDA experiment. GERDA is a neutrinoless ...doubleβ decay experiment which operates high-purity germanium detectors enriched in 76 Ge in an ultralow background environment at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy. Searches were performed for pseudoscalar and vector particles in the mass region from 60 keV / c 2 to 1 MeV / c 2 . No evidence for a dark matter signal was observed, and the most stringent constraints on the couplings of super-WIMPs with masses above 120 keV / c 2 have been set. As an example, at a mass of 150 keV / c 2 the most stringent direct limits on the dimensionless couplings of axionlike particles and dark photons to electrons of g a e < 3 × 10 − 12 and α ′ / α < 6.5 × 10 − 24 at 90% credible interval, respectively, were obtained.
Neutrinoless double-
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β
decay of
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Ge is searched for with germanium detectors where source and detector of the decay are identical. For the success of future experiments it is important to increase the mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in
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Ge. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the
Gerda
setup. The measured resolutions at the
Q
-value for double-
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decay of
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Ge (
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Q
β
β
= 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array (
Gerda
) experiment and an accumulated exposure of 8.5 kg
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·
year, the background index after analysis cuts is measured to be
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4
.
9
-
3.4
+
7.3
×
10
-
4
counts
/
(
keV
·
kg
·
year
)
around
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Q
β
β
. This work confirms the feasibility of IC detectors for the next-generation experiment
Legend
.
Neutrinoless double-
decay of
Ge is searched for with germanium detectors where source and detector of the decay are identical. For the success of future experiments it is important to increase the ...mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in
Ge. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the Gerda setup. The measured resolutions at the
-value for double-
decay of
Ge (
= 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array (Gerda) experiment and an accumulated exposure of 8.5 kg
year, the background index after analysis cuts is measured to be
around
. This work confirms the feasibility of IC detectors for the next-generation experiment Legend.
In this article we explore the availability of radiopure tungsten and its potential as high density shield material for low background applications. For compact shield designs, conventionally, lead ...is used. Metallic tungsten and tungsten pseudo-alloys reach higher densities up to 19.3 gcm\(^{-3}\) and do not exhibit a significant \(^{210}\)Pb activity, which is a typical intrinsic contamination in lead. Within several \(\gamma\)-ray screening campaigns we were able to identify tungsten samples with activities similar or better than 1 mBqkg\(^{-1}\) in \(^{232}\)Th, \(^{40}\)K, \(^{60}\)Co and the second part of the \(^{238}\)U decay chain. In cooperation with a manufacturer we further reduced a persisting contamination in the first part of the \(^{238}\)U decay chain by a factor of \(\sim\)2.5 down to (305\(\pm\)30) mBqkg\(^{-1}\). With Monte Carlo simulations, the construction of prototype tungsten-based setups and dedicated measurements, the shield capability of tungsten in comparison to lead was extensively studied. Specifically, the impact of cosmogenic radiation on the background at shallow depth was investigated. We showed that a 6-40% reduction (depending on the exact shield configuration) in the muon-induced neutron fluence is achievable by replacing lead with an equivalent amount of tungsten regarding the suppression of external \(\gamma\)-radiation. Overall, many benefits using tungsten especially for low energy applications below a few 100 keV are found. The pseudo-tungsten alloy presented in this work paves the way for several applications especially regarding background suppression in particle and astroparticle physics search programs.
Using an 185-kg NaITl array, COHERENT has measured the inclusive electron-neutrino charged-current cross section on ^{127}I with pion decay-at-rest neutrinos produced by the Spallation Neutron Source ...at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy (≤50 MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of 9.2_{-1.8}^{+2.1}×10^{-40} cm^{2}. This corresponds to a value that is ∼41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on ^{127}I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be 5.2_{-3.1}^{+3.4}×10^{-40} and 2.2_{-0.5}^{+0.4}×10^{-40} cm^{2}, respectively.
The GERmanium Detector Array (
Gerda
) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double-beta decay of
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Ge into
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Se+2e
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-
.
Gerda
has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new
76
Ge enriched detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the
Hades
underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for
Gerda
Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the accuracy of pulse shape simulation codes.
The GERmanium Detector Array (
Gerda
) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double-beta decay of
76
Ge into
76
...Se+2e
-
.
Gerda
has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new
76
Ge enriched detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the
Hades
underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for
Gerda
Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the accuracy of pulse shape simulation codes.
Abstract We search for tri-nucleon decays of $$^{76}$$ 76 Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the ...threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to $$^{73}$$ 73 Cu, $$^{73}$$ 73 Zn, and $$^{73}$$ 73 Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of $$^{73}$$ 73 Ga to $$^{73}$$ 73 Ge (stable). We search for the $$^{73}$$ 73 Ga decay exploiting the fact that it dominantly populates the 66.7 keV $$^{73m}$$ 73 m Ga state with half-life of 0.5 s. The nnn-decays of $$^{76}$$ 76 Ge that proceed via $$^{73m}$$ 73 m Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2 $$\times $$ × 10 $$^{26}$$ 26 yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
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