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
.
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.
Abstract The GERmanium Detector Array ( Gerda ) experiment operated enriched high-purity germanium detectors in a liquid argon cryostat, which contains 0.33% of $$^{36}$$ 36 Ar, a candidate isotope ...for the two-neutrino double-electron capture (2 $$\nu $$ ν ECEC) and therefore for the neutrinoless double-electron capture (0 $$\nu $$ ν ECEC). If detected, this process would give evidence of lepton number violation and the Majorana nature of neutrinos. In the radiative 0 $$\nu $$ ν ECEC of $$^{36}$$ 36 Ar, a monochromatic photon is emitted with an energy of 429.88 keV, which may be detected by the Gerda germanium detectors. We searched for the $$^{36}$$ 36 Ar 0 $$\nu $$ ν ECEC with Gerda data, with a total live time of 4.34 year (3.08 year accumulated during Gerda Phase II and 1.26 year during Gerda Phase I). No signal was found and a 90% CL lower limit on the half-life of this process was established $$T_{1/2} >1.5\cdot 10^{22} $$ T 1 / 2 > 1.5 · 10 22 year.
We search for tri-nucleon decays of
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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
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73
Cu,
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73
Zn, and
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73
Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of
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73
Ga to
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73
Ge (stable). We search for the
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73
Ga decay exploiting the fact that it dominantly populates the 66.7 keV
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73
m
Ga state with half-life of 0.5 s. The nnn-decays of
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76
Ge that proceed via
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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
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\begin{document}$$\times $$\end{document}
×
10
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26
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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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
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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-
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\begin{document}$$\beta $$\end{document}
β
decay of
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76
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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\begin{document}$$\cdot $$\end{document}
·
year, the background index after analysis cuts is measured to be
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\begin{document}$$4.9^{+7.3}_{-3.4}\times 10^{-4} \ \text {counts}/(\text {keV} \cdot \text {kg} \cdot \text {year})$$\end{document}
4
.
9
-
3.4
+
7.3
×
10
-
4
counts
/
(
keV
·
kg
·
year
)
around
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\begin{document}$$Q_{\beta \beta }$$\end{document}
Q
β
β
. This work confirms the feasibility of IC detectors for the next-generation experiment
Legend
.
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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