The cross section
σ
(
E
ν
) for solar-neutrino capture by the
76
Ge nucleus is calculated. The effect of Gamow-Teller resonances on the rate of neutrino capture in the reaction
76
Ge (
ν, e
−
)
76
As ...is studied. It is shown that the contribution of high-lying Gamow-Teller resonances to the charge-exchange strength function increases the rate of solar-neutrino capture by 25% to 50%, depending on the normalization method and on the inclusion of the quenching effect.
Pulse shape discrimination for Gerda Phase I data Agostini, M.; Allardt, M.; Andreotti, E. ...
European physical journal. C, Particles and fields,
10/2013, Letnik:
73, Številka:
10
Journal Article
Recenzirano
Odprti dostop
The
Gerda
experiment located at the Laboratori Nazionali del Gran Sasso of INFN searches for neutrinoless double beta (0
νββ
) decay of
76
Ge using germanium diodes as source and detector. In Phase I ...of the experiment eight semi-coaxial and five BEGe type detectors have been deployed. The latter type is used in this field of research for the first time. All detectors are made from material with enriched
76
Ge fraction. The experimental sensitivity can be improved by analyzing the pulse shape of the detector signals with the aim to reject background events. This paper documents the algorithms developed before the data of Phase I were unblinded. The double escape peak (DEP) and Compton edge events of 2.615 MeV
γ
rays from
208
Tl decays as well as two-neutrino double beta (2
νββ
) decays of
76
Ge are used as proxies for 0
νββ
decay.
For BEGe detectors the chosen selection is based on a single pulse shape parameter. It accepts 0.92±0.02 of signal-like events while about 80 % of the background events at
Q
ββ
=2039 keV are rejected.
For semi-coaxial detectors three analyses are developed. The one based on an artificial neural network is used for the search of 0
νββ
decay. It retains 90 % of DEP events and rejects about half of the events around
Q
ββ
. The 2
νββ
events have an efficiency of 0.85±0.02 and the one for 0
νββ
decays is estimated to be
. A second analysis uses a likelihood approach trained on Compton edge events. The third approach uses two pulse shape parameters. The latter two methods confirm the classification of the neural network since about 90 % of the data events rejected by the neural network are also removed by both of them. In general, the selection efficiency extracted from DEP events agrees well with those determined from Compton edge events or from 2
νββ
decays.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double ...beta decay (...) of ...Ge. Germanium detectors made of material with an enriched ...Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ...Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ...Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.
The cross section sigma(E.sub.v) forsolar-neutrino capture by the sup.76Ge nucleus is calculated. The effect of Gamow--Teller resonances on the rate of neutrino capture in the reaction sup.76Ge(v, ...e.sup.-)sup.76As is studied. It is shown that the contribution of high-lying Gamow--Teller resonances to the charge-exchange strength function increases the rate of solar-neutrino capture by 25% to 50%, depending on the normalization method and on the inclusion of the quenching effect.
An optimized digital shaping filter has been developed for the
Gerda
experiment which searches for neutrinoless double beta decay in
76
Ge. The
Gerda
Phase I energy calibration data have been ...reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10 % at the
Q
value for
0
ν
β
β
decay in
76
Ge is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping filter.
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.
The GERmanium Detector Array (Gerda) experiment located at the INFN Gran Sasso Laboratory (Italy), is looking for the neutrinoless double beta decay of 76Ge, by using high-purity germanium detectors ...made from isotopically enriched material. The combination of the novel experimental design, the careful material selection for radio-purity and the active/passive shielding techniques result in a very low residual background at the Q-value of the decay, about 10−3 cts/(keV-kg-yr). This makes GERDA the first experiment in the field to be background-free for the complete design exposure of 100 kg-yr. A search for neutrinoless double beta decay was performed with a total exposure of 46.7 kg-yr: 23.2 kg-yr come from the second phase (Phase II) of the experiment, in which the background is reduced by about a factor of ten with respect to the previous phase. The analysis presented in this paper includes 12.4 kg-yr of new Phase II data. No evidence for a possible signal is found: the lower limit for the half-life of 76Ge is 8.0 * 1025 yr at 90% CL. The experimental median sensitivity is 5.8 * 1025 yr. The experiment is currently taking data. As it is running in a background-free regime, its sensitivity grows linearly with exposure and it is expected to surpass 1026 yr within 2018.
The results are presented from calculating capture cross section σ(
E
ν
) of solar neutrinos by
76
Ge nuclei. Experimental data on strength function
S
(
E
), obtained in the charge-exchange
76
Ge(
3
...He,
t
)
76
As reaction, are used in these calculations. The effect the resonance structure of strength function
S
(
E
) has on cross section σ(
E
ν
) is examined. It is shown that the giant Gamow–Teller resonance alone makes a contribution of ~20%, and the contribution of lower-lying excitations in the continuous spectrum part is even larger. These contributions must be considered in calculations for background events in experiments on double beta decay of the GERDA (LEGEND) type.
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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