The GERDA experiment searches for the lepton number violating neutrinoless double beta decay of \(^{76}\)Ge (\(^{76}\)Ge \(\rightarrow\) \(^{76}\)Se + 2e\(^-\)) operating bare Ge diodes with an ...enriched \(^{76}\)Ge fraction in liquid argon. The exposure for BEGe-type detectors is increased threefold with respect to our previous data release. The BEGe detectors feature an excellent background suppression from the analysis of the time profile of the detector signals. In the analysis window a background level of \(1.0_{-0.4}^{+0.6}\cdot10^{-3}\) cts/(keV\(\cdot\)kg\(\cdot\)yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0\(\nu\beta\beta\) experiment. No signal is observed and a new 90 \% C.L. lower limit for the half-life of \(8.0\cdot10^{25}\) yr is placed when combining with our previous data. The median expected sensitivity assuming no signal is \(5.8\cdot10^{25}\) yr.
The GERDA collaboration is performing a sensitive search for neutrinoless double beta decay of \(^{76}\)Ge at the INFN Laboratori Nazionali del Gran Sasso, Italy. The upgrade of the GERDA experiment ...from Phase I to Phase II has been concluded in December 2015. The first Phase II data release shows that the goal to suppress the background by one order of magnitude compared to Phase I has been achieved. GERDA is thus the first experiment that will remain background-free up to its design exposure (100 kg yr). It will reach thereby a half-life sensitivity of more than 10\(^{26}\) yr within 3 years of data collection. This paper describes in detail the modifications and improvements of the experimental setup for Phase II and discusses the performance of individual detector components.
The GERmanium Detector Array (GERDA) experiment located at the INFN Gran Sasso Laboratory (Italy), is looking for the neutrinoless double beta decay of Ge76, 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 1e-3 counts/(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 47.7 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 Ge76 is 8.0e25 yr at 90% CL. The experimental median sensitivity is 5.8e25 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 1e26 yr within 2018.
Neutrinoless double-\(\beta\) decay of \(^{76}\)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 \(^{76}\)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-\(\beta\) decay of \(^{76}\)Ge (Q\(_{\beta\beta}\) = 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\(\cdot\)yr, the background index after analysis cuts is measured to be \(4.9^{+7.3}_{-3.4}\times 10^{-4}\) counts /(keV\(\cdot\)kg\(\cdot\)yr) around Q\(_{\beta\beta}\). This work confirms the feasibility of IC detectors for the next-generation experiment LEGEND.
The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-\(\beta\) (\(0\nu\beta\beta\)) decay of \(^{76}\)Ge, whose discovery would have ...far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in \(^{76}\)Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of \(5.2\times10^{-4}\) counts/(keV\(\cdot\)kg\(\cdot\)yr) in the signal region and met the design goal to collect an exposure of 100 kg\(\cdot\)yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg\(\cdot\)yr of total exposure. A limit on the half-life of \(0\nu\beta\beta\) decay in \(^{76}\)Ge is set at \(T_{1/2}>1.8\times10^{26}\) yr at 90% C.L., which coincides with the sensitivity assuming no signal.
We present the first search for bosonic super-WIMPs as keV-scale dark matter candidates performed with the GERDA experiment. GERDA is a neutrinoless double-beta decay experiment which operates ...high-purity germanium detectors enriched in \(^{76}\)Ge in an ultra-low 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 axion-like particles and dark photons to electrons of \(g_{ae} < 3 \cdot 10^{-12}\) and \({\alpha'}/{\alpha} < 6.5 \cdot 10^{-24}\) at 90% credible interval, respectively, were obtained.
A discovery that neutrinos are not the usual Dirac but Majorana fermions, i.e. identical to their antiparticles, would be a manifestation of new physics with profound implications for particle ...physics and cosmology. Majorana neutrinos would generate neutrinoless double-\(\beta\) (\(0\nu\beta\beta\)) decay, a matter-creating process without the balancing emission of antimatter. So far, 0\(\nu\beta\beta\) decay has eluded detection. The GERDA collaboration searches for the \(0\nu\beta\beta\) decay of \(^{76}\)Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg\(\cdot\)yr, we observe no signal and derive a lower half-life limit of T\(_{1/2}\) > 0.9\(\cdot\)10\(^{26}\) yr (90% C.L.). Our T\(_{1/2}\) sensitivity assuming no signal is 1.1\(\cdot\)10\(^{26}\) yr. Combining the latter with those from other \(0{\nu}\beta\beta\) decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 - 0.16 eV, with corresponding sensitivities to the absolute mass scale in \(\beta\) decay of 0.15 - 0.44 eV, and to the cosmological relevant sum of neutrino masses of 0.46 - 1.3 eV.
Coherent elastic neutrino-nucleus scattering (CE\(\nu\)NS) is a process in which neutrinos scatter on a nucleus which acts as a single particle. Though the total cross section is large by neutrino ...standards, CE\(\nu\)NS has long proven difficult to detect, since the deposited energy into the nucleus is \(\sim\) keV. In 2017, the COHERENT collaboration announced the detection of CE\(\nu\)NS using a stopped-pion source with CsI detectors, followed up the detection of CE\(\nu\)NS using an Ar target. The detection of CE\(\nu\)NS has spawned a flurry of activities in high-energy physics, inspiring new constraints on beyond the Standard Model (BSM) physics, and new experimental methods. The CE\(\nu\)NS process has important implications for not only high-energy physics, but also astrophysics, nuclear physics, and beyond. This whitepaper discusses the scientific importance of CE\(\nu\)NS, highlighting how present experiments such as COHERENT are informing theory, and also how future experiments will provide a wealth of information across the aforementioned fields of physics.
On March 6, 2016 at 21:36:51 UT, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was recorded ...by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa31.4) and pyroxene (Fs25.4) clearly indicate that Stubenberg is an LL6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind‐implanted noble gases. Data on the bulk chemistry, IR spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed LL chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (CRE) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to <20 cm from short‐lived radionuclide data. In combination, this might suggest a complex exposure history for Stubenberg.
Abstract
On March 6, 2016 at 21:36:51
UT
, extended areas of Upper Austria, Bavaria (Germany) and the southwestern part of the Czech Republic were illuminated by a very bright bolide. This bolide was ...recorded by instruments in the Czech part of the European Fireball Network and it enabled complex and precise description of this event including prediction of the impact area. So far six meteorites totaling 1473 g have been found in the predicted area. The first pieces were recovered on March 12, 2016 on a field close to the village of Stubenberg (Bavaria). Stubenberg is a weakly shocked (S3) fragmental breccia consisting of abundant highly recrystallized rock fragments embedded in a clastic matrix. The texture, the large grain size of plagioclase, and the homogeneous compositions of olivine (Fa
31.4
) and pyroxene (Fs
25.4
) clearly indicate that Stubenberg is an
LL
6 chondrite breccia. This is consistent with the data on O, Ti, and Cr isotopes. Stubenberg does not contain solar wind‐implanted noble gases. Data on the bulk chemistry,
IR
spectroscopy, cosmogenic nuclides, and organic components also indicate similarities to other metamorphosed
LL
chondrites. Noble gas studies reveal that the meteorite has a cosmic ray exposure (
CRE
) age of 36 ± 3 Ma and that most of the cosmogenic gases were produced in a meteoroid with a radius of at least 35 cm. This is larger than the size of the meteoroid which entered the Earth's atmosphere, which is constrained to <20 cm from short‐lived radionuclide data. In combination, this might suggest a complex exposure history for Stubenberg.
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