Probing Majorana neutrinos with double-β decay Agostini, M; Bakalyarov, A M; Balata, M ...
Science (American Association for the Advancement of Science),
09/2019, Volume:
365, Issue:
6460
Journal Article
Peer reviewed
Open access
A discovery that neutrinos are Majorana fermions would have profound implications for particle physics and cosmology. The Majorana character of neutrinos would make possible the neutrinoless double-β ...(0νββ) decay, a matter-creating process without the balancing emission of antimatter. The GERDA Collaboration searches for the 0νββ decay of
Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg⋅year, we observe no signal and derive a lower half-life limit of
> 0.9 × 10
years (90% C.L.). Our
sensitivity, assuming no signal, is 1.1 × 10
years. Combining the latter with those from other 0νββ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 to 0.16 electron volts.
Abstract
Conservative mechanical systems are considered. Each system is supposed to admit a family of non-degenerate symmetric periodic motions. For the entire set of systems, they form a family of ...conditionally periodic oscillations, which is assumed to contain a symmetrical periodic motion. Universal couplings for mechanical systems are proposed such that they play the role of controls that ensure the existence, stability, and stabilization of oscillations at the same time for the whole system. Those couplings provide the natural, i.e. without involving any additional controls, stabilization of the oscillation. In addition, mechanical systems perform the synchronization in frequency and phase.
We study mechanical systems each of which admits a family of periodic motions when the systems are not coupled. It is proved that a necessary condition for the existence of a cycle in a coupled ...system is the nondegeneracy of periodic motions in all possibly but one subsystem. The structure and specific type of the coupling control are found. The problems of existence, stability, and natural stabilization of oscillations are solved. It is shown that the cycle synchronizes the oscillations of mechanical systems in frequency and phase. The paper develops the idea of stabilizing the oscillations of a coupled system by selecting a suitable coupling control between subsystems.
Synthine and T-6 propellant are studied as new basic solvents for creating liquid organic scintillators. The light attenuation length in these solvents (both those obtained from the manufacturer and ...those subjected to chromatographic purification on Al
O
) was measured along with the relative light yield of scintillators based on them. The chemical composition of synthine was determined by the method of chromato-mass spectrometry and UV spectrophotometry. A Nd-loaded scintillator (
9 g/L) based on a synthine–pseudocumene mixture was created, and its light yield (LY 60
) was measured with respect to a scintillator based on linear alkyl benzene (LAB).
This paper considers coupled conservative systems, each admitting a family of single-frequency oscillations without coupling. The oscillations of the entire system are stabilized. Smooth autonomous ...universal coupling controls are found. An orbitally asymptotically stable cycle is constructed. The natural stabilization of such a cycle is established. The oscillations of conservative systems are synchronized by frequency and phase.
A modification of the LENS (Low Energy Neutrino Spectroscopy) project for spectroscopy of solar neutrinos with energies above about 715 keV on the basis of new technologies and solutions is examined. ...The respective detector employs
In nuclei as a target for neutrinos. The creation of a detector containing about 200 t of a scintillator loaded with 10 t of indium will make it possible to measure, within five years, the energy spectra of solar neutrinos from
Be, neutrinos from the CNO cycle, and
neutrinos with small systematic errors. The detector was simulated in the form of a set of cells of a liquid scintillator doped with indium (about 10
in weight). Necessary technical conditions for detector cells are formulated, and the possible counting rate for events induced by internal and external backgrounds and characterized by an energy release of 600 to 1600 keV is estimated. It is shown that such a detector is implementable, in principle.
Abstract
Currants are important berry crops cultivated for medicinal purposes. Most currant cultivars are crossings between Ribes nigrum varieties, while many Ribes species are not used in ...hybridisation. Recent research on Ribes crossbreeding is scarce. Hybridisation of wild species can improve reproductive success and the taste of fruit. However, hybrids of certain currant species cannot produce fully formed berries. Crossbreeding of currant species was performed in Northwest Russia (Saint Petersburg Botanical Garden). The research included both introduced (R. sachalinense, R. sanguineum, R. rubrum, R. hispidulum, R. mandschuricum, R. spicatum, R. latifolium) and native species (R. aureum, R. alpinum, R. nigrum). The research aimed to identify the hybridisation system, pollination mechanisms and hybrids with the highest percentage of fruit and seed set. Pollen fertility and viability were assessed. Pollen is fertile (acetocarmin staining: 80.3% for R. alpinum and 96.0% for R. mandschuricum); germination is active on nutrient medium and in situ, especially in R. sachalinense, R. aureum and R. spicatum (54.2–41.8%). Pollen germination can be irregular. Flowers were castrated before pollination. Optimal hybrids with a high percentage of fruit set were identified: R. alpinum x R. mandschuricum, R. alpinum x R. aureum, R. sachalinense x R. sanguineum, R. rubrum, R. hispidulum.
Low background segmented liquid scintillator detector, doped with an indium as a target for solar neutrino registration, can be used for measuring total solar neutrino spectrum including
neutrinos. A ...detector consisting of small modules filled with liquid scintillator in the volume of 1–2 L is considered. Silicon matrices are used for light collection. The background of indium beta-activity is suppressed by triple coincidences. The detector of such a type can measure
Be neutrino flux with high accuracy and independently check the measurement performed by the Borexino Collaboration.
Abstract
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
...$$^{76}$$
76
Ge into
$$^{76}$$
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.
Pulse shape discrimination for Gerda Phase I data Agostini, M.; Allardt, M.; Andreotti, E. ...
The European physical journal. C, Particles and fields,
10/2013, Volume:
73, Issue:
10
Journal Article
Peer reviewed
Open access
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.
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