The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) 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 5.2×10^{-4} counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100 kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg yr of total exposure. A limit on the half-life of 0νββ decay in ^{76}Ge is set at T_{1/2}>1.8×10^{26} yr at 90% C.L., which coincides with the sensitivity assuming no signal.
This numerical study deals with the distinction between autoignition and propagation driven reaction zones using an autoignition index (AI). It allows a clear identification of the two burning ...regimes based on the relative contribution of two reactions for hydroperoxyl (HO2) chemistry. AI was applied to a lifted methane–air jet in a hot (1350 K) vitiated coflow, namely the Cabra flame configuration. Large Eddy Simulation (LES) were performed using the Dynamic Thickened Flame model (DTF) with an Analytically Reduced Chemistry (ARC) mechanism with 22 transported species, as well as 18 species in Quasi-Steady State (QSS) approximation. A detailed validation of the numerical methods is presented. Comparisons with experimental data are in good agreement for mixture fraction, temperature and species mass fractions for both a fine and a coarse mesh. In a detailed analysis of the flame structure, AI identifies autoignition as dominant over propagation at the flame base. Autoignition pockets are close to the lean most reactive mixture fraction. Lean and rich propagation is recognized to dominate in regions located at higher mixture fractions closer to the centerline with significantly higher heat release rates compared to autoignition.
Experiments searching for rare processes like neutrinoless double beta decay heavily rely on the identification of background events to reduce their background level and increase their sensitivity. ...We present a novel machine learning based method to recognize one of the most abundant classes of background events in these experiments. By combining a neural network for feature extraction with a smaller classification network, our method can be trained with only a small number of labeled events. To validate our method, we use signals from a broad-energy germanium detector irradiated with a
228
Th gamma source. We find that it matches the performance of state-of-the-art algorithms commonly used for this detector type. However, it requires less tuning and calibration and shows potential to identify certain types of background events missed by other methods.
Probing Majorana neutrinos with double-β decay Agostini, M; Bakalyarov, A M; Balata, M ...
Science (American Association for the Advancement of Science),
09/2019, Letnik:
365, Številka:
6460
Journal Article
Recenzirano
Odprti dostop
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.
The impurity density in high-purity germanium detectors is crucial to understand and simulate such detectors. However, the information about the impurities provided by the manufacturer, based on Hall ...effect measurements, is typically limited to a few locations and comes with a large uncertainty. As the voltage dependence of the capacitance matrix of a detector strongly depends on the impurity density distribution, capacitance measurements can provide a path to improve the knowledge on the impurities. The novel method presented here uses a machine-learned surrogate model, trained on precise GPU-accelerated capacitance calculations, to perform full Bayesian inference of impurity distribution parameters from capacitance measurements. All steps use open-source Julia software packages. Capacitances are calculated with
SolidStateDetectors.jl
, machine learning is done with
Flux.jl
and Bayesian inference performed using
BAT.jl
. The capacitance matrix of a detector and its dependence on the impurity density is explained and a capacitance bias-voltage scan of an
n
-type true-coaxial test detector is presented. The study indicates that the impurity density of the test detector also has a radial dependence.
Events from alpha interactions on the surfaces of germanium detectors are a major contribution to the background in germanium-based searches for neutrinoless double-beta decay. Surface events are ...subject to charge trapping, affecting their pulse shape and reconstructed energy. A study of alpha events on the passivated end-plate of a segmented true-coaxial n-type high-purity germanium detector is presented. Charge trapping is analysed in detail and an existing pulse-shape analysis technique to identify alpha events is verified with mirror pulses observed in the non-collecting channels of the segmented test detector. The observed radial dependence of charge trapping confirms previous results. A dependence of the probability of charge trapping on the crystal axes is observed for the first time. A first model to describe charge trapping effects within the framework of the simulation software
SolidStateDetectors.jl
is introduced. The influence of metalisation on events from low-energy gamma interactions close to the passivated surface is also presented.
We analyse, in NLO, the physical properties of the discrete eigenvalue solution for the BFKL equation. We show that a set of eigenfunctions with positive eigenvalues,
ω
, together with a small ...contribution from a continuum of eigenfunctions with negative
ω
, provide an excellent description of high-precision HERA
F
2
data in the region,
x
<
0.001
,
Q
2
>
6
GeV
2
. The phases of the eigenfunctions can be obtained from a simple parametrisation of the pomeron spectrum, which has a natural motivation within BFKL. The data analysis shows that the first eigenfunction decouples completely or almost completely from the proton. This suggests that there exists an additional ground state, which is naturally saturated and may have the properties of the soft pomeron.
Upgrade for Phase II of the Gerda experiment Agostini, M.; Bakalyarov, A. M.; Balata, M. ...
The European physical journal. C, Particles and fields,
05/2018, Letnik:
78, Številka:
5
Journal Article
Recenzirano
Odprti dostop
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
year
). It will reach thereby a half-life sensitivity of more than
10
26
year 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.
Sahidisch ist der wichtigste Literaturdialekt des Koptischen. Seit langem gelten moderne kritische Editionen der sahidischen Übersetzung des Neuen Testaments als Desiderat der Forschung. Ein ...Forschungsprojekt (P29315) des Österreichischen Wissenschaftsfonds (FWF) ermöglichte eine kritische Edition des sahidischen Johannesevangeliums. Ihr liegen 172 verschiedene, zu großen Teilen fragmentarisch erhaltene, Handschriften zugrunde.
OBJECTIVE:--Type 2 diabetes and obesity have genetic and environmental determinants. We studied the effects of different environments on these diseases in Pima Indians in Mexico and the U.S. RESEARCH ...DESIGN AND METHODS--Adult Pima-Indian and non-Pima populations in the Sierra Madre mountains of Mexico were examined using oral glucose tolerance tests and assessments for obesity, physical activity, and other risk factors. Results were compared with those from Pima Indians in Arizona. Both Pima populations were typed for DNA polymorphisms to establish their genetic similarity. RESULTS:--The age- and sex-adjusted prevalence of type 2 diabetes in the Mexican Pima Indians (6.9%) was less than one-fifth that in the U.S. Pima Indians (38%) and similar to that of non-Pima Mexicans (2.6%). The prevalence of obesity was similar in the Mexican Pima Indians (7% in men and 20% in women) and non-Pima Mexicans (9% in men and 27% in women) but was much lower than in the U.S. Pima Indians. Levels of physical activity were much higher in both Mexican groups than in the U.S. Pima Indians. The two Pima groups share considerable genetic similarity relative to other Native Americans. CONCLUSIONS:--The much lower prevalence of type 2 diabetes and obesity in the Pima Indians in Mexico than in the U.S. indicates that even in populations genetically prone to these conditions, their development is determined mostly by environmental circumstances, thereby suggesting that type 2 diabetes is largely preventable. This study provides compelling evidence that changes in lifestyle associated with Westernization play a major role in the global epidemic of type 2 diabetes.
PDF
