Final Results of GERDA on the Two-Neutrino Double-ß Decay Half-Life of

We present the measurement of the two-neutrino double-ß decay rate of ^{76}Ge performed with the GERDA Phase II experiment. With a subset of the entire GERDA exposure, 11.8 kg yr, the half-life of the process has been determined: T_{1/2}^{2ν}=(2.022±0.018_{stat}±0.038_{syst})×10^{21} yr. This is the most precise determination of the ^{76}Ge two-neutrino double-ß decay half-life and one of the most precise measurements of a double-ß decay process. The relevant nuclear matrix element can be extracted: M_{eff}^{2ν}=(0.101±0.001).

Erratum: First Search for Bosonic Superweakly Interacting Massive Particles with Masses up to 1 MeV/c

This corrects the article DOI: 10.1103/PhysRevLett.125.011801.

First Search for Bosonic Superweakly Interacting Massive Particles with Masses up to 1 MeV/c

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 double-ß 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_{ae}<3×10^{-12} and α^{'}/α<6.5×10^{-24} at 90% credible interval, respectively, were obtained.

Final Results of GERDA on the Search for Neutrinoless Double-ß Decay.

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-ß (0νßß) 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 0νßß 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.

Aporphinoid alkaloids inhibit biofilm formation of Yersinia enterocolitica isolated from sausages.

AIMS OF THE STUDY: The ability of Yersinia enterocolitica strains to form biofilms and the capacity of different alkaloids to inhibit biofilm formation were investigated. METHODS AND RESULTS: The capacity to form biofilm on polystyrene of 31 Y. enterocolitica strains was evaluated. Biofilm and quorum sensing (QS) inhibition of 17 alkaloids were assayed; furthermore, minimum biofilm inhibitory concentration (MBIC) was determined. The capacity to form biofilms among the examined strains seemed to be a strain-related feature. The best biofilm inhibitors at 100 µmol l-1 were oliverine (1), guatterine (3), liriodenine (4), oliveridine (5) and pachypodanthine (6), which showed biofilm inhibition higher than 87%. Pachypodanthine (6) was the most effective compound with MBIC value of 12·5 µmol l-1 at subinhibitory concentration and also was able to inhibit QS system and reduce yenR expression at this concentration. CONCLUSION: This is the first study to demonstrate that oliverine, liriodenine, and pachypodanthine are able to inhibit biofilm formation of Y. enterocolitica without critically disturbing its growing capacity. At MBIC, pachypodanthine inhibited biofilm formation and QS. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of aporphinoid alkaloids as biofilms inhibitory agents might potentially be useful to treat biofilm-associated infections in the future.

Aporphinoid alkaloids as antimicrobial agents against Yersinia enterocolitica.

Foodborne diseases have become a health issue worldwide, mainly due to the consumption of contaminated foods that are either raw, improperly heat treated or cross-contaminated after adequate heat treatment foods. A group of alkaloids extracted from plants were tested to evaluate their antimicrobial effect against different strains of Yersinia enterocolitica and other foodborne bacteria. The results obtained reveal that oliveridine and pachypodanthine inhibited Y. enterocolitica growth, with MIC values of 25 µmol l-1 and 100 µmol l-1 respectively. The results indicated that both alkaloids are good growth inhibitors, but oliveridine showed greater inhibitory effect with lower MIC values. Inhibitory alkaloids can be developed as potential antimicrobials in food system to prevent or treat foodborne diseases, thus contributing to solve the global issue of contaminated food consumption. SIGNIFICANCE AND IMPACT OF THE STUDY: Alkaloids are abundant secondary metabolites in plants and represent one of the most widespread class of compounds endowed with multiple and varied pharmacological properties. In this work, we propose two aporphinoid alkaloids extracted from plants as new antimicrobial agents. Oliveridine and pachypodanthine inhibited Yersinia enterocolitica growth for up to 96 h of culture. This is the first reported study of the activity of these alkaloids as antimicrobial compounds.

Improved Limit on Neutrinoless Double-ß Decay of

The GERDA experiment searches for the lepton-number-violating neutrinoless double-ß decay of ^{76}Ge (^{76}Ge→^{76}Se+2e^{-}) operating bare Ge diodes with an enriched ^{76}Ge fraction in liquid argon. The exposure for broad-energy germanium type (BEGe) 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}×10^{-3} counts/(keV kg yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0νßß experiment. No signal is observed and a new 90% C.L. lower limit for the half-life of 8.0×10^{25} yr is placed when combining with our previous data. The expected median sensitivity assuming no signal is 5.8×10^{25} yr.

Final Results of the OPERA Experiment on ν_{τ} Appearance in the CNGS Neutrino Beam.

The OPERA experiment was designed to study ν_{µ}→ν_{τ} oscillations in the appearance mode in the CERN to Gran Sasso Neutrino beam (CNGS). In this Letter, we report the final analysis of the full data sample collected between 2008 and 2012, corresponding to 17.97×10^{19} protons on target. Selection criteria looser than in previous analyses have produced ten ν_{τ} candidate events, thus reducing the statistical uncertainty in the measurement of the oscillation parameters and of ν_{τ} properties. A multivariate approach for event identification has been applied to the candidate events and the discovery of ν_{τ} appearance is confirmed with an improved significance level of 6.1σ. |Δm_{32}^{2}| has been measured, in appearance mode, with an accuracy of 20%. The measurement of the ν_{τ} charged-current cross section, for the first time with a negligible contamination from ν[over ¯]_{τ}, and the first direct evidence for the ν_{τ} lepton number are also reported.

Large-scale individual thyroid monitoring following nuclear accidents by means of non-spectrometric devices.

In order to properly respond to an emergency caused by an accident in a nuclear power plant with a spread of radionuclides in the atmosphere, we propose a field procedure to perform a large-scale individual thyroid monitoring of internal contamination due to inhalation of 131I, by means of non-spectrometric equipment, in particular dose rate meters. Specific attention is paid to the individual monitoring of children, because of the very high radiosensitivity of the child's thyroid to the carcinogenic effects of ionising radiation. The device performance was evaluated by measuring mock iodine sources provided in the Child and Adult Thyroid Monitoring After Reactor Accident (CAThyMARA) intercomparison and, just for a scintillator dose rate meter, by means of 60 s acquisitions of healthy volunteers' thyroids. All the devices showed a remarkable accuracy in quantification of equivalent 131I activity in the thyroids of persons of all ages. The selected scintillator dose rate meter showed detection limit values resulting in a maximum committed equivalent dose to thyroid HT, assuming an acute 131I inhalation occurred five days before the measurement, equal to 10 mSv (related to five-year-old children). Considering the level of HT values associated with the calculated detection limit activities, the proposed procedure has a significant sensitivity to be used for fast internally thyroid monitoring in nuclear or radiological emergencies, allowing daily monitoring a large amount of individuals.

Discovery of τ Neutrino Appearance in the CNGS Neutrino Beam with the OPERA Experiment.

The OPERA experiment was designed to search for ν_{µ}→ν_{τ} oscillations in appearance mode, i.e., by detecting the τ leptons produced in charged current ν_{τ} interactions. The experiment took data from 2008 to 2012 in the CERN Neutrinos to Gran Sasso beam. The observation of the ν_{µ}→ν_{τ} appearance, achieved with four candidate events in a subsample of the data, was previously reported. In this Letter, a fifth ν_{τ} candidate event, found in an enlarged data sample, is described. Together with a further reduction of the expected background, the candidate events detected so far allow us to assess the discovery of ν_{µ}→ν_{τ} oscillations in appearance mode with a significance larger than 5σ.

Search for tri-nucleon decays of 76Ge in GERDA.

We search for tri-nucleon decays of 76Ge 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 73Cu, 73Zn, and 73Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of 73Ga to 73Ge (stable). We search for the 73Ga decay exploiting the fact that it dominantly populates the 66.7 keV 73mGa state with half-life of 0.5 s. The nnn-decays of 76Ge that proceed via 73mGe 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 1.2×1026 yr  (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.

Liquid argon light collection and veto modeling in GERDA Phase II.

The ability to detect liquid argon scintillation light from within a densely packed high-purity germanium detector array allowed the Gerda experiment to reach an exceptionally low background rate in the search for neutrinoless double beta decay of 76 Ge. Proper modeling of the light propagation throughout the experimental setup, from any origin in the liquid argon volume to its eventual detection by the novel light read-out system, provides insight into the rejection capability and is a necessary ingredient to obtain robust background predictions. In this paper, we present a model of the Gerda liquid argon veto, as obtained by Monte Carlo simulations and constrained by calibration data, and highlight its application for background decomposition.

OPERA tau neutrino charged current interactions.

The OPERA experiment was designed to discover the vτ appearance in a vµ beam, due to neutrino oscillations. The detector, located in the underground Gran Sasso Laboratory, consisted of a nuclear photographic emulsion/lead target with a mass of about 1.25 kt, complemented by electronic detectors. It was exposed from 2008 to 2012 to the CNGS beam: an almost pure vµ beam with a baseline of 730 km, collecting a total of 1.8·1020 protons on target. The OPERA Collaboration eventually assessed the discovery of vµâ†’vτ oscillations with a statistical significance of 6.1 σ by observing ten vτ CC interaction candidates. These events have been published on the Open Data Portal at CERN. This paper provides a detailed description of the vτ data sample to make it usable by the whole community.

Characterization of 30 76 Ge enriched Broad Energy Ge detectors for GERDA Phase II.

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 Ge into 76 Se+2e - . Gerda has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new 76Ge 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.

Probing Majorana neutrinos with double-ß decay.

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-ß (0νßß) decay, a matter-creating process without the balancing emission of antimatter. The GERDA Collaboration searches for the 0νßß decay of 76Ge 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 T 1/2 > 0.9 × 1026 years (90% C.L.). Our T 1/2 sensitivity, assuming no signal, is 1.1 × 1026 years. Combining the latter with those from other 0νßß decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 to 0.16 electron volts.

[A 2-year evaluation of different methods of dental caries prophylaxis in a sample school-aged population]. / Valutazione a due anni di vari metodi di profilassi della carie dentaria su un campione di popolazione in età scolare.

Caries is currently considered to be the most widespread disease affecting mankind; it is calculated in fact that around 90% of the world population suffers from caries. Carious pathology therefore plays a key role, not least due to the high social costs which it entails, and, for this reason, research into appropriate methods of prevention which can to some extent limit the incidence of caries are of particular interest. MATERIALS AND METHODS. The study was performed in a group of 1475 selected primary-school children. After having subdivided the population in three groups, an initial dental examination was carried out and the results obtained were quantified by calculating DMFT. The first group (492 children) was instructed to follow the rules of oral and dietary hygiene. The second group (501 children), in addition to the instructions given to the first group, also received fluoro-prophylactic treatment. Lastly, the third group (482 children) were used as a reference sample and did not receive any form of instruction or treatment. RESULTS. After two years DMFT values were increased in all three groups; in detail, values rose 0.41 in the first group, 0.38 in the second group, and 0.81 in the third group. DISCUSSION AND CONCLUSIONS. Scrupulous oral hygiene and a correct diet represent a prophylactic measure of outstanding importance in terms of carious pathology. The minimum difference observed between the first and second groups should probably be attributed to the fact that fluoro-prophylactic treatment requires a period of more than 24 months before appreciable results can be seen.