Measurement of the 2νßß Decay Half-Life of

We report on the results obtained with the global CUPID-0 background model, which combines the data collected in the two measurement campaigns for a total exposure of 8.82 kg×yr of ^{82}Se. We identify with improved precision the background sources within the 3 MeV energy region, where neutrinoless double ß decay of ^{82}Se and ^{100}Mo is expected, making more solid the foundations for the background budget of the next-generation CUPID experiment. Relying on the excellent data reconstruction, we measure the two-neutrino double ß-decay half-life of ^{82}Se with unprecedented accuracy: T_{1/2}^{2ν}=[8.69±0.05(stat)_{-0.06}^{+0.09}(syst)]×10^{19} yr.

[Cytochrome bd as Antioxidant Redox Enzyme].

One of the main functions of enzyme complexes that constitute electron transport (respiratory) chains of organisms is to maintain cellular redox homeostasis by oxidizing reducing equivalents, NADH and quinol. Cytochrome bd is a unique terminal oxidase of the chains of many bacteria including pathogenic species. This redox enzyme couples the oxidation of ubiquinol or menaquinol by molecular oxygen to the generation of proton motive force, a universal energy currency. The latter is used by the organism to produce ATP, another cellular energy currency, via oxidative phosphorylation. Escherichia coli contains two bd-type oxidases, bd-I and bd-II, encoded by the cydAB and appCB operons, respectively. Surprisingly, both bd enzymes make a further contribution to molecular mechanisms of maintaining the appropriate redox balance in the bacterial cell by means of elimination of reactive oxygen species, such as hydrogen peroxide. This review summarizes recent data on the redox-modulated H2O2-scavenging activities of cytochromes bd-I and bd-II from E. coli. The possibility of such antioxidant properties in cytochromes bd from other bacteria is also discussed.

Final Result on the Neutrinoless Double Beta Decay of

CUPID-0, an array of Zn^{82}Se cryogenic calorimeters, was the first medium-scale demonstrator of the scintillating bolometers' technology. The first project phase (March 2017-December 2018) allowed the most stringent limit on the neutrinoless double beta decay half-life of the isotope of interest, ^{82}Se, to be set. After a six month long detector upgrade, CUPID-0 began its second and last phase (June 2019-February 2020). In this Letter, we describe the search for neutrinoless double beta decay of ^{82}Se with a total exposure (phase I+II) of 8.82 kg yr^{-1} of isotope. We set a limit on the half-life of ^{82}Se to the ground state of ^{82}Kr of T_{1/2}^{0ν}(^{82}Se)>4.6×10^{24} yr (90% credible interval), corresponding to an effective Majorana neutrino mass m_{ßß}<(263-545) meV. We also set the most stringent lower limits on the neutrinoless decays of ^{82}Se to the 0_{1}^{+}, 2_{1}^{+}, and 2_{2}^{+} excited states of ^{82}Kr, finding 1.8×10^{23} yr, 3.0×10^{23} yr, and 3.2×10^{23} yr (90% credible interval) respectively.

Final Result of CUPID-0 Phase-I in the Search for the

CUPID-0 is the first pilot experiment of CUPID, a next-generation project for the measurement of neutrinoless double beta decay (0νDBD) with scintillating bolometers. The detector, consisting of 24 enriched and 2 natural ZnSe crystals, has been taking data at Laboratori Nazionali del Gran Sasso from June 2017 to December 2018, collecting a ^{82}Se exposure of 5.29 kg×yr. In this Letter we present the phase-I results in the search for 0νDBD. We demonstrate that the technology implemented by CUPID-0 allows us to reach the lowest background for calorimetric experiments: (3.5_{-0.9}^{+1.0})×10^{-3} counts/(keV kg yr). Monitoring 3.88×10^{25} ^{82}Se nuclei×yr we reach a 90% credible interval median sensitivity of T_{1/2}^{0ν}>5.0×10^{24} yr and set the most stringent limit on the half-life of ^{82}Se 0νDBD: T_{1/2}^{0ν}>3.5×10^{24} yr (90% credible interval), corresponding to m_{ßß}<(311-638) meV depending on the nuclear matrix element calculations.

Evidence of Single State Dominance in the Two-Neutrino Double-ß Decay of

We report on the measurement of the two-neutrino double-ß decay of ^{82}Se performed for the first time with cryogenic calorimeters, in the framework of the CUPID-0 experiment. With an exposure of 9.95 kg yr of Zn^{82}Se, we determine the two-neutrino double-ß decay half-life of ^{82}Se with an unprecedented precision level, T_{1/2}^{2ν}=[8.60±0.03(stat) _{-0.13}^{+0.19}(syst)]×10^{19} yr. The very high signal-to-background ratio, along with the detailed reconstruction of the background sources allowed us to identify the single state dominance as the underlying mechanism of such a process, demonstrating that the higher state dominance hypothesis is disfavored at the level of 5.5σ.

First Result on the Neutrinoless Double-ß Decay of

We report the result of the search for neutrinoless double beta decay of ^{82}Se obtained with CUPID-0, the first large array of scintillating Zn^{82}Se cryogenic calorimeters implementing particle identification. We observe no signal in a 1.83 kg yr ^{82}Se exposure, and we set the most stringent lower limit on the 0νßß ^{82}Se half-life T_{1/2}^{0ν}>2.4×10^{24} yr (90% credible interval), which corresponds to an effective Majorana neutrino mass m_{ßß}<(376-770) meV depending on the nuclear matrix element calculations. The heat-light readout provides a powerful tool for the rejection of α particles and allows us to suppress the background in the region of interest down to (3.6_{-1.4}^{+1.9})×10^{-3} counts/(keV kg yr), an unprecedented level for this technique.

Are nanoporous materials radiation resistant?

The key to perfect radiation endurance is perfect recovery. Since surfaces are perfect sinks for defects, a porous material with a high surface to volume ratio has the potential to be extremely radiation tolerant, provided it is morphologically stable in a radiation environment. Experiments and computer simulations on nanoscale gold foams reported here show the existence of a window in the parameter space where foams are radiation tolerant. We analyze these results in terms of a model for the irradiation response that quantitatively locates such window that appears to be the consequence of the combined effect of two length scales dependent on the irradiation conditions: (i) foams with ligament diameters below a minimum value display ligament melting and breaking, together with compaction increasing with dose (this value is typically ∼5 nm for primary knock on atoms (PKA) of ∼15 keV in Au), while (ii) foams with ligament diameters above a maximum value show bulk behavior, that is, damage accumulation (few hundred nanometers for the PKA's energy and dose rate used in this study). In between these dimensions, (i.e., ∼100 nm in Au), defect migration to the ligament surface happens faster than the time between cascades, ensuring radiation resistance for a given dose-rate. We conclude that foams can be tailored to become radiation tolerant.

A transmission electron microscopy study of the effect of interfaces on bubble formation in He-implanted Cu-Nb multilayers.

Magnetron sputtered thin films of Cu, Nb, and Cu-Nb multilayers with 2.5 and 5 nm nominal layer thickness were deposited on Si and implanted with 4He+ and 3He+ ions. Secondary ion mass spectroscopy and nuclear reaction analysis, respectively, were used to measure the 4He+ and 3He+ concentration profile with depth inside the films. Cross-sectional transmission electron microscopy was used to characterize the helium bubbles. Analysis of the contrast from helium bubbles in defocused transmission electron microscope images showed a minimum bubble diameter of 1.25 nm. While pure Cu and Nb films showed bubble contrast over the entire range of helium implantation, the multilayers exhibited bubbles only above a critical He concentration that increased almost linearly with decreasing layer thickness. The work shows that large amounts of helium can be trapped at incoherent interfaces in the form of stable, nanometer-size bubbles.

Background identification in cryogenic calorimeters through α - α delayed coincidences.

Localization and modeling of radioactive contaminations is a challenge that ultra-low background experiments are constantly facing. These are fundamental steps both to extract scientific results and to further reduce the background of the detectors. Here we present an innovative technique based on the analysis of α - α delayed coincidences in 232 Th and 238 U decay chains, developed to investigate the contaminations of the ZnSe crystals in the CUPID-0 experiment. This method allows to disentangle surface and bulk contaminations of the detectors relying on the different probability to tag delayed coincidences as function of the α decay position.

Mechanical Response of He-Implanted Amorphous SiOC/Crystalline Fe Nanolaminates.

This study investigates the microstructural evolution and mechanical response of sputter-deposited amorphous silicon oxycarbide (SiOC)/crystalline Fe nanolaminates, a single layer SiOC film, and a single layer Fe film subjected to ion implantation at room temperature to obtain a maximum He concentration of 5 at. %. X-ray diffraction and transmission electron microscopy indicated no evidence of implantation-induced phase transformation or layer breakdown in the nanolaminates. Implantation resulted in the formation of He bubbles and an increase in the average size of the Fe grains in the individual Fe layers of the nanolaminates and the single layer Fe film, but the bubble density and grain size were found to be smaller in the former. By reducing the thicknesses of individual layers in the nanolaminates, bubble density and grain size were further decreased. No He bubbles were observed in the SiOC layers of the nanolaminates and the single layer SiOC film. Nanoindentation and scanning probe microscopy revealed an increase in the hardness of both single layer SiOC and Fe films after implantation. For the nanolaminates, changes in hardness were found to depend on the thicknesses of the individual layers, where reducing the layer thickness to 14 nm resulted in mitigation of implantation-induced hardening.

Search of the neutrino-less double beta decay of 82 Se into the excited states of 82 Kr with CUPID-0.

The CUPID-0 experiment searches for double beta decay using cryogenic calorimeters with double (heat and light) read-out. The detector, consisting of 24 ZnSe crystals 95 % enriched in 82 Se and two natural ZnSe crystals, started data-taking in 2017 at Laboratori Nazionali del Gran Sasso. We present the search for the neutrino-less double beta decay of 82 Se into the 0 1 + , 2 1 + and 2 2 + excited states of 82 Kr with an exposure of 5.74 kg · yr (2.24 × 10 25  emitters · yr). We found no evidence of the decays and set the most stringent limits on the widths of these processes: Γ ( 82 Se → 82 Kr 0 1 + )8.55 × 10 - 24  yr - 1 , Γ ( 82 Se → 82 Kr 2 1 + ) < 6.25 × 10 - 24  yr - 1 , Γ ( 82 Se → 82 Kr 2 2 + )8.25 × 10 - 24  yr - 1 (90 % credible interval).

Analysis of cryogenic calorimeters with light and heat read-out for double beta decay searches.

The suppression of spurious events in the region of interest for neutrinoless double beta decay will play a major role in next generation experiments. The background of detectors based on the technology of cryogenic calorimeters is expected to be dominated by α particles, that could be disentangled from double beta decay signals by exploiting the difference in the emission of the scintillation light. CUPID-0, an array of enriched Zn 82 Se scintillating calorimeters, is the first large mass demonstrator of this technology. The detector started data-taking in 2017 at the Laboratori Nazionali del Gran Sasso with the aim of proving that dual read-out of light and heat allows for an efficient suppression of the α background. In this paper we describe the software tools we developed for the analysis of scintillating calorimeters and we demonstrate that this technology allows to reach an unprecedented background for cryogenic calorimeters.

CUPID-0: the first array of enriched scintillating bolometers for 0 ν ß ß decay investigations.

The CUPID-0 detector hosted at the Laboratori Nazionali del Gran Sasso, Italy, is the first large array of enriched scintillating cryogenic detectors for the investigation of 82 Se neutrinoless double-beta decay ( 0 ν ß ß ). CUPID-0 aims at measuring a background index in the region of interest (RoI) for 0 ν ß ß at the level of 10 - 3  counts/(keV kg years), the lowest value ever measured using cryogenic detectors. CUPID-0 operates an array of Zn 82 Se scintillating bolometers coupled with bolometric light detectors, with a state of the art technology for background suppression and thorough protocols and procedures for the detector preparation and construction. In this paper, the different phases of the detector design and construction will be presented, from the material selection (for the absorber production) to the new and innovative detector structure. The successful construction of the detector lead to promising preliminary detector performance which is discussed here.

First array of enriched Zn[Formula: see text]Se bolometers to search for double beta decay.

The R&D activity performed during the last years proved the potential of ZnSe scintillating bolometers to the search for neutrino-less double beta decay, motivating the realization of the first large-mass experiment based on this technology: CUPID-0. The isotopic enrichment in [Formula: see text]Se, the Zn[Formula: see text]Se crystals growth, as well as the light detectors production have been accomplished, and the experiment is now in construction at Laboratori Nazionali del Gran Sasso (Italy). In this paper we present the results obtained testing the first three Zn[Formula: see text]Se crystals operated as scintillating bolometers, and we prove that their performance in terms of energy resolution, background rejection capability and intrinsic radio-purity complies with the requirements of CUPID-0.

Novel lipid-lowering properties of Vaccinium myrtillus L. leaves, a traditional antidiabetic treatment, in several models of rat dyslipidaemia: a comparison with ciprofibrate.

Vaccinium myrtillus L. (blueberry) leaf infusions are traditionally used as a folk medicine treatment of diabetes. To further define this therapeutical action, a dried hydroalcoholic extract of the leaf was administered orally to streptozotocin-diabetic rats for 4 days. Plasma glucose levels were consistently found to drop by about 26% at two different stages of diabetes. Unexpectedly, plasma triglyceride (TG) were also decreased by 39% following treatment. Subsequent to the latter observation, possible lipid-lowering properties of the extract were investigated on other models of hyperlipidaemia and ciprofibrate, a well-established hypolipidaemic drug, was used as a reference compound. Both drug reduced TG levels of rats on hyperlipidaemic diet in a dose-dependent fashion. When administered at single doses over the same experimental period, blueberry and ciprofibrate were effective in lowering TG concentrations in ethanol-treated normolipidaemic animals and in genetically hyperlipidaemic Yoshida rats. Unlike ciprofibrate, however, blueberry failed to prevent the rise in plasma TG elicited by fructose and did not affect free fatty acid levels in any of the above experimental conditions. In rats treated with Triton WR-1339, blueberry feeding induced an hypolipidaemic activity one hour after injection but proved to be ineffective at later time points, thus suggesting that its hypolipidaemic action may reflect improved TG-rich lipoprotein catabolism. In addition, ciprofibrate and the extract were tested for antithrombotic activity using a collagen-triggered model of venous thrombosis in diabetic and Yoshida rats. Only ciprofibrate, however, significantly reduced thrombus formation in diabetics, possibly because of its effects on free fatty acid metabolism, whereas no effect was observed in Yoshida rats. In conclusion, the present findings indicate that active consituent(s) of Vaccinium myrtillus L. leaves may prove potentially useful for treatment of dyslipidaemiae associated with impaired TG-rich lipoprotein clearance.