Search

A new study of double beta decay processes in natural Zr isotopes using Zr metal samples and an ultra-low-background high-purity germanium detectors was performed at Laboratori Nazionali del Gran Sasso of INFN (Italy). Two data sets were collected with a 736.35 g and a 129.94 g Zr metal over 59.7 days and 37.3 days, respectively, and were used for a detailed analysis. A new limit on the double beta decay of $$^{94}$$ 94 Zr to the 1st excited level of $$^{94}$$ 94 Mo was set as $$T_{1/2}^{\beta \beta } > 2.1\times 10^{20}~\text {year}$$ T 1 / 2 β β > 2.1 × 10 20 year , which is a factor of three better than the previous result. It is shown that the current radiopurity of Zr metal (tens of Bq/kg), produced via two methods, do not comply with the radiopurity requirements for low-background experiments. Hence, we propose to use a purified ZrCl$$_{4}$$ 4 powder in an optimized geometry as a new approach for future experiments with extended sensitivity focused on studies of rare nuclear processes in Zr isotopes.

Cs2HfCl6 (CHC) and Cs2ZrCl6 (CZC) single crystals were grown by a vertical Bridgman method. Luminescence and charge trapping properties were studied in CHC crystals by the correlated measurements of electron paramagnetic resonance (EPR), radioluminescence (RL) and thermally stimulated luminescence (TSL) techniques. CZC crystals were studied by the same set of measurements in order to find correlations between CHC and CZC crystals. EPR spectra measured before and after X-ray irradiation in both CHC and CZC samples were attributed with the typical signals of the Vk(a) hole trapping center (Cl2− pseudomolecular ion), which has recently been reported though the magnitude of the signal was much smaller in the CZC crystal. Besides the Vk(a) signal, another spectrum was observed in both samples; however, its intensity was at a very low level. It has been tentatively ascribed to the complex HCl-related hole trapping center. TSL glow curves measured in both CHC and CZC samples within the 10–500 K temperature range were composed of 6–8 complex peaks. The dominating peak at about 100–120 K originates from the de-trapping of holes at the Vk(a) trapping center. Scintillation characteristics of CHC crystal were studied over the temperature range of 9–295 K. Scintillation decay curves were fitted by three components. The CHC crystal demonstrated a much similar light yield of ca. 20 500 ph per MeV at room temperature and 9 K. The temperature dependence of the scintillation light output exhibits an unusual s-shaped character with the drop at around 100 K that correlates well with the decrease in the Vk(a) EPR signal, evidencing detrapping of holes trapped at the Vk(a) center in the CHC crystal. Therefore, the Vk(a) center was assumed to be the part of Hf3+–Cl2− self-trapped exciton (STE) that participates in the emission above 100 K becoming “frozen” below 100 K. RL and TSL spectra were complex in the CHC sample composed of two and three overlapping bands, respectively. One of the components peaking at 2.65 eV originated from the Zr-related STE.

Crystals of metal hexachlorides Cs

As one of the primordial radioactive isotopes, $$^{232}\mathrm{Th}$$ 232Th mainly undergoes $$\alpha $$ α -decay with a half-life of $$1.402\cdot 10^{10}$$ 1.402·1010 years. However, it is also one of 35 double beta decay candidates in which the single $$\beta $$ β -decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle were measured in a HPGe well-detector at the Gran Sasso Underground Laboratory with a total exposure of 3.25 g$$\times $$ × d. We obtain half-life limits on all double beta decay modes of $$^{232}\mathrm{Th}$$ 232Th to excited states of $$^{232}\mathrm{U}$$ 232U on the order of $$10^{11-15}$$ 1011-15 years. For the most likely transition into the 0$$^+_1$$ 1+ state we find a lower half-life limit of $$6.7\cdot 10^{14}$$ 6.7·1014 years (90% C.I.). These are the first constraints on double beta decay excited state transition in $$^{232}\mathrm{Th}$$ 232Th .

International audience; CUPID-0 is a pilot experiment in scintillating cryogenic calorimetry for the search of neutrino-less double beta decay. 26 ZnSe crystals were operated continuously in the first project phase (March 2017 - December 2018), demonstrating unprecedented low levels of background in the region of interest at the Q-value of $^{82}\rm{Se}$. From this successful experience comes a demonstration of full alpha to beta/gamma background separation, the most stringent limits on the $^{82}\rm{Se}$ neutrino-less double beta decay, as well as the most precise measurement of the $^{82}$Se half-life. After a detector upgrade, CUPID-0 began its second and last phase (June 2019 - February 2020). We present the latest results on the neutrino-less double beta decay of $^{82}\rm{Se}$ with the full isotope exposure of $8.82~\rm{kg}\times\rm{yr}$. We set a lower bound to the ground state half life $\rm{T}_{1/2}( ^{82}\rm{Se})>4.6\times10^{24}$ yr (90 % C.I.). We review the most recent results from a Bayesian search for spectral distortions to the $^{82}\rm{Se}$ double-beta decay spectrum due to exotic decay modes.

The past few decades have seen major developments in the design and operation of cryogenic particle detectors. This technology offers an extremely good energy resolution - comparable to semiconductor detectors - and a wide choice of target materials, making low temperature calorimetric detectors ideal for a variety of particle physics applications. Rare event searches have continued to require ever greater exposures, which has driven them to ever larger cryogenic detectors, with the CUORE experiment being the first to reach a tonne-scale, mK-cooled, experimental mass. CUORE, designed to search for neutrinoless double beta decay, has been operational since 2017 at a temperature of about 10 mK. This result has been attained by the use of an unprecedentedly large cryogenic infrastructure called the CUORE cryostat: conceived, designed and commissioned for this purpose. In this article the main characteristics and features of the cryogenic facility developed for the CUORE experiment are highlighted. A brief introduction of the evolution of the field and of the past cryogenic facilities are given. The motivation behind the design and development of the CUORE cryogenic facility is detailed as are the steps taken toward realization, commissioning, and operation of the CUORE cryostat. The major challenges overcome by the collaboration and the solutions implemented throughout the building of the cryogenic facility will be discussed along with the potential improvements for future facilities. The success of CUORE has opened the door to a new generation of large-scale cryogenic facilities in numerous fields of science. Broader implications of the incredible feat achieved by the CUORE collaboration on the future cryogenic facilities in various fields ranging from neutrino and dark matter experiments to quantum computing will be examined., Comment: 45 pages, 14 figures

A 510 day long-term measurement of a 45.3 g platinum foil acting as the sample and high voltage contact in an ultra-low-background high purity germanium detector was performed at Laboratori Nazionali del Gran Sasso (Italy). The data was used for a detailed study of double beta decay modes in natural platinum isotopes. Limits are set in the range $\mathcal{O}(10^{14} - 10^{19})$ yr (90% C.L.) for several double beta decay transitions to excited states confirming, and partially extending existing limits. The highest sensitivity of the measurement, greater than $10^{19}$ yr, was achieved for the two neutrino and neutrinoless double beta decay modes of the isotope $^{198}$Pt. Additionally, novel limits for inelastic dark matter scattering on $^{195}$Pt are placed up to mass splittings of approximately 500 keV. We analyze several techniques to extend the sensitivity and propose a few approaches for future medium-scale experiments with platinum-group elements., Comment: 15 pages, 3 figures, updated from journal review

Charge trapping and energy transfer processes are investigated in PbMoO4 single crystals by electron paramagnetic resonance (EPR) and wavelength-resolved thermally stimulated luminescence (TSL) in a correlated manner. New signals produced by two differently perturbed Mo5+ centers (Mo2 and Mo3) were observed in EPR spectra measured in the crystals after 420 nm light irradiation. Two sets of spin-Hamiltonian parameters, g tensor and the 95,97Mo, 207Pb (super) hyperfine tensors, have been determined and analyzed in terms of crystal field and LCAO-MO theories. A significant overlap of the Mo 5d1 and 6s6p ligand Pb orbitals was deduced for the Mo3 whereas the Mo2 center seemed to be not or very slightly affected by the lead orbitals. The obtained TSL results allowed to suppose the existence of at least six glow peaks produced by the de-trapping of charge carrier traps either of intrinsic nature or somehow stabilized by nearby accidental impurities. The peaks having maxima at 51 K, 79 K, and 89 K, in particular, were attributed to the Mo2 and Mo3 centers thermal destruction due to the observed correspondence between the kinetic parameters (trap depths and frequency factors) determined separately for the glow peaks and the EPR intensity thermal decay curves of these centers. The Mo2 EPR decay curve is rather complex experiencing two-step trend probably due to trapped electron recombination with some holes released below 60 K. It was further confirmed by the TSL emission maximum relatively large red shift (~ 100 nm) compared to the much smaller offset measured in radioluminescence. This phenomenon, observed also in samples obtained from extra-pure starting materials, was explained by three-component origin of the spectra, each having its own thermal fading rate. One of them ceased to exist above 60 K. The discussion of the obtained results is provided in comparison with other representatives of the scheelite tungstate and molybdate-based single crystals.

The studies and attempts to detail identification of the antique coin by means of analytical methods are described. The region of origin of the material components and the coin production period are determined. The coin material consists of copper (79%) and lead (16%) mined in the Limni deposit (eastern part of Cyprus). Copper-lead alloy is also doped with tin at 3%. The alloy also contains iron and arsenic as impurities at the level of 1%. The coin is classified as a small coin (folis) of the monetary system of Constantine Great. The production phase of the folis with high accuracy can be attributed to the second half of 324 BC. It is assumed that dilution of expensive copper with a large amount of cheap lead (16%) caused by the need for substantial savings in coin material due to an economic crisis in the Roman Empire after a long civil war. At the same time, the version of coin manufacturing by a counterfeiter is rejected.

Rare event physics demands very detailed background control, high-performance detectors, and custom analysis strategies. Cryogenic calorimeters combine all these ingredients very effectively, representing a promising tool for next-generation experiments. CUPID-0 is one of the most advanced examples of such a technique, having demonstrated its potential with several results obtained with limited exposure. In this paper, we present a further application. Exploiting the analysis of delayed coincidence, we can identify the signals caused by the $^{220}$Rn-$^{216}$Po decay sequence on an event-by-event basis. The analysis of these events allows us to extract the time differences between the two decays, leading to a new evaluation of $^{216}$ half-life, estimated as (143.3 $\pm$ 2.8) ms., 5 pages, 2 figures

We explore the reach of low-background experiments made of small quantities of heavy nuclear isotopes in probing the parameter space of inelastic dark matter that is kinematically inaccessible to classic direct detection experiments. Through inelastic scattering with target nuclei, dark matter can yield a signal either via nuclear recoil or nuclear excitation. We present new results based on this approach, using data from low-energy gamma quanta searches in low-background experiments with Hf and Os metal samples, and measurements with CaWO$_4$ and PbWO$_4$ crystals as scintillating bolometers. We place novel bounds on WIMPy inelastic dark matter up to mass splittings of about 640 keV, and provide forecasts for the reach of future experiments., Comment: 14 pages, 7 figures, 3 tables, matched published version

A search for alpha and double beta decays of ytterbium isotopes was performed with an ultra low-background high purity germanium detector at Gran Sasso Underground Laboratory (Italy). A 194.7 g Yb$$_2$$ 2 (C$$_2$$ 2 O$$_4$$ 4 )$$_3$$ 3 powder sample was measured for 11.3 days with a total Yb exposure of 1.25 kg$$\times $$ × day. Half-life limits for $$\alpha $$ α -decay modes of $$^{168}\mathrm Yb$$ 168 Y b , $$^{170}\mathrm Yb$$ 170 Y b , $$^{171}\mathrm Yb$$ 171 Y b , $$^{172}\mathrm Yb$$ 172 Y b , $$^{173}\mathrm Yb$$ 173 Y b , $$^{174}\mathrm Yb$$ 174 Y b and $$^{176}\mathrm Yb$$ 176 Y b into the first excited states have been obtained between $$6\times 10^{14}$$ 6 × 10 14 years and $$2\times 10^{16}$$ 2 × 10 16 years. These are the first experimental constraints of these decay modes. Double electron capture of $$^{168}\mathrm Yb$$ 168 Y b and double beta decay of $$^{176}\mathrm Yb$$ 176 Y b into the first excited 2$$^+$$ + and 0$$^+$$ + states could be excluded with limits between $$1\times 10^{14}$$ 1 × 10 14 years to $$8\times 10^{16}$$ 8 × 10 16 years. This improves the experimental information on some of the decay modes compared to previous constraints.

This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axion-like particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 gram Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 gram-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section $\bar{\sigma}_{e}$ is constrained for dark matter masses from 0.5--$10^{4} $MeV$/c^{2}$; in the mass range from 1.2--50 eV$/c^{2}$ the dark photon kinetic mixing parameter $\varepsilon$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above mentioned mass ranges are $\bar{\sigma}_{e}\,=\,8.7\times10^{-34}$ cm$^{2}$, $\varepsilon\,=\,3.3\times10^{-14}$, and $g_{ae}\,=\,1.0\times10^{-9}$., Comment: 5 pages + title and references, 3 figures and 1 table

A convincing observation of neutrino-less double beta decay (0$\nu$DBD) relies on the possibility of operating high energy-resolution detectors in background-free conditions. Scintillating cryogenic calorimeters are one of the most promising tools to fulfill the requirements for a next-generation experiment. Several steps have been taken to demonstrate the maturity of this technique, starting from the successful experience of CUPID-0. The CUPID-0 experiment demonstrated the complete rejection of the dominant alpha background measuring the lowest counting rate in the region of interest for this technique. Furthermore, the most stringent limit on the $^{82}$Se 0$\nu$DBD was established running 26 ZnSe crystals during two years of continuous detector operation. In this contribution we present the final results of CUPID-0 Phase I including a detailed model of the background, the measurement of the $^{82}$Se 2$\nu$DBD half-life and the evidence that this nuclear transition is single state dominated., Comment: 40th International Conference on High Energy physics - ICHEP2020 July 28 - August 6, 2020 Prague, Czech Republic (virtual meeting)

For the first time, vanadium of biological origin, extracted from centrifugal fraction of vanadium-storing blood cells of the Ascidia sydneiensis samea species, was characterized as regards its isotopic composition and content of natural radioactive elements potassium (K), thorium (Th) and uranium (U). The natural abundance of vanadium isotopes has been confirmed with high accuracy, thus excluding a possible selectivity within bio-chemical reactions of vanadium concentration in blood cells from seawater. A large potassium concentration (up to 5500 × 10−6 g g−1) was found in the blood cell samples. The concentration of thorium was determined to be about 30 × 10−9 g g−1, while the uranium concentration was about 150 × 10−9 g g−1. Hence, a highly efficient two-stage purification approach with a total vanadium recovery of better than 70% was developed and applied. The final concentrations of K

We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axionlike particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from 40 eV/c2 to 500 keV/c2 for both candidates, excluding previously untested parameter space for masses below ∼1 keV/c2. For the kinetic mixing of dark photons, values below 10−15 are reached for particle masses around 100 eV/c2; for the axioelectric coupling of axionlike particles, values below 10−12 are reached for particles with masses in the range of a few-hundred eV/c2.

A PbMoO4 single crystal as a perspective detector for neutrinoless double beta decay experiment was grown by the Czochralski technique from high purity raw materials including archaeological lead. Charge trapping and energy transfer phenomena in this crystal have been studied by electron paramagnetic resonance (EPR) and wavelength-resolved thermally stimulated luminescence (TSL). EPR revealed several impurities, which however do not participate in the charge trapping processes: Gd3+, Cr3+, Mn2+. Self-trapped electron and (MoO4)3--VPb centers creation under laser light was confirmed. At least six glow peaks related to the thermal release of the charge carriers were observed having maxima at 41 K, 53 K, 83 K, 90 K, 105 K and 118 K. The peak at 41 K was ascribed to the de-trapping of self-trapped electrons. The 53 K one, in particular, is created by re-trapping processes. Partial cleaning procedure followed by the initial rise method allow to determine the trap depths and frequency factors for the 90 K and 105 K glow peaks. They have been referred to the (MoO4)3--VPb decay. A three-component analysis of the spectra could explain the observed 100 nm red shift of the thermo-luminescence emission maximum.

International audience; A convincing observation of neutrino-less double beta decay (0vDBD) relies on the possibility of operating high-energy resolution detectors in background-free conditions. Scintillating cryogenic calorimeters are one of the most promising tools to fulfill the requirements for a next-generation experiment. Several steps have been taken to demonstrate the maturity of this technique, starting form the successful experience of CUPID-0. The CUPID-0 experiment collected almost 10 kg y of exposure, running 26 Zn82Se crystals during two years of continuous detector operation. The complete rejection of the dominant α background was demonstrated, measuring the lowest counting rate in the region of interest for this technique. Furthermore, the most stringent limit on the 82Se 0vDBD was established. In this contribution we present the final results of CUPID-0 phase-I, including a detailed model of the background and the measurement of the 2vDBD half-life.

We present limits on spin-independent dark matter-nucleon interactions using a $10.6$ $\mathrm{g}$ Si athermal phonon detector with a baseline energy resolution of $\sigma_E=3.86 \pm 0.04$ $(\mathrm{stat.})^{+0.19}_{-0.00}$ $(\mathrm{syst.})$ $\mathrm{eV}$. This exclusion analysis sets the most stringent dark matter-nucleon scattering cross-section limits achieved by a cryogenic detector for dark matter particle masses from $93$ to $140$ $\mathrm{MeV}/c^2$, with a raw exposure of $9.9$ $\mathrm{g}\cdot\mathrm{d}$ acquired at an above-ground facility. This work illustrates the scientific potential of detectors with athermal phonon sensors with eV-scale energy resolution for future dark matter searches., Comment: 7 pages, 4 figures, this version includes ancillary files from official data release

We report on the measurement of the two-neutrino double-β 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-β 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.

An attempt to identify artifacts using only analytical research methods is described. The regions of origin and production period of the lead anchor stock are determined, by investigating both the material of the stock and various inclusions into the stock’s material. Based on results of a complex of physical investigations, the stock is found to be made of high purity lead (99.95%) from the Lavrion mine (Greece). Its production relates to the period of AD 1st century – the beginning of AD 2nd century. It is assumed that the presence of a large amount of inclusions indicates the need for significant material savings for the production of the stock during the period of the depletion of lead deposits. The nail, founded inside the stock body, believed to be put into the casting mold, as a guard.

A newly developed experimental technique based on 169Tm-containing cryogenic bolometer detector was employed in order to perform the search for solar axions. The inclusion of target material into the active detector volume allowed for significant increase in sensitivity to axion parameters. A short 6.6 days measurement campaign with 8.18 g detector crystal yielded the following limits on axion couplings: | g A γ ( g A N 0 + g A N 3 ) ≤ 1.44 × 10 − 14 GeV − 1 and | g A e ( g A N 0 + g A N 3 ) ≤ 2.81 × 10 − 16 . The achieved results demonstrate high scalability potential of presented experimental approach.

The internal contamination (radio-purity) of a cesium hafnium chloride (Cs 2 HfCl 6 ) crystal scintillator and its starting material (CsCl, HfCl 4 initial and after 3-fold static sublimation purification) was studied by HR-ICP-MS and with an ultra-low-background high purity germanium (ULB-HPGe) detector deep underground. This study was conducted for the purpose of assessing the feasibility of using CHC as a potential detector to the search for rare α decay occurring in Hafnium isotopes. Despite the low radio-purity of starting material, the resulting analysis concluded that the grown CHC crystal is free of nuclides of the U/Th natural decay chain. Only a limit was set on their activities to a few mBq/kg. However, the crystal was found to contain artificial and cosmogenic radionuclides: 137 Cs at 0.8 Bq/kg, 132 Cs at 25 mBq/kg, 134 Cs at 52 mBq/kg and 181 Hf at 14 mBq/kg.

This paper reports on the development of a technology involving $$^{100}\hbox {Mo}$$ 100 Mo -enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass ( $$\sim 1~\hbox {kg}$$ ∼ 1 kg ), high optical quality, radiopure $$^{100}\hbox {Mo}$$ 100 Mo -containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2–0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of $$^{100}\hbox {Mo}$$ 100 Mo (3034 keV) is 4–6 keV FWHM. The rejection of the $$\alpha $$ α -induced dominant background above 2.6 MeV is better than $$8\sigma $$ 8 σ . Less than $$10~\upmu \hbox {Bq/kg}$$ 10 μ Bq/kg activity of $$^{232}\hbox {Th}\, (^{228}\hbox {Th})$$ 232 Th ( 228 Th ) and $$^{226}\hbox {Ra}$$ 226 Ra in the crystals is ensured by boule recrystallization. The potential of $$^{100}\hbox {Mo}$$ 100 Mo -enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only $$10~\hbox {kg}\times \hbox {d}$$ 10 kg × d exposure: the two neutrino double-beta decay half-life of $$^{100}\hbox {Mo}$$ 100 Mo has been measured with the up-to-date highest accuracy as $$T_{1/2}$$ T 1 / 2 = [6.90 ± 0.15(stat.) ± 0.37(syst.)] $$\times ~10^{18}~\hbox {years}$$ × 10 18 years . Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of $$^{100}\hbox {Mo}$$ 100 Mo .

The results of investigation into cesium hafnium chloride (Cs 2 HfCl 6 ) scintillating crystals as a promising detector to search for rare nuclear processes occurring in Hf isotopes is reported. The light output, quenching factor, and pulse-shape characteristics have been investigated at room temperature. The scintillation response of the crystal induced by α -particles and γ -quanta were studied to determine possibility of particle discrimination. Using the optimal filter method we obtained clear separation between signals with a factor of merit (FOM) = 9.3. This indicates that we are able to fully separate signals originating from α -particles and γ -quanta. Similar fruitful discrimination power was obtained by applying the mean time method (FOM = 7) and charge integration method (FOM = 7.5). The quenching factor for collimated 4 MeV α -particles is found to be 0.36, showing that α -particles generate more than a third of the light compared to γ -quanta at the same energy.

A complex method for refining lead by distillation in vacuum has been described. A brief comparative description of different methods of lead refining was submitted. Analysis of different methods showed that to increase the efficiency of lead deep cleaning the development of complex refining processes is required. The computational studies of the behavior of impurity elements in the ancient lead are performed. The ideal coefficients of impurities separation αi are calculated at lead distillation temperatures. The range of volatile and nonvolatile impurities was detected by magnitude αi in lead. Performed computational studies of the impurity elements behavior in lead formed the basis for developing an integrated method of deep refining of ancient lead. To implement this approach the special distillation device was developed, and the procedure of deep purification of lead was described.The results of the study of the deep refining ancient lead have been demonstrated. The cleaning high efficiency of the proposed approach, combined with high performance and yield of the suitable product, was shown. A pilot batch of ancient lead containing base metal > 99.998 wt. % suitable for growing high quality scintillation crystals PbWO4 and PbMoO4 has been produced.

The current results of direct dark matter searches are controversial. The long-standing dark-matter claim from the DAMA/LIBRA collaboration is excluded by null-results of several other experiments. However, a comparison of the results by experiments with different detector materials introduces model dependencies. The R&D project COSINUS (Cryogenic Observatory for SIgnatures seen in Next-generation Underground Searches) aims to develop cryogenic detectors based on (hygroscopic) sodium iodide (NaI). If successful, such detectors could be used in future experiments to investigate the origin of the annual modulation signal seen by the NaI-based scintillation detectors of the DAMA/LIBRA experiment. COSINUS detectors should be able to simultaneously detect phonons and scintillation light produced by a particle interaction inside the NaI crystal. This technique allows for an active suppression of β/γ backgrounds as well as detailed studies of a large variety of dark-matter models predicting nuclear interactions. For such kind of studies only moderate exposures of ≲100kg-days are needed. In addition to the projected sensitivities of COSINUS detectors, we also show the result of first tests using (only mildly hygroscopic) caesium iodide (CsI) crystals as target material. For this measurement we achieved an energy threshold of ∼4.7 keV for nuclear recoils.

We present the search for Lorentz violation in the double beta decay of ^{82}Se~with CUPID-0, using an exposure of 9.95 kg x y. We found no evidence for the searched signal and set a limit on the isotropic components of the Lorentz violating coefficient of $\mathring{a}_{\text{of}}^{(3)} < 4.1\cdot10^{-6}$ GeV (90\% Credible Interval). This results is obtained with a Bayesian analysis of the experimental data and fully includes the systematic uncertainties of the model. This is the first limit on $\mathring{a}_{\text{of}}^{(3)}$ obtained with a scintillating bolometer, showing the potentiality of this technique.