Search

Rare-event search experiments located on-surface, such as short-baseline reactor neutrino experiments, are often limited by muon-induced background events. Highly efficient muon vetos are essential to reduce the detector background and to reach the sensitivity goals. We demonstrate the feasibility of deploying organic plastic scintillators at sub-Kelvin temperatures. For the NUCLEUS experiment, we developed a cryogenic muon veto equipped with wavelength shifting fibers and a silicon photo multiplier operating inside a dilution refrigerator. The achievable compactness of cryostat-internal integration is a key factor in keeping the muon rate to a minimum while maximizing coverage. The thermal and light output properties of a plastic scintillation detector were examined. We report first data on the thermal conductivity and heat capacity of the polystyrene-based scintillator UPS-923A over a wide range of temperatures extending below one Kelvin. The light output was measured down to 0.8 K and observed to increase by a factor of 1.61 ± 0.05 compared to 300 K. The development of an organic plastic scintillation muon veto operating in sub-Kelvin temperature environments opens new perspectives for rare-event searches with cryogenic detectors at sites lacking substantial overburden. [ABSTRACT FROM AUTHOR]

An experiment to search for 2ε-, εβ+ - and 2β+ -decays of 106Cd, using a 215 g cadmium tungstate scintillation crystal enriched at 66 % by 106Cd (106CdWO4) is carried out at the Gran Sasso underground laboratory (Italy). Events in the 106CdWO4 detector are recorded in (anti)coincidences with two large-volume CdWO4 scintillation counters. The design of the detector system, calibration and background measurements, methods, and results of data analysis to determine key detector characteristics are described. The experimental data are compared with Monte Carlo simulation results, and a background model is constructed. The radioactive contamination of the setup components is studied. The sensitivity of the experiment approaches the level of theoretical predictions for the 2Vεβ + -decay channel, while for other possible 2β-decay channels it is already on the level of lim T1/2 ~ 1021 - 1022 years. [ABSTRACT FROM AUTHOR]

DAMA/LIBRA is an experiment investigating the presence of Dark Matter particles in the Galactic halo. The target detectors are ultra-radiopure NaI(Tl) crystal scintillators. They are placed inside a low-background set-up at the underground Gran Sasso National Laboratory (LNGS) of the I.N.F.N.. DAMA/LIBRA has been in operation in two phases by pursuing the annual modulation as signature to point-out in a model-independent way the presence and the features of the Dark Matter (DM) signal in the counting rate. In its second phase of measurement, DAMA/LIBRA–phase2, it has been working with a lower software energy threshold with respect to DAMA/LIBRA–phase1. DAMA/LIBRA–phase2 confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 11.8 σ C.L. in the energy region (1–6) keV. In the energy region (2–6) keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1, the achieved C.L. for the full exposure (2.86 ton × yr, 22 annual cycles) is 13.7 σ ; the modulation amplitude of the single-hit scintillation events is: (0. 0 1 0 1 4 ± 0. 0 0 0 7 4) cpd/kg/keV, and the measured period and phase are well in agreement with those expected for DM particles. Detailed studies have excluded that the observed modulation is due to systematics or side reaction. In this proceedings the results achieved so far by the DAMA/LIBRA experiment and the new ones corresponding to two new annual cycles of data will be presented. Future perspectives of the experiment will be addressed. [ABSTRACT FROM AUTHOR]

The ZnWO4 crystal scintillator is a promising detector for low counting experiments thanks to the high level of radiopurity and reasonably high optical and scintillation properties. In particular, ZnWO4 scintillators can be utilized in the searches for double beta processes, in the investigation of rare alpha decays and Dark Matter. In fact, one of its main characteristics is to be an anisotropic detector. In the case of interaction of heavy particles or nuclear recoils, the light output and the time profile of the scintillation pulse depend on the direction of the particles with respect to the crystal axes; no difference is observed for γ / β radiation. These anisotropic features can offer a unique possibility to exploit the so-called directionality approach in order to investigate the presence of the Dark Matter candidates which induces nuclear recoils. In fact, their use can overcome the difficulty of detecting extremely short nuclear recoil traces. [ABSTRACT FROM AUTHOR]

Recently, efforts on the building of Hf-based crystal scintillators have been performed. The so-called "source = detector" approach has been implemented to study rare nuclear processes in Hf isotopes with higher efficiency with respect to the HP-Ge spectrometry. In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes are presented. [ABSTRACT FROM AUTHOR]

Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. Their use can overcome the difficulty of detecting extremely short nuclear recoil tracks. In this paper, we present recent measurements performed on the anisotropic response of a ZnWO4 crystal scintillator to nuclear recoils in the framework of the ADAMO project. The anisotropic features of the ZnWO4 crystal scintillators were initially measured with α particles; those results have also been confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained using a neutron generator at ENEA-Casaccia and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). The anisotropy of the light response for nuclear recoils in the ZnWO4 crystal scintillator has been determined at 5.4 standard deviations. These results open the possibility to realize a pioneering experiment to investigate the above-mentioned DM candidates by means of the directionality. [ABSTRACT FROM AUTHOR]

A radiopure cadmium tungstate scintillator enriched in 1 0 6 Cd to 66% ( 1 0 6 CdWO4) operates in coincidence (anticoincidence) with two CdWO4 scintillation counters to search for double-beta processes in 1 0 6 Cd. After 26033 h of data taking, no effects were observed. The half-life limits on the different channels of 1 0 6 Cd double-beta decay were set at the level of T 1 / 2 ∼ 1 0 2 0 − 1 0 2 2 yr. A new stage of the experiment is running with an improved sensitivity to all the decay channels thanks to reduction of the background and improvement of the energy resolution. [ABSTRACT FROM AUTHOR]

The half-life of 212 Po was measured with the highest up-to-date accuracy as T 1 / 2 = 295.1 (4) ns by using thorium-loaded liquid scintillator. [ABSTRACT FROM AUTHOR]

Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach in order to investigate the presence of those Dark Matter (DM) candidates inducing nuclear recoils. In fact, their use can overcome the difficulty of detecting extremely short nuclear recoil traces. In this paper we present recent measurements performed on the anisotropic response of a ZnWO 4 crystal scintillator to nuclear recoils, in the framework of the ADAMO project. The anisotropic features of the ZnWO 4 crystal scintillators were initially measured with α particles; those results have been also confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained by using a neutron generator at ENEA-CASACCIA and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). From these measurements, the anisotropy of the light response for nuclear recoils in the ZnWO 4 crystal scintillator has been determined at 5.4 standard deviations. [ABSTRACT FROM AUTHOR]

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The radioactive contamination of a BaF scintillation crystal with mass of 1.714 kg was measured over 101 hours in the low-background DAMA/R&D set-up deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (LNGS, Italy). The half-life of Po (present in the crystal scintillator due to contamination by radium) was measured as $ T_{1/2}({}^{212}Po)$ = 298.8±0.8( stat.)±1.4( syst.) ns by the analysis of the events' pulse profiles. The Rn nuclide is known as 100% decaying via the emission of the $ \alpha$ particle with T = 3.82 d; however, its $ \beta$ decay is also energetically allowed with $ Q_{\beta}=24\pm 21$ keV. Search for decay chains of events with specific pulse shapes characteristic for $ \alpha$ or for $ \beta/\gamma$ signals and with known energies and time differences allowed us to set, for the first time, the limit on the branching ratio of Rn relatively to $ \beta$ decay as $ B_{\beta} < 0.13$ % at 90% C.L. (equivalent to limit on partial half-life $ T_{1/2}^{\beta}> 8.0$ y). The half-life limits of Pb, Rn and Ra relatively to 2 $ \beta$ decays are also improved in comparison with the earlier results. [ABSTRACT FROM AUTHOR]

The DAMA project is an observatory for rare processes operating deep underground at the Gran Sasso National Laboratory of the I.N.F.N.. In particular, the main apparatus DAMA/LIBRA is mainly dedicated to the investigation of the presence of Dark Matter (DM) particles in the galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA and the former DAMA/Nal (exposed masses: ≃250 kg and ≃ 100 kg of highly radiopure Nal(Tl), respectively) experiments have released so far a total exposure of 1.17tonxyr, collected over 13 annual cycles. They have obtained a positive model independent result for the presence of DM particles in the galactic halo at 8.9σ C.L.. Some of the obtained results are shortly summarized and future perspectives mentioned. [ABSTRACT FROM AUTHOR]

The DAMA/LIBRA experiment is mainly dedicated to the investigation on DM particles in the Galactic halo by exploiting the model independent Dark Matter (DM) annual modulation signature. The present DAMA/LIBRA and the former DAMA/NaI (exposed masses: about 250 kg and about 100 kg of highly radiopure NaI(Tl), respectively) experiments have released so far a total exposure of 1.17 t . yr collected over 13 annual cycles; they provide a model independent evidence of the presence of DM particles in the galactic halo at 8.9 σ C.L. The data of another annual cycle in the same DAMA/LIBRA running conditions are at hand. After the substitution (at fall 2010) of all the photomultipliers (PMTs) with new ones, having higher quantum efficiency, DAMA/LIBRA has entered the phase 2; that substitution has allowed to lower the software energy threshold of the experiment in the present data taking. Future perspectives are mentioned. [ABSTRACT FROM AUTHOR]

In the anisotropic scintillators the light output and the pulse shape for heavy particles ( p, α, nuclear recoils) depend on the direction with respect to the crystal axes; the response to γ/ β radiation is isotropic instead. This feature offers the possibility to study the directionality approach, which is applicable in the particular case of those Dark Matter candidate particles inducing just nuclear recoils. Among the anisotropic scintillators, the ZnWO has unique features, which make it an excellent candidate for this type of research, and there is still plenty of room for the improvement of its performances. In this paper the possibility of a low background pioneer experiment (named ADAMO-Anisotropic detectors for DArk Matter Observation) to exploit deep underground the directionality approach by using anisotropic ZnWO scintillators is discussed. [ABSTRACT FROM AUTHOR]

Searches for non-paulian nuclear processes, i.e. processes normally forbidden by the Pauli–Exclusion–Principle (PEP) with highly radiopure NaI(Tl) scintillators allow the test of this fundamental principle with high sensitivity. Status and perspectives are addressed. [ABSTRACT FROM AUTHOR]

Abstract: In this paper the performances and the potential of applications of a CeCl3 scintillator are investigated. In particular, the light response, the energy resolution, the light ratio, the discrimination capability and the main radioactive contaminants have been studied. All the measured features put forward the CeCl3 scintillator as an interesting detector medium for several possible applications in the field of Nuclear and Particle Physics and, potentially, of Medical Imaging. [Copyright &y& Elsevier]

The search for double-β processes in 108Cd and 114Cd was realized by using data of the low-background experiment with the CdWO4 crystal scintillator at the Gran Sasso National Laboratories of the INFN. New improved half-life limits on double-beta processes were established, in particular T 1/2 0ν2ɛ( ^108Cd ) ≥ 1.0(2.7)×1018 yr, T 1/2 2ν2β( ^114Cd ) ≥ 1.3(2.1)×1018 yr, and T 1/2 0ν2β( ^114Cd ) ≥ 1.1(2.5)×1021 yr at 90(68)% C.L. [ABSTRACT FROM AUTHOR]

DAMA is an observatory for rare processes based on the development and use of various kinds of radiopure scintillators; it is operative deep underground at the Gran Sasso National Laboratory of the INFN. Several low background setups have been realized and many rare processes have been investigated. In particular, the DAMA/NaI setup ( ≃ 100kg highly radiopure NaI(Tl)) has effectively investigated the model-independent annual modulation signature; the data of seven annual cycles (total exposure of 107731kg × d) have offered a 6.3σ C.L. model-independent evidence for the presence of a Dark Matter particle component in the galactic halo. Some of the many possible corollary model-dependent quests for the candidate particle have also been investigated. At present, the second-generation DAMA/LIBRA setup ( ≃ 250kg highly radiopure NaI(Tl)) is in operation deep underground. This paper summarizes the main aspects. [ABSTRACT FROM AUTHOR]

The DAEMONs (DArk Electric Matter Objects) have been suggested as a possible exotic component in cosmic rays able to contribute to the Dark Matter; they belong to the wide class of the Elementary Black Holes (EBH) deeply discussed in literature. A preliminary possible DAEMONs direct detection, at ≃3σ C.L., was originally suggested by the sea-level St. Petersburg experiment (SPb); a DAEMONs flux: (1.0±0.3) DAEMONs/(days m2 sr) can be derived. Here the results obtained by the sea-level NEMESIS experiment, which has exploited the same detection approach, are presented; they restrict the DAEMONs flux to be less than 0.32 DAEMONs/(days m2 sr) at 90% C.L. [ABSTRACT FROM AUTHOR]

Abstract: The presence of Dark Matter (DM) particles in the galactic halo can be unambiguously pointed out in a model-independent way by exploiting the DM annual modulation signature with an apparatus of specific features placed deep underground. At present DAMA/LIBRA is running at the Gran Sasso National Laboratory of the I.N.F.N. and has presented so far the results obtained with the data collected in the first six annual cycles (exposure 0.87 ton yr). When including the exposure of the former DAMA/NaI experiment (0.29 ton yr), the total exposure is 1.17 ton yr for 13 annual cycles, a value order of magnitude larger than those typically released in the field. These DAMA/LIBRA data have further confirmed the model-independent evidence of the presence of Dark Matter particles in the galactic halo on the basis of the exploited DM signature (8.9 C.L. for the cumulative exposure). [Copyright &y& Elsevier]

Abstract: The radioactive contamination of ZnWO4 crystal scintillators has been measured deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN in Italy with a total exposure 3197kgh. Monte Carlo simulation, time–amplitude and pulse–shape analyses of the data have been applied to estimate the radioactive contamination of the ZnWO4 samples. One of the ZnWO4 crystals has also been tested by ultra-low background γ spectrometry. The radioactive contaminations of the best ZnWO4 samples are estimated to be less than 0.002mBq/kg (228Th and 226Ra), the total α activity is 0.18mBq/kg. The β active 65Zn and the α active 180W have been detected in ZnWO4 crystals. The effect of the re-crystallization on the radiopurity of the ZnWO4 crystal has been studied. The radioactive contamination of the ceramic components of the set-ups used in the crystals growth has been checked by low background γ spectrometry. Some ideas for future improvement of the radiopurity level of ZnWO4 crystal scintillators are briefly discussed. [ABSTRACT FROM AUTHOR]

Abstract: Double beta processes in 64Zn, 70Zn, 180W, and 186W have been searched for with the help of large volume (0.1–0.7 kg) low background ZnWO4 crystal scintillators at the Gran Sasso National Laboratories of the INFN (Italy). The total measurement time exceeds ten thousand hours. New improved half-life limits on double electron capture and electron capture with positron emission in 64Zn have been set, in particular (all the limits are at 90% C.L.): , , and . In addition, new bounds were set for different modes of 2β processes in 70Zn, 180W, and 186W at the level of 1017–1020 yr. [Copyright &y& Elsevier]