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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\\[\\cdot \\]yr (2.24\\[\\times \\]10\\[^{25}\\] emitters\\[\\cdot \\]yr). We found no evidence of the decays and set the most stringent limits on the widths of these processes: \\[\\varGamma \\](\\[^{82}\\]Se \\[\\rightarrow ^{82}\\]Kr\\[_{0_1^+}\\])8.55\\[\\times \\]10\\[^{-24}\\] yr\\[^{-1}\\], \\[\\varGamma \\] (\\[^{82}\\] Se \\[\\rightarrow ^{82}\\] Kr \\[_{2_1^+}\\])\\[\\,{<}\\,6.25 \\,{\\times }\\,10^{-24}\\] yr\\[^{-1}\\], \\[\\varGamma \\](\\[^{82}\\]Se \\[\\rightarrow ^{82}\\]Kr\\[_{2_2^+}\\])8.25\\[\\times \\]10\\[^{-24}\\] yr\\[^{-1}\\] (90\\[\\%\\] credible interval).

The TRISTAN project is the upgrade of the KATRIN experiment designed for the search of sterile neutrinos by replacing the current KATRIN detector with a multipixel SDD (Silicon Drift Detector) matrix. We have characterized SDDs response to electrons using a SEM (Scanning Electron Microscope) as an electron source and a Geant4-based simulation whose output is processed with an empirical function to reproduce data. We have crosschecked this model by reconstructing backscattering measurements obtained using a radioactive electron source.

CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrinoless double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg year to search for the neutrinoless double beta decay of$$^{70}$$70 Zn and for the neutrinoless positron-emitting electron capture of$$^{64}$$64 Zn. We found no evidence for these decays and set 90$$\\%$$% credible interval limits of$$\\hbox {T}_{1/2}^{0\\nu \\beta \\beta }$$T 1 / 2 0 ν β β ($$^{70}$$70 Zn) > 1.6$$10^{21}$$10 21 year and$$\\hbox {T}_{1/2}^{0\\nu EC \\beta +}$$T 1 / 2 0 ν E C β + ($$^{64}$$64 Zn) > 1.2$$\\times 10^{22}$$× 10 22 year, surpassing by more than one order of magnitude the previous experimental results (Belli et al. in J Phys G 38(11):115107, https://doi.org/10.1088/0954-3899/38/11/115107 , 2011).

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 232Th and 238U 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.

We present the application of a simplified thermal model for the description of the response function of low-temperature calorimeters consisting of TeO 2 crystals read-out by NTD thermistors operated at temperatures T ∼ 10 mK. Relying on both the analysis of the NTD load curves (from which we measured the main thermal conductances of the system) (Biassoni et al. in J Low Temp Phys 206:80–96, 2022) and on the analysis of the shape of thermal pulses acquired at different temperatures, we identified and quantified the physical parameters that determine the characteristic time constants of the pulses. In particular, we identified three different contributions to the heat capacity of the detector: the crystal phonon system (scaling as T 3 ), the NTD electron system (scaling as T ) and a term related to the metalization process of the NTD electrodes (scaling as T - 2 ).

When simulating the response of a particle detector to an energy deposition, the pulse shape and the electronic noise are important features to be taken into account. In this work, we present a method to simulate a continuous stream of detector-like data, produced to mock the salient characteristics of the chosen setup. This technique allows the full reproduction of an experimental measurement, as well as providing a predictive tool to validate or train new analysis procedures. We present the algorithm used to produce these data, and we test its capabilities by reproducing the data output of an high-purity germanium detector.

The response of particle detectors to different types of radiation is not necessarily identical and, in some cases, neglecting this behavior can lead to a misinterpretation of the acquired data. While commercial radioactive sources are in general suitable to investigate the response to β ’s and γ ’s, in the case of α ’s the need for custom-made sources arises from the intrinsic properties of α radiation, which imposes that the emitter directly faces the detector. In this work, we show how to flexibly produce α sources to be employed in multiple studies of detector characterization. These are obtained starting from a set of primary sources obtained from the collection of radioactive 228 Ra ions at the ISOLDE facility at CERN. We illustrate the potential of this technique with practical cases of application to scintillators and bolometric detectors and examples of the results obtained so far.

The KATRIN (Karlsruhe Tritium Neutrino) experiment investigates the energetic endpoint of the tritium beta-decay spectrum to determine the effective mass of the electron anti-neutrino. The collaboration has reported a first mass measurement result at this TAUP-2019 conference. The TRISTAN project aims at detecting a keV-sterile neutrino signature by measuring the entire tritium beta-decay spectrum with an upgraded KATRIN system. One of the greatest challenges is to handle the high signal rates generated by the strong activity of the KATRIN tritium source while maintaining a good energy resolution. Therefore, a novel multi-pixel silicon drift detector and read-out system are being designed to handle rates of about 100 Mcps with an energy resolution better than 300 eV (FWHM). This report presents succinctly the KATRIN experiment, the TRISTAN project, then the results of the first 7-pixels prototype measurement campaign and finally describes the construction of the first TRISTAN module composed of 166 SDD-pixels as well as its implementation in KATRIN experiment.

Thermal detectors are a powerful instrument for the search of rare particle physics events. Inorganic crystals are classically used as thermal detectors held in supporting frames made of copper. In this work, a novel approach to the operation of thermal detectors is presented, where TeO 2 crystals are cooled down to ∼  10 mK in a light structure built with plastic materials. The advantages of this approach are discussed.

CUPID-0 is the first pilot experiment of CUPID, a next-generation project searching for neutrinoless double beta decay. In its first scientific run, CUPID-0 operated 26 ZnSe cryogenic calorimeters coupled to light detectors in the underground Laboratori Nazionali del Gran Sasso. In this work, we analyzed a ZnSe exposure of 11.34 kg year to search for the neutrinoless double beta decay of 70 Zn and for the neutrinoless positron-emitting electron capture of 64 Zn. We found no evidence for these decays and set 90 % credible interval limits of T 1 / 2 0 ν β β ( 70 Zn) > 1.6 10 21 year and T 1 / 2 0 ν E C β + ( 64 Zn) > 1.2 × 10 22 year, surpassing by more than one order of magnitude the previous experimental results (Belli et al. in J Phys G 38(11):115107, https://doi.org/10.1088/0954-3899/38/11/115107 , 2011).