Investigation on rare nuclear processes in Hf nuclides

In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes is presented. In particular, the investigations using HP-Ge spectrometry and Hf-based crystal scintillators are focused; the potentiality and the results of the "source = detector" approach are underlined. In addition, a short introduction concerning the impact of such kind of research in the context of astroparticle and nuclear physics is pointed out. In particular, the study of α decay and double beta decay of 174Hf, 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels have been discussed. The observation of α decay of 174Hf isotope to the ground state with a T1/2=7.0(1.2)×1016 y is reported and discussed. No decay was detected for α decay of 174Hf isotope at the first excited level of daughter and of 176Hf, 177Hf, 178Hf, 179Hf, 180Hf isotopes either to the ground state or to the lower bounded levels. The T1/2 lower limits for these decays are at the level of 1016–1020 y. Nevertheless, the T1/2 lower limits for the transitions of 176Hf→172Yb (0+→0+) and 177Hf→173Yb (7/2−→5/2−) are near to the theoretical predictions, giving hope to their observation in the near future. All the other experimental limits (∼1016–1020 y) are absolutely far from the theoretical expectations. The experiments investigating the 2ϵ and ϵβ+ processes in 174Hf are also reported; the obtained half-life limits are set at the level of 1016–1018 y. Moreover, we estimate the T1/2 of 2ν2ϵ of 174Hf decay at the level of (0.3–6) × 1021 y (at now the related measured lower limit is 7.1×1016 y)

LUCE: A milli-Kelvin calorimeter experiment to study the electron capture of 176Lu

The LUCE (LUtetium sCintillation Experiment) project will search for the 176Lu electron capture based on a milli-Kelvin calorimetric approach. This decay is of special interest in the field of nuclear structure, with implications for the s-process and for a better comprehension of the nuclear matrix elements of neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) and two-neutrino double beta decay (2{\nu}\b{eta}\b{eta}). Possible impacts also include the development of a new class of coherent elastic neutrino-nucleus scattering (CE{\nu}NS) and spin-dependent (independent) dark matter detectors. We report on the current status and design of a novel detector cryogenic-module for the measurement of the electron capture and detail a future measurement plan.Comment: proceeding

Pushing the frontier of WIMPy inelastic dark matter: Journey to the end of the periodic table

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 versio

Double beta decay search with CUPID-0: Results and Perspectives

International audienceCUPID-0 is the first large mass experiment based on cryogenic calorimeters (bolometers) that implements the dual read-out of light and heat for background rejection. The detector, consisting of 24 enriched Zn$^{82}$Se crystals (5.28 kg of $^{82}$Se), is taking data in the underground LNGS (Italy) from March 2017. In this contribution we present the analysis that allowed to set the most stringent limit on the half-life of neutrino-less double beta decay of $^{82}$Se. We prove that the particle identification, enabled by the simultaneous read-out of heat and light, provides an unprecedented background level for cryogenic calorimeters of few 10$^{−3}$ counts/keV/kg/y. Finally, we discuss the impact of these results on next generation projects

A Search for Low-mass Dark Matter via Bremsstrahlung Radiation and the Migdal Effect in SuperCDMS

In this paper, we present a re-analysis of SuperCDMS data using a profile likelihood approach to search for sub-GeV dark matter particles (DM) through two inelastic scattering channels: bremsstrahlung radiation and the Migdal effect. By considering possible inelastic scattering channels, experimental sensitivity can be extended to DM masses that would otherwise be undetectable through the DM-nucleon elastic scattering channel, given the energy threshold of current experiments. We exclude DM masses down to $220~\textrm{MeV}/c^2$ at $2.7 \times 10^{-30}~\textrm{cm}^2$ via the bremsstrahlung channel. The Migdal channel search excludes DM masses down to $30~\textrm{MeV}/c^2$ at $5.0 \times 10^{-30}~\textrm{cm}^2$.Comment: This paper is being withdrawn due to an error in data selection during the analysis. Although incorrect, the limits are roughly representative of the sensitivity. The new corrected version of the result will be uploaded once read