![]() ![]() Thermal signals can be induced by electrons emitted in 0 νββ decays but also other background radiation, for example, γ and α particles from residual radioactive contaminants or cosmic ray muons.ĬUORE is protected by several means against backgrounds that can mimic a 0 νββ decay. 1c) is instrumented with a neutron-transmutation-doped germanium thermistor (NTD) 17 that converts thermal pulses into electric signals and a heater 18 to inject reference heat pulses for thermal gain stabilization 19. In a cryogenic calorimeter, the energy deposited by impinging radiation in the absorber crystal is turned into heat, resulting in a temperature rise (Extended Data Fig. In this Article, we describe the performance of CUORE over a four-year measurement campaign and the results of a new high-sensitivity 0 νββ decay search with over 1 t yr of TeO 2 exposure. To fully exploit the potential of TeO 2 crystals as cryogenic calorimeters, the CUORE Collaboration designed and built to our knowledge the largest dilution refrigerator ever constructed, capable of cooling approximately 1.5 t of material to a temperature of approximately 10 mK and maintaining it for years with a 90% duty cycle (1 t = 1,000 kg). The latter, in the form of TeO 2 cryogenic calorimeters, is used by the Cryogenic Underground Observatory for Rare Events, CUORE 10, 11. A worldwide quest is ongoing, involving a range of nuclei such as 76Ge 6, 7, 136Xe 8, 9 and 130Te. The 0 νββ decay signature is a peak in the spectrum of summed energy of the two emitted electrons at the mass difference ( Q ββ) between the parent and daughter nuclei. At this time, experimental searches for 0 νββ decay are the most sensitive means to corroborate this framework. ![]() A minimal extension of the standard model Lagrangian adds heavy Majorana neutrinos that mix with the known neutrinos to produce a set of light Majorana neutrinos, explaining the observed light neutrino masses 5 and at the same time providing a mechanism to explain the baryon asymmetry in the universe 2. This decay can be mediated by various non-standard model mechanisms involving Majorana neutrino masses. We highlight that this process creates two electrons, namely two matter particles 4. ![]() A promising process to experimentally test B − L is neutrinoless double beta (0 νββ) decay, in which a nucleus of mass number A and charge Z decays by the emission of only two electrons: ( A, Z) → ( A, Z + 2) + 2 e −. Nevertheless, the observation of neutrino oscillations indicates the incompleteness of the standard model: they imply non-vanishing neutrino masses, requiring an extension of the standard model, and violate three accidental symmetries connected to the flavour lepton numbers L e, L μ and L τ, leaving the difference between the baryon and lepton number, B − L, as the only unprobed quantity. The standard model of particle physics is a successful paradigm for the number, properties and interactions of fundamental particles. We discuss potential applications of the advances made with CUORE to other fields such as direct dark matter, neutrino and nuclear physics searches and large-scale quantum computing, which can benefit from sustained operation of large payloads in a low-radioactivity, ultralow-temperature cryogenic environment. We find no evidence for 0 νββ decay and set a lower bound of the process half-life as 2.2 × 10 25 years at a 90 per cent credibility interval. CUORE, operating just 10 millikelvin above absolute zero, has pushed the state of the art on three frontiers: the sheer mass held at such ultralow temperatures, operational longevity, and the low levels of ionizing radiation emanating from the cryogenic infrastructure. Here we show results from the search for 0 νββ decay of 130Te, using the latest advanced cryogenic calorimeters with the CUORE experiment 3. Given the profound consequences of such Majorana neutrinos, among which is a potential explanation for the matter–antimatter asymmetry of the universe via leptogenesis 2, the Majorana nature of neutrinos commands intense experimental scrutiny globally one of the primary experimental probes is neutrinoless double beta (0 νββ) decay. The possibility that neutrinos may be their own antiparticles, unique among the known fundamental particles, arises from the symmetric theory of fermions proposed by Ettore Majorana in 1937 1. ![]()
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