Abstract
Neutrinoless double beta decay (0nubb) is one of the most sensitive probes for physics beyond the Standard Model, providing unique information on the nature of neutrinos. In this paper we review the status and outlook for bolometric 0nubb decay searches. We summarize recent advances in background suppression demonstrated using bolometers with simultaneous readout of heat and light signals. We simulate several configurations of a future CUORE-like bolometer array which would utilize these improvements and present the sensitivity reach of a hypothetical next-generation bolometric 0nubb experiment. We demonstrate that a bolometric experiment with the isotope mass of about 1 ton is capable of reaching the sensitivity to the effective Majorana neutrino mass (|mee|) of order 10-20 meV, thus completely exploring the so-called inverted neutrino mass hierarchy region. We highlight the main challenges and identify priorities for an R&D program addressing them.
Highlights
Neutrino oscillation experiments have provided compelling experimental evidence that neutrinos are massive and exhibit flavor mixing, but the absolute mass scale and the quantum nature of these particles remain unknown.In the standard framework of three-neutrino oscillations, the square mass differences Δm212 and |Δm223| measured by neutrino oscillation experiments leave open three different possibilities for the ordering of the neutrino masses: normal hierarchy (NH), with m1 < m2 m3, inverted hierarchy (IH), with m3 m1 < m2 and degenerate hierarchy (DH), with m1 m2 m3
Contemporary efforts are focused on so-called second generation experiments (CUORE [32], SuperNEMO [33], nEXO [34], [18], LUCIFER [35], GERDA II [36], SNO+ [37], for a full list see [38,39]) with the goal of approaching the IH region at |mee| ≤ 50 meV, while considerable R&D is devoted to new techniques which could contribute to the full exclusion of the IH mass region (|mee| ≤ 10 meV)
The ability of a scintillating bolometer, or of a bolometer with Cherenkov light readout, to separate α events from βs and γ s is demonstrated in Fig. 4 where we have collected the most recent results obtained with ZnSe, CdWO4, ZnMoO4, and TeO2
Summary
Neutrino oscillation experiments have provided compelling experimental evidence that neutrinos are massive and exhibit flavor mixing, but the absolute mass scale and the quantum nature of these particles (that is, if they are Dirac or Majorana fermions) remain unknown. Oscillation experiments are not able to measure two fundamental properties of the neutrino: its nature (i.e. its quantum field structure) and its absolute mass. If the neutrino is found to be Majorana, one can simultaneously achieve constraints on the absolute mass scale. Observation of 0νββ process would demonstrate unambiguously that lepton number is not strictly conserved.
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