Speaker
Description
NuDoubt++ is a novel detector concept designed to explore double beta plus (DBD+) decays with unprecedented sensitivity.
Double beta decay is a rare second-order weak nuclear process in which two nucleons transform simultaneously. It can occur in the two-neutrino mode (2𝜈𝛽𝛽), allowed within the Standard Model, or in the neutrinoless mode (0𝜈𝛽𝛽), which violates lepton number conservation and would signal new physics, such as the Majorana nature of neutrinos. While searches for 0𝜈𝛽𝛽 aim to probe the absolute neutrino mass scale and the mechanism of mass generation, measurements of the 2𝜈 mode provide essential input for validating nuclear matrix element (NME) calculations and modeling intermediate nuclear states.
To date, most experimental efforts have focused on the 𝛽−𝛽− channel due to its favorable phase space factors and the broader availability of candidate isotopes. In contrast, proton-to-neutron conversion modes, collectively known as double beta plus decays, such as double positron decay 𝛽+𝛽+, positron emitting electron capture 𝛽+𝐸𝐶, and double electron capture 2𝐸𝐶, remain largely unexplored. DBD+ processes provide complementary sensitivity to nuclear structure, with candidate isotopes spanning a wide range of masses and deformations.
In this work, we present NuDoubt++, a novel detector concept optimized for exploring positron-emitting double beta decay channels with unprecedented sensitivity. The detector combines hybrid and opaque scintillation technologies with advanced light-readout techniques to enhance positron signature detection and background rejection. Preliminary sensitivity estimates indicate that a 1-tonne-week exposure could probe the parameter space relevant for 2𝜈𝛽+𝛽+ and 2𝜈𝛽+𝐸𝐶 decays in the candidate isotope ⁷⁸Kr, while offering the potential to explore 0𝜈𝛽+𝛽+ decay with sensitivities well beyond current experimental limits.