Search for Double Beta Plus Decays with NuDoubt++

Abstract

The NuDoubt++ experiment proposes a novel detector concept to search for double beta plus decays using a hybrid opaque liquid scintillator. This design combines recent advances in scintillator technologies (namely, slow and opaque media, and optimized wavelength-shifting fibers coupled to silicon photomultipliers) to achieve improved particle identification and background rejection. We present the physics motivations, detector design, first prototype layout, and expected sensitivities for both standard and exotic modes, using 78Kr as an initial target isotope. With this approach, NuDoubt++ aims to make the first observation of positron emitting Standard Model two-neutrino modes and improve current constraints on Beyond Standard Model neutrinoless processes.

arXiv comment4 pages, 2 figures, contribution to the 2025 Electroweak session of the 59th Rencontres de Moriond