Speaker
Description
The third-forbidden non-unique $\beta$-decay of Rubidium-87 to Strontium-87 (Q$_\beta = 282.275$ keV) provides a sensitive probe of nuclear matrix element (NME) calculations and the quenching of the axial-vector coupling constant ($g_A$). To investigate this, we have developed a 10 mol% rubidium-doped Csl scintillator, forming an intrinsic ‘source-in-detector' configuration with an activity of approximately 100 Bq. This configuration enables high detection efficiency and minimal energy loss for low-energy electrons from $\beta$-decay.
We report the detector performance, including light yield, energy resolution, and nonlinear response. By precisely characterizing the $\beta$-spectrum shape, we search for kink signatures to explore the heavy sterile neutrinos in the $\mathcal{O}$(100) keV/c$^2$ mass range.