CDEX BEGe 0vbb 2022

W. H. Dai, H. Ma, Q. Yue et al.
Search for neutrinoless double-beta decay of 76Ge with a natural broad energy germanium detector
Phys. Rev. D 106, 032012 (2022)
A natural broad energy germanium (BEGe) detector is operated in the China Jinping Underground Laboratory (CJPL) for a feasibility study of building the next generation experiment of the neutrinoless double-beta (0\textup{$\nu\beta\beta$}) decay of $^{76}$Ge. The setup of the prototype facility, characteristics of the BEGe detector, background reduction methods and data analysis are described in this paper. A background index of 6.4$\times$10$^{-3}$ counts/(keV$\cdot$kg$\cdot$day) is achieved and 1.86 times lower than our previous result of the CDEX-1 detector. No signal is observed with an exposure of 186.4 kg$\cdot$day, thus a limit on the half life of $^{76}$Ge 0\textup{$\nu\beta\beta$} decay is set at T$_{1/2}^{0\nu}$ $>$ 5.62×10$^{22}$ yr at 90\% C.L.. The limit corresponds to an effective Majorana neutrino mass in the range of 4.6 $\sim$ 10.3 eV, dependent on the nuclear matrix elements.