Search for neutrinoless double-beta decay of Ge 76 with a natural broad energy germanium detector

Abstract

A natural broad energy germanium detector is operated in the China Jinping Underground Laboratory for a feasibility study of building the next generation experiment of the neutrinoless double-beta (0νββ) decay of Ge76. The setup of the prototype facility, characteristics of the broad energy germanium detector, background reduction methods, and data analysis are described in this paper. A background index of 6.4×10-3 counts/(keV kg 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 day, thus a limit on the half life of Ge76 0νββ decay is set at T1/20ν>5.62×1022 yr at 90% C.L. The limit corresponds to an effective Majorana neutrino mass in the range of 4.6-10.3 eV, dependent on the nuclear matrix elements. © 2022 American Physical Society.