Probing Majorana neutrinos with double-β decay.

Agostini, M; Bakalyarov, A M; Balata, M; Barabanov, I; Baudis, L; Bauer, C; Bellotti, E; Belogurov, S et al. · Science · 2019

basic_science · Level V

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Abstract

A discovery that neutrinos are Majorana fermions would have profound implications for particle physics and cosmology. The Majorana character of neutrinos would make possible the neutrinoless double-β (0νββ) decay, a matter-creating process without the balancing emission of antimatter. The GERDA Collaboration searches for the 0νββ decay of <sup>76</sup>Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg⋅year, we observe no signal and derive a lower half-life limit of <i>T</i> <sub>1/2</sub> > 0.9 × 10<sup>26</sup> years (90% C.L.). Our <i>T</i> <sub>1/2</sub> sensitivity, assuming no signal, is 1.1 × 10<sup>26</sup> years. Combining the latter with those from other 0νββ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 to 0.16 electron volts.