Probing Majorana neutrinos with double-β decay.
M AgostiniA M BakalyarovM BalataI BarabanovL BaudisC BauerE BellottiS BelogurovA BettiniL BezrukovD BorowiczV BrudaninR BrugneraA CaldwellC CattadoriA ChernogorovT ComellatoV D'AndreaE V DemidovaN Di MarcoA DomulaE DoroshkevichV EgorovR FalkensteinM FominaA GangapshevA GarfagniniM GiordanoP GrabmayrV GurentsovK GusevJ HakenmüllerA HegaiM HeiselS HemmerR HillerW HofmannM HultL V InzhechikJózsef Janicskó-CsáthyJ JochumM JunkerV KazalovY KermaïdicT KihmI V KirpichnikovA KirschA KishA KlimenkoR KneißlK T KnöpfleO KochetovV N KornoukhovP KrauseV V KuzminovMatthias LaubensteinA LazzaroM LindnerI LippiA LubashevskiyB LubsandorzhievG LutterC MacolinoB MajorovitsW ManeschgM MiloradovicR MingazhevaM MisiaszekP MoseevI NemchenokK PanasLuciano PandolaK PelczarL PertoldiP PiseriA PulliaC RansomS RiboldiN RumyantsevaC SadaE SalaF SalamidaC SchmittB SchneiderS SchönertA-K SchützO SchulzM SchwarzB SchwingenheuerO SelivanenkoE ShevchikM ShirchenkoH SimgenA SmolnikovL StancoD StukovL VanhoeferA A VasenkoA VeresnikovaK von SturmV WagnerA WegmannT WesterC WiesingerM WojcikE YanovichI ZhitnikovS V ZhukovD ZinatulinaA ZschockeA J ZsigmondK ZuberG Zuzelnull nullPublished in: Science (New York, N.Y.) (2019)
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 76Ge 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 T 1/2 > 0.9 × 1026 years (90% C.L.). Our T 1/2 sensitivity, assuming no signal, is 1.1 × 1026 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.
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