Final Results of GERDA on the Search for Neutrinoless Double- β Decay

Agostini, M.; Araujo, G. R.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Baudis, L.; Bauer, C.; Bellotti, E.; Belogurov, S.; Bettini, A.; Bezrukov, L.; Biancacci, V.; Borowicz, D.; Bossio, E.; Bothe, V.; Brudanin, V.; Brugnera, R.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; Comellato, T.; D'Andrea, V.; Demidova, E. V.; Di Marco, N.; Doroshkevich, E.; Fischer, F.; Fomina, M.; Gangapshev, A.; Garfagnini, A.; Gooch, C.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hakenmuller, J.; Hemmer, S.; Hiller, R.; Hofmann, W.; Huang, J.; Hult, M.; Inzhechik, L. V.; Janicsko Csathy, J.; Jochum, J.; Junker, M.; Kazalov, V.; Kermaidic, Y.; Khushbakht, H.; Kihm, T.; Kirpichnikov, I. V.; Klimenko, A.; Kneissl, R.; Knopfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Krause, P.; Kuzminov, V. V.; Laubenstein, M.; Lazzaro, A.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Manzanillas, L.; Miloradovic, M.; Mingazheva, R.; Misiaszek, M.; Moseev, P.; Muller, Y.; Nemchenok, I.; Panas, K.; Pandola, L.; Pelczar, K.; Pertoldi, L.; Piseri, P.; Pullia, A.; Ransom, C.; Rauscher, L.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salamida, F.; Schonert, S.; Schreiner, J.; Schutt, M.; Schutz, A. -K.; Schulz, O.; Schwarz, M.; Schwingenheuer, B.; Selivanenko, O.; Shevchik, E.; Shirchenko, M.; Shtembari, L.; Simgen, H.; Smolnikov, A.; Stukov, D.; Vasenko, A. A.; Veresnikova, A.; Vignoli, C.; Von Sturm, K.; Wester, T.; Wiesinger, C.; Wojcik, M.; Yanovich, E.; Zatschler, B.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zschocke, A.; Zsigmond, A. J.; Zuber, K.; Zuzel, G.

doi:10.1103/PhysRevLett.125.252502

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of Ge76, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in Ge76, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2×10-4 counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100 kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg yr of total exposure. A limit on the half-life of 0νββ decay in Ge76 is set at T1/2>1.8×1026 yr at 90% C.L., which coincides with the sensitivity assuming no signal.