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1. Final Results of GERDA on the Two-Neutrino Double-β Decay Half-Life of ^{76}Ge.

Author

Agostini M, Alexander A, Araujo GR, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Belogurov S, Bettini A, Bezrukov L, Biancacci V, Bossio E, Bothe V, Brugnera R, Caldwell A, Calgaro S, Cattadori C, Chernogorov A, Chiu PJ, Comellato T, D'Andrea V, Demidova EV, Di Giacinto A, Di Marco N, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hackenmüller S, Hemmer S, Hofmann W, Huang J, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kilgus K, Kirpichnikov IV, Klimenko A, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lehnert B, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Manzanillas L, Marshall G, Miloradovic M, Mingazheva R, Misiaszek M, Morella M, Müller Y, Nemchenok I, Neuberger M, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Ransom C, Rauscher L, Redchuk M, Riboldi S, Rumyantseva N, Sada C, Sailer S, Salamida F, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Sullivan S, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

We present the measurement of the two-neutrino double-β decay rate of ^{76}Ge performed with the GERDA Phase II experiment. With a subset of the entire GERDA exposure, 11.8 kg yr, the half-life of the process has been determined: T_{1/2}^{2ν}=(2.022±0.018_{stat}±0.038_{syst})×10^{21}  yr. This is the most precise determination of the ^{76}Ge two-neutrino double-β decay half-life and one of the most precise measurements of a double-β decay process. The relevant nuclear matrix element can be extracted: M_{eff}^{2ν}=(0.101±0.001).

Published
2023
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2. Liquid argon light collection and veto modeling in GERDA Phase II.

Author

Agostini M, Alexander A, Araujo GR, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Belogurov S, Bettini A, Bezrukov L, Biancacci V, Bossio E, Bothe V, Brugnera R, Caldwell A, Calgaro S, Cattadori C, Chernogorov A, Chiu PJ, Comellato T, D'Andrea V, Demidova EV, Di Giacinto A, Di Marco N, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hofmann W, Hult M, Inzhechik LV, Csáthy JJ, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kilgus K, Kirpichnikov IV, Klimenko A, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lehnert B, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Manzanillas L, Marshall G, Miloradovic M, Mingazheva R, Misiaszek M, Morella M, Müller Y, Nemchenok I, Neuberger M, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Rauscher L, Redchuk M, Riboldi S, Rumyantseva N, Sada C, Sailer S, Salamida F, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Sullivan S, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wegmann A, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

The ability to detect liquid argon scintillation light from within a densely packed high-purity germanium detector array allowed the Gerda experiment to reach an exceptionally low background rate in the search for neutrinoless double beta decay of 76 Ge. Proper modeling of the light propagation throughout the experimental setup, from any origin in the liquid argon volume to its eventual detection by the novel light read-out system, provides insight into the rejection capability and is a necessary ingredient to obtain robust background predictions. In this paper, we present a model of the Gerda liquid argon veto, as obtained by Monte Carlo simulations and constrained by calibration data, and highlight its application for background decomposition., (© The Author(s) 2023.)

Published
2023
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3. Search for tri-nucleon decays of 76 Ge in GERDA.

Author

Agostini M, Alexander A, Araujo G, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Belogurov S, Bettini A, Bezrukov L, Biancacci V, Bossio E, Bothe V, Brugnera R, Caldwell A, Calgaro S, Cattadori C, Chernogorov A, Chiu PJ, Comellato T, D'Andrea V, Demidova EV, Di Giacinto A, Di Marco N, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hofmann W, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kilgus K, Kirpichnikov IV, Klimenko A, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Manzanillas L, Marshall G, Misiaszek M, Morella M, Müller Y, Nemchenok I, Neuberger M, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Rauscher L, Redchuk M, Riboldi S, Rumyantseva N, Sada C, Sailer S, Salamida F, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Sullivan S, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

We search for tri-nucleon decays of 76 Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to 73 Cu, 73 Zn, and 73 Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of 73 Ga to 73 Ge (stable). We search for the 73 Ga decay exploiting the fact that it dominantly populates the 66.7 keV 73 m Ga state with half-life of 0.5 s. The nnn-decays of 76 Ge that proceed via 73 m Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2 × 10 26  yr  (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude., (© The Author(s) 2023.)

Published
2023
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4. Erratum: First Search for Bosonic Superweakly Interacting Massive Particles with Masses up to 1  MeV/c^{2} with GERDA [Phys. Rev. Lett. 125, 011801 (2020)].

Author

Agostini M, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Borowicz D, Bossio E, Bothe V, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Di Marco N, Doroshkevich E, Egorov V, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hiller R, Hofmann W, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kirpichnikov IV, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lazzaro A, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Miloradovic M, Mingazheva R, Misiaszek M, Moseev P, 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, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stukov D, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

This corrects the article DOI: 10.1103/PhysRevLett.125.011801.

Published
2022
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5. Calibration of the Gerda experiment.

Author

Agostini M, Araujo G, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Biancacci V, Bossio E, Bothe V, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Marco ND, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hiller R, Hofmann W, Huang J, Hult M, Inzhechik LV, Csáthy JJ, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kirpichnikov IV, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, 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, Müller Y, Nemchenok I, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Ransom C, Rauscher L, Riboldi S, Rumyantseva N, Sada C, Salamida F, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

The GERmanium Detector Array (Gerda) collaboration searched for neutrinoless double- β decay in 76 Ge with an array of about 40 high-purity isotopically-enriched germanium detectors. The experimental signature of the decay is a monoenergetic signal at Q β β = 2039.061 ( 7 )  keV in the measured summed energy spectrum of the two emitted electrons. Both the energy reconstruction and resolution of the germanium detectors are crucial to separate a potential signal from various backgrounds, such as neutrino-accompanied double- β decays allowed by the Standard Model. The energy resolution and stability were determined and monitored as a function of time using data from regular 228 Th calibrations. In this work, we describe the calibration process and associated data analysis of the full Gerda dataset, tailored to preserve the excellent resolution of the individual germanium detectors when combining data over several years., (© The Author(s) 2021.)

Published
2021
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6. Characterization of inverted coaxial 76 Ge detectors in GERDA for future double- β decay experiments.

Author

Agostini M, Araujo G, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Biancacci V, Bossio E, Bothe V, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Marco ND, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hofmann W, Huang J, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kirpichnikov IV, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, 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, Müller Y, Nemchenok I, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Ransom C, Rauscher L, Riboldi S, Rumyantseva N, Sada C, Salamida F, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

Neutrinoless double- β decay of 76 Ge is searched for with germanium detectors where source and detector of the decay are identical. For the success of future experiments it is important to increase the mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in 76 Ge. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the Gerda setup. The measured resolutions at the Q -value for double- β decay of 76 Ge ( Q β β  = 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array (Gerda) experiment and an accumulated exposure of 8.5 kg · year, the background index after analysis cuts is measured to be 4 . 9 - 3.4 + 7.3 × 10 - 4 counts / ( keV · kg · year ) around Q β β . This work confirms the feasibility of IC detectors for the next-generation experiment Legend., (© The Author(s) 2021.)

Published
2021
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7. Final Results of GERDA on the Search for Neutrinoless Double-β Decay.

Author

Agostini M, Araujo GR, Bakalyarov AM, 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 EV, Di Marco N, Doroshkevich E, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hiller R, Hofmann W, Huang J, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kirpichnikov IV, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, 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, Müller 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, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Shtembari L, Simgen H, Smolnikov A, Stukov D, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of ^{76}Ge, whose discovery would have far-reaching implications in cosmology and particle physics. By operating bare germanium diodes, enriched in ^{76}Ge, 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 ^{76}Ge is set at T_{1/2}>1.8×10^{26}  yr at 90% C.L., which coincides with the sensitivity assuming no signal.

Published
2020
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8. First Search for Bosonic Superweakly Interacting Massive Particles with Masses up to 1  MeV/c^{2} with GERDA.

Author

Agostini M, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Borowicz D, Bossio E, Bothe V, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Di Marco N, Doroshkevich E, Egorov V, Fischer F, Fomina M, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hemmer S, Hiller R, Hofmann W, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Khushbakht H, Kihm T, Kirpichnikov IV, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lazzaro A, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Miloradovic M, Mingazheva R, Misiaszek M, Moseev P, 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, Schönert S, Schreiner J, Schütt M, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stukov D, Vasenko AA, Veresnikova A, Vignoli C, von Sturm K, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zatschler B, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

We present the first search for bosonic superweakly interacting massive particles (super-WIMPs) as keV-scale dark matter candidates performed with the GERDA experiment. GERDA is a neutrinoless double-β decay experiment which operates high-purity germanium detectors enriched in ^{76}Ge in an ultralow background environment at the Laboratori Nazionali del Gran Sasso (LNGS) of INFN in Italy. Searches were performed for pseudoscalar and vector particles in the mass region from 60  keV/c^{2} to 1  MeV/c^{2}. No evidence for a dark matter signal was observed, and the most stringent constraints on the couplings of super-WIMPs with masses above 120  keV/c^{2} have been set. As an example, at a mass of 150  keV/c^{2} the most stringent direct limits on the dimensionless couplings of axionlike particles and dark photons to electrons of g&#95;{ae}<3×10^{-12} and α^{'}/α<6.5×10^{-24} at 90% credible interval, respectively, were obtained.

Published
2020
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9. Probing Majorana neutrinos with double-β decay.

Author

Agostini M, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Borowicz D, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Di Marco N, Domula A, Doroshkevich E, Egorov V, Falkenstein R, Fomina M, Gangapshev A, Garfagnini A, Giordano M, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hegai A, Heisel M, Hemmer S, Hiller R, Hofmann W, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Kihm T, Kirpichnikov IV, Kirsch A, Kish A, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Krause P, Kuzminov VV, Laubenstein M, Lazzaro A, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Miloradovic M, Mingazheva R, Misiaszek M, Moseev P, Nemchenok I, Panas K, Pandola L, Pelczar K, Pertoldi L, Piseri P, Pullia A, Ransom C, Riboldi S, Rumyantseva N, Sada C, Sala E, Salamida F, Schmitt C, Schneider B, Schönert S, Schütz AK, Schulz O, Schwarz M, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stanco L, Stukov D, Vanhoefer L, Vasenko AA, Veresnikova A, von Sturm K, Wagner V, Wegmann A, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

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 76 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 T 1/2 > 0.9 × 10 26 years (90% C.L.). Our T 1/2 sensitivity, assuming no signal, is 1.1 × 10 26 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., (Copyright © 2019 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.)

Published
2019
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10. Characterization of 30 76 Ge enriched Broad Energy Ge detectors for GERDA Phase II.

Author

Agostini M, Bakalyarov AM, Andreotti E, Balata M, Barabanov I, Baudis L, Barros N, Bauer C, Bellotti E, Belogurov S, Benato G, Bettini A, Bezrukov L, Bode T, Borowicz D, Brudanin V, Brugnera R, Budjáš D, Caldwell A, Cattadori C, Chernogorov A, D'Andrea V, Demidova EV, Di Marco N, Domula A, Doroshkevich E, Egorov V, Falkenstein R, Freund K, Gangapshev A, Garfagnini A, Gooch C, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hegai A, Heisel M, Hemmer S, Hiller R, Hofmann W, Hult M, Inzhechik LV, Csáthy JJ, Jochum J, Junker M, Kazalov V, Kermaïdic Y, Kihm T, Kirpichnikov IV, Kirsch A, Kish A, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Kuzminov VV, Laubenstein M, Lazzaro A, Lehnert B, Liao Y, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Marissens G, Miloradovic M, Mingazheva R, Misiaszek M, Moseev P, Nemchenok I, Panas K, Pandola L, Pelczar K, Pullia A, Ransom C, Riboldi S, Rumyantseva N, Sada C, Salamida F, Salathe M, Schmitt C, Schneider B, Schönert S, Schütz AK, Schulz O, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stanco L, Vanhoefer L, Vasenko AA, Veresnikova A, von Sturm K, Wagner V, Wegmann A, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zhitnikov I, Zhukov SV, Zinatulina D, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

The GERmanium Detector Array (Gerda) is a low background experiment located at the Laboratori Nazionali del Gran Sasso in Italy, which searches for neutrinoless double-beta decay of 76 Ge into 76 Se+2e - . Gerda has been conceived in two phases. Phase II, which started in December 2015, features several novelties including 30 new 76 Ge enriched detectors. These were manufactured according to the Broad Energy Germanium (BEGe) detector design that has a better background discrimination capability and energy resolution compared to formerly widely-used types. Prior to their installation, the new BEGe detectors were mounted in vacuum cryostats and characterized in detail in the Hades underground laboratory in Belgium. This paper describes the properties and the overall performance of these detectors during operation in vacuum. The characterization campaign provided not only direct input for Gerda Phase II data collection and analyses, but also allowed to study detector phenomena, detector correlations as well as to test the accuracy of pulse shape simulation codes., (© The Author(s) 2019.)

Published
2019
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11. Improved Limit on Neutrinoless Double-β Decay of ^{76}Ge from GERDA Phase II.

Author

Agostini M, Bakalyarov AM, Balata M, Barabanov I, Baudis L, Bauer C, Bellotti E, Belogurov S, Bettini A, Bezrukov L, Biernat J, Bode T, Borowicz D, Brudanin V, Brugnera R, Caldwell A, Cattadori C, Chernogorov A, Comellato T, D'Andrea V, Demidova EV, Di Marco N, Domula A, Doroshkevich E, Egorov V, Falkenstein R, Gangapshev A, Garfagnini A, Grabmayr P, Gurentsov V, Gusev K, Hakenmüller J, Hegai A, Heisel M, Hemmer S, Hiller R, Hofmann W, Hult M, Inzhechik LV, Janicskó Csáthy J, Jochum J, Junker M, Kazalov V, Kermaidic Y, Kihm T, Kirpichnikov IV, Kirsch A, Kish A, Klimenko A, Kneißl R, Knöpfle KT, Kochetov O, Kornoukhov VN, Kuzminov VV, Laubenstein M, Lazzaro A, Lindner M, Lippi I, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Majorovits B, Maneschg W, Miloradovic M, Mingazheva R, Misiaszek M, Moseev P, Nemchenok I, Panas K, Pandola L, Pelczar K, Pertoldi L, Pullia A, Ransom C, Riboldi S, Rumyantseva N, Sada C, Salamida F, Schmitt C, Schneider B, Schönert S, Schütz AK, Schulz O, Schwingenheuer B, Selivanenko O, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stanco L, Vanhoefer L, Vasenko AA, Veresnikova A, von Sturm K, Wagner V, Wegmann A, Wester T, Wiesinger C, Wojcik M, Yanovich E, Zhitnikov I, Zhukov SV, Zinatulina D, Zschocke A, Zsigmond AJ, Zuber K, and Zuzel G

Abstract

The GERDA experiment searches for the lepton-number-violating neutrinoless double-β decay of ^{76}Ge (^{76}Ge→^{76}Se+2e^{-}) operating bare Ge diodes with an enriched ^{76}Ge fraction in liquid argon. The exposure for broad-energy germanium type (BEGe) detectors is increased threefold with respect to our previous data release. The BEGe detectors feature an excellent background suppression from the analysis of the time profile of the detector signals. In the analysis window a background level of 1.0&#95;{-0.4}^{+0.6}×10^{-3}  counts/(keV kg yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0νββ experiment. No signal is observed and a new 90% C.L. lower limit for the half-life of 8.0×10^{25}  yr is placed when combining with our previous data. The expected median sensitivity assuming no signal is 5.8×10^{25}  yr.

Published
2018
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12. A Compton scattering setup for pulse shape discrimination studies in germanium detectors.

Author

von Sturm K, Belogurov S, Brugnera R, Garfagnini A, Lippi I, Modenese L, Rosso D, and Turcato M

Abstract

Pulse shape discrimination is an important handle to improve sensitivity in low background experiments. A dedicated setup was built to investigate the response of high-purity germanium detectors to single Compton scattered events. Using properly collimated γ-ray sources, it is possible to select events with known interaction location. The aim is to correlate the position dependent signal shape with geometrical and electrical properties of the detector. We report on design and performance of the setup with a first look on data., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Published
2017
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13. Determination of dead-layer variation in HPGe detectors.

Author

Andreotti E, Hult M, Marissens G, Lutter G, Garfagnini A, Hemmer S, and von Sturm K

Abstract

The dead-layer uniformity of the top surface of two high purity germanium detectors has been studied using a novel automated scanning set-up that allows a fine-grained topography of a detector's top and lateral surfaces. Comparisons between measurements and Monte Carlo simulations allowed implementation of a dead-layer variation into the detector model, which reproduces the measurements results. The effect of the non-uniform dead-layer on activity determinations based on low-energy γ-rays (i.e. below ~100 keV) has been determined to be of the order of 10% or more., (© 2013 Published by Elsevier Ltd.)

Published
2014
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14. Results on neutrinoless double-β decay of 76Ge from phase I of the GERDA experiment.

Author

Agostini M, Allardt M, Andreotti E, Bakalyarov AM, Balata M, Barabanov I, Barnabé Heider M, Barros N, Baudis L, Bauer C, Becerici-Schmidt N, Bellotti E, Belogurov S, Belyaev ST, Benato G, Bettini A, Bezrukov L, Bode T, Brudanin V, Brugnera R, Budjáš D, Caldwell A, Cattadori C, Chernogorov A, Cossavella F, Demidova EV, Domula A, Egorov V, Falkenstein R, Ferella A, Freund K, Frodyma N, Gangapshev A, Garfagnini A, Gotti C, Grabmayr P, Gurentsov V, Gusev K, Guthikonda KK, Hampel W, Hegai A, Heisel M, Hemmer S, Heusser G, Hofmann W, Hult M, Inzhechik LV, Ioannucci L, Janicskó Csáthy J, Jochum J, Junker M, Kihm T, Kirpichnikov IV, Kirsch A, Klimenko A, Knöpfle KT, Kochetov O, Kornoukhov VN, Kuzminov VV, Laubenstein M, Lazzaro A, Lebedev VI, Lehnert B, Liao HY, Lindner M, Lippi I, Liu X, Lubashevskiy A, Lubsandorzhiev B, Lutter G, Macolino C, Machado AA, Majorovits B, Maneschg W, Misiaszek M, Nemchenok I, Nisi S, O'Shaughnessy C, Pandola L, Pelczar K, Pessina G, Pullia A, Riboldi S, Rumyantseva N, Sada C, Salathe M, Schmitt C, Schreiner J, Schulz O, Schwingenheuer B, Schönert S, Shevchik E, Shirchenko M, Simgen H, Smolnikov A, Stanco L, Strecker H, Tarka M, Ur CA, Vasenko AA, Volynets O, von Sturm K, Wagner V, Walter M, Wegmann A, Wester T, Wojcik M, Yanovich E, Zavarise P, Zhitnikov I, Zhukov SV, Zinatulina D, Zuber K, and Zuzel G

Abstract

Neutrinoless double beta decay is a process that violates lepton number conservation. It is predicted to occur in extensions of the standard model of particle physics. This Letter reports the results from phase I of the Germanium Detector Array (GERDA) experiment at the Gran Sasso Laboratory (Italy) searching for neutrinoless double beta decay of the isotope (76)Ge. Data considered in the present analysis have been collected between November 2011 and May 2013 with a total exposure of 21.6 kg yr. A blind analysis is performed. The background index is about 1 × 10(-2) counts/(keV kg yr) after pulse shape discrimination. No signal is observed and a lower limit is derived for the half-life of neutrinoless double beta decay of (76)Ge, T(1/2)(0ν) >2.1 × 10(25) yr (90% C.L.). The combination with the results from the previous experiments with (76)Ge yields T(1/2)(0ν)>3.0 × 10(25) yr (90% C.L.).

Published
2013
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