Measurement of the 85Kr specific activity in the GERDA liquid argon

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

doi:10.1140/epjc/s10052-025-14135-8

Measurement of the ⁸⁵Kr specific activity in the GERDA liquid argon

Eur Phys J C Part Fields. 2025;85(5):518. doi: 10.1140/epjc/s10052-025-14135-8. Epub 2025 May 12.

Authors

M Agostini¹, A Alexander¹, G Araujo², A M Bakalyarov³, M Balata⁴, I Barabanov⁵, L Baudis², C Bauer⁶, S Belogurov^{5

7

8}, A Bettini^{9

10}, L Bezrukov⁵, V Biancacci¹¹, E Bossio^{12

13}, V Bothe⁶, R Brugnera^{9

10}, A Caldwell¹⁴, S Calgaro^{9

10}, C Cattadori¹⁵, A Chernogorov^{7

3}, P-J Chiu², T Comellato¹², V D'Andrea¹¹, E V Demidova⁷, N Di Marco¹⁶, E Doroshkevich⁵, M Fomina¹⁷, A Gangapshev^{6

5}, A Garfagnini^{9

10}, C Gooch¹⁴, P Grabmayr¹⁸, V Gurentsov⁵, K Gusev^{17

3

12}, J Hakenmüller^{6

19}, S Hemmer¹⁰, W Hofmann⁶, J Huang², M Hult²⁰, L V Inzhechik^{5

21}, J Janicskó Csáthy^{12

22}, J Jochum¹⁸, M Junker⁴, V Kazalov⁵, Y Kermaïdic⁶, H Khushbakht¹⁸, T Kihm⁶, K Kilgus¹⁸, I V Kirpichnikov⁷, A Klimenko^{17

6

23}, K T Knöpfle⁶, O Kochetov¹⁷, V N Kornoukhov^{5

8}, P Krause¹², V V Kuzminov⁵, M Laubenstein⁴, M Lindner⁶, I Lippi¹⁰, A Lubashevskiy¹⁷, B Lubsandorzhiev⁵, G Lutter²⁰, C Macolino¹¹, B Majorovits¹⁴, W Maneschg⁶, G Marshall¹, M Misiaszek²⁴, M Morella¹⁶, Y Müller², I Nemchenok^{17

23}, M Neuberger¹², L Pandola²⁵, K Pelczar²⁰, L Pertoldi^{12

10}, P Piseri²⁶, A Pullia²⁶, C Ransom², L Rauscher¹⁸, M Redchuk¹⁰, S Riboldi²⁶, N Rumyantseva^{17

3}, C Sada^{9

10}, S Sailer⁶, F Salamida¹¹, S Schönert¹², J Schreiner⁶, A-K Schütz^{18

27}, O Schulz¹⁴, M Schwarz¹², B Schwingenheuer⁶, O Selivanenko⁵, E Shevchik¹⁷, M Shirchenko¹⁷, L Shtembari¹⁴, H Simgen⁶, A Smolnikov^{17

6}, D Stukov³, S Sullivan⁶, A A Vasenko⁷, A Veresnikova⁵, C Vignoli⁴, K von Sturm^{9

10}, T Wester²⁸, C Wiesinger¹², M Wojcik²⁴, E Yanovich⁵, B Zatschler²⁸, I Zhitnikov¹⁷, S V Zhukov³, D Zinatulina¹⁷, A Zschocke¹⁸, K Zuber²⁸, G Zuze²⁴; GERDA Collaboration*

Affiliations

¹ Department of Physics and Astronomy, University College London, London, UK.
² Physik-Institut, Universität Zürich, Zurich, Switzerland.
³ National Research Centre "Kurchatov Institute", Moscow, Russia.
⁴ INFN Laboratori Nazionali del Gran Sasso, Assergi, Italy.
⁵ Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia.
⁶ Max-Planck-Institut für Kernphysik, Heidelberg, Germany.
⁷ Institute for Theoretical and Experimental Physics, NRC "Kurchatov Institute", Moscow, Russia.
⁸ NRNU MEPhI, Moscow, Russia.
⁹ Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Padua, Italy.
¹⁰ INFN Padova, Padua, Italy.
¹¹ INFN Laboratori Nazionali del Gran Sasso and Università degli Studi dell'Aquila, L'Aquila, Italy.
¹² Physik Department, Technische Universität München, Munich, Germany.
¹³ Present Address: IRFU, CEA, Université Paris-Saclay, Gif-sur-Yvette, France.
¹⁴ Max-Planck-Institut für Physik, Munich, Germany.
¹⁵ INFN Milano Bicocca, Milan, Italy.
¹⁶ INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi, Italy.
¹⁷ Joint Institute for Nuclear Research, Dubna, Russia.
¹⁸ Physikalisches Institut, Eberhard Karls Universität Tübingen, Tübingen, Germany.
¹⁹ Present Address: Duke University, Durham, NC USA.
²⁰ European Commission, JRC-Geel, Geel, Belgium.
²¹ Moscow Institute of Physics and Technology, Moscow, Russia.
²² Present Address: Semilab Zrt, Budapest, Hungary.
²³ Dubna State University, Dubna, Russia.
²⁴ Institute of Physics, Jagiellonian University, Kraków, Poland.
²⁵ INFN Laboratori Nazionali del Sud, Catania, Italy.
²⁶ Dipartimento di Fisica, Università degli Studi di Milano and INFN Milano, Milan, Italy.
²⁷ Present Address: Nuclear Science Division, Berkeley, USA.
²⁸ Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany.

Abstract

The radioactive isotope ⁸⁵Kr is found in significant quantities in the atmosphere largely due to nuclear industry. Its $β$ -decay with a half-life of 10.7 years and a Q-value of 687 keV is a dangerous background source for low-threshold noble gas and liquid detectors, which distill their detector medium from air. The Gerda experiment was operating high-purity germanium detectors immersed in a clean liquid argon bath deep underground to search for neutrinoless double beta decay with unprecedented sensitivity. The ⁸⁵Kr specific activity in the liquid argon at the start of the second phase of the experiment has been determined to be $(0.36 \pm 0.03)$ mBq/kg through an analysis of the full subsequent data set that exploits the excellent $γ$ -ray spectroscopic capabilities of Gerda.