Search for Double Beta Decays of Xe 134 with EXO-200 Phase II

(EXO-200 Collaboration)

doi:10.1103/vpny-23wq

Search for Double Beta Decays of Xe 134 with EXO-200 Phase II

(EXO-200 Collaboration)

Research output: Contribution to journal › Article › peer-review

Abstract

EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% Xe136 and 19.098% Xe134. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of Xe136. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for 0νββ and 2νββ decay of Xe134 with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life T1/20ν≥3.7×1023 yr and T1/22ν≥2.6×1021 yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of Xe134 of T1/20ν≥8.7×1023 (90% CL) and the second strongest constraint on the two-neutrino decay of T1/22ν≥2.9×1021 (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the 2νββ and 0νββ decays of Xe134 to the lowest excited state of Ba134.

Original language	English
Article number	232502
Journal	Physical Review Letters
Volume	136
Issue number	23
DOIs	https://doi.org/10.1103/vpny-23wq
State	Published - Jun 12 2026
Externally published	Yes

Funding

This work was supported by Grants from the NSF (No. PHY-2111213 and No. PHY-2514767) as well as from the DOE (No. DE-SC0020509). EXO-200 was supported by the DOE (No. DE-SC0017970, No. DE-FG02-01ER41166, No. DE-SC0021383, No. DE-SC0014517) and NSF in the USA, the NSERC in Canada (CRC-2019-00399, SAPPJ-2017-00029), the SNF in Switzerland, the IBS in Korea, the RFBR (18-02-00550) in Russia, the DFG in Germany, and CAS and ISTCP in China. The EXO-200 data analysis and simulation uses resources of the SLAC Shared Scientific Data Facility (S3DF). We gratefully acknowledge the KARMEN Collaboration for supplying the cosmic-ray veto detectors, as well as the WIPP for their hospitality.

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10.1103/vpny-23wq

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@article{adad47a7a7d04857bd510e5e2b8bdb06,

title = "Search for Double Beta Decays of Xe 134 with EXO-200 Phase II",

abstract = "EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672\% Xe136 and 19.098\% Xe134. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of Xe136. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for 0νββ and 2νββ decay of Xe134 with Phase II EXO-200 data, with median 90\% CL exclusion sensitivity to half-life T1/20ν≥3.7{\texttimes}1023 yr and T1/22ν≥2.6{\texttimes}1021 yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of Xe134 of T1/20ν≥8.7{\texttimes}1023 (90\% CL) and the second strongest constraint on the two-neutrino decay of T1/22ν≥2.9{\texttimes}1021 (90\% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the 2νββ and 0νββ decays of Xe134 to the lowest excited state of Ba134.",

author = "\{(EXO-200 Collaboration)\} and \{Al Kharusi\}, S. and G. Anton and I. Badhrees and Barbeau, \{P. S.\} and V. Belov and T. Bhatta and M. Breidenbach and T. Brunner and Cao, \{G. F.\} and Cen, \{W. R.\} and C. Chambers and B. Cleveland and M. Coon and A. Craycraft and T. Daniels and L. Darroch and Daugherty, \{S. J.\} and J. Davis and S. Delaquis and \{Der Mesrobian-Kabakian\}, A. and R. Devoe and A. Dolgolenko and Dolinski, \{M. J.\} and J. Echevers and B. Eckert and W. Fairbank and D. Fairbank and J. Farine and S. Feyzbakhsh and P. Fierlinger and Fu, \{Y. S.\} and D. Fudenberg and P. Gautam and R. Gornea and G. Gratta and C. Hall and Hansen, \{E. V.\} and J. Hoessl and P. Hufschmidt and M. Hughes and A. Iverson and A. Jamil and C. Jessiman and Jewell, \{M. J.\} and A. Johnson and A. Karelin and Kaufman, \{L. J.\} and T. Koffas and R. Kr{\"u}cken and Yahne, \{D. R.\}",

note = "Publisher Copyright: {\textcopyright} 2026 American Physical Society.",

year = "2026",

month = jun,

day = "12",

doi = "10.1103/vpny-23wq",

language = "English",

volume = "136",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "23",

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TY - JOUR

T1 - Search for Double Beta Decays of Xe 134 with EXO-200 Phase II

AU - (EXO-200 Collaboration)

AU - Al Kharusi, S.

AU - Anton, G.

AU - Badhrees, I.

AU - Barbeau, P. S.

AU - Belov, V.

AU - Bhatta, T.

AU - Breidenbach, M.

AU - Brunner, T.

AU - Cao, G. F.

AU - Cen, W. R.

AU - Chambers, C.

AU - Cleveland, B.

AU - Coon, M.

AU - Craycraft, A.

AU - Daniels, T.

AU - Darroch, L.

AU - Daugherty, S. J.

AU - Davis, J.

AU - Delaquis, S.

AU - Der Mesrobian-Kabakian, A.

AU - Devoe, R.

AU - Dolgolenko, A.

AU - Dolinski, M. J.

AU - Echevers, J.

AU - Eckert, B.

AU - Fairbank, W.

AU - Fairbank, D.

AU - Farine, J.

AU - Feyzbakhsh, S.

AU - Fierlinger, P.

AU - Fu, Y. S.

AU - Fudenberg, D.

AU - Gautam, P.

AU - Gornea, R.

AU - Gratta, G.

AU - Hall, C.

AU - Hansen, E. V.

AU - Hoessl, J.

AU - Hufschmidt, P.

AU - Hughes, M.

AU - Iverson, A.

AU - Jamil, A.

AU - Jessiman, C.

AU - Jewell, M. J.

AU - Johnson, A.

AU - Karelin, A.

AU - Kaufman, L. J.

AU - Koffas, T.

AU - Krücken, R.

AU - Yahne, D. R.

PY - 2026/6/12

Y1 - 2026/6/12

N2 - EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% Xe136 and 19.098% Xe134. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of Xe136. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for 0νββ and 2νββ decay of Xe134 with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life T1/20ν≥3.7×1023 yr and T1/22ν≥2.6×1021 yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of Xe134 of T1/20ν≥8.7×1023 (90% CL) and the second strongest constraint on the two-neutrino decay of T1/22ν≥2.9×1021 (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the 2νββ and 0νββ decays of Xe134 to the lowest excited state of Ba134.

AB - EXO-200 was a leading double beta decay experiment consisting of a single-phase, enriched liquid xenon time projection chamber filled with an admixture of 80.672% Xe136 and 19.098% Xe134. The detector operated at the Waste Isolation Pilot Plant between 2010 and 2018 and was designed to search for double beta decay of Xe136. Data were acquired in two phases separated by a period of detector upgrades. We report on the search for 0νββ and 2νββ decay of Xe134 with Phase II EXO-200 data, with median 90% CL exclusion sensitivity to half-life T1/20ν≥3.7×1023 yr and T1/22ν≥2.6×1021 yr, respectively. No statistically significant signal is observed for either decay mode. We set a world-leading lower limit on the half-life of the neutrinoless decay mode of Xe134 of T1/20ν≥8.7×1023 (90% CL) and the second strongest constraint on the two-neutrino decay of T1/22ν≥2.9×1021 (90% CL), a threefold improvement over the EXO-200 Phase I measurement. New constraints are also set for the 2νββ and 0νββ decays of Xe134 to the lowest excited state of Ba134.

UR - https://www.scopus.com/pages/publications/105043050007

U2 - 10.1103/vpny-23wq

DO - 10.1103/vpny-23wq

M3 - Article

AN - SCOPUS:105043050007

SN - 0031-9007

VL - 136

JO - Physical Review Letters

JF - Physical Review Letters

IS - 23

M1 - 232502

ER -

Search for Double Beta Decays of Xe 134 with EXO-200 Phase II

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