Search for two-neutrino double electron capture on 124Xe with the XMASS-I detector

• Published in: Physics letters. B Vol. 759; no. C; pp. 64 - 68
• Main Authors: Abe, K., Hiraide, K., Ichimura, K., Kishimoto, Y., Kobayashi, K., Kobayashi, M., Moriyama, S., Nakagawa, K., Nakahata, M., Norita, T., Ogawa, H., Sekiya, H., Takachio, O., Takeda, A., Yamashita, M., Yang, B.S., Kim, N.Y., Kim, Y.D., Tasaka, S., Liu, J., Martens, K., Suzuki, Y., Fujita, R., Hosokawa, K., Miuchi, K., Oka, N., Onishi, Y., Takeuchi, Y., Kim, Y.H., Lee, J.S., Lee, K.B., Lee, M.K., Fukuda, Y., Itow, Y., Kegasa, R., Masuda, K., Takiya, H., Uchida, H., Nishijima, K., Fujii, K., Murayama, I., Nakamura, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-08-2016; Elsevier
• Subjects: Double electron capture; Liquid xenon; Neutrino; Liquid xenon; Double electron capture; Neutrino
• ISSN: 0370-2693; 1873-2445
• DOI: 10.1016/j.physletb.2016.05.039

Double electron capture is a rare nuclear decay process in which two orbital electrons are captured simultaneously in the same nucleus. Measurement of its two-neutrino mode would provide a new reference for the calculation of nuclear matrix elements whereas observation of its neutrinoless mode would demonstrate lepton number violation. A search for two-neutrino double electron capture on 124Xe is performed using 165.9 days of data collected with the XMASS-I liquid xenon detector. No significant excess above background was observed and we set a lower limit on the half-life as 4.7×1021 years at 90% confidence level. The obtained limit has ruled out parts of some theoretical expectations. We obtain a lower limit on the 126Xe two-neutrino double electron capture half-life of 4.3×1021 years at 90% confidence level as well.