Search for two-neutrino double-beta decay of ¹³⁶Xe to the excited state of ¹³⁶Ba with the complete EXO-200 dataset*

S. Al Kharusi, G. Anton, I. Badhrees, P. S. Barbeau, D. Beck, V. Belov, Trilochan Bhatta, M. Breidenbach, T. Brunner, G. F. Cao

Abstract

Abstract A new search for two-neutrino double-beta (2 νββ ) decay of 136 Xe to the <?CDATA $0_1^ + $?> excited state of 136 Ba is performed with the full EXO-200 dataset. A deep learning-based convolutional neural network is used to discriminate signal from background events. Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two. With the addition of the Phase II dataset taken with an upgraded detector, the median 90% confidence level half-life sensitivity of 2 νββ decay to the <?CDATA $0_1^ + $?> state of 136 Ba is <?CDATA $ 2.9 \times 10^{24} $?> yr using a total 136 Xe exposure of 234.1 kg yr. No statistically significant evidence for 2 νββ decay to the <?CDATA $0_1^ + $?> state is observed, leading to a lower limit of <?CDATA $ T^{2\nu}_{1/2}(0^+ \rightarrow 0^+_1) \gt 1.4\times10^{24} $?> yr at 90% confidence level, improved by 70% relative to the current world's best constraint.

Locations

• arXiv (Cornell University) - View - PDF
• OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) - View
• Chinese Physics C - View