A new search for two-neutrino double-beta(2vββ) decay of136Xe to the 01+excited state of136Ba is performed with the full EXO-200 dataset.A deep learning-based convolutional neural network is used to discriminate sig...
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A new search for two-neutrino double-beta(2vββ) decay of136Xe to the 01+excited state of136Ba is performed with the full EXO-200 dataset.A deep learning-based convolutional neural network is used to discriminate signal from background *** detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of *** the addition of the Phase Ⅱ dataset taken with an upgraded detector,the median 90%confidence level half-life sensitivity of 2vββ decay to the 01+state of136Ba is 2.9 × 1024yr using a total136Xe exposure of 234.1 kg *** statistically significant evidence for 2vββ decay to the 01+state is observed,leading to a lower limit of T1/22v(0+→01+)>1.4×1024yr at 90% confidence level,improved by 70% relative to the current world’s best constraint.
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