Abstract

A search for neutrinoless double-β decay (0νββ) in ^{136}Xe is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Relative to previous analyses, the signal detection efficiency has been raised from 80.8% to 96.4±3.0%, and the energy resolution of the detector at the Q value of ^{136}Xe 0νββ has been improved from σ/E=1.23% to 1.15±0.02% with the upgraded detector. Accounting for the new data, the median 90%confidence level 0νββ half-life sensitivity for this analysis is 5.0×10^{25} yr with a total ^{136}Xe exposure of 234.1kg yr. No statistically significant evidence for 0νββ is observed, leading to a lower limit on the 0νββ half-life of 3.5×10^{25} yr at the 90%confidence level.

Highlights

  • Background errors Spectral shape agreementBackground model Other [8] Total errorSignal detection efficiency Fiducial volume Partial 3D cut Light-to-charge ratio Denoising misreconstructed Other [13] Phase I (%)2.8 < 0.4 0.9 ÁÁÁ < 1.0 3.1 Phase II (%)2.6 < 0.4 0.9 1.0 < 1.0 3.1 resolution at the 0νββ decay energy of Qββ 1⁄4 2457.83 Æ 0.37 keV [24]

  • A search for neutrinoless double-β decay (0νββ) in 136Xe is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events

  • In addition to the new data acquired between June 2017 and October 2018, this search introduces several analysis developments to optimize the detector sensitivity to 0νββ, including the incorporation of a deep neural network (DNN) to discriminate between background and signal events

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Summary

Introduction

A search for neutrinoless double-β decay (0νββ) in 136Xe is performed with the full EXO-200 dataset using a deep neural network to discriminate between 0νββ and background events. Accounting for the new data, the median 90% confidence level 0νββ half-life sensitivity for this analysis is 5.0 × 1025 yr with a total 136Xe exposure of 234.1 kg yr.

Results
Conclusion

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