Measurement of the Spectral Shape of the beta-decay of 137Xe to the Ground State of 137Cs in EXO-200 and Comparison with Theory

Abstract

We report on a comparison between the theoretically predicted and experimentally measured spectra of the first-forbidden non-unique $\beta$-decay transition ${}^{137}\text{Xe}(7/2^{-})\to {}^{137}\text{Cs}(7/2^{+})$. The experimental data were acquired by the EXO-200 experiment during a deployment of an AmBe neutron source. The ultra-low background environment of EXO-200, together with dedicated source deployment and analysis procedures, allowed for collection of a pure sample of the decays, with an estimated signal-to-background ratio of more than 99-to-1 in the energy range from 1075 to 4175 keV. In addition to providing a rare and accurate measurement of the first-forbidden non-unique $\beta$-decay shape, this work constitutes a novel test of the calculated electron spectral shapes in the context of the reactor antineutrino anomaly and spectral bump.

arXiv commentVersion as accepted by PRL

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Cited by in corpus (6)

• Toward the discovery of matter creation with neutrinoless double-beta decay
• Improved calculations of beta decay backgrounds to new physics in liquid xenon detectors
• Search for MeV Electron Recoils from Dark Matter in EXO-200
• First measurements with a new $\beta$-electron detector for spectral shape studies
• $g_{\mathrm{A}}$-sensitive $\beta$ spectral shapes in the mass $A=86-99$ region assessed by the nuclear shell model
• Study of beta spectrum shapes relevant to the prediction of reactor antineutrino spectra