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arXiv · 1910.10459

New evidence supporting the existence of the hypothetic X17 particle

A. J. Krasznahorkay·M. Csatlos·L. Csige·J. Gulyas·M. Koszta·B. Szihalmi·J. Timar·D. S. Firak·A. Nagy·N. J. Sas·A. Krasznahorkay
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Abstract

We observed electron-positron pairs from the electro-magnetically forbidden M0 transition depopulating the 21.01 MeV 0$^-$ state in $^4$He. A peak was observed in their $e^+e^-$ angular correlations at 115$^\circ$ with 7.2$\sigma$ significance, and could be described by assuming the creation and subsequent decay of a light particle with mass of $m_\mathrm{X}c^2$=16.84$\pm0.16 (stat) \pm 0.20 (syst)$ MeV and $\Gamma_\mathrm{X}$= $3.9\times 10^{-5}$ eV. According to the mass, it is likely the same X17 particle, which we recently suggested [Phys. Rev. Lett. 116, 052501 (2016)] for describing the anomaly observed in $^8$Be.

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A. J. Krasznahorkay, M. Csatlos, L. Csige, J. Gulyas, M. Koszta, B. Szihalmi, J. Timar, D. S. Firak, A. Nagy, N. J. Sas, A. Krasznahorkay. 2019-10-23. New evidence supporting the existence of the hypothetic X17 particle. https://arxiv.org/abs/1910.10459

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