New evidence supporting the existence of the hypothetic X17 particle

A. J. Krasznahorkay, M. Csatlos, L. Csige +8

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 $e^{+}{e}^{-}$ an…