Several examples of the production of electron-positron pairs were found in the interactions with emulsion of fragments resulting from the collision of $^{12}\mathrm{C}$ and $^{22}\mathrm{Ne}$ projectiles of 4.5 and $4.2 \frac{\mathrm{GeV}}{c}$ per nucleon, respectively with emulsion nuclei. Taking into account the effect of the background, the results seem to suggest the existence of new neutral boson with mass $1.60\ifmmode\pm\else\textpm\fi{}0.59 \frac{\mathrm{MeV}}{c}$ and a lifetime (0.15 \ifmmode\pm\else\textpm\fi{} 0.01) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}14}$ sec.