The search for the identity of dark matter (DM) is in an exciting and rapidly developing era. The WIMPs were considered as one of the most favorable dark matter (DM) candidates for the last thirty years. However, strong constraints from direct-detection experiments with the absence of new physics signals from the LHC, have been painting such models as increasingly constrained and tuned. Researchers turn their attention to search for less massive DM candidates, i.e. light dark matter of MeV scale. The so-called dark photon is proposed as an electromagnetic force carrier for dark matter, which has a mass on the MeV scale, a short life time, and it decays mostly into electron-positron (e+ - e-) pairs.
	In our recent work, we were searching for such e+-e- pairs in high-energy nuclear transitions.  We measured the e+ - e− angular correlation in internal pair creation for the M1 transition depopulating the 18.15 MeV state in 8Be, and observed a peak-like deviation from the predicted angular correlation for the internal pair creation. To the best of our knowledge, no nuclear physics related description of such deviation can be made. The deviation between the experimental and theoretical angular correlations is significant and can be described by assuming the creation and subsequent decay of a Jπ=1+ vector boson with mass m0c2 = 16.70(61) MeV.
	I am going to show the reliability of the data obtained, will place such a particle into context with other experimental results, and discuss the possible theoretical understanding of the results.