Anomaly in the decay of 8Be and 4He—can an observed light boson mediate low-energy nucleon–nucleon interactions?

Abstract

We present a hypothesis that the reported anomaly in the folding angle distribution of electron–positron pairs, emitted in the decay of the excited levels of nucleus 8Be and 4He, can be related to the cluster structure of the decaying state. In particular, we suggest that the potentially reported boson with rest mass m X = 17 MeV can mediate the nucleon–nucleon interaction at the low-energy regime of QCD, in the weakly bound cluster state p + 7Li, and p + 3H. We explore possible equations of state of symmetric nuclear matter, corresponding to the vector meson mass m v = 17 MeV, obtained using relativistic mean field theory of nuclear force using QHD-I. We find several relations for boson masses, based on concepts of chiral symmetry breaking. Both model approaches thus point toward apparent restoration of chiral symmetry in nucleon–nucleon interaction at large distances, possibly via bounce into a false instanton vacuum. The possible existence of a boson with rest mass m X = 17 MeV in the decay of high lying excited states of 8Be and 4He could shed new light in one of the long-lasting open questions in nuclear physics.