On the creation of the 17 MeV X boson in the 17.6 MeV M1 transition of⁸Be

Abstract

Electron-positron angular correlations were remeasured for the 17.6 MeV (Jπ = 1+ → 0+) ground state transition in 8Be using an improved setup compared to one we used previously. Significant deviations from the internal pair creation was observed at large angles in the angular correlations, which supports that, in an intermediate step, a neutral isoscalar particle with a mass of 17.0±0.5 (stat)±0.5 (sys) MeV/c2 and Jπ = 1+ was created.