A new publication in Physics suggests that there may be a fifth force of nature – joining gravity, electromagnetic and strong and weak nuclear forces.
The possibility first emerged when observations of the decay of an isotope of Beryllium showed an unexplained excess of electron/positron pairs diverging from each other at a preferred angle (instead of the angle varying with the energy of the excitation of the Beryllium nucleus). The results suggested a new particle, a force-carrying boson, with a distinctive mass of 17 MeV, albeit with a tiny lifespan.
Now, experiments with excited Helium nuclei have yielded the same result.
The particle is provisionally named X17.
The new particle interacts with neutrons, which has physicists excited that the particle may be linked with the gravitational interactions of dark matter.