The four fundamental forces of nature – gravitation, electromagnetism, and the weak and strong nuclear forces, have been known for decades. It is now possible that a recent discovery of a previously unknown subatomic particle could in fact be evidence of a fifth fundamental force of nature.
The Hungarian Academy of Sciences conducted research in mid-2015 searching for “dark photons” that would signify unseen dark matter. Scientists believe dark matter makes up about 85 percent of the universes mass. During the study, the Hungarian experimental nuclear physicists detected a radioactive decay anomaly that indicates the existence of a light particle 30 times heavier than an electron, but they weren’t able to claim that it was a new force. Although an excess of events indicated a new particle, there was not enough data to confirm whether it was a force-carrying particle or a matter particle.
UCI researchers led by Jonathan Feng, professor of physics & astronomy, studied the Hungarian researchers’ data as well as all other previous experiments in this area. They concluded that the evidence strongly disfavors both dark photons and matter particles. Synthesizing all existing data, the UCI team proposed a new theory: the discovery could indicate a fifth fundamental force. Feng does however emphasize that further experiments are required to confirm the theory.
If a fifth force has indeed been discovered, it would completely change scientist’s understanding of the universe, with consequences for the unification of dark matter and forces.
The UCI researches believe that the particle discovered by the Hungarian team may be a “protophobic X boson” rather than a dark photon. Normal electric force acts on electrons and protons, but this newfound boson interacts at an extremely limited range with only electrons and neutrons. Co-author Timothy Tait, professor of physics & astronomy at UCI, notes that no other boson with the same characteristic has ever been observed, hence the name ‘X boson,’ where ‘X’ simply means unknown.
As the particle is light, laboratories with enough energies required to make it have been around since the ’50s and ’60s. The particle has not been spotted before simply because its interactions are very feeble. Now that experimental groups working in small labs around the world know where to look, they could easily follow up the initial claims.
This scientific breakthrough, like many others, opens an entirely new field of inquiry. Feng is intrigued by the possibility of the manifestation of one grander, more fundamental force. This might be proven if it is found that this potential fifth force joins the electromagnetic, and strong and weak nuclear forces.
Based on physicists’ understanding of the standard model, Feng also speculates that there may be a separate dark sector with its own matter and forces. If this is the case, these two sectors might talk to and interact with one another through veiled, but fundamental interactions. In a broader sense, this would fit in with the Hungarian’s original research to understand the nature of dark matter.
Paper was published in the journal of Physical Review Letters.