A Potential Newly Discovered Subatomic Particle Could Prove a "Fifth Force" of Nature

The possible discovery of a previously unknown subatomic particle last year led some physicists to speculate that it might be evidence of a fifth fundamental force of nature. Now, the idea just got more support from research published in the journal Physical Review Letters. 

We're already familiar with the four fundamental forces of gravity, electromagnetism and strong and weak nuclear forces. This mysterious fifth force could be an indication of the dark sector of the universe, which includes an invisible substance called dark matter. According to NASA, dark matter makes up about 27% of the universe.

"If confirmed by further experiments, this discovery of a possible fifth force would completely change our understanding of the universe, with consequences for the unification of forces and dark matter," Jonathan Feng, lead author on the new study, said in a statement.

Feng and his team first analyzed experimental results from researchers at the Hungarian Academy of Sciences who found evidence of a "dark photon," which is a particle that some physicists think could make up dark matter. However, the results were very preliminary.

The 'X boson': After continuing research, Feng and his team think the particle that the Hungarian lab found isn't a dark photon, but rather a "protophobic X boson" that only feebly interacts with neutrons and electrons.

"There's no other boson that we've observed that has this same characteristic," co-author Timothy Tait said in the statement. "Sometimes we also just call it the 'X boson,' where 'X' means unknown."

They think the X boson and its possible fifth force is related to the electromagnetic and strong and weak nuclear forces, but it's also possible that the fifth force is related to the dark sector.

"It's possible that these two sectors talk to each other and interact with one another through somewhat veiled but fundamental interactions," Feng said. "This dark sector force may manifest itself as this protophobic force we're seeing as a result of the Hungarian experiment. In a broader sense, it fits in with our original research to understand the nature of dark matter."

The research is still in its preliminary phase, but if it's confirmed by other labs, it could help us unravel the mysteries of dark matter. 

The good news is that "because the new particle is so light, there are many experimental groups working in small labs around the world that can follow up the initial claims, now that they know where to look," Feng said.