LOS ANGELES, Aug 16: The possible discovery of a previously unknown subatomic particle may indicate that a fifth fundamental force of nature exists, a revolutionary finding that could change our understanding of dark matter and the universe, scientists say.
“For decades, we’ve known of four fundamental forces: gravitation, electromagnetism, and the strong and weak nuclear forces,” said Jonathan Feng, professor at University of California, Irvine (UCI) in the US.
“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,” Feng said.
The researchers came upon a mid-2015 study by experimental nuclear physicists at the Hungarian Academy of Sciences who were searching for “dark photons,” particles that would signify unseen dark matter, which physicists say makes up about 85 per cent of the universe’s mass.
The research pointed to the existence of a light particle just 30 times heavier than an electron.
“The experimentalists were not able to claim that it was a new force,” Feng said.
“They simply saw an excess of events that indicated a new particle, but it was not clear to them whether it was a matter particle or a force-carrying particle,” he said.
The team studied previous research and showed that the evidence strongly disfavours both matter particles and dark photons.
They proposed a new theory, however, that synthesises all existing data and determined that the discovery could indicate a fifth fundamental force.
The study demonstrates that instead of being a dark photon, the particle may be a “protophobic X boson.”
While the normal electric force acts on electrons and protons, this newfound boson interacts only with electrons and neutrons – and at an extremely limited range.
“There’s no other boson that we’ve observed that has this same characteristic. Sometimes we also just call it the ‘X boson,’ where ‘X’ means unknown,” said Timothy Tait, professor at UCI.
Like many scientific breakthroughs, this one opens entirely new fields of inquiry, researchers said.
One direction that intrigues Feng is the possibility that this potential fifth force might be joined to the electromagnetic and strong and weak nuclear forces as “manifestations of one grander, more fundamental force.”
Feng speculated that there may also be a separate dark sector with its own matter and forces.
“It’s possible that these two sectors talk to each other and interact with one another through somewhat veiled but fundamental interactions,” he 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,” Feng said.
The study was published in the journal Physical Review Letters. (AGENCIES)
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