Physicists May Have Discovered a Fifth Force of Nature

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An example of simulated data modeled for the CMS particle detector on the Large Hadron Collider. CERN

Physicists tell us the universe is controlled by just four fundamental forces. Gravity and electromagnetism operate on a scale we can readily recognize, while the strong and weak forces act on the atomic level to connect atoms or break them apart.

Most of physics can be understood with these forces, but there are anomalies — hints that our understanding of nature is missing something. For this reason, some physicists suspect there may be a mysterious fifth force, such as a force that helps explain the nature of dark matter.

And according to new research, we may be getting close to unmasking it.

Scientists at the Institute for Nuclear Research at the Hungarian Academy of Sciences (Atomki) were studying how an excited helium atom emitted light as it decayed, CNN reports. The particles reportedly split at the unusual angle of 115 degrees, a behavior that can't be explained by our current understanding of physics.

Posted on the preprint repository arXiv, the findings point to a mysterious particle known as X17, which might connect "our visible world with the dark matter," lead scientist Attila Krasznahorkay tells CNN.

If these results can be replicated, "this would be a no-brainer Nobel Prize," adds Jonathan Feng, a professor of physics and astronomy at the University of California, Irvine, who has followed Krasznahorkay's research for years.

The new discovery builds on earlier findings, reported in 2016 in the journal Physical Review Letters. In that study, Krasznahorkay and his colleagues fired protons at a lithium-7 atom, producing unstable beryllium-8 nuclei that then decayed and released pairs of electrons and positrons. Physicists would normally expect the number of observed pairs to drop as the angle separating the electron's and positron's trajectories increases, according to Nature News. At about 140 degrees, however, the number of such emissions went up, creating a "bump" (when the number of pairs were compared with the angle) before falling again at higher angles. According to Krasznahorkay, this suggests the emergence of a new particle, X17.

The Hungarian team's research was initially overlooked until an American team led by Feng ran their own numbers on the same data, apparently confirming the find. Feng's team suggested the new boson is indeed carrying a fifth force that could rewrite the book on our understanding of existence.

The original reason for the Hungarian team's experiment was to search for a theoretical "dark photon," a proposed electromagnetic force carrier for dark matter, similar to the way regular photons carry the electromagnetic force for normal matter. The new super-light boson may not have been the dark photon they were looking for, but its discovery could turn out to be similarly profound.

“We are very confident about our experimental results,” Krasznahorkay told Nature in 2016. Unless the team missed something, he added, the odds of this being a flukey result are 1 in 200 billion.

Scientists need to confirm the results of the 2016 experiment to advance this intriguing possibility, and these new findings are part of that ongoing replication effort. According to Feng, unless some experimental error has been overlooked, the chances that this doesn't reveal a fifth force of nature are 1 in 1 trillion.

This still isn't definitive evidence, but as Feng tells CNN, if other researchers can repeat these results with a third type of atom, "that would blow the cover off this thing."