Theoretical physicists speak of four fundamental forces of nature. They are gravity, electromagnetism, and the strong and weak nuclear forces that rule the inner workings of atoms. In recent months, the physics community has been buzzing with word of evidence for a possible 5th fundamental force. On August 14, 2016, physicists at University of California, Irvine announced they have confirmed evidence for this force on theoretical grounds, using experimental data acquired by Hungarian scientists in 2015. The journal Physical Review Letters has published the Irvine scientists’ study.
Jonathan Feng, professor of physics and astronomy at University of California, Irvine and lead author of the new theoretical study said:
If confirmed by further experiments, this discovery of a possible 5th force would completely change our understanding of the universe, with consequences for the unification of forces and dark matter.
The UCI researchers analyzed data published last year from experimental nuclear physicists at the Hungarian Academy of Sciences. The Hungarian scientists, led by Attila Krasznahorkay, had been searching for dark photons, hypothetical elementary particles proposed as a carrier for dark matter. The Irvine scientists’ statement said:
The Hungarians’ work uncovered a radioactive decay anomaly that points to the existence of a light particle just 30 times heavier than an electron.
The experimentalists weren’t able to claim that it was a new force. 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.
After study the Hungarian researchers data, as well as previous experiments in this area, the UCI group was able to show on theoretical grounds that the evidence strongly disfavors both matter particles and dark photons. They proposed a new theory that synthesizes the existing data and determined that the discovery could indicate a 5th fundamental force.
The statement about the new work said it demonstrates that, instead of being a dark photon, the particle may be what scientists call a protophobic X boson. Timothy Tait, a co-author of the study, explained:
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.
If it exists, this newfound boson interacts only with electrons and neutrons – and at an extremely limited range, these scientists said.
Feng noted that further experiments are crucial:
The particle is not very heavy, and laboratories have had the energies required to make it since the ’50s and ’60s.
But the reason it’s been hard to find is that its interactions are very feeble. That said, 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.
Like many scientific breakthroughs, this one opens entirely new fields of inquiry. One direction that intrigues Feng is the possibility that this potential 5th force might be joined to the electromagnetic and strong and weak nuclear forces as:
… manifestations of one grander, more fundamental force.
Feng also speculated on a possible, 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. 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.
Bottom line: Theoretical physicists at University of California, Irvine (UCI) announce evidence for a possible 5th fundamental force of nature.