We are inquisitive and intellectual beings. We have always sought for our origin and purpose. On this errand of discovering ourselves, the knowledge we had have soared. Every time we came to conclude our story, a new discovery arose.

X17 Force and Particle

The X17 force assumed to be the fifth fundamental force by the scientific world is a new possible truth that is tending to push the frontiers of our understanding.


In the beginning, there came a concept of force. The concept of force including gravitational force was well established by Sir Issac Newton. The improvement in science saw the discovery of electromagnetic, strong, and weak force afterward. Finally, we had four fundamental force that runs the Universe.

When we were ready to explain everything with those four forces, something popped up, the anomalies in the mass of Galaxies. There were masses and energies which we could not detect. They were found to account for 95 percent of our Universe and called dark matter and dark energy. Then the quest to explain such unknowns surged rapidly.

The very quest opened room for an explanation of various anomalies stepping above the well-established principles. So, breaching the four fundamental forces border to assume X17 particle and X17 force was inevitable in explaining some anomalies.

Let us know this force carrier X17 particle and the X17 force before arguing its existence as the fifth fundamental force.

X17 particle and X17 force

X17 particle is a hypothetical particle proposed by Hungarian Physicist, Krasznahorkay and his colleagues, while, X17 force is force associated with this particle.

This particle was hypothesized to explain the anomaly in the nuclear transition in 8-Beryllium. Krasznahorkay and his team were studying the dark photons. They impinge proton on Lithium to make an unstable Beryllium. The Beryllium emitted electron-positron pairs at an angle of 140 degrees. This was not supposed to happen. The observed energy released was nearly 17 Mega electron volts.

This observed anomaly in the trajectory was accounted for by light and neutral Boson, a force carrier particle. Later, the result Jonathan Feng and colleagues found that the anomalies could be explained by the assumption of protophobic X – Boson with mass around 17 Mega electron volts. So, this particle was named X17 particle.

The force this particle carried was then called the X17 force. There are already four fundamental forces in nature. So, this happens to be a possible candidate for the fifth fundamental force.

Is it really the fifth fundamental force?

As already mentioned, it has traits to become the fifth fundamental force. But, the lack of peer review and failed attempts to discover such anomaly by agencies like CERN has failed to establish it as a fifth fundamental force. But, Krasznahorkay and his team have again discovered the same anomaly in Helium and published a paper online further supporting X17 particle.

Yet, the paper they published is to be peer-reviewed and their results need to be further scrutinized by others, for the establishment of X17 force as the fifth fundamental force. So, the idea of X17 force as a fifth fundamental force is still in doubt. But, the possibility is not ruled out yet. Even if it is ruled out, we might see other candidates in the future, since the understanding of the dark world is beyond the well-accepted standard model and physics is always likely to amaze us.

What impact can it have in Physics?

According to Jonathan Feng and the team, it is not a dark photon but rather a photophobic Boson. This means that it won’t explain the dark world but redefines the standard model. It is inconsistent with the standard model. So, the confirmation of this theory leads us beyond the standard model.

Also, physicists are skeptical about the theory proposed by Jonathan Feng and the team. They still assume this to be a pathway to discovering the dark world, the world beyond our sight. These assumptions require strong ground to be well established. Either way, it’s confirmation is going to take us beyond the four fundamental forces and the standard model.

Further attempts for the detection

There are different teams targeting the confirmation or trying to refute the existence of X17 force and its associated particle. LHCb at CERN, Jefferson Laboratory, Chinese Academy of Sciences, and many other laboratories are searching for the existence of this proposed particle.

Refuted or confirmed, either way, it is going to enrich the particle physics and take us closer to the world beyond the visible world, the dark world.

Ashwin Khadka is a PhD Scholar in Nano Energy and Thermofluid Lab in Korea University, Republic of Korea under Korean Government Scholarship Program. He has a Masters Degree in Physics from Tribhuvan University, Kathmandu, Nepal. He is a science enthusiast, researcher and writer.