X17 Particle: Could It Be a Fifth Force Contributing to the Universe’s Stability?
Is there a fifth force contributing to the stability of the universe? For years, the search for dark matter, along with the particles and forces expected to interact with it, has resulted in numerous false starts. Despite extensive efforts, any concrete evidence for the existence of this invisible matter—believed to constitute the majority of the known universe—has remained elusive.
However, in 2015, a group of Hungarian researchers proposed the discovery of a particle they named X17, which might interact with dark matter in some way.
The Discovery of the X17 Particle
The Hungarian team recently provided further evidence supporting the existence of the X17 particle through a second experiment. If confirmed, this discovery could revolutionize our understanding of physics. Yet, not everyone in the scientific community is convinced, and new experimental approaches are being developed to uncover the truth.
Led by Attila Krasznahorkay from the Hungarian Academy of Sciences’ Institute for Nuclear Research (ATOMKI), the team initially studied the disintegration of the beryllium-8 nucleus in 2015. They observed an anomaly in the emitted pairs of electrons and positrons (antimatter counterparts of electrons) that suggested the presence of a mysterious particle—what they dubbed the X17 particle.
Recently, they observed a similar anomaly during the disintegration of a helium-4 nucleus. “We explored the decay of high-energy atomic states, first in beryllium-8 and then in helium-4,” explained Krasznahorkay. “We noticed a small but distinct gap between expected results and experimental data.”
To explain this discrepancy, the researchers proposed the existence of a new particle, which forms inside the atomic nucleus and is emitted as an electron-positron pair.
The Hunt for the X17 Particle
While most particle detection methods, such as those employed at the Large Hadron Collider (LHC) in Geneva, focus on high-energy collisions, the Hungarian team has taken a different approach. At CERN, the LHC smashes protons together at extremely high energies to observe the resulting particle emissions. However, the Hungarian team’s method involves analyzing the nuclear disintegration of materials bombarded with protons.
According to Jesse Thaler of MIT’s Center for Theoretical Physics, who was not involved in the experiment, the X17 particle’s 17 MeV energy scale is “impossible to investigate using the LHC, which operates at much higher energies.”
Since the Hungarian team published their findings in 2015, other scientists have attempted to verify the existence of the X17 particle, but have so far been unsuccessful.
A New Force in Nature?
In 2016, an independent analysis suggested that if the X17 particle exists, it might represent a “fifth force” in nature, possibly linked to dark matter. Daniel Alves, a particle physicist at Los Alamos National Laboratory who was not part of the Hungarian team, stated, “This fifth force implies a new particle mediating new interactions or forces. It’s possible this particle is part of a larger ‘dark sector,’ interacting with dark matter particles. It could be a gateway to this hidden world.”
Not everyone agrees, though. Some scientists, like theoretical physicist Matt Strassler from Harvard University, who was not involved in the research, have raised concerns about the particle’s potential instability. The fact that only the Hungarian team has been able to observe it has led some to question whether the results are due to an experimental error.
Strassler also pointed out the unusual properties the X17 particle would need to possess, stating, “It’s difficult to create a particle that interacts more with neutrons and electrons than with protons and neutrinos. It makes the story less believable.”
Ongoing Efforts to Find X17
Despite skepticism, the search for the X17 particle continues. CERN’s NA64 collaboration attempted to find evidence of the particle, but was unsuccessful. When the Large Hadron Collider is upgraded in the next year or two, researchers hope to use the LHCb experiment to look for signs of the X17 particle by analyzing another particle, the beauty quark.
Alves and his team at Los Alamos are also exploring the possibility of finding the X17 particle by studying neutron-capture processes, where one neutron is absorbed by another nucleus. Alves believes this method could yield new results, even though it differs from the Hungarian team’s approach, which focused on the disintegration of atomic nuclei.
The Future of X17
The discovery of the X17 particle is still far from certain, but it has generated significant excitement in the scientific community. It may take years of further research to determine whether the X17 particle truly exists. If it does, it could open a new chapter in our understanding of physics and provide insight into the mysteries of dark matter.
As Krasznahorkay himself said, “I believe it exists, but I also have some harsh critics.”
