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X17 particle

X17 particle

The X17 particle is a hypothetical subatomic particle proposed to be a boson.

X17 is a hypothetical subatomic particle referred to in October, 2019, by a Hungarian team of researchers, lead by Attila Krasznahorkay Institute for Nuclear Research at the Hungarian Academy of Sciences. The research team reported in arXiv that they observed evidence that X17 is a new boson. The name X17 comes from the mass calculated to be about 17 megaelectronvolts. Evidence for X17 came from observations of the decay of an isotope of helium. As an excited helium atom decayed it emitted light and particles split at an angle the could not be explained by known physics.

The Hungarian researchers stated that their observations were similar to an anomaly they had seen with the decay of beryllium-8 in 2016, and that it was likely the same X17 particle was responsible. Observing radioactive decay of beryllium-8, the scientists found unexpected light emissions that suggested an unknown particle was created. In both experiments, the researchers observed behavior that did not follow the law of conservation of energy. Krasznahorkay’s team reported in 2016 that the deviation between experimental and theoretical angular correlations could be described by assuming the creation and subsequent decay of a boson. Researchers from University of California, Irvine, led by Jonathan Feng brought further attention to the research when they analysed the data concerning the potential boson and calculated that the new boson could be carrying a fifth fundamental force. Feng’s group referred to the unseen fifth force in action as a “protophobic force” meaning it was as though the particles were “afraid of protons”.

Bosons are particles in quantum mechanics that carry energy and function to hold matter together and control interactions between physical forces. Since each of the four fundamental forces has a boson to go with it, evidence for a new boson points to the existence of a fifth force of nature. The four accepted fundamental forces of nature are gravity, electromagnetism, the strong nuclear force and the weak nuclear force. The fifth force could help explain the nature of dark matter. Jonathan Feng said in 2016 that a fifth force could lead to a unified theory that joins electromagnetic, strong and weak forces as, “manifestations of one grander, more fundamental force”.


October 23, 2019
New evidence supporting the existence of the hypothetical X17 particle

In this paper published in arXiv Hungarian researchers observed evidence for a new boson, from the decay of an isotpe of helium, which they refer to as the X17 particle. The mass of the particle is calculated at about 17 megaelectronvolts.

April 25, 2016
Evidence for a Protophobic Fifth Force from 8Be Nuclear Transitions
January 26, 2016
Observation of Anomalous Internal Pair Creation in Be8: A Possible Indication of a Light, Neutral Boson



Further reading


The Fifth Force of Nature Could Be Real and Fantastic

Caroline Delbert


November 20, 2019

Documentaries, videos and podcasts





Mark Mancini
December 23, 2019
The Standard Model of physics provides a framework for the subatomic world of all energies. Could a possible newfound carrier boson expand the definition of that framework?
November 26, 2019
The Wire
Stumbling upon a particle during an experiment is one thing. Explaining what that particle is and why it behaves the way it does is quite another.


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