Under-the-radar research published earlier this year in the journal Physical Review Letters may have discovered a previously unknown fifth fundamental force of nature: a new boson which is only 34 times heavier than the electron and which does not violate the laws of physics.
The study, which was the topic of reports by Nature and Popular Science this week, was led by Attila Krasznahorkay at the Hungarian Academy of Sciences’s Institute for Nuclear Research in Debrecen and went largely unnoticed until a second team of researchers reviewed their results in April and concluded that it was plausible that they had found a fifth fundamental force.
Currently, there are four known fundamental forces of nature: gravity, which holds planets and galaxies together; electromagnetism, which binds our molecules together; strong nuclear forces, which hold atomic nuclei together; and weak nuclear forces, which help some kinds of atoms go through radioactive decay. Together, these forces explain the majority of observable physics.
Over the years, there have been many claims that a fifth fundamental force exists, but as of yet, no researchers have been able to find evidence to substantiate this proposition. The inability of the standard model to explain dark matter, the invisible particles believed to make an estimated three-fourths of the universe, has led scientists to ramp up the search for new forces or particles to help explain this phenomenon, including so-called “dark photons.”
Exact nature of the discovery remains unknown
In fact, Krasznahorkay’s team was searching for evidence of dark photons, but the team which reviewed those earlier findings believe that the group may have discovered something different. The Hungarian scientists fired protons at lithium-7 targets to create unstable beryllium-8 nuclei, which they decayed and emitted pairs of electrons and positrons, according to Nature.
The standard model indicated that they should have seen the number of observed pairs decrease as the angle separating the trajectory of the electron and positron increased, but according to the results of their study, there was an increase of emissions at an angle of approximately 140º, then a decrease again at higher angles. Krasznahorkay believes that this brief uptick is evidence that some of the beryllium-8 nuclei emitted excess energy in the form of a new particle.
This particle, which is estimated to have a mass of about 17 megaelectronvolts (MeV) and which would then decay into an electron–positron pair, may either be a dark photon or a protophobic X boson, the former of which would couple to electrons and protons and the latter of which would couple to electrons and neutrons.
While the investigation continues into exactly what they might have found, Krasznahorkay and his colleagues are confident that it is not simple an anomaly, as they reported that they have been able to repeat the results several times over a three-year span. They added that they had been able to eliminate every possible source of error, which is true, means that the odds of them witnessing such an event without something unusual happening were just one in 200 billion, said Nature.
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Image credit: MTA-Atomki
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