Scientists are closer to discovering a fifth force of nature, according to new data from the Fermi National Accelerator Laboratory (Fermilab) in Illinois. The results come from experiments that measured the behaviour of muons, heavy cousins of electrons, in a magnetic field, reports theguardian.com.
Muons act like tiny magnets that spin around the direction of the magnetic field, similar to a spinning top.
However, they also wobble as they spin, and the frequency of this wobble can be predicted by the standard model of particle physics, which describes three of the four known fundamental forces: the electromagnetic force and the strong and weak nuclear forces.
The standard model, however, does not account for the fourth force, gravity, or for dark matter, a mysterious substance that makes up about 27% of the universe. Moreover, the experiments at Fermilab showed that the muons wobbled more than expected, suggesting that there might be another force at play, beyond the standard model.
Dr Mitesh Patel from Imperial College London, who was involved in the experiments, said: “We’re talking about a fifth force because we can’t necessarily explain the behaviour [in these experiments] with the four we know about.”
One possible explanation for the discrepancy is that there are new particles that interact with muons and affect their wobble. These particles could be the carriers of a fifth force of nature, similar to how photons carry the electromagnetic force.
Prof Jon Butterworth from University College London, who works on the Atlas experiment at the Large Hadron Collider (LHC) at Cern, said: “If the measurements don’t line up with the prediction, that could be a sign that there is some unknown particle appearing in the loops – which could, for example, be the carrier of a fifth force.”
The findings are not yet conclusive, as there is still some uncertainty around the theoretical prediction of the wobble frequency. Patel said that more data and analysis are needed to confirm or rule out the existence of a fifth force. He also noted that other experiments at LHC and elsewhere are looking for signs of new physics beyond the standard model.
Butterworth said: “If the discrepancy is confirmed, we will be sure there is something new and exciting but we won’t be sure exactly what it is.”
The results from Fermilab were published in Physical Review Letters and are based on data from 2018. The experiments will continue until 2024, collecting more data and improving the precision of the measurements.