19 September 2023
By Michelle Starr

Snips
According to a comprehensive new analysis under quantum chromodynamics, the dark photon is a much better fit for the observed results of particle collider experiments than the standard model of particle physics, by quite a wide margin.

In fact, a team of researchers led by physicist Nicholas Hunt-Smith of the ARC Centre of Excellence for Dark Matter Particle Physics and the University of Adelaide in Australia calculated a confidence level of 6.5 sigma, suggesting the odds that dark photons don't explain the observations are in the ballpark of one in a billion.

"The existence of dark matter has been firmly established from its gravitational interactions, yet its precise nature continues to elude us despite the best efforts of physicists around the world," says Anthony Thomas, a physicist at the University of Adelaide.

"The key to understanding this mystery could lie with the dark photon, a theoretical massive particle that may serve as a portal between the dark sector of particles and regular matter."

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One possibility is that hypothetical dark photons are involved somehow. Just as normal photons are a force carrier for electromagnetism – light – dark photons could be connected to dark matter.

Hunt-Smith and his colleagues at the University of Adelaide and the Jefferson Lab in the US investigated the products of particle collisions to search for evidence of these elusive particles.

"In our latest study," Thomas says, "we examine the potential effects that a dark photon could have on the complete set of experimental results from the deep inelastic scattering process."

Deep inelastic scattering refers to a specific way that particles can scatter following a high-energy collision. Using data from a number of particle colliders, the researchers explored the possibility that dark photons play a subtle role in the way particles diverge following an impact.

They also included a particular thorn in the side of the standard model, the muon magnetic anomaly. Measurements of the way the muon jiggles in a strong magnetic field disagree with standard model predictions by 3 to 4 standard deviations, hinting at the activity of forces yet to be studied.

They found that introducing the possibility of a dark photon not only increases the preference for the dark photon as a candidate, it significantly reduces the muon magnetic anomaly.

The research has been published in the Journal of High Energy Physics.
https://link.springer.com/article/10.1007/JHEP09(2023)096