Dark Photons: The Key to Unraveling the Dark Matter Mystery?

Dark Matter Photon Particle Physics Art Concept Illustration

A global team of scientists has delved deeper into understanding the complex nature of dark matter, which comprises a staggering 84% of the universe’s matter content. Their focus has been on the ‘dark photon’, a theoretical particle that might bridge the gap between the elusive dark sector and regular matter.

New insights into dark matter emerge as researchers explore the ‘dark photon’ hypothesis, challenging the standard model hypothesis.

“Dark matter makes up 84 percent of the matter in the universe but we know very little about it,” said Professor Anthony Thomas, Elder Professor of Physics, 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.”

“Our work shows that the dark photon hypothesis is preferred over the standard model hypothesis at a significance of 6.5 sigma, which constitutes evidence for a particle discovery.” — Professor Anthony Thomas

The Dark Photon and Its Significance

Regular matter, of which we and our physical world are made up of, is far less abundant than dark matter: five times more dark matter exists than regular matter. Finding out more about dark matter is one of the greatest challenges for physicists around the world.

The dark photon is a hypothetical hidden sector particle, proposed as a force carrier similar to the photon of electromagnetism but potentially connected to dark matter. Testing existing theories about dark matter is one of the approaches that scientists such as Professor Thomas, along with colleagues Professor Martin White, Dr Xuangong Wang, and Nicholas Hunt-Smith, who are members of the Australian Research Council (ARC) Centre of Excellence for Dark Matter Particle Physics, are pursuing in order to gain more clues into this elusive but highly important substance.

Insights From Particle Collisions

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

Analysis of the by-products of the collisions of particles accelerated to extremely high energies gives scientists good evidence of the structure of the subatomic world and the laws of nature governing it.

In particle physics, deep inelastic scattering is the name given to a process used to probe the insides of hadrons (particularly the baryons, such as protons and neutrons), using electrons, muons, and neutrinos.

“We have made use of the state-of-the-art Jefferson Lab Angular Momentum (JAM) parton distribution function global analysis framework, modifying the underlying theory to allow for the possibility of a dark photon,” said Professor Thomas.

“Our work shows that the dark photon hypothesis is preferred over the standard model hypothesis at a significance of 6.5 sigma, which constitutes evidence for a particle discovery.”

The team, which includes scientists from the University of Adelaide and colleagues at the Jefferson Laboratory in Virginia, USA, has published its findings in the Journal of High Energy Physics.

Reference: “Global QCD analysis and dark photons” by N. T. Hunt-Smith, W. Melnitchouk, N. Sato, A. W. Thomas, X. G. Wang and M. J. White on behalf of the Jefferson Lab Angular Momentum (JAM) collaboration, 15 September 2023, Journal of High Energy Physics.
DOI: 10.1007/JHEP09(2023)096


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