New insights into dark matter emerge as researchers probe ‘the dark’. photon‘ hypothesis, challenging the standard model hypothesis.
An international team of scientists led by experts from the University of Adelaide has uncovered further clues in their search for insights into the nature of dark matter.
“Dark matter makes up 84 percent of the matter in the universe, but we know very little about it,” said Professor Anthony Thomas, senior professor of physics at the University of Adelaide.
“The existence of dark matter has been firmly established based on its gravitational interactions, yet its exact nature still eludes us despite the best efforts of physicists around the world.”
“The key to understanding this mystery could lie in the dark photon, a theoretical matter particle that can serve as a portal between the dark particle sector and regular matter.”
“Our work shows that the dark photon hypothesis is favored over the Standard Model hypothesis with a significance of 6.5 sigma, providing evidence for the discovery of particles.” — Professor Anthony Thomas
The dark photon and its meaning
The regular matter of which we and our physical world are composed is much less abundant than dark matter: there is five times as much dark matter as ordinary matter. Finding out more about dark matter is one of the biggest challenges for physicists around the world.
A dark photon is a hypothetical particle with a hidden sector, proposed as a force carrier similar to the photon of electromagnetism, but potentially associated with dark matter. Testing existing theories about dark matter is one approach 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) Center of Excellence for Dark Matter Particle Physics, are trying to more clues to this elusive but very important substance.
Observations from particle collisions
“In our latest study, we investigate the potential effects that a dark photon could have on a complete set of experimental results from the deep inelastic scattering process,” Professor Thomas said.
Analysis of the byproducts of collisions of particles accelerated to extremely high energies provides scientists with good evidence of the structure of the subatomic world and the laws of nature that govern it.
In particle physics, deep inelastic scattering is the name given to the process used to probe the interiors of hadrons (especially baryons such as protons and neutrons), using electrons, muons and neutrinos.
“We used the Jefferson Lab’s state-of-the-art global Angular Momentum (JAM) distribution function framework and modified the underlying theory to allow for the dark photon,” said Professor Thomas.
“Our work shows that the dark photon hypothesis is favored over the Standard Model hypothesis with a significance of 6.5 sigma, providing evidence for the discovery of particles.”
The team, which includes scientists from the University of Adelaide and colleagues from the Jefferson Laboratory in Virginia, USA, published their findings in Journal of High Energy Physics.
Reference: “Global QCD Analysis and Dark Photons” by NT Hunt-Smith, W. Melnitchouk, N. Sato, AW Thomas, XG Wang, and MJ White on behalf of the Jefferson Lab Angular Momentum (JAM) Collaboration, 15 September 2023, Journal of High Energy Physics.