Scientists at the Lawrence Livermore National Laboratory (LLNL) believe that dark matter may be composed of electrically charged particles that are bound by a yet-unknown force and have somehow managed to escape detection. The theory could be verified with the help of the Large Hadron Collider (LHC) particle accelerator.
Dark matter makes up over 80 percent of the mass in our universe, but we know little about its nature. Astrophysicists know it must exist from its gravitational effects on large clusters of galaxies, but they have been unable to spot it because this elusive substance interacts weakly with both ordinary matter and itself. In fact, so little is known about dark matter that scientists are still speculating as to what it's even made of.
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Through a combination of computer simulations and theoretical results, researchers Pavlos Vranas and colleagues have now developed a "stealth dark matter" model that could help unravel the mystery of why dark matter behaves like it does, what particles make it up, and what force binds them. Crucially, the model offers assumptions that physicists should be able to test using CERN's Large Hadron Collider (LHC) particle accelerator.
The stealth dark matter model predicts that dark matter is stable, but also produces large quantities of electrically charged, unstable nuclear particles. These short-lived particles, now long decayed, would have left a definite mark in the very early universe, with the extremely high plasma temperatures forcing them to interact with ordinary matter.
"These interactions in the early universe are important because ordinary and dark matter abundances today are strikingly similar in size, suggesting this occurred because of a balancing act performed between the two before the universe cooled," says Vranas.
As temperatures slowly dropped, dark matter would have then started to bond under the influence of a new and still unknown form of strong interaction, growing into electrically neutral clusters several hundred times heavier than a proton.
According to the Vranas and colleagues, the LHC is powerful enough to roll back the clock and reproduce the conditions that would have led to the crucial early interaction between dark matter and ordinary matter. Though the charged particles wouldn't be observed directly, the world's largest particle accelerator could detect a telltale electrical signature that would validate this theory.
Dark matter is currently thought to be completely inert to electromagnetic radiation, so it would be remarkable to discover that it is in fact composed of electrically charged particles which have somehow managed to avoid detection.
A paper describing the advance will be published in an upcoming edition of the journal Physical Review Letters.
Source: LLNLView gallery - 2 images