Dark matter is funny stuff. According to scientists' calculations, it makes up roughly 85% percent of the universe. All of the stars and nebulae and galaxies we can observe, or can theoretically observe, are only 15% of the story. The rest is a hypothetical type of matter that doesn't interact with electromagnetic radiation—such as light—at all. We can see it affected by gravity—if not for dark matter, the math says, galaxies would be unable to stay together and would fling their constituent stars and star systems into deep space like a group of over-zealous toddlers on a merry-go-round—but we have never directly observed dark matter. It's a holy grail of sorts for modern science. The math says it's there, and if we can prove it's there we don't have to re-do the math.
The Large Hadron Collider at CERN in Switzerland has proven itself really good at not making physicists re-do their math. After the detection of the Higgs boson, the famed "god particle" that seems to be the responsible for giving other particles mass, scientists are setting their sights on using the 27-kilometer particle accelerator to to hunt down the elusive dark matter once and for all.
Scientists at the University of Chicago and Fermilab laid out their plans in a paper in the journal Physical Review Letters earlier this month. Entitled Enhancing Long-Lived Particles Searches at the LHC with Precision Timing Information, the paper details a plan and technique to trap and observe dark matter. Central to this plan is the Higgs boson itself, which may, according to the researchers, act as a "portal to the dark world." Scientists now believe that there are some dark matter particles that can, very rarely, interact with our world. These "long-lived particles" are the ones that scientists think they can trap. Professor LianTao Wang at the University of Chicago explains:
"We know for sure there’s a dark world, and there’s more energy in it than there is in ours.
One particularly interesting possibility is that these long-lived dark particles are coupled to the Higgs boson in some fashion—that the Higgs is actually a portal to the dark world. It’s possible that the Higgs could actually decay into these long-lived particles."
If so, it would mean that dark matter is already created inside the particle accelerator, and all physicists would need to do it just filter it out. Which is much easier said than done. There are more than one billion collisions per second while the LHC is running, and given that dark matter is already invisible, it's a tough nut to crack.
The key, according to researchers, is that the dark matter particles would be heavier than the others, which would make them move and decay a little slower—by about one billionth of a second—than the rest of the particles created in the LHC. According to Jia Liu, one of the paper's authors:
"If it’s that heavy, it costs energy to produce, so its momentum would not be large—it would move more slowly than the speed of light.”
So in order to detect the dark matter particles, scientists would need to be able to detect particles that decay one billionth of a second slower than the rest—something the authors of the paper say is well within the abilities of the LHC. The Large Hadron Collider is currently undergoing improvements and upgrades that will increase it's effectiveness tenfold, and scientists are already working on building the dark matter trap. When the LHC comes back online in 2021, all three of the particle detectors will be outfitted with the new system. And maybe, just maybe, there will finally be proof that 85% of our universe actually exists.