Dark Matter
Part of supersymmetry’s appeal is that it contains so many new particles. Perhaps one of them might have the right properties to explain dark matter – an as yet unknown substance that makes up more than 80 percent of all matter in the universe. Astronomers have ample evidence of its existence, and have shown that it interacts gravitationally with ordinary matter, but have no real idea what exactly it might be.
The leading candidate for dark matter is a supersymmetric partner to the neutrino called the neutralino. This particle would be much heavier than the neutrino but would fly through ordinary matter as easily as a bullet through thick fog. There are currently many searches underway to directly detect such particles, watching a large mass of atoms until one of them gets hit, but it’s possible that the LHC could have produced one by now.
No neutralinos have been seen at the LHC but scientists are not too worried. Dark matter exists and it will only be a matter of time before we are able to see it in a laboratory.
Image: The Bullet Cluster, where two galaxy clusters are crashing into one another, provides excellent evidence of dark matter. X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.