http://www.sciencemag.org/news/2017...kly_2017-03-24&et_rid=41087911&et_cid=1235549 85 % of matter we cannot find , Is the theory real or mathematical fudge factor ? Please Register or Log in to view the hidden image! The electron beam at Jefferson Laboratory creates copious photons in the hopes that a few may be dark. By Adrian ChoMar. 23, 2017 , 9:00 AM Scientists hunting unseen dark matter are looking deeper into the shadows. With searches for a favored dark matter candidate—weakly interacting massive particles (WIMPs)—coming up empty, physicists are now turning to the hypothetical "dark sector": an entire shadow realm of hidden particles. The concept "has been percolating for 7 or 8 years, but it's really coming to the fore now," says Jonathan Feng, a theorist at the University of California, Irvine (UCI). This week, physicists will meet at the University of Maryland, College Park, for a workshop, sponsored by the U.S. Department of Energy (DOE), to mull ideas for a possible $10 million dark matter experiment that could go ahead in the next few years. The effort would complement the agency's current experiments, including the flagship WIMP search, LZ, a $76 million subterranean detector under construction in Lead, South Dakota. And many researchers believe DOE should focus on the dark sector. Jim Siegrist, DOE's associate director for high-energy physics in Washington, D.C., says the goal is to fill in any gap in DOE's searches for dark matter, which makes up 85% of the universe's matter: "Is there anything we're missing?" WIMPs, dreamed up in the 1980s, once seemed the perfect candidate for dark matter, which shapes the visible universe with its gravity. WIMPs would weigh a few hundred times as much as a proton and interact only through gravity and the weak nuclear force. A simple calculation suggests just enough of them should linger from the big bang to account for dark matter today—a selling point known as the "WIMP miracle." In addition, WIMPs emerge naturally in many versions of supersymmetry, a concept that solves key technical problems in the standard model of the known particles. However, physicists have yet to detect WIMPs bumping into atomic nuclei in underground detectors. And the world's most powerful atom smasher, the Large Hadron Collider (LHC) in Switzerland, has seen no sign of supersymmetry or WIMPs. The no-shows have led physicists to turn to the dark sector. They speculate that dark matter might consist not of a single massive particle tacked onto the standard model, but of a slew of lighter particles and forces with tenuous connections to known particles (see illustration). For example, in the familiar universe, massless photons convey the electromagnetic force; in the dark sector, a massive dark photon would convey a dark version of electromagnetism. Theorists generally expect that ordinary and dark photons would subtly intertwine or "mix." Very rarely, then, a particle interaction that would normally produce a high-energy photon would instead produce a dark photon.