Science wrote:In search for unseen dark matter, physicists turn to shadow realm
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?"
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.
Higgs bosons and neutrinos would connect similarly to the dark sector. Thanks to these portals, the infant universe should have produced the right amount of dark matter, much as in the WIMP miracle.
Beware the Dark Sector!