With no sign of superpartners emerging from the LHC, some physicists are seriously considering the possibility that particles addressing the hierarchy problem belong to what’s called a hidden sector.
A hidden sector is a family of particles that may interact with each other but which don’t feel the effects of the Standard Model’s three forces – strong, electromagnetic and weak.
A hidden sector of particles could help solve the hierarchy problem, said Zackaria Chacko, a physicist at the University of Maryland who was one of the first to propose this idea in the early 2000s.
“Naively, the way you can think about it is, the Standard Model particles want to pull their Higgs up and make the Higgs heavy,” he said. Chacko’s model is called “Twin Higgs,” since the Higgs, like all the other Standard Model particles, would have a twin living in the hidden sector. In that case, an electron-like particle in the hidden sector would appear as a millicharged one in the Standard Model sector.
Physicists have invoked long-lived particles and hidden sectors to address virtually all the fundamental problems currently plaguing physics, including issues such as dark matter and the matter-antimatter asymmetry of the universe.