Higgs Boson 'Portal' May Reveal New Clues to Dark Energy

Particle physics has many mysteries, but one of them is why dark matter, which is observed to dominate energy density of the universe, has a remarkably small (but not zero) value. In fact, this value is so small that it's around 120 orders of magnitude less than would be expected based on fundamental physics. Now, scientists may have found a way to solve this mystery.

Researchers believe that the recently discovered Higgs boson could hold the clue to resolving this puzzle. It could potentially provide a "portal" to physics that could help explain some of the attributes of the enigmatic dark energy, and help resolve the cosmological constant problem.

In order to look at dark matter a bit more closely, the researchers examined a possible small coupling between the Higgs particle and possible new particles likely to be associated with what is conventionally called the Grand Unified Scale. This scale is perhaps 16 orders of magnitude smaller than the size of a proton, at which the three known non-gravitational forces in nature might converge into a single theory.

If the coupling occurred, it could result in the existence of another background field in nature in addition to the Higgs field. This, in turn, would contribute an energy density to empty space of precisely the correct scale to correspond to the observed energy density.

The universe is currently expanding at an accelerated rate. Yet this acceleration cannot be accounted for on the basis of matter alone. Putting energy in empty space produces a repulsive gravitational force opposing the attractive force produced by matter, including the dark matter that is inferred to dominate the mass of essentially all galaxies.

Because of this, it's thought that "dark energy" contributes up to 70 percent of the total energy density of the universe while observable matter contributes only 2 to 5 percent with the remaining 25 percent or so coming from dark matter. Yet the source of dark matter and the reason its magnitude doesn't match the inferred magnitude of energy in empty space is not current understood.

"Our paper makes progress in one aspect of this problem," said Krauss, one of the researchers, in a news release. "Now that the Higgs boson has been discovered, it provides a possible 'portal' to physics at much higher energy scales through very small possible mixings and couplings to new scalar fields which may operate at these scales. We demonstrate that the simplest small mixing, related to the ratios of the scale at which electroweak physics operates, and a possible Grand Unified Scale, produces a possible contribution to the vacuum energy today of precisely the correct order of magnitude to account for the observed dark energy."

The findings are published in the journal Physical Review Letters.