Five things we don’t know about the Higgs boson

1. So far, scientists have determined that the boson’s properties — such as its interaction strength — match those predicted by the standard model, but with an uncertainty of around 10%. This is not good enough to show the subtle differences predicted by new physics theories.
2. Physicists have seen the Higgs boson decay into only the heaviest matter particles, such as the bottom quark. They now want to check whether it interacts in the same way with particles from lighter families, known as generations.
3. The Higgs boson has mass, so it should interact with itself, and the rate of this self-interaction is crucial to understanding the Universe. But such events — for example, the decay of an energetic Higgs boson to two less-energetic ones — are extremely rare and haven’t been conclusively observed yet.
4. Physicists want to know the lifetime of the Higgs — how long, on average, it sticks around before decaying to other particles — because any deviation from predictions could point to interactions with unknown particles, such as those that make up dark matter.
5. Some theories that extend the standard model predict that the Higgs boson is made up of other particles, or that there are different types of Higgs boson. Future observations could provide evidence if any of these exotic predictions are true.